Capturing the impacts of human activities on reported forest greenhouse gas emissions ·...

Capturing the impacts of human activities on reported forest greenhouse gas emissions

Werner A. Kurz

Natural Resources CanadaCanadian Forest Service

2025 and Beyond: Modeling the land sector’s role in achieving GHG mitigation and adaptation goals

8th Forestry and Agriculture Greenhouse Gas Modeling ForumShepherdstown, Sept 26 - 28, 2016

AcknowledgementsThe approach presented here is the result of the collaboration between the Canadian

Forest Service of Natural Resources Canada and the Pollutant Inventories and Reporting

Division of Environment and Climate Change Canada.

ECCC:

Doug MacDonald

Dominique Blain

Shari Hayne

Ana Blondel

NRCan:

Werner Kurz

Tony Lemprière

Max Fellows

Scott Morken

Carolyn Smyth

Mark Hafer

Eric Neilson

Karin Simonson

Alison Beatch

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Outline

Background

Motivation

Methods

Results

Discussion

Conclusions

3

Background

Managed Land Proxy (MLP): IPCC default approach

The IPCC Managed Land Proxy assumes that emissions and

removals from anthropogenic activities in the land sector can be

approximated as those from managed lands.

However, natural disturbances contribute large direct and indirect

(delayed) emissions. These contribute to large interannual

variability and trends in reported estimates.

The impacts of natural disturbances mask trends in emissions

resulting from changes in human activities, including mitigation

efforts.

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Motivation

Develop a method that better reflects the impacts of human

activities and integrated land management on trends in reported

greenhouse gas emission inventories in Canada’s forest sector.

Our analysis is exploring methods to exclude the emissions and

subsequent removals of greenhouse gasses resulting from

uncontrollable natural disturbances such as wildfire, insects and

storms in the managed forest (i.e. forest land remaining forest land).

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IPCC methodological options

The 2010 IPCC report from the Expert

Meeting Report on “Revisiting the

Use of Managed Land as a Proxy for

Estimating National Anthropogenic

Emissions and Removals”:

reviewed the MLP shortcomings,

introduced five possible

approaches to estimating

anthropogenic emissions in the

land sector, and

concluded that further work is

required before any alternative to

the MLP can be recommended.

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IPCC 2010 lists five methodological options

Maintenance of the managed land proxy

Component separation (quantify the influence of different drivers and

then identify which drivers contribute to anthropogenic emissions)

Comparison of two time series (that represent two different levels of

human activities, e.g. current management and no management, or

improved management vs. business as usual management)

Default factors and optimal fingerprinting (without quantifying the

relative contributions, apply a default factor which indicates the impact

of the human activity)

Activity based approach (estimate emissions by different activities and

sum up anthropogenic contributions)

Source: IPCC 2010

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IPCC 2010 Conclusions

[T]he managed land proxy has several shortcomings

For some countries and circumstances, use of the managed land

proxy may lead to emission and removal estimates dominated by

natural effects occurring on managed land and this would need to

be recognised where inventory estimates were used in estimates of

anthropogenic or management effects.

[T]here is also a requirement to be able to identify the impact of

mitigation and management efforts even where these are

overwhelmed by the impacts of natural processes (e.g. natural

disturbances) or where these are obscured by inter-annual variations

in greenhouse gas fluxes.

[F]urther work by the scientific community will result in more mature

approaches which can be assessed at a later date.

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Outline

Background

Motivation

Methods

Results

Discussion

Conclusions

9

A new approach

The 2010 IPCC Expert Meeting Report introduced the notion of

“Component Separation” but focussed on “drivers of fluxes” such as

CO2 fertilization, atmospheric N-deposition and climate change (i.e.

the issues addressed in the “factoring out” discussions.)

The report also introduced an activity-based approach in which the

emissions associated with anthropogenic activities in the land sector

are estimated and summed.

Here we develop a new combined approach that allows us to estimate

separately the emissions and removals from

1. lands subject to forest management, and

2. lands affected by natural disturbances (causing >20% mortality),

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A new approach

Is a land-based approach.

Estimates the E/R for the entire managed forest (FL-FL).

E/R from lands affected by stand-replacing ND are excluded from

reporting for 60 years.

E/R from lands affected by ND causing >20% mortality after 1990

are excluded from reporting until pre-disturbance aboveground

biomass is reached.

Therefore, the remaining reported E/R better quantify the impacts

of forest management, including mitigation activities.

Forest management activities on excluded lands cause re-entry

into reporting.

The sum of reported and excluded emissions is equal to the

reported FL-FL values in the conventional national forest GHG

inventory.

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Explanation of concept

Applies to all managed forest land.

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Managed Forest Land (FL-FL)


All stands originate either from stand-replacing natural disturbance

(ND, typically fire) or clearcut harvest.

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Harvest Origin ND Origin

(>=60 yrs old)


Stand-replacing wildfire excludes stands from reporting for 60 years

Red = excluded from reporting

Green = reported

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Harvest OriginND Origin

(>=60 yrs old)

ND Origin

(<60 yrs old)


Natural disturbances after 1990 that cause > 20% biomass mortality

excluded from reporting until pre-disturbance biomass is reached.


Green = reported

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(>=60 yrs old)

ND Origin

(<60 yrs old)

ND >20% mortality after 1990

(not yet at pre-disturbance biomass)


Lands affected by ND > 20% mortality after 1990 re-enter the

reporting when they reach pre-disturbance biomass.


Green = reported

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(>=60 yrs old)

ND Origin

(<60 yrs old)


( < pre-disturbance biomass)

ND >20% mortality

after 1990

(> pre-disturbance biomass)


ND lands affected by forest management activities (e.g. salvage

logging, planting, rehabilitation) re-enter the reporting.


Green = reported

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(>=60 yrs old)

ND Origin

(<60 yrs old)


( < pre-disturbance biomass)

ND >20% mortality

after 1990

(> pre-disturbance biomass)

ND followed

by FM

Decision tree for the separation of lands In the initial forest inventory all stands in FL-FL are established either

following a stand-replacing natural disturbance (ND) or following harvest.

Stand

established

following

ND?

Include in reporting

Stand

reached

pre ND

biomass

stocks?

>= 60

years since

ND?

Partial ND

with > 20%

mortality?

Exclude from reporting

Yes

Yes

No

No

Yes No

Has any

FM activity

occurred

since ND?

No

No

YesYes

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Implementation through separation of land fluxes

The CBM-CFS3 is used to estimate emissions and removals in

Canada’s forest sector.

The model allows for the estimation of emissions and removals in about

2.7 million stands across Canada’s managed forest.

The activity data time series starts in 1990 – we do not have data on

partial disturbances prior to 1990.

The 1990 inventory identifies for each stand the age and whether or not

the stand was established from wildfire or harvest.

The goal of the implementation is to separate the emissions and

removals into reported and excluded fluxes.

To obtain a better understanding of the contribution to the reported and

excluded fluxes we stratified the stands into seven land components.

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The seven component fluxes represent managed forest lands subject to human or natural

disturbances:

Harvest

1. Clear cut harvest before 1990 (included)

2. Clear cut or partial harvest after 1990 (included)

Stand replacing NDs

3. Before 1990, and more than 60 years ago (included)

4. Before 1990, less than 60 years old (excluded)

5. After 1990, less than 60 years old (excluded)

*. [ After 1990, more than 60 years old (would be included but is not observed) ]

Partial NDs

6. After 1990, reached pre-disturbance AGB (included)

7. After 1990, not yet reached pre-disturbance AGB (excluded)

Reported fluxes are the sum of categories 1, 2, 3 and 6

Excluded fluxes are the sum of categories 4, 5 and 7

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Implementation through separation of land fluxes

Implementation

Technical details

During a model simulation, stands affected by natural or human

disturbances are assigned a “flag”.

Stands are monitored in each time step to determine if certain rules

(age or biomass criteria) are met and if yes “flags” are updated.

When the results database is compiled, fluxes are summarised by time

step and various reporting categories, including FL-FL, administrative

and ecological reporting zones, as well as the seven components.

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Carbon Budget Model of the

Canadian Forest Sector (CBM-CFS3) An operational-scale model of forest C dynamics.

Builds on 25+ years of experience

Allows forest managers to assess carbon implications of

forest management: increase sinks, reduce sources

Available at carbon.cfs.nrcan.gc.ca

Outline

Background

Motivation

Methods

Results

Discussion

Conclusions

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Reported and excluded area by category

Reported area is approximately constant over time (98.7 to 101.3% of 25 year avg. 186.6 Mha)

Excluded area is approximately constant over time (94.7 to 106.3% of 25 year avg. 45.5 Mha)

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4: nd_pre_1990 <60 yrs (excluded)

5 and 7: nd_post_1990 (excluded)

6: u_nd_post_1990 (re-entered after ND)

3: ND_pre_1990 (re-entered after 60 yrs)

1: h_pre_1990

2: harvest_post_1990

Reported

Excluded

Implementation (preliminary results)

Sum of reported and excluded fluxes equals the NIR (excluding HWP)

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Contribution of fluxes in stands affected after (Jan 1st 1990) by harvest

(left) or natural disturbances with more than 20% mortality (right).

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Contribution of fluxes in stands clear-cut harvested prior to 1990 (left)

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Contribution to fluxes of lands affected by stand-replacing ND (SRND)

over 60 years ago, or by partial ND with more than 20% mortality that

have reached pre-disturbance biomass (left) and lands affected by

SRND prior to 1990 but less than 60 years ago (right).

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Implementation

Sum fluxes into reported and excluded categories.

Excluded categories will still be shown in NIR for transparency but

reported values will be the basis for entries into CRF tables for FL-FL

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Sum of reported and excluded fluxes equals the NIR (excluding HWP)

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FL-FL Reported Emissions from NIR 2016

are not correlated with human activities.

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Revised Reported Emissions

are more closely correlated with human activities.

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FL-FL

Revised Reported Emissions plus HWP emissions

are also closely correlated with activities.

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FL-FL and HWP

Outline

Background

Motivation

Methods

Results

Discussion

Conclusions

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DiscussionWhy do lands subject to ND more than 60 years ago re-enter the reporting?

Sustainable forest management is based on the concept that the amount of timber

harvested annually does not exceed the amount of regrowth. The total area of forest on

which the timber yield estimation and other forest management objectives are based is

larger than the area that has historically been harvested in Canada. In some areas of

Canada forests are being cut that have never before been harvested (although they will

have been disturbed previously by natural disturbances).

Thus the “managed forest” land area that is part of the sustainable management planning

process is larger than the area of forest previously harvested in Canada. The “managed

forest” area also includes lands that are never permitted to be harvested because they

serve other ecological functions such as riparian buffers, conservation areas and parks.

Timber rotations in the managed forests of Canada typically are 60 years or longer. Thus

stands that are 60 years or older are included in the management planning process. To

reflect that these lands are part of the managed forest we report emissions and removals

in stands that have been subject to stand-replacing wildfire 60 or more years ago.

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DiscussionWhy the 20% mortality threshold for partial natural disturbances?

Stands affected by partial natural disturbances post 1990 are excluded from the reporting

only if the annual disturbance caused at least 20% mortality of aboveground biomass.

Disturbances with less than 20% mortality are considered part of forest dynamics.

Why re-entry when pre-disturbance biomass carbon stocks are reached?

Given the large area affected by insect disturbances, a criterion must be defined that

allows stands to re-enter the reporting. We selected above-ground biomass carbon

stocks because these are more readily monitored than total ecosystem carbon stocks.

Why re-entry when forest management follows natural disturbance?

Emissions associated with salvage logging, site preparation, slash burning or planting of

lands previously affected by natural disturbances must be reported. Therefore, forest

management activities on stands excluded from the reporting bring these stands back

into the reporting and emissions and subsequent removals are reported following salvage

logging.

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Next Steps

Implementation and analyses are ongoing.

While a spatially-explicit modelling approach is not required, it may

increase “transparency” by documenting areas that are temporarily

excluded from the reporting.

Developing capability to implement spatially-explicit approach based

on next generation tools (moja.global).

Goal is to incorporate annual time series of disturbance maps

obtained from remote sensing.

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Landsat-derived annual time series of land-

cover change with attribution 1985 - 2011:

Source:Mike Wulder and Joanne White: http://forests.foundryspatial.com Source: Hermosilla, T, M.A. Wulder, J.C. White, N.C. Coops, G.W. Hobart, Rem.Sens. Env., 170: 121-132.

http://dx.doi.org/10.1016/j.rse.2015.09.004

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http://forests.foundryspatial.com/

http://dx.doi.org/10.1016/j.rse.2015.09.004

The new approach successfully improves the reporting of

human impacts on forest sector GHG emission inventories

by removing the impacts of natural disturbances.

The approach builds on the component separation approach

proposed by the IPCC.

Further refinements to data and model are planned, but only

some will be implemented for NIR2017.

Conclusions

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Thank you

[email protected]

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