Impacts of Climate Change on LMB Fisheries Phase 2 NV - Copy€¦ · Prepared for the Fisheries...

ASSESSMENT OF THE IMPACT OF CLIMATE CHANGE

ON FISHERIES RESOURCES UNDER DIFFERENT

CLIMATE CHANGE CONDITIONS AND SCENARIOS IN

THE LOWER MEKONG BASIN

Draft report

Prepared for the Fisheries Programme and Climate Change Adaptation

Initiative of the Mekong River Commission

Prepared by: Mauricio E. Arias, PhD

May 18, 2016

Impact of climate change on fisheries of the Lower Mekong Basin: Phase 2 draft report

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Contents

Executive Summary ......................................................................................................................... 7

1 Introduction ........................................................................................................................... 10

2 Background ............................................................................................................................ 12

2.1 Effects of flood alteration ....................................................................................................... 12

2.2 Effects of salt intrusion on freshwater fish ............................................................................. 13

Effects of increase water temperature ............................................................................................... 14

3 Description of MRC future scenarios and data .................................................................... 17

3.1 Scenarios description ............................................................................................................. 17

3.2 Data used for habitat-based changes in total wild fish yields .................................................. 19

3.3 Data used for impacts of salt intrusion on aquaculture ........................................................... 19

4 Habitat-based changes in total wild fish yields ..................................................................... 20

4.1 Methodology ......................................................................................................................... 20

4.2 Results and discussion ............................................................................................................ 22

4.3 Limitations ............................................................................................................................. 34

4.4 Recommended adaptation options ........................................................................................ 34

5 Impacts of salt intrusion on aquaculture .............................................................................. 34

5.1 Methodology ......................................................................................................................... 37

5.2 Results and discussion ............................................................................................................ 39

5.3 Limitations ............................................................................................................................. 56

5.4 Recommended adaptation options ........................................................................................ 57

6 Conclusions ............................................................................................................................ 59

References .................................................................................................................................... 61


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List of Figures

Figure 1. Process diagram of GIS model used to estimate shifts in habitats. .............................. 22

Figure 2. Map showing estimated extent of the baseline flood zone and rice paddies in the

Lower Mekong .............................................................................................................................. 23

Figure 3. Shifts in flood zone and rice paddies as a result of scenarios with no development for

the short-term (2030s) horizon. ................................................................................................... 29

Figure 4. Shifts in flood zone and rice paddies as a result of scenarios with no development for

the medium-term (2060s) horizon. .............................................................................................. 30

Figure 5. Shifts in flood zone and rice paddies as a result of scenarios with development for the

short-term (2030s) horizon. .......................................................................................................... 31

Figure 6. Shifts in flood zone and rice paddies as a result of scenarios with development for the

medium-term (2060s) horizon. ..................................................................................................... 32

Figure 7. Time series of total aquaculture production per country highlights the overwhelming

contribution from Vietnam and the burst that the industry experienced since the late 1990s. . 37

Figure 8. Map of maximum salt intrusion (maximum salinity) for the baseline scenarios

displaying aquaculture-relevant salinity categories ..................................................................... 42

Figure 9. Shifts in salt intrusion zones for medium climate change sensitivity scenarios (RCP 4.5)

with no development. ................................................................................................................... 43

Figure 10. Shifts in salt intrusion zones for high climate change sensitivity scenarios (RCP 8.5)

with no development. 2030s time horizon displayed on the left column and 2060s in the right

column. ......................................................................................................................................... 44


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Figure 11. Shifts in salt intrusion zones for medium climate change sensitivity scenarios (RCP

4.5) with development. ................................................................................................................. 45

Figure 12. Shifts in salt intrusion zones for high climate change sensitivity scenarios (RCP 8.5)

with development. ........................................................................................................................ 46

Figure 13. Area affected by maximum salt intrusion of 1-4 g/L (low effect on aquaculture) by

province. ....................................................................................................................................... 50

Figure 14. Area affected by maximum salt intrusion of 5-20 g/L (potential effect on aquaculture)

by province. ................................................................................................................................... 51

Figure 15. Area affected by maximum salt intrusion greater than 20 g/L (acute effects on

aquaculture) by province. ............................................................................................................. 52

Figure 16. Estimated aquaculture production in the Delta proportional to acute salinity

intrusion. ..................................................................................................................................... 55


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List of Tables

Table 1. Summary of drivers and effects of impacts of climate change on wild fisheries and

aquaculture.. ................................................................................................................................. 16

Table 2. Description of climate change scenarios from MRC's CCAI to be considered in this

assessment. All scenarios considered sea level rise, and two time horizons (2030s and 2060s)

with/without corresponding development plans. ........................................................................ 18

Table 3. Summary of data used in this assessment. ..................................................................... 19

Table 4. Change in fisheries habitat for all scenarios assessed. ................................................... 25

Table 5. Changes in total fish yields as a function of shifts in habitats.. ...................................... 28

Table 6. Changes in extent of areas with max salt intrusion of 1-4 ppt (low impact to

aquaculture). ................................................................................................................................. 47

Table 7. Changes in extent of areas with max salt intrusion of 5-20 ppt (potential impact to

aquaculture). ................................................................................................................................. 48

Table 8. Changes in extent of areas with max salt intrusion greater than 20 ppt (acute impact to

aquaculture). ................................................................................................................................. 49

Table 9. Estimated changes in aquaculture production proportional to extent of salt intrusion

greater than 20 ppt (acute impact to aquaculture).. .................................................................... 54


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Definition of terms and acronyms

Ectotherm Group of animals (including fish) that cannot regulate their body temperature,

and instead rely on their environmental to maintain their optimal body

temperature.

Flood zone Maximum extent of the floodplain with a depth of at least 50 cm.

GCM global circulation models

LMB Lower Mekong Basin

RCP representative carbon emissions

GISS-E2-R-CC Model developed by NASA’s Goddard Institute for Space Studies

GFDL-CM3 Coupled Physical Model developed by the Geophysical Fluid Dynamics

Laboratory of the US National Oceanography and Atmospheric Administration

IPSL-CM5A-MR Model developed by the Institut Pierre Simon LaPLace Climate Modelling Centre


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Executive Summary

Global warming is expected to bring significant changes to the hydrology of the Mekong basin

and this could have substantial implications for capture and aquaculture fisheries in the LMB,

which have an inmense value to the economy, food security, and heritage of the region.

Therefore, the overall objective of this report is to assess the impacts of climate change on wild

fish catches and aquaculture under different climate change conditions and scenarios in the

LMB and provide policy recommendations for climate change adaptations with regards to

capture fisheries and aquaculture development in the LMB.

The first analytical tasks of this report assessed the impacts of flood-driven habitat changes on

wild fisheries. This assessment found that the magnitude of changes in habitat cover is

expected to be greater for the flood zone than for the rice paddies. Overall, a wide range of

variable projections were found according to all factors considered in the climate change

scenarios without development, with shifts in the flood zone from -5922 km2 (-13%) to +6293

km2 (+13.7%), and shifts in rice paddies from -3597 km2 (-2.7%) to 3043 km2 (+2.3%).

Cumulative yields from both habitats could experience a net change of -155,000 tons yr--1 (-5%

from baseline) to 97,000 tons yr--1 (+4%) for all future scenarios. Small changes are expected in

the short-term when development is absent from the scenarios; however, losses become much

more significant in the short term when development is considered. Conversely, this tendency

is not as strong when comparing scenarios in the medium term.

The second analytical task of this report assessed the impact of salt intrusion on aquaculture.

Overall, the Delta-wide area with maximum salinity intrusion above 20 ppt is expected to


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increase by 257-2292 km2 (mean increase by 1900 km2). Dong Thap, An Giang, Vinh Long, or

Can Tho –where more than 60% of the current production takes placed– are not expected to

experienced acutely impacting salt intrusion. On the contrary, great losses are expected in Ca

Mau Province, most of which will become virtually unfeasible for freshwater aquaculture.

Overall, most future climate change scenarios show minor losses (1 to 6%) in delta-wide

aquaculture production compared to baseline conditions.

Future adaptation strategies should focus on those areas expected to be resilient by the

unfavorable conditions dictated by climate change and development. In terms of capture

fisheries, rice paddies production appeared to be marginally unaffected by climate-driven

flooding shifts. Hence, programs to promote and enhance fish production within rice paddies

could greatly build resilience in the region, in particular if rice agriculture continues to expand

in the lower Mekong, and scenario that was not considered in this assessment. In terms of

aquaculture, some of the provinces further up the terrain elevation were shown to be largely

unaffected by acute salt intrusion in the future, thus aquaculture in these (most productive)

provinces is likely to remain uncompromised by salinity. Therefore, it is recommended that

plans to maintain productivity and enhance the quality of aquaculture in these provinces

continue. There are, however, other climate driven factors that could detrimentally affect

aquaculture in these provinces, including storm damages, extreme drought and pollution,

among others, and future assessments could evaluate their role in the future of aquaculture in

the Delta.


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Acknowledgements

The authors would like to thank Dr. Roel Boumans for support on preliminary versions of this

report, and Dr. Michael Cooperman for his insightful view on impacts of higher temperatures

on Mekong fish.

Special thanks also to the CCIA and FP staff who provided support and fruitful comments

through this project, especially Dr. So Nam, Dr. Nguyen Huong Thuy Phan, Mr. Peng Bun Ngor,

and Mr. Vanna Nuon. Thanks also to Dr. Benjamin Docker for comments on previous drafts of

this report.


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1 Introduction

Climate change is expected to bring impacts to societies around the world, in particular those in

which livelihoods are heavily depended upon natural resources. Such is the case of the Lower

Mekong River (LMB), where fisheries and rice agriculture play an important role in the heritage,

economy, and food nutrition of the four nations that shared this lower portion of the river

basin. Global warming is expected to bring significant changes to the hydrological cycle of the

basin and its floodplains (Hoang et al., 2015; Kingston et al., 2011; Lauri et al., 2012; Västilä et

al., 2010), which could have important implications for the habitats and primary productivity

that support fisheries in the LMB (Arias et al., 2012; Arias et al., 2014). However, there is very

little information related to how fisheries in the LMB would be affected by climate change.

The 2011-2015 Climate Change and Adaptation Initiative (CCAI) of the Mekong River

Commission (MRC) has carried out a comprehensive assessment of impacts and adaptation

strategies to climate change by the various sectors and stakeholders of the Mekong’s water

resources. In partnership with the MRC’s Fisheries Programme, a request for an assessment of

the impacts of climate change on fisheries of the LMB was placed. The main purpose of this

report is to fulfill this knowledge gap, which is an important outcome of the overall objectives

for both the CCAI and FP during the 2011-2015 period.

The overall objective of this report is to assess the impacts of climate change on wild fish

catches and aquaculture under different climate change conditions and scenarios in the LMB

and provide policy recommendations for climate change adaptations with regards to capture

fisheries and aquaculture development in the LMB. In order to be consistent with previous MRC


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technical reports and the umbrella CCAI assessment, this report is primarily based on sources of

information directly provided by the MRC with regards to both fisheries and climate change.

The next sections of this report are structured as follows: In section 2, the most relevant

literature review with regards to impacts of climate change on freshwater fisheries is

summarized. In Section 3, the data and future scenarios used throughout the report are

described. In section 4, estimates of wild fish yields as a function of habitat type are presented.

In section 5, an assessment of the impacts of salt intrusion on aquaculture is presented. Both

sections 4 and 5 conclude with a statement of limitations and a discussion of recommendations

for climate adaptations. Finally, section 6 presents a recapture of the entire report and

summarizes the main findings and recommendations from this study.

2 Background

This section provides a literature review of the main climate change drivers that could cause

impacts on capture and aquaculture freshwater fisheries. Overall, climate change causes a large

series of regional and local processes that affect fisheries from several angles, and publications

such as Cochrane et al. (2009) and Ficke et al. (2007) provide a comprehensive overview of

what all these drivers and impacts can be for fisheries around the world. The intention of this

section is to synthesize that information and provide a concise review of those aspects that are

most relevant to freshwater fisheries in the LMB and which have shown the clearest evidence

of effects. As such, three main drivers will be reviewed: flood alterations, sea level rise, and

higher temperature. For each of these three, an attempt is made at highlighting particular

processes and direct effects that they will have on freshwater capture and aquaculture

fisheries. A summary of the key points reviewed in this section is presented in Error! Reference

source not found..

2.1 Effects of flood alteration

Changes in the hydrological regime and variability could have implications to capture fisheries

populations via a number of direct biological mechanisms as well as indirect ecological effects.

Arguably the most direct effect that flooding intensity has on fish in large river systems like the

Mekong is through its role on fish population density and recruitment (Halls and Welcomme,

2004; Linhoss et al., 2012), which can explain why higher floods are typically associated with

increased fish yields in the Mekong (Halls et al., 2013). This relationship, on the contrary, also

implies that increase frequency and intensity of droughts could have a negative effect on


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populations (Ficke et al., 2007), and that antecedent years are also of importance for the yields

on a particular year. Changes on the flood regime can also have an effect on fish yields via

more indirect ecological pathways. In general, changes in the extent of flooding could alter the

access and features of floodplain habitats that fish use for feeding and spawning, plus it would

affect the allochthonous input of material into the aquatic system (Ficke et al., 2007). In

addition, a smaller extent of inundation in a floodplain would also translate into reduced

spawning habitat. A particular case study in the Tonle Sap demonstrated how hydrological

alterations caused by development and climate change scenario could alter the extent of

habitat for broad indicator fish guilds (Arias et al., 2014).

Reviewed effects of flood alteration on aquaculture appear to be less process-based than what

has been published for capture fisheries, and rather, focuses more on episodic impacts during

particular situations of flood or drought. As the frequency of large floods increase, for instance,

a higher risk for damages to farm infrastructure can occur, which then can reduce aquaculture

production (Handisyde et al., 2006). Moreover, large floods can also facilitate the escape of

stock, as well as the introduction of predators into the enclosures (Handisyde et al., 2006).

Negative effects can also occur as a result of drought, in particular the increase of

concentration of pollutants during low water conditions, as well as temperature and salinity

increases, which are reviewed in more detail in the following two sub-sections.

2.2 Effects of salt intrusion on freshwater fish

Water salinity imposes one of the greatest barriers to freshwater organisms, and therefore salt

intrusion resulting from sea level rise is a direct threat to both capture and aquaculture


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fisheries in the LMB, in particular in the Vietnam Delta. Salinity simply creates a biological

threshold to aquaculture, and once this threshold is reached, there are no other solution but to

migrate (in the case of capture fisheries) or relocate (aquaculture) to waters that meet the

optimal criteria for a particular species. Studies on tolerance of aquaculture species most

common in the Delta (Pangasianodon hypophthalmus) have shown that they tolerate water

salinity up to 13 ppt without any effects on growth rates, but their survival rate declines

drastically (over 60%) once salinity is greater than 20 ppt (Halls and Johns, 2013 after

Castaneda et al., 2010). In addition to the reduction of optimal area for freshwater aquaculture,

another important consideration is that salinity may alter the floodplain ecosystems that act as

nursery for some fish species (Handisyde et al., 2006). Moreover, salt intrusion, even if it is not

above fish biological thresholds, can trigger water chemistry alterations, which can then lead to

other effects on aquatic biota (Ficke et al., 2007).

2.3 Effects of increase water temperature

Most literature related to impacts of climate change on fish actually primarily discusses the

effects that could occur via changes in water temperature. Most literature, however, discusses

the impacts on cold-water species (e.g. salmonoids), and only a limited number of studies have

focused on warm-water fishes (Comte et al., 2013), and even less in the tropics. In general,

studies that assessed the spatial distribution of warm water species (e.g., Cyprinidae) have

shown a positive effect of climate change on their range of habitat suitability (Cochrane et al.,

2009; Comte et al., 2013). These findings are not necessarily applicable to tropical fish in river

basins like the Amazon, Congo and Mekong, in which fish would have to travel extremely long


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distances to reach areas where they can experience their optimal temperature in the future

(Wright et al., 2009).

Research on habitat suitability does not necessarily take into account the physiological

constrains that extreme heat could have on ectotherm species in the tropics, which already live

very close to the boundary of their temperature optimal upper limit (Tewksbury et al., 2008).

Tropical freshwater fish have limited ability to adapt to rising water temperatures, according to

Dr. Michael Cooperman, a fish ecologist currently carrying out experiments to determine upper

temperature thresholds on Mekong fish. Copperman raises the point that as temperature

increases, fish energy use becomes less efficient, thus more energy would be required to carry

out the same amount of work; yet, results of ongoing research show that fish cannot increase

their energy budgets as temperature increases. Overall, this ongoing research suggests that

tropical freshwater fish (in particular in the Mekong) are likely to experience negative effects of

global warming, but the exact magnitude of these effects on fish biology remain inconclusive

(M. Cooperman, personal communication).

In addition to direct effects on fish biology, there are a number of environmental and ecological

impacts related to higher temperatures that would affect capture and aquaculture fisheries.

First, higher water temperatures would lower the solubility of oxygen in water, greatly limiting

those fish that require high levels of dissolved oxygen (Ficke et al., 2007). Moreover, higher

temperatures increase the toxicity of a number of pollutants, including organophosphates and

heavy metals (Ficke et al., 2007). This factor could become highly detrimental as higher

pollution loads are expected with agricultural and urban development, and especially during


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periods of drought when these toxic substances could become extremely concentrated. Higher

temperatures can also lead to increase disease vectors on aquaculture (Cochrane et al., 2009).

Nonetheless, not all future effects of higher temperature will be negative. For instance, higher

temperatures lead to higher rates of aquatic primary production (Cochrane et al., 2009), which

then leads to greater basal food sources to maintain the foodweb that support freshwater

fisheries.

In short, climate change is expected to cause a number of direct and indirect effects on fish

biology and ecology, which will ultimately result on several consequences to capture and

aquaculture fisheries (Table 2). Most assessments and early arguments on impacts of climate

change have been made on temperate, cold water fishes, but those that have studied tropical

fish have made various –and highly inconclusive– arguments of both negative and positive

impacts of climate change on fisheries resources.

Table 1. Summary of drivers and effects of impacts of climate change on wild fisheries and aquaculture. Arrows

highlight presume direction (positive or negative) for catches. Please see references in the corresponding

document sections.

Climate drivers Wild fish Aquaculture

Flood

alterations

• Increased success of invasive species (-)

• Altered recruitment (-/+)

• Allochthonous input of material into the

aquatic system (-/+)

• Affect extent of habitats (-/+)

• Episodic disease and predator

introduction (-)

• poor water quality during drought (-)

• escape of stock (-)

Increase

Temperature

• Expanded habitat suitability northward (+)

• Decrease metabolic energy efficiency (-)

• Increase primary productivity (+)

• Higher disease risk (-)

• Increase toxicity of pollutants (-)

Sea level rise • Loss of nursery ecosystems (-)

• Altered water chemistry (-)

• Loss of optimal area (-)

• Damage with storm surges (-)


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3 Description of MRC future scenarios and data

This section gives an overall description of the future scenarios and datasets that were used for

this study. As an umbrella constraint/objective, this study only used products that were derived

from previous and ongoing MRC studies and that are stored in house by the organization. Thus,

it is important to first present this section as scenario and data availability greatly shaped the

study methodology presented in the following section.

3.1 Scenarios description

Overall, 21 scenarios (a baseline plus 20 future scenarios) were assessed, representing three

different global circulation models (GCMs), two representative carbon emissions (RCPs), two

time horizons (2030s and 2060s) and the development conditions associated with these time

horizons. Table 2 presents a summary of the scenario descriptions. The first GCM analyzed,

GISS-E2-R-CC by NASA’s Goddard Institute for Space Studies represents an overall drier future

climate. The second GCM used, GFDL-CM3, is the Coupled Physical Model developed by the

Geophysical Fluid Dynamics Laboratory of the US National Oceanography and Atmospheric

Administration, and it represents an overall wetter future climate over the Mekong. The third

GCM analyzed was the IPSL-CM5A-MR, developed by the Institut Pierre Simon LaPLace Climate

Modelling Centre, and it represents a future climate with increase seasonality (that is, wetter

wet seasons and drier dry seasons). Each of these three GCMs was assessed for a

representative concentration pathway (RCP) of 4.5, which represents a climate with medium

sensitivity to greenhouse emissions. GISS-E2-R-CC and GFDL-CM3 were also assessed for the


18

RCP 8.5, which represents a climate with high sensitivity to greenhouse gas emissions. Each of

these five combinations were assessed for two different time horizons: 2030s, representing

short-term impacts, and 2060s, representing medium term impacts. As aggressive plans for

water resources development in the Mekong are expected for these two time horizons, the

combination of scenarios described above were first simulated assuming no further

development after 2000 (referred as scenarios with no development in the rest of the report),

and then assuming the Basin Development Plan 2 (BDP2) development scenarios for the 2030s

(foreseeable future) and 2060s ( long term development scenario; MRC, 2011). All future

scenarios include the effects of sea level rise.

Table 2. Description of climate change scenarios from MRC's CCAI to be considered in this assessment. All

scenarios considered sea level rise, and two time horizons (2030s and 2060s) with/without corresponding

development plans.

No. Type of scenarios Emission

scenarios

GCM Climate

sensitivity

Sea

level

rise

Time

horizon Level of

change

Pattern of

change

Medium climate change scenarios

29,

32

Medium Drier RCP4.5 GISS-E2-R-CC Medium Yes 2030s,

2060s

28,

31

Medium Wetter RCP4.5 GFDL-CM3 Medium Yes 2030s,

2060s

30,

33

Medium Wetter wet

seasons & drier

dry seasons

RCP4.5 IPSL-CM5A-

MR

Medium Yes 2030s,

2060s

High climate change scenarios

11,

14

High Drier RCP8.5 GISS-E2-R-CC High Yes 2030s,

2060s

10,

13

High Wetter RCP8.5 GFDL-CM3 High Yes 2030s,

2060s


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3.2 Data used for habitat-based changes in total wild fish yields

Three different datasets (in GIS format) were used for the first task of this assessment. The first

two were used to define the flood zone, and consisted of a shapefile of the permanent water

features (rivers, lakes, and reservoirs) in the LMB, and the simulation results in raster format

from the hydrodynamic model ISIS of the extent of flooding with a depth of at least 50 cm for

the different scenarios assessed. The second dataset was the land use/land cover map of the

LMB for 2003 used to define the baseline area of rice paddies. The same dataset has been used

hydrological (MRC, 2011) and fisheries (Hortle and Bamrungrach, 2015) investigations by the

MRC.

3.3 Data used for impacts of salt intrusion on aquaculture

The second task of this assessment focused on aquaculture and it primarily used three datasets.

The first dataset, provided by the MRC FP, consisted of annual estimates of aquaculture

production aggregated at the provincial level up to 2013. The second dataset consisted of a

shapefile of provinces in all four countries. Last, simulation results in GIS raster format from the

hydrodynamic model ISIS that represented the spatial extent of maximum salinity at a 200m by

200m horizontal grid resolution. These maps were assessed for the baseline and future

scenarios.

Table 3. Summary of data used in this assessment.

Data description Time

series

Spatial

data

Name/code in MRC database

Permanent water bodies X Rivmain_poly.shp

Flood duration maps for baseline (2000)

and CC scenarios

X f-xx-nn-h50


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Water salinity maps for baseline and CC

scenarios)

X s-xx-yy-conc

Land use/land cover 2003 X Landcover2003

Annual aquaculture production data by

province

X aquacculture production (by

LMB province).xlsx

Map of provinces X Provinces_2009.shp

4 Habitat-based changes in total wild fish yields

The first component being addressed in this assessment is the impact of climate change on

total wild fish yields of the lower Mekong. This component uses a similar approach as the one

used in the MRC Technical Paper No. 47 (Hortle and Bamrungrach, 2015) to make the linkage

among flooding, habitats and fish yields for the baseline scenarios. Using spatial changes in the

flood zone as the main driver affected by climate change and development, this first

component assumes a direct link between flooding depth/extent and the main habitats of

importance to fisheries: flood zone and rice fields. Areal rates of fish yields for these two coarse

types of habitats are used to crudely estimate total catch and potential future shifts as a result

of climate change and development.

4.1 Methodology

The first step in this assessment consisted in determining the baseline extent of habitat zones

and their basis of change. Rice paddies were extracted from the 2003 land use/land cover map

available through the MRC GIS database. Second, the area of the flood zone, defined by Hortle

and Bamrungrach (2015) as the extent of flooding during a representative wet year (2000), was

determined from ISIS simulation results that represent the maximum extent of flooding with a


21

depth of at least 50 cm. This simulation product was deemed appropriate to represent a

division between rice paddies and the flood zone, since conventional rice paddies cannot

typically survive for more than a few days under water deeper than 50 cm of depth.

Following the methodology from Hortle and Bamrungrach (2015), the extent of rice paddies in

the LMB was estimated as the area classified in the land use/land cover map of 2003 outside of

the flood zone. Such estimates were implemented in an ArcGIS model, which simply estimated

the total area (in square kilometers) of permanent water bodies, the flood zone, and rice

paddies (Figure 1). By using the flood extent results from ISIS as its only input parameter, this

model was then used to estimate the expected shifts in areas of habitats for all future scenarios

assessed.

In order to estimates fish yields from the area extent of rice paddies and flood zones, the

methodology used by Hortle and Bamrungrach (2015) was again used. In the MRC Technical

Paper No. 47, a constant range of areal production rates per habitat type are used: 100-200

kg/ha/yr in the flood zone and 50-100 kg/ha/yr in rice paddies. Total fish yields per habitat

were then estimated as a simple product of the total area of each habitat times the areal

production rate:

��ℎ �� ,� = �� ,� ∗ ��

��ℎ ��,� = ��,� ∗ ��

Where ��ℎ �� and ��ℎ �� area the total fish yields in the flood zone and in rice

paddies, respectively; �� and ��are the total area of flood zone and rice paddies,


22

respectively, on each scenario �; �� is the areal rate of fish production in the flood zone,

ranging from 100 to 200 kg/ha/yr; and ��is the areal rate of fish production in rice

paddies, ranging from 50 to 100 kg/ha/yr. The contribution of reservoirs was also included, and

a range of 75-225 kt/yr was used for all scenarios.

Figure 1. Process diagram of GIS model used to estimate shifts in habitats.

4.2 Results and discussion

This part of the assessment first estimated that the baseline historical area of the flood zone

and permanent water bodies was 45,898 km2 and rice paddies were 134,587 km2. As it is shown

in Figure 2, the baseline map resembles the patterns that are well known in the region, with

vast rice cultivation in the Thai fraction of the basin (especially in the Pak-Mun basins) and the

flood zone covering most of the Tonle Sap and Vietnam Delta. The baseline area estimated are


23

comparable to the results of the MRC Technical Paper No. 47 (Hortle and Bamrungrach 2015),

thus considered a good benchmark for estimating future changes caused by climate change.

Figure 2. Map showing estimated extent of the baseline flood zone and rice paddies in the Lower Mekong

Results for the shifts in the extent of flood zone and rainfed habitats according to different

climate change scenarios and conditions are presented in Table 4, and Figure 3 to Figure 6.

Overall, a wide range of variable projections were found according to all three factors (GCM,

RCP and time horizon) considered in the climate change scenarios without development, with

shifts in the flood zone from -5922 km2 (-13%) to +6293 km2 (+13.7%), and shifts in rice paddies

Coverage of fisheries habitats for the baseline scenario

Rice paddies

Flood zone

ProvincesLMB

100 0 10050 Kilometers

±


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from -3597 km2 (-2.7%) to +3043 km2 (+2.3%). Among the three different factors, RCP appears

to have the least effect on habitat shifts followed by GCM, while time horizon has the greatest

influence. When considering development scenarios, it appears as if in the short term (2030s)

proposed infrastructure could worsen the effect of climate change on habitat shifts by

approximately a four-fold on flood zone and three-fold on rice paddies. On the contrary, the

effects of development are much more variable on the medium term horizon, since the

worsening effect from baseline is just a fraction larger than the effects of development in the

short term.

Overall, shifts in the flood zone are expected to be larger than rice paddies both in terms of the

overall magnitude (flood zone shifts of -10502 to 6807 km2 versus rice paddies shifts of -3907 to

5596 km2) as well as proportional to the original baseline area (-23 to 15% versus -3 to 4%).

These differences could have very important implications for fisheries, since the flood zone is

thought to be more productive per unit area than rice paddies. However, rice currently covers a

larger fraction of the basin, so despite producing less fish per unit area, they might play a

greater contribution to the total annual yield as it will be further described in the following

paragraph. It is important to note that the calculations made for this study do not take into

account the expansion of rice paddies with time as demand for agriculture increases, tendency

which will make rice paddies an overwhelmingly larger contributor to capture fisheries.


25

Table 4. Change in fisheries habitat for all scenarios assessed. Expected patterns of change according to scenario

are as follows: GFDL-CM3 (wetter), GISS-E2-R-CC (drier), IPSL-CM5A-MR (greater seasonal variability). Please see

Table 1 for a more detail description of the climate change scenarios assessed.

Scenario

description

Total Area

Change from baseline

Percent change from

baseline

Flood zone

(km2)

Rice paddies

(km2)

Flood zone

(km2)

Rice

paddies

(km2)

Flood zone

(%)

Rice paddies

(%)

Baseline 45,898 134,587 - - - -

Scenarios no development

Short term horizon (2030s)

GFDL-CM3 4.5 46,747 134,092 849 -495 1.8 -0.4

GISS-E2-R-CC 4.5 43,741 135,821 -2,157 1,234 -4.7 0.9

IPSL-CM5A-MR 4.5 46,718 134,065 820 -522 1.8 -0.4

GFDL-CM3 8.5 48,721 132,981 2,823 -1,606 6.2 -1.2

GISS-E2-R-CC 8.5 42,042 136,808 -3,856 2,221 -8.4 1.7

Medium term horizon (2060s)

GFDL-CM3 4.5 49,955 132,300 4,057 -2,287 8.8 -1.7

GISS-E2-R-CC 4.5 43,706 135,806 -2,192 1,219 -4.8 0.9

IPSL-CM5A-MR 4.5 47,705 133,463 1,807 -1,124 3.9 -0.8

GFDL-CM3 8.5 52,191 130,990 6,293 -3,597 13.7 -2.7

GISS-E2-R-CC 8.5 39,976 137,630 -5,922 3,043 -12.9 2.3

Scenarios with development


GFDL-CM3 4.5 48,569 133,018 2,671 -1,569 5.8 -1.2

GISS-E2-R-CC 4.5 37,781 139,041 -8,117 4,454 -17.7 3.3

IPSL-CM5A-MR 4.5 41405 137092 -4,493 2,505 -9.8 1.9

GFDL-CM3 8.5 50,104 132,069 4,206 -2,518 9.2 -1.9

GISS-E2-R-CC 8.5 35,396 140,183 -10,502 5,596 -22.9 4.2


GFDL-CM3 4.5 48,002 133,414 2,104 -1,173 4.6 -0.9

GISS-E2-R-CC 4.5 42,455 136,505 -3,443 1,918 -7.5 1.4

IPSL-CM5A-MR 4.5 48,372 133,099 2,474 -1,488 5.4 -1.1

GFDL-CM3 8.5 52,705 130,680 6,807 -3,907 14.8 -2.9

GISS-E2-R-CC 8.5 38,537 138,205 -7,361 3,618 -16.0 2.7

Total fish yields from the flood zone in the LMB during the baseline period were estimated at

458,000-917,000 tons annually, and fish yields from rice paddies were estimated at 672,000-


26

1,345,000 tons per year (Table 4; Figure 7). This provides a total wild fish yield of 1,206,000 to

2,488,000 tons per year (including production in reservoirs, assumed to be constant for all

scenarios), which is consistent with the estimates from MRC Technical Paper No. 47 (Hortle and

Bamrungrach, 2015). Since changes in fish yields were proportional to changes in habitat areas,

most of the trends and patterns according to scenarios presented above are consistent with

fish yields; First at all, the magnitude of changes in fish yields are expected to be greater for the

flood zone than in the rice paddies. Considering scenarios with no development alone, for

instance, yields in the flood zone are expected to change by -60,000 to 125,000 tons yr--1 (-13 to

+9%), compared to changes by -18,000 to +30,000 tons yr-1 (-3 to +2%) in yields from rice

paddies.

Cumulative changes in total fish yields as a result of shifts in both habitat types lead to a net

change of -155,000 tons yr--1 (-5% from baseline) to +97,000 tons yr--1 (+4%) for all future

scenarios (Table 4; Figure 7). For scenarios with no future development, very small changes (-

31,000 to +12,000 tons yr-1) were estimated in the short term (2030s) for medium sensitivity

(RCP 4.5) scenarios for all 3 GCMs, and only minor changes (±2% from baseline) for high

sensitivity (RCP 8.5) scenarios (Figure 7). The magnitude of changes double for the medium

term scenarios, for which expected changes range from -89,000 to +89,000 tons yr-1 (-13 to +

14 of total baseline yield). When development scenarios are considered, it appears as if they

could result in a much more detrimental condition in the short term, with more than a three-

fold increase in changes (-118,000 to +65,000 tons yr-1) when compared to the scenarios with

no development. Conversely, scenarios for the medium term with development are much more


27

similar to their counterparts without development, and even smaller in the case of the GFDL

RCP 4.5 (wetter climate with medium sensitivity).

Table 5. Changes in total fish yields as a function of shifts in habitats. Expected patterns of change according to scenario are as follows: GFDL-CM3 (wetter),

GISS-E2-R-CC (drier), IPSL-CM5A-MR (greater seasonal variability). Please see Table 1 for a more detail description of the climate change scenarios assessed.

Scenario description Total fish yield (kt/yr) Change from baseline (ktons/yr) Change from baseline (%)

Flood zone Rice paddies Total Flood zone Rice paddies Total Flood zone Rice paddies Total

Baseline 458 - 917 672 - 1345 1206 - 2488 - - - - - -

Scenarios with no development


GFDL-CM3 4.5 467 - 934 670 - 1340 1212 - 2500 8 - 16 -3 - -5 6 - 12 2 0 0

GISS-E2-R-CC 4.5 437 - 874 679 - 1358 1191 - 2458 -22 - -44 6 - 12 -16 - -31 -5 1 -1

IPSL-CM5A-MR 4.5 467 - 934 670 - 1340 1212 - 2500 8 - 16 -3 - -6 5 - 11 2 0 0

GFDL-CM3 8.5 487 - 974 664 - 1329 1227 - 2529 28 - 56 -9 - -17 20 - 40 6 -1 2

GISS-E2-R-CC 8.5 420 - 840 684 - 1368 1179 - 2433 -39 - -78 11 - 22 -28 - -55 -8 2 -2


GFDL-CM3 4.5 499 - 999 661 - 1323 1236 - 2547 40 - 81 -12 - -23 29 - 58 9 -2 2

GISS-E2-R-CC 4.5 437 - 874 679 - 1358 1191 - 2457 -22 - -44 6 - 12 -16 - -32 -5 1 -1

IPSL-CM5A-MR 4.5 477 - 954 667 - 1334 1219 - 2513 18 - 36 -6 - -12 12 - 24 4 -1 1

GFDL-CM3 8.5 521 - 1043 654 - 1309 1251 - 2578 62 - 125 -18 - -36 44 - 89 14 -3 4

GISS-E2-R-CC 8.5 399 - 799 688 - 1376 1162 - 2400 -60 - -119 15 - 30 -45 - -89 -13 2 -4

Scenarios with development


GFDL-CM3 4.5 485 - 971 665 - 1330 1225 - 2526 26 - 53 -8 - -16 18 - 37 6 -1 2

GISS-E2-R-CC 4.5 377 - 755 695 - 1390 1148 - 2371 -82 - -163 22 - 44 -59 - -118 -18 3 -5

IPSL-CM5A-MR 4.5 414 - 828 685 - 1370 1174 - 2424 -45 - -90 12 - 25 -33 - -65 -10 2 -3

GFDL-CM3 8.5 501 - 1002 660 - 1320 1236 - 2547 42 - 84 -13 - -26 29 - 58 9 -2 2

GISS-E2-R-CC 8.5 353 - 707 700 - 1401 1129 - 2334 -106 - -211 27 - 55 -78 - -155 -23 4 -6


GFDL-CM3 4.5 480 - 960 667 - 1334 1222 - 2519 21 - 42 -6 - -12 15 - 30 5 -1 1

GISS-E2-R-CC 4.5 424 - 849 682 - 1365 1182 - 2439 -35 - -69 9 - 19 -25 - -50 -8 1 -2

IPSL-CM5A-MR 4.5 483 - 967 665 - 1330 1224 - 2523 24 - 49 -8 - -15 17 - 34 5 -1 1

GFDL-CM3 8.5 527 - 1054 653 - 1306 1255 - 2585 68 - 136 -20 - -40 48 - 97 15 -3 4

GISS-E2-R-CC 8.5 385 - 770 691 - 1382 1151 - 2377 -74 - -148 18 - 36 -56 - -112 -16 3 -5

Figure 3. Shifts in flood zone and rice paddies as a result of scenarios with no development for the short-term

(2030s) horizon. Expected patterns of hydrological change according to scenario are as follows: GFDL-CM3

(wetter), GISS-E2-R-CC (drier), IPSL-CM5A-MR (greater seasonal variability).


30

Figure 4. Shifts in flood zone and rice paddies as a result of scenarios with no development for the medium-term

(2060s) horizon. Expected patterns of change according to scenario are as follows: GFDL-CM3 (wetter), GISS-E2-

R-CC (drier), IPSL-CM5A-MR (greater seasonality)


31

Figure 5. Shifts in flood zone and rice paddies as a result of scenarios with development for the short-term


R-CC (drier), IPSL-CM5A-MR (greater seasonality).


32

Figure 6. Shifts in flood zone and rice paddies as a result of scenarios with development for the medium-term


R-CC (drier), IPSL-CM5A-MR (greater seasonal variability).


33

Figure 7. Yields of wild fish per habitat for all scenarios assessed. Columns represent the average estimate,

whereas the lower and upper error bars represent the minimum and maximum estimate, respectively. Expected

patterns of hydrological change according to scenario are as follows: GFDL-CM3 (wetter), GISS-E2-R-CC (drier),

IPSL-CM5A-MR (greater seasonal variability).

4.3 Limitations

Arguably the most important limitation of this study is the assumption of a constant fish yield

rate per habitat. This limitation was partially overcome by carrying out the calculations for a

range of values (50-100 tons/ha/yr in rice paddies, and 100-200 tons/ha/yr in the flood zone)

that broadly represent the variability in these rates. Still, it is unlikely that these rates are

constant from region to region and from time to time. Even when focusing on one particular

habitat, there are probably a large number of environmental and management factors that

would promote or discourage fish production on a particular location. What is more important,

it is probable that these rates change –in addition to the extent of habitats as it was evaluated

in this assessment– change in the future as a function of climate drivers and development

practices. Moreover, the overly simplistic method to estimate fish yields –which for consistency

was adapted from a recent MRC Technical note– does not take into account other important

climate-driven factors such as flood level and derived indicators, which have been shown to

significantly affect particular fisheries in the LMB (Halls et al., 2013).

4.4 Recommended adaptation options

The first recommendation related to this part of the assessment is to overcome the

aforementioned limitation of over-simplicity in the fish yield estimates. This can only occur with

a much better understanding of those factors that affect capture fisheries across space and

time in the LMB. As there are excellent and long-standing monitoring programmes in some of

the river fisheries (Dai in Cambodia and Lee in Lao), similar continuous efforts should be

established to monitor fish yields for different habitats across countries. Once a multi-year

record of observations is recorded, it would be possible to establish a relationship between


35

habitat-based fish yields and environmental factors affected by climate change and

development.

In terms of adaptation strategies, it is recommended that practices to enhance production in

resilient areas are identified and promoted. This study has shown that only minor changes are

expected in fish yields from rice paddies, thus studying and promoting practices that maximize

production within these areas appear to be a reasonable adaptation strategy. What is more,

areas of rice paddies are still expanding in some regions of the LMB, and therefore promoting

multi-use of these areas could partially mitigate the negative effect of climate change and

development on fisheries in the flood zone. Moreover, the estimates from this study has shown

that in the medium term (2060s), the development of water resources infrastructure could

partially buffer the impacts of climate change on capture fisheries. While there are multiple

mechanisms why and how this may occur, it is critical that infrastructure development

occurring now and in upcoming years does take into account strategies to encourage fisheries

sustainability.


36

5 Impacts of salt intrusion on aquaculture

The second analytical component of this assessment quantified the potential impact of climate

change on aquaculture production at the provincial level. As it was summarized in section 2, it

was assumed that aquaculture in the LMB could be affected in the future as a result of (1) salt

intrusion, (2) temperature changes, and (3) hydrological changes. In order to assess the impacts

from any of these three drivers, it is critical to know the temporal and spatial variation in both

environmental factors and aquaculture production. Given the good information available on

sea level rise and salt intrusion in the Delta, this component focused on that particular driver.

With more than five times the production of Thailand, Cambodia and Lao PDR combined,

Vietnam is without question the largest aquaculture country in the LMB (Figure 8), and

therefore the focus of this assessment is very justifiable and highly relevant to the overall

wellbeing of the LMB. Given the imminent problematic of salt intrusion in the Mekong, this part

of the assessment focused on 11 provinces in Vietnam, for which a GIS approach was used to

assess shifts in salt intrusion patterns and potential effects to aquaculture production.


37

Figure 8. Time series of total aquaculture production per country highlights the overwhelming contribution from

Vietnam and the burst that the industry experienced during the 2000s.

5.1 Methodology

The first part of this assessment focused on 11 provinces in the Vietnam Delta that are

expected to have any increase in salinity. Maps of salt intrusion for baseline and future climate

have been developed by the MRC IKMP from simulations using the hydrodynamic model ISIS.

Three sets of maps have been generated by IKMP representing different exposure levels

(concentration and duration) for different hydrological years for each scenario: (1) areas where

salinity is greater than 1 g/L for at least one day; (2) areas where salinity is greater than 4 g/L

for at least one day; and (3) maximum salinity. Studies on aquaculture fish species in the Delta

(Pangasius hypophthalmus) have shown that individuals’ growth is only affected at

concentrations above 13 ppt and mortality rates increase drastically only when salinity goes

beyond 20ppt (Halls and Johns, 2013 after Castaneda et al., 2010). Therefore, results from

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

1995 2000 2005 2010

Ann

ual a

quac

ultu

re p

rodu

ctio

n (M

illio

n to

ns) Vietnam

Lao PDR

Thailand

Cambodia


38

those maps with maximum salinity seemed more appropriate for this assessment than those

maps with salt intrusion concentrations below what could be dangerous for aquaculture in the

delta. Moreover, the assessment was carried out using the map of a dry hydrological year

(1998), in which salt intrusion is expected to be the worst.

For the purposes of this assessment, salt intrusion maps for baseline and future scenarios were

categorized into 3 different classes that represent the potential level of harm to freshwater

aquaculture:

• 1 – 4 g/L: salinity of low impact to aquaculture

• 5 – 20 g/L: salinity of potential impact to aquaculture

• Greater than 20 g/L: salinity with acute impacts to aquaculture

Once the salt intrusion maps were classified, summary statistics of the extent of each salt

intrusion class were developed for the eleven Vietnamese provinces in the Delta region. Results

for the 20 future scenarios are presented as areal shifts (km2 and %) from baseline conditions.

In order to assess potential changes to aquaculture production, areal shifts in salt intrusion

were linked to annual aquaculture data for the 11 Delta provinces. First, annual provincial

estimates for the year 2010 were selected as baseline. Aquaculture production increased

exponentially in Vietnam since the late 1990s (Figure 8), presumably as a function of multiple

factors that are unlikely to be related to climate, including increase investments, expansion of

markets, improved technology, among others; thus, using the estimates for a recent year when

the growth in production has slowed down could mask better the effects of non-climate

factors. In addition, 2010 was a relatively dry year of similar hydrological conditions as 1998,


39

and therefore it is likely that it reflects the salinity conditions that were experienced for the

year for which salinity maps were available. Using the aforementioned salinity and aquaculture

baseline information, the potential provincial productivity per unit of usable area (��) was

estimated as follows:

�� =��,�

(�� − ��,�)

Where ��,�represents aquaculture production during 2010 for province p, �� is the total area

of province p, and ��,� is the area of the province that experienced acute salinity intrusion

(greater than 20 ppt) for the baseline year. Assuming that ��remains constant, future

aquaculture production (��,�) for future scenario � was estimated as follows:

��,� = �� ∗ �� ∗ 1 − ��,�� "

Where ��,� represents the acute salinity intrusion during a dry year in scenario �.

5.2 Results and discussion

Results from the classification of salt intrusion for the baseline period (year 1998) are shown in

the map of

Figure 9. Under current conditions, all provinces except for Dong Thap and An Giang experience

minor salt intrusion, nine experience maximum salinity of 5 – 20 g/L, and five experience

salinity intrusion greater than 20g/L in some portion of their territories: 4% of Tien Giang, 37%


40

of Ben Tre, 8% of Soc Tran, 34% of Bac Lieu, and 53% of Ca Mau. Detail results of shifts to this

spatial patterns of salt intrusion as a result of future scenarios are mapped in Figure 10

(medium climate change sensitivity; RCP 4.5), Figure 11 (high climate change sensitivity; RCP

8.5), Figure 12 (RCP 4.5 with development), and Figure 13 (RCP 8.5 with development). Actual

values per specific province are tabulated and summarized graphically for zones of low impact

salt intrusion (Table 6 and Figure 14 ), potential impacts (Table 7 and Figure 15), and acute salt

intrusion (Table 8 and Figure 16).

In general, delta-wide areas with low impact intrusion (1-4ppt) are expected to decrease for all

scenarios by 1215-2085 km2, with the exception of the long-term horizon of the scenario of the

drier climate with high sensitivity (GISS-E2-R-CC RCP 8.5 2060s), for which a delta-wide increase

low impact intrusion zone is expected to increase by 476-522 km2 (Table 6; Figure 14). It is

important to note that those provinces that were shown to experience low salt intrusion in the

past (Dong Thap and An Giang) could have very limited changes in salinity intrusion in the

future, with the exception again of the long-term horizon of the scenario of drier climate with

high sensitivity considering development (Figure 13, lower right frame).

Changes in zones of salt intrusion with potential impacts to aquaculture (5-20 ppt) have a larger

dependency on scenario specific conditions (Table 7; Figure 15). Generally, short-term horizon,

medium sensitivity scenarios show a basinwide increase of potentially impacting salt intrusion

zone by 255 to 1499 km2, whereas among the high sensitivity scenarios only the drier climate

scenario shows an increase. When considering the longer time horizon, both the drier and more

variability climate scenarios show an increase of potentially impacting salinity of 752-1739 km2,


41

whereas the wetter scenarios show a decrease of 1412-2761 km2. The inclusion of development

in future scenarios typically counteracts potentially impacting salt intrusion, except for the long-

term horizon, drier climate with high sensitivity scenario.

Results of changes to the zone of salinity with acute impacts to aquaculture represent the most

consistent set of results across provinces and across scenarios (Table 8; Figure 16). Overall, the

Delta-wide area with maximum salinity intrusion above 20 ppt is expected to increase by 257-

2292 km2 (mean increase by 1900 km2). Clearly, some provinces will be more affected by severe

salt intrusion than others. For instance, Dong Thap, An Giang, Vinh Long, or Can Tho are not

expected to experienced acutely impacting salt intrusion, whereas an additional 27-357 km2 of

Soc Trang (for a total of 8 to 19% of the province), 7-357 km2 of Bac Lieu (for a total of 34 to

43% of the province), and 168-1576 km2 of Ca Mau (for a total of 56 to 83% of the province) will

experience severe salt intrusion.


42

Figure 9. Map of maximum salt intrusion (maximum salinity) for the baseline scenarios displaying aquaculture-

relevant salinity categories

CA MAU

KIEN GIANG

TAKAEV

AN GIANG

CAN THO

KANDAL

DONG THAP

SOC TRANG

BEN TRE

BAC LIEU

PREY VEAENG

TRA VINH

SVAY RIENG

KAMPOT

TIEN GIANG

VINH LONG

KAMPONG SPUEU

PHNOM PENH

KRONG KAEB

KAMPONG CHAMRivers

LMB provinces

Salt intrusion for baseline conditionsMaximum salinity

1 - 4 g/L (low impact to aquaculture)

5 - 20 (potential impact to aquaculture)

> 20 g/L (acute impact to aquaculture)

30 0 3015 Kilometers


43

Figure 10. Shifts in salt intrusion zones for medium climate change sensitivity scenarios (RCP 4.5) with no

development. 2030s time horizon displayed on the left column and 2060s in the right column. Expected patterns

of change according to scenario are as follows: GFDL-CM3 (wetter), GISS-E2-R-CC (drier), IPSL-CM5A-MR (greater

seasonal variability). Please see Table 1 for a more detail description of the climate change scenarios assessed.


44

Figure 11. Shifts in salt intrusion zones for high climate change sensitivity scenarios (RCP 8.5) with no





45

Figure 12. Shifts in salt intrusion zones for medium climate change sensitivity scenarios (RCP 4.5) with





46

Figure 13. Shifts in salt intrusion zones for high climate change sensitivity scenarios (RCP 8.5) with development.

2030s time horizon displayed on the left column and 2060s in the right column. Expected patterns of change

according to scenario are as follows: GFDL-CM3 (wetter), GISS-E2-R-CC (drier), IPSL-CM5A-MR (greater seasonal

variability). Please see Table 1 for a more detail description of the climate change scenarios assessed.

Table 6. Changes in extent of areas with max salt intrusion of 1-4 ppt (low impact to aquaculture). All areas are in units of km2. Expected patterns of change

according to scenario are as follows: GFDL-CM3 (wetter), GISS-E2-R-CC (drier), IPSL-CM5A-MR (greater seasonal variability). Please see Table 1 for a more

detail description of the climate change scenarios assessed.

Scenario

description

Area of salt intrusion per province (change from baseline)

Dong

Thap

An

Giang

Tien

Giang Kien Giang Ben tre Can Tho Vinh Long Tra Vinh Soc Trang Bac Lieu Ca Mau

Total all

provinces

Baseline 0 11 305 1604 323 508 700 436 615 754 557 5814



GFDL-CM3 4.5 0 (0) 11 (0) 301 (-4) 1101 (-503) 361 (38) 235 (-273) 732 (32) 480 (43) 244 (-370) 503 (-251) 61 (-496) 4034 (-1780)

GISS-E2-R-CC 4.5 0 (0) 12 (1) 480 (174) 1044 (-559) 153 (-170) 679 (171) 767 (67) 33 (-403) 90 (-524) 499 (-255) 57 (-500) 3819 (-1995)

IPSL-CM5A-MR 4.5 0 (0) 13 (2) 333 (28) 1058 (-546) 256 (-67) 265 (-243) 826 (126) 428 (-8) 315 (-300) 658 (-96) 74 (-483) 4231 (-1583)

GFDL-CM3 8.5 0 (0) 21 (10) 302 (-4) 1150 (-454) 355 (32) 203 (-305) 694 (-6) 798 (362) 286 (-329) 549 (-205) 59 (-498) 4421 (-1393)

GISS-E2-R-CC 8.5 0 (0) 20 (9) 697 (391) 1023 (-581) 96 (-227) 737 (229) 654 (-47) 4 (-432) 79 (-536) 501 (-254) 56 (-501) 3871 (-1943)


GFDL-CM3 4.5 0 (0) 0 (-12) 288 (-18) 775 (-829) 401 (78) 32 (-476) 529 (-172) 925 (489) 712 (97) 675 (-80) 115 (-442) 4455 (-1359)

GISS-E2-R-CC 4.5 9 (9) 17 (6) 696 (390) 1111 (-492) 62 (-261) 770 (262) 800 (99) 49 (-387) 94 (-520) 532 (-222) 56 (-501) 4201 (-1613)

IPSL-CM5A-MR 4.5 0 (0) 19 (7) 487 (182) 1138 (-465) 144 (-179) 592 (83) 822 (121) 296 (-140) 189 (-426) 530 (-224) 57 (-500) 4278 (-1536)

GFDL-CM3 8.5 0 (0) 10 (-1) 272 (-34) 1339 (-265) 394 (71) 68 (-440) 500 (-201) 902 (466) 443 (-172) 483 (-271) 56 (-501) 4471 (-1343)

GISS-E2-R-CC 8.5 0 (0) 15 (4) 424 (119) 1690 (86) 181 (-142) 897 (388) 1118

(418)

280 (-156) 403 (-212) 917 (163) 407 (-150) 6336 (522)

Development scenarios


GFDL-CM3 4.5 0 (0) 22 (11) 266 (-39) 1304 (-299) 433 (110) 47 (-462) 297 (-403) 1038

(602)

449 (-166) 512 (-242) 56 (-501) 4428 (-1386)

GISS-E2-R-CC 4.5 0 (0) 21 (10) 387 (81) 1098 (-506) 242 (-81) 422 (-86) 831 (131) 317 (-119) 233 (-381) 506 (-248) 57 (-500) 4119 (-1695)

IPSL-CM5A-MR 4.5 0 (0) 23 (12) 312 (7) 1241 (-363) 356 (33) 193 (-315) 696 (-5) 663 (227) 308 (-307) 509 (-245) 57 (-500) 4363 (-1451)

GFDL-CM3 8.5 0 (0) 27 (15) 292 (-13) 1233 (-371) 486 (163) 31 (-477) 56 (-644) 952 (515) 464 (-151) 509 (-245) 57 (-500) 4110 (-1704)

GISS-E2-R-CC 8.5 3 (3) 23 (12) 668 (363) 1071 (-533) 70 (-253) 750 (242) 483 (-217) 4 (-433) 87 (-527) 508 (-246) 57 (-500) 3729 (-2085)


GFDL-CM3 4.5 0 (0) 23 (12) 302 (-4) 1353 (-251) 311 (-12) 75 (-434) 527 (-173) 986 (550) 407 (-208) 558 (-196) 54 (-503) 4599 (-1215)

GISS-E2-R-CC 4.5 0 (0) 17 (5) 482 (176) 1097 (-507) 167 (-156) 641 (133) 852 (152) 300 (-136) 159 (-456) 501 (-254) 53 (-504) 4273 (-1541)

IPSL-CM5A-MR 4.5 0 (0) 24 (13) 272 (-33) 1296 (-308) 414 (91) 80 (-428) 568 (-133) 934 (498) 401 (-214) 499 (-255) 54 (-503) 4547 (-1267)

GFDL-CM3 8.5 0 (0) 23 (12) 305 (0) 1164 (-439) 479 (156) 25 (-484) 89 (-612) 917 (481) 512 (-103) 490 (-264) 53 (-504) 4061 (-1753)

GISS-E2-R-CC 8.5 641

(641)

91 (80) 831 (525) 1378 (-226) 0 (-324) 1933

(1425)

708 (8) 73 (-364) 216 (-399) 363 (-391) 52 (-505) 6290 (476)


48

Table 7. Changes in extent of areas with max salt intrusion of 5-20 ppt (potential impact to aquaculture). All areas are in units of km2. No salt intrusion at

this concentration range expected in Dong Thap. Expected patterns of change according to scenario are as follows: GFDL-CM3 (wetter), GISS-E2-R-CC

(drier), IPSL-CM5A-MR (greater seasonal variability). Please see Table 1 for a more detail description of the climate change scenarios assessed.

Scenario

description Area of salt intrusion per province (change from baseline)

An

Giang

Tien

Giang Kien Giang Ben tre Can Tho Vinh Long Tra Vinh Soc Trang Bac Lieu Ca Mau

Total all

provinces

Baseline 24 591 3072 1073 0 10 1866 2416 144 1612 10808



GFDL-CM3 4.5 23 (-1) 647 (56) 3420 (349) 1214 (142) 0 (0) 1 (-8) 1816 (-50) 2463 (47) 878 (733) 619 (-993) 11086 (278)

GISS-E2-R-CC 4.5 25 (0) 738 (147) 3595 (523) 1381 (309) 10 (10) 172 (162) 2262 (396) 2621 (205) 895 (751) 604 (-1008) 12307 (1499)

IPSL-CM5A-MR 4.5 22 (-2) 690 (99) 3210 (138) 1306 (233) 0 (-1) 36 (26) 1867 (1) 2406 (-10) 772 (627) 751 (-861) 11063 (255)

GFDL-CM3 8.5 10 (-14) 669 (78) 3061 (-11) 1209 (136) 0 (-1) 1 (-8) 1497 (-369) 2421 (5) 841 (697) 634 (-978) 10347 (-461)

GISS-E2-R-CC 8.5 26 (1) 758 (167) 3627 (556) 1404 (332) 28 (28) 386 (376) 2291 (425) 2601 (185) 894 (750) 597 (-1015) 12616 (1809)


GFDL-CM3 4.5 0 (-25) 617 (26) 1747 (-1325) 1170 (98) 0 (-1) 0 (-10) 1370 (-496) 2016 (-400) 359 (215) 764 (-848) 8047 (-2761)

GISS-E2-R-CC 4.5 19 (-5) 792 (201) 3494 (423) 1425 (353) 37 (37) 398 (389) 2246 (380) 2616 (200) 900 (755) 615 (-997) 12546 (1739)

IPSL-CM5A-MR 4.5 17 (-8) 727 (136) 3451 (379) 1395 (322) 0 (0) 123 (113) 1999 (133) 2537 (121) 874 (730) 623 (-989) 11750 (942)

GFDL-CM3 8.5 0 (-25) 678 (87) 2392 (-680) 1173 (100) 0 (-1) 0 (-10) 1393 (-473) 2278 (-138) 867 (722) 612 (-1000) 9396 (-1412)

GISS-E2-R-CC 8.5 18 (-6) 678 (87) 3101 (30) 1183 (111) 48 (48) 61 (52) 2022 (155) 2608 (192) 244 (99) 1592 (-20) 11560 (752)



GFDL-CM3 4.5 7 (-17) 649 (58) 2849 (-222) 1157 (84) 0 (-1) 0 (-10) 1112 (-755) 2262 (-154) 763 (619) 577 (-1035) 9379 (-1428)

GISS-E2-R-CC 4.5 13 (-11) 690 (99) 3481 (409) 1320 (248) 0 (0) 41 (31) 1978 (112) 2481 (65) 835 (691) 593 (-1019) 11436 (629)

IPSL-CM5A-MR 4.5 6 (-18) 665 (74) 3156 (84) 1221 (148) 0 (0) 0 (-10) 1632 (-234) 2398 (-18) 823 (678) 593 (-1019) 10498 (-310)

GFDL-CM3 8.5 1 (-23) 550 (-41) 2738 (-334) 1069 (-3) 0 (-1) 0 (-10) 1089 (-777) 2227 (-189) 735 (590) 569 (-1043) 8982 (-1826)

GISS-E2-R-CC 8.5 19 (-5) 750 (159) 3643 (572) 1444 (371) 16 (15) 529 (519) 2291 (425) 2604 (188) 841 (696) 583 (-1029) 12724 (1916)


GFDL-CM3 4.5 0 (-25) 719 (128) 2745 (-326) 1266 (193) 0 (-1) 0 (-10) 1267 (-599) 2324 (-92) 724 (579) 595 (-1017) 9644 (-1164)

GISS-E2-R-CC 4.5 22 (-2) 753 (162) 3539 (468) 1370 (297) 1 (1) 56 (47) 1994 (128) 2549 (133) 818 (674) 544 (-1068) 11652 (844)

IPSL-CM5A-MR 4.5 4 (-20) 652 (61) 2854 (-218) 1166 (93) 0 (-1) 0 (-10) 1361 (-506) 2300 (-116) 789 (645) 581 (-1031) 9711 (-1097)

GFDL-CM3 8.5 1 (-23) 637 (46) 2626 (-445) 1111 (38) 0 (-1) 0 (-10) 1118 (-748) 2193 (-223) 697 (552) 556 (-1056) 8943 (-1865)

GISS-E2-R-CC 8.5 25 (1) 810 (219) 3742 (671) 1451 (378) 338

(338)

762 (753) 2222 (355) 2227 (-189) 1023

(878)

556 (-1056) 13160 (2352)

Table 8. Changes in extent of areas with max salt intrusion greater than 20 ppt (acute impact to aquaculture). All areas are in units of km2. No salt intrusion

at this concentration expected in Dong Thap, An Giang, Can Tho, or Vinh Long. Expected patterns of change according to scenario are as follows: GFDL-CM3

(wetter), GISS-E2-R-CC (drier), IPSL-CM5A-MR (greater seasonal variability). Please see Table 1 for a more detail description of the climate change scenarios

assessed.

Area of salt intrusion per province (change from baseline)

Scenario description Tien Giang Kien Giang Ben tre Tra Vinh Soc Trang Bac Lieu Ca Mau Total all provinces

Baseline 65 10 844 1 259 807 2755 4740



GFDL-CM3 4.5 67 (2) 133 (124) 675 (-169) 6 (6) 579 (320) 946 (139) 4247 (1492) 6657 (1916)

GISS-E2-R-CC 4.5 72 (7) 208 (199) 719 (-126) 6 (6) 585 (326) 945 (138) 4267 (1512) 6805 (2064)

IPSL-CM5A-MR 4.5 68 (3) 121 (111) 691 (-153) 6 (6) 558 (299) 839 (31) 4103 (1348) 6389 (1649)

GFDL-CM3 8.5 67 (2) 151 (141) 680 (-164) 6 (6) 574 (315) 911 (103) 4234 (1479) 6626 (1886)

GISS-E2-R-CC 8.5 76 (11) 222 (213) 753 (-91) 7 (6) 616 (357) 950 (143) 4275 (1520) 6903 (2162)


GFDL-CM3 4.5 61 (-5) 325 (315) 651 (-193) 6 (6) 497 (238) 832 (24) 4048 (1293) 6422 (1682)

GISS-E2-R-CC 4.5 76 (11) 217 (207) 766 (-78) 7 (7) 586 (327) 912 (104) 4257 (1503) 6825 (2084)

IPSL-CM5A-MR 4.5 70 (5) 197 (187) 714 (-130) 7 (6) 567 (308) 910 (103) 4248 (1493) 6716 (1975)

GFDL-CM3 8.5 66 (1) 242 (233) 651 (-193) 7 (6) 539 (280) 907 (100) 4260 (1505) 6675 (1935)

GISS-E2-R-CC 8.5 72 (7) 10 (0) 889 (45) 0 (-1) 286 (27) 814 (7) 2923 (168) 4997 (257)



GFDL-CM3 4.5 60 (-5) 129 (120) 627 (-217) 6 (5) 542 (283) 952 (145) 4294 (1539) 6613 (1873)

GISS-E2-R-CC 4.5 67 (2) 224 (214) 690 (-154) 7 (6) 578 (319) 989 (182) 4278 (1523) 6836 (2096)

IPSL-CM5A-MR 4.5 65 (0) 213 (203) 670 (-175) 6 (6) 573 (315) 986 (178) 4278 (1523) 6794 (2054)

GFDL-CM3 8.5 58 (-7) 133 (123) 601 (-243) 6 (5) 545 (286) 965 (157) 4302 (1547) 6611 (1871)

GISS-E2-R-CC 8.5 75 (9) 222 (213) 739 (-105) 7 (6) 605 (347) 996 (189) 4288 (1533) 6935 (2195)


GFDL-CM3 4.5 68 (3) 137 (127) 675 (-169) 7 (6) 532 (273) 931 (124) 4279 (1524) 6631 (1891)

GISS-E2-R-CC 4.5 72 (7) 230 (220) 717 (-127) 7 (7) 588 (329) 1017 (210) 4331 (1576) 6965 (2225)

IPSL-CM5A-MR 4.5 62 (-3) 203 (194) 638 (-206) 7 (6) 554 (295) 970 (162) 4293 (1538) 6729 (1989)

GFDL-CM3 8.5 2060s 60 (-5) 147 (137) 621 (-223) 7 (6) 529 (270) 961 (154) 4319 (1564) 6645 (1905)

GISS-E2-R-CC 8.5 2060s 74 (9) 270 (261) 803 (-41) 6 (6) 596 (337) 960 (153) 4320 (1565) 7032 (2292)

Figure 14. Area affected by maximum salt intrusion of 1-4 g/L (low effect on aquaculture) by province. All areas

are in units of km2. Expected patterns of change according to scenario are as follows: GFDL-CM3 (wetter), GISS-

E2-R-CC (drier), IPSL-CM5A-MR (greater seasonal variability). Please see Table 1 for a more detail description of

the climate change scenarios assessed.

0

1000

2000

3000

4000

5000

6000

7000A

rea

of

ma

xim

um

sa

lt i

ntr

usi

on

of

1-4

g/L

Extent of low salt intrusion (1-4 g/L) for scenarios with no development

Ca Mau

Bac Lieu

Soc Trang

Tra Vinh

Vinh Long

Can Tho

Ben tre

Kien Giang

Tien Giang

An Giang

Dong Thap

0

1000

2000

3000

4000

5000

6000

7000

Baseline 2030s 2030s 2030s 2030s 2030s 2060s 2060s 2060s 2060s

4.5 4.5 4.5 8.5 8.5 4.5 4.5 4.5 8.5

GFDL-

CM3

GISS-E2-

R-CC

IPSL-

CM5A-

MR

GFDL-

CM3

GISS-E2-

R-CC

GFDL-

CM3

GISS-E2-

R-CC

IPSL-

CM5A-

MR

GFDL-

CM3

Are

a o

f m

axim

um

sal

t in

tru

sio

n o

f 1-

4 g

/L

Scenario.

Extent of low salt intrusion (1-4 g/L) for scenarios with development

Ca Mau

Bac Lieu

Soc Trang

Tra Vinh

Vinh Long

Can Tho

Ben tre

Kien Giang

Tien Giang

An Giang

Dong Thap


51

Figure 15. Area affected by maximum salt intrusion of 5-20 g/L (potential effect on aquaculture) by province.

Expected patterns of change according to scenario are as follows: GFDL-CM3 (wetter), GISS-E2-R-CC (drier), IPSL-

CM5A-MR (greater seasonal variability). Please see Table 1 for a more detail description of the climate change

scenarios assessed.

0

2000

4000

6000

8000

10000

12000

14000

Baseline 2030s 2030s 2030s 2030s 2030s 2060s 2060s 2060s 2060s 2060s

Are

a o

f m

axi

mu

m s

alt

intr

usi

on

of

5 -

20

g/L

Extent of medium intrusion (5-20 g/L) for scenarios with no development

Ca Mau

Bac Lieu

Soc Trang

Tra Vinh

Vinh Long

Can Tho

Ben tre

Kien Giang

Tien Giang

An Giang

Dong Thap

0

2000

4000

6000

8000

10000

12000

14000


4.5 4.5 4.5 8.5 8.5 4.5 4.5 4.5 8.5

GFDL-

CM3

GISS-E2-

R-CC

IPSL-

CM5A-

MR

GFDL-

CM3

GISS-E2-

R-CC

GFDL-

CM3

GISS-E2-

R-CC

IPSL-

CM5A-

MR

GFDL-

CM3

Are

a o

f m

axi

mu

m s

alt

in

tru

sio

n o

f 5

-20

g/L

Scenario

Extent of medium salt intrusion (5-20 g/L) for scenarios with development

Ca Mau

Bac Lieu

Soc Trang

Tra Vinh

Vinh Long

Can Tho

Ben tre

Kien Giang

Tien Giang

An Giang

Dong Thap


52

Figure 16. Area affected by maximum salt intrusion greater than 20 g/L (acute effects on aquaculture) by

province. All areas are in units of km2. Expected patterns of change according to scenario are as follows: GFDL-

CM3 (wetter), GISS-E2-R-CC (drier), IPSL-CM5A-MR (greater seasonal variability). Please see Table 1 for a more


0

1000

2000

3000

4000

5000

6000

7000

8000A

rea

of

ma

xim

um

sa

lt i

ntr

usi

on

of

5 -

20

g/L

Extent of strong salt intrusion (>20 g/L) for scenarios with no development

Ca Mau

Bac Lieu

Soc Trang

Tra Vinh

Vinh Long

Can Tho

Ben tre

Kien Giang

Tien Giang

An Giang

Dong Thap

0

1000

2000

3000

4000

5000

6000

7000

8000


4.5 4.5 4.5 8.5 8.5 4.5 4.5 4.5 8.5

GFDL-

CM3

GISS-E2-

R-CC

IPSL-

CM5A-

MR

GFDL-

CM3

GISS-E2-

R-CC

GFDL-

CM3

GISS-E2-

R-CC

IPSL-

CM5A-

MR

GFDL-

CM3

Are

a o

f m

axi

mu

m s

alt

in

tru

sio

n o

f 1

-4 g

/L

Scenario

Extent of strong salt intrusion (>20 g/L) for scenarios with development

Ca Mau

Bac Lieu

Soc Trang

Tra Vinh

Vinh Long

Can Tho

Ben tre

Kien Giang

Tien Giang

An Giang

Dong Thap


53

Impacts of salt intrusion on aquaculture production were assessed by assuming that an increase

in the provincial area with a maximum salinity above 20 ppt will have an inversely proportional

decrease in aquaculture production. Overall, most scenarios of climate change show minor

losses (1 to 6%) in delta-wide aquaculture production compared to baseline conditions (Table 9;

Figure 17). The only exceptions to this trend are the two scenarios of medium-term horizon

with high climate sensitivity and development (GFDL-CM3 8.5 and GISS-E2-R-CC 8.5 for the

2060s), which actually show an increase in the total Delta production by 10-11%. Delta-wide

changes to aquaculture, however, are not expected to be evenly distributed among provinces,

and a great fraction of the expected changes can be tracked to only a few provinces. On the one

hand, losses in Ca Mau (an average loss of 59148 tons yr-1 for scenarios with no development,

or 59% of baseline production) alone could be up to ten times higher than at the next most

affected province, Soc Trang (average loss of 5852 tons yr-1 for scenarios with no development).

On the other hand, Ben Tre is expected to be favored in the future, with a potential increase in

production by 6831-94416 tons yr-1 in all but one scenario (medium term horizon of a drier

climate with high sensitivity). Furthermore, since no changes in acute salinity were estimated

for Dong Thap, An Giang, Can Tho, and Vinh Long, where 23%, 20%, 12%, and 9% of the current

Delta’s aquaculture production take place, respectively, a majority of the delta-based

aquaculture could in fact be unaffected by the simulated future acute salinity extent into the

floodplains.

Table 9. Estimated changes in aquaculture production proportional to extent of salt intrusion greater than 20 ppt (acute impact to aquaculture). Dong Thap,

An Giang, Can Tho, or Vinh Long absent from table as no salt intrusion at this acute concentration expected in these provinces. Expected patterns of change

according to scenario are as follows: GFDL-CM3 (wetter), GISS-E2-R-CC (drier), IPSL-CM5A-MR (greater seasonal variability). Please see Table 1 for a more


Tien Giang Kien Giang Ben Tre Tra Vinh Soc Trang Bac Lieu Ca Mau All provinces

Aquaculture production 2010 (tons) 87925 46637 124850 53823 63440 63814 108963 1489671

Province area (km2) 1716 5756 2255 2302 3298 2348 5208 34339

% area of acute salinity baseline year 4 0 37 0 8 34 53 14

Production per usable land (ton/km2) 53 8 88 23 21 41 44

Changes in aquaculture production proportional to losses in usable land, tons/yr (%)

No development scenarios


GFDL-CM3 4.5 -148 (-1) -1007 (-3) 14889 (11) -144 (-1) -6694 (-11) -5765 (-10) -66283 (-61) -65148 (-5)

GISS-E2-R-CC 4.5 -405 (-1) -1616 (-4) 11070 (8) -150 (-1) -6810 (-11) -5732 (-9) -67169 (-62) -70809 (-5)

IPSL-CM5A-MR 4.5 -209 (-1) -907 (-2) 13498 (10) -150 (-1) -6257 (-10) -1313 (-3) -59882 (-55) -55217 (-4)

GFDL-CM3 8.5 -113 (-1) -1152 (-3) 14443 (11) -148 (-1) -6593 (-11) -4307 (-7) -65711 (-61) -63578 (-5)

GISS-E2-R-CC 8.5 -620 (-1) -1730 (-4) 8026 (6) -161 (-1) -7471 (-12) -5945 (-10) -67528 (-62) -75428 (-6)


GFDL-CM3 4.5 213 (0) -2562 (-6) 17062 (13) -150 (-1) -4985 (-8) -1028 (-2) -57452 (-53) -48900 (-4)

GISS-E2-R-CC 4.5 -620 (-1) -1686 (-4) 6830 (5) -164 (-1) -6841 (-11) -4340 (-7) -66756 (-62) -73573 (-5)

IPSL-CM5A-MR 4.5 -269 (-1) -1523 (-4) 11460 (9) -154 (-1) -6448 (-11) -4285 (-7) -66340 (-61) -67557 (-5)

GFDL-CM3 8.5 -56 (-1) -1893 (-5) 17009 (13) -155 (-1) -5848 (-10) -4163 (-7) -66885 (-62) -61988 (-5)

GISS-E2-R-CC 8.5 -390 (-1) -8 (-1) -4042 (-4) 3 (0) -574 (-1) -305 (-1) -7480 (-7) -12794 (-1)



GFDL-CM3 4.5 247 (0) -977 (-3) 19143 (15) -140 (-1) -5913 (-10) -6008 (-10) -68390 (-63) -62035 (-5)

GISS-E2-R-CC 4.5 -154 (-1) -1741 (-4) 13558 (10) -152 (-1) -6674 (-11) -7551 (-12) -67669 (-63) -70379 (-5)

IPSL-CM5A-MR 4.5 -32 (-1) -1655 (-4) 15406 (12) -150 (-1) -6578 (-11) -7412 (-12) -67656 (-63) -68075 (-5)

GFDL-CM3 8.5 370 (0) -1003 (-3) 21437 (17) -137 (-1) -5981 (-10) -6534 (-11) -68717 (-64) -60561 (-5)

GISS-E2-R-CC 8.5 -531 (-1) -1731 (-4) 9230 (7) -159 (-1) -7245 (-12) -7829 (-13) -68109 (-63) -76372 (-6)


GFDL-CM3 4.5 -184 (-1) -1038 (-3) 14942 (11) -153 (-1) -5712 (-10) -5152 (-9) -67701 (-63) -64994 (-5)

GISS-E2-R-CC 4.5 -418 (-1) -1791 (-4) 11226 (8) -166 (-1) -6872 (-11) -8717 (-14) -70033 (-65) -76769 (-6)

IPSL-CM5A-MR 4.5 138 (0) -1576 (-4) 18191 (14) -152 (-1) -6176 (-10) -6742 (-11) -68315 (-63) -64630 (-5)

GFDL-CM3 8.5 3728 (4) -1039 (-3) 94416 (75) -141 (-1) -238 (-1) 27048 (42) 52879 (48) 176656 (11)

GISS-E2-R-CC 8.5 2959 (3) -2041 (-5) 78291 (62) -131 (-1) -1640 (-3) 27091 (42) 52830 (48) 157361 (10)

Figure 17. Estimated aquaculture production in the Delta proportional to acute salinity intrusion. Expected

patterns of change according to scenario are as follows: GFDL-CM3 (wetter), GISS-E2-R-CC (drier), IPSL-CM5A-MR

(greater seasonal variability).

0

2

4

6

8

10

12

14

16A

nn

ua

l a

qu

acu

ltu

re p

rod

uct

ion

(to

ns)

x 1

00

00

0 Aquaculture production proportional to increase in acute salinity (scenarios

without development)

Ca Mau

Bac Lieu

Soc Trang

Tra Vinh

Vinh Long

Can Tho

Ben tre

Kien Giang

Tien Giang

An Giang

Dong Thap

0

2

4

6

8

10

12

14

16

18


4.5 4.5 4.5 8.5 8.5 4.5 4.5 4.5 8.5

GFDL-

CM3

GISS-E2-

R-CC

IPSL-

CM5A-

MR

GFDL-

CM3

GISS-E2-

R-CC

GFDL-

CM3

GISS-E2-

R-CC

IPSL-

CM5A-

MR

GFDL-

CM3

An

nu

al

aq

ua

cult

ure

pro

du

ctio

n (

ton

s)x

10

00

00

Scenario

Aquaculture production proportional to increase in acute salinity (scenarios

with development)

Ca Mau

Bac Lieu

Soc Trang

Tra Vinh

Vinh Long

Can Tho

Ben tre

Kien Giang

Tien Giang

An Giang

Dong Thap


56

5.3 Limitations

A number of assumptions had to be made in order to carry out this study and provide

meaningful estimates given the data and modeling results that were available. First, this study

assumed no sensitivity to multi-year variability in climate and salt intrusion dynamics. This is an

important factor to consider, given that the most tangible effect of climate change in the

Mekong region is the increase variability, rather than trends in average environmental

variables. In order to overcome this assumption, however, historical climate data and time

series modeling results of salt intrusion would have been necessary, but unfortunately those

data are not available at the time. Even if that information was available, it is difficult to infer

climate sensitivity from the aquaculture time series, because of the exponential growth that the

aquaculture industry experienced during the period of record (Figure 8) that were most likely

driven by financial investments and technological improvements in the industry, rather than

any climate factors.

Another important assumption that was made in this assessment relates to the sensitivity of

aquaculture species to salinity. Clearly, different fish species may have different tolerances to

salinity, hence this study provide a range of changes in salinity intrusion zones, and inferences

on changes to aquaculture production were only made based on the salinity level that is well

known to cause biological limitation to relevant freshwater aquaculture species relevant to the

Mekong Delta. Another factor related to salt intrusion that was not incorporated in the

assessment is the interplay of salinity with other water quality indicators, which may influence

fish biology (Ficke et al., 2007) and hence aquaculture production.


57

5.4 Recommended adaptation options

Evidence from the exponential increase in aquaculture production in the Delta suggests that

understanding the sensitivity and exposure of freshwater aquaculture to salinity are only one

fraction of what is needed to understand the overall vulnerability of the industry to future

climate conditions. As it was suggested by several authors (e.g., Allison et al., 2009; Halls and

Johns, 2013; Handisyde et al., 2006), a complete measure of vulnerability should also

incorporate the adaptation capacity that aquaculture may or may not have in the region. This

factor is complex –yet important– to assess, as it not necessarily depends on the magnitude of

the impact (in this case salt intrusion), but rather in the level of human and social capital, as

well as governance structure of those affected (Allison et al., 2009). Hence, a comprehensive

evaluation of aquaculture vulnerability to the different MRC climate change scenarios will

provide very insightful information for focal management activities.

An important finding from this assessment is that those provinces that are current responsible

for 63% of the Delta’s freshwater aquaculture (Dong Thap, An Giang, Can Tho, and Vinh Long)

could remain unaffected by salt intrusion, thus their contribution to the region’s total

production could become even larger. It is therefore important that efforts to maintain

productivity and enhance the quality of aquaculture are prioritize in these provinces that will

play an even more important role in the future.

As it was also noted in the first task described in section 4 of this report, water infrastructure

development in the medium term could improve the conditions to promote freshwater

fisheries in the LMB, in particular in the Delta. Given the high uncertainty related with


58

infrastructure establishment in the region, this factor remains highly speculative and should not

be used as an excuse to promote water resources development indiscriminately. Instead, it

should be used as an indicator that there are much opportunities for improvement and that

future development in the Mekong could and should be planned as a mechanism to enhance

adaptation capacity to future climate in the region.


59

6 Conclusions

Climate change is expected to bring significant impacts to the water resources of the Mekong

River Basin as well as those sectors that depend on them. With regards to freshwater fisheries,

it is commonly agreed that climate change could alter this sector via (1) Changes in water

temperature, (2) hydrological alterations, and (3) salt intrusion. While the first subject was

reviewed, this assessment primarily focused on the latter two drivers of change, for which

simulation results from the ongoing hydrological assessment of climate change by MRC’s CCIA

are available. The study focused on wild fisheries in the floodplains and rice paddies as well as

aquaculture in the Mekong Delta, which together account for a vast majority of the basin’s total

fish yields.

With regards to wild fish yields, this assessment found that the magnitude of changes is

expected to be greater for the flood zone than in the rice paddies. In terms of the cumulative

yields from both habitats, small changes are expected in the short-term when development is

absent from the scenarios; however, losses become much more significant in the short term

when development is considered. Conversely, this tendency is not as strong when comparing

scenarios in the medium term.

With regards to aquaculture, this assessment found that minor changes to the current

production could be expected as a result of severe salt intrusion in the Delta. More than 60% of

the current production takes place in four provinces (Dong Thap, An Giang, Can Tho, and Vinh

Long) that do not experience acute salinity intrusion and according to this assessment, are not

likely to experience acute salt intrusion in the short to medium term. On the contrary, great


60

losses are expected in Ca Mau Province, most of which will become virtually unfeasible for

freshwater aquaculture.

Future adaptation strategies should focus on those areas that were shown to be resilient (and

even benefited) by future conditions dictated by climate change and development. In terms of

wild fish, rice paddies production appeared to be marginally unaffected by climate-driven

flooding shifts. Hence, programs to promote and enhance fish production within rice paddies

could greatly build resilience in the region, in particular if rice agriculture continues to expand

in the lower Mekong, a (probable) scenario that was not considered in this assessment. In

terms of aquaculture, some of the provinces further up the terrain elevation were shown to be

largely unaffected by acute salt intrusion in the future, thus aquaculture in these (most

productive) provinces is likely to remain uncompromised by salinity. Therefore, it is

recommended that plans to maintain productivity and enhance the quality of aquaculture in

these provinces continue. There are, however, other climate driven factors that could

detrimentally affect aquaculture in these provinces, including storm damages, extreme drought

and pollution, among others, and future assessments could evaluate their role in the future of

aquaculture in the Delta.


61

References

Allison, E.H., Perry, A.L., Badjeck, M.-C., Neil Adger, W., Brown, K., Conway, D., Halls, A.S.,

Pilling, G.M., Reynolds, J.D., Andrew, N.L., 2009. Vulnerability of national economies to

the impacts of climate change on fisheries. Fish and fisheries 10, 173–196.

Arias, M.E., Cochrane, T.A., Elliott, V., 2014a. Modelling future changes of habitat and fauna in

the Tonle Sap wetland of the Mekong. Environmental Conservation 41, 165–175.

doi:10.1017/S0376892913000283

Arias, M.E., Cochrane, T.A., Kummu, M., Killeen, T.J., Piman, T., Caruso, B.S., 2012. Quantifying

changes in flooding and habitats in the Tonle Sap Lake (Cambodia) caused by water

infrastructure development and climate change in the Mekong Basin. Journal of

Environmental Management 112, 53–66.

Arias, M.E., Cochrane, T.A., Kummu, M., Lauri, H., Koponen, J., Holtgrieve, G.W., Piman, T.,

2014b. Impacts of hydropower and climate change on drivers of ecological productivity

of Southeast Asia’s most important wetland. Ecological Modelling 272, 252–263.

Cochrane, K., De Young, C., Soto, D., Bahri, T., 2009. Climate change implications for fisheries

and aquaculture. FAO Fisheries and aquaculture technical paper 530, 212.

Comte, L., Buisson, L., Daufresne, M., Grenouillet, G., 2013. Climate-induced changes in the

distribution of freshwater fish: observed and predicted trends. Freshwater Biology 58,

625–639.

Ficke, A.D., Myrick, C.A., Hansen, L.J., 2007. Potential impacts of global climate change on

freshwater fisheries. Reviews in Fish Biology and Fisheries 17, 581–613.

Halls, A.S., Johns, M., 2013. Assessment of the vulnerability of the Mekong Delta Pangasius

catfish industry to development and climate change in the Lower Mekong Basin. Report

prepared for the sustainable fisheries partnership 2013.

Halls, A.S., Paxton, B.R., Hall, N., Hortle, K.G., So, N., Chheng, P., Peng, B.N., Boonsong, S., 2013.

Integrated Analysis of Data from MRC Fisheries Monitoring Programmes in the Lower

Mekong Basin (No. MRC Technical Paper No. 33). Mekong River Commission, Phnom

Penh, Cambodia.

Halls, A.S., Welcomme, R.L., 2004. Dynamics of river fish populations in response to

hydrological conditions: a simulation study. River Research and Applications 20, 985–

1000.

Handisyde, N.T., Ross, L.G., Badjeck, M.C., Allison, E.H., 2006. The effects of climate change on

world aquaculture: a global perspective. Department for International Development.

Hoang, L.P., Lauri, H., Kummu, M., Koponen, J., van Vliet, M.T.H., Supit, I., Leemans, R., Kabat,

P., Ludwig, F., 2015. Mekong River flow and hydrological extremes under climate

change. Hydrol. Earth Syst. Sci. Discuss. 2015, 11651–11687. doi:10.5194/hessd-12-

11651-2015

Hortle, K.G., Bamrungrach, P., 2015. Fisheries Habitat and Yield in the Lower Mekong Basin (No.

MRC Technical Paper No. 47.). Mekong River Commission, Phnom Penh, Cambodia.

Kingston, D., Thompson, J., Kite, G., 2011. Uncertainty in climate change projections of

discharge for the Mekong River Basin. Hydrol. Earth Syst. Sci 15, 1459–1471.


62

Lauri, H., de Moel, H., Ward, P.J., Räsänen, T.A., Keskinen, M., Kummu, M., 2012. Future

changes in Mekong River hydrology: impact of climate change and reservoir operation

on discharge. Hydrol. Earth Syst. Sci. 16, 4603–4619. doi:10.5194/hess-16-4603-2012

Linhoss, A.C., Muñoz-Carpena, R., Allen, M.S., Kiker, G., Mosepele, K., 2012. A flood pulse driven

fish population model for the Okavango Delta, Botswana. Ecological Modelling 228, 27–

38. doi:10.1016/j.ecolmodel.2011.12.022

MRC, 2011. Assessment of Basin-wide Development Scenarios (Main Report). Basin

Development Plan Programme, Phase 2. Mekong River Commission, Vientiane, Lao PDR.

Tewksbury, J.J., Huey, R.B., Deutsch, C.A., 2008. Putting the heat on tropical animals. SCIENCE,

Ecology Perspectives 320, 1296.

Västilä, K., Kummu, M., Sangmanee, C., Chinvanno, S., 2010. Modelling climate change impacts

on the flood pulse in the Lower Mekong floodplains. Journal of Water and Climate

Change 1, 67–86. doi:10.2166/wcc.2010.008

Wright, S.J., Muller-Landau, H.C., Schipper, J.A.N., 2009. The future of tropical species on a

warmer planet. Conservation biology 23, 1418–1426.

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