Climate change impacts on recent crop yield trendsand rural migration patterns

Rachel Licker

August 19th, 2013NCAR IAM Meeting

Wheat yield gap fraction over Eastern and Western Europe

Licker et al. (2010) Glob. Ecol. Biogeography

What drives the striking yield gap between E. & W. Europe?

Picardy Region of France and Rostov Oblast of Russia

• Globally important producers of wheat• Examples of high and low yielding agriculture

(Monfreda et al., 2008)

How has climate driven yield trends in global breadbaskets?

Climate – Crop Yield Relationships

Picardy Region of France

• Located in northern France

• 19518 km2 (slightly smaller than New Jersey)

• Second largest wheat producing region in France

• France = 5th largest wheat producer, 2nd largest exporter

• Yields are among highest in the world (8.4 T/ha)

• As with much of Europe, yields are stagnating

Climate – Crop Yield Relationships

Rostov Oblast of Russia

• Located in southern Russia

• 100,800 km2 (slightly smaller than Kentucky)

• Part of Southern Federal District – main wheat producer

• Russia = 4th largest wheat producer, 4th largest exporter

• Yields are on the lower side (2.8 T/ha)

• Yields fell after USSR collapse & began recovery in late 90s

Climate – Crop Yield Relationships

Average climate: a closer look

• Analyzed historical, daily weatherstation data from the regions

• 1973-2010

• Compared many aspects of climate:

• Annual, seasonal & monthlyTmax, Tmin, Tave, Precip

• Frequency of extreme temp.s• Onset of spring and fall• Length of growing season

Licker et al., 2013, Agr. Forest Meteorol.

Climate – Crop Yield Relationships

Average climate

• Picardy: Maritime climate

• Longer growing season• More precipitation

• Rostov: Continental climate

• Greater seasonal variation(colder winters, warmer summers)

• More extreme temperatures

Climate – Crop Yield RelationshipsRecent climate change

• Both regions: significant changes in climate (1973-2010)

Rostov: changes in most variables

• Strongest in summer• Ex: Tmax 4°C warmer

Picardy: many changes

• Strongest in fall and spring• Ex: Spring Tave 2.4°C warmer

Climate – Crop Yield Relationships

Climate sensitivities

• Compared year-to-year changes in climate & yields

Rostov and Picardy’s winter wheat yields

• Sensitive to many aspects of climate

• Main climate drivers differ

• Rostov: Late spring & early summer conditions

• Picardy: Summer & fall conditions

Climate – Crop Yield Relationships

Climate change impacts

Picardy

• Overlap in aspects of climate that yields are sensitive to& aspects that have changed

Estimated climate change impact:

Counteracted 11%of yield trend

Climate – Crop Yield Relationships

Climate change impacts

Rostov

• Not much overlap in aspects of climate that yields are sensitive to & aspects that have changed

Likely no net impact

Social factors:more importantdrivers

Secondary impacts of climate change

- Many implications of such changes in crop yield trends due to climate change:

• More direct: Changes in commodity prices, food access, etc.

• Indirect: e.g., link between climate change, crop yield trends & human migration patterns, e.g.:

- Feng et al. (2012): US Corn Belt: crop yields due to extreme events, out-migration of adult population

- Gray and Mueller (2012): Crop failures in Bangladesh migration of rural households not engaged in ag.

Climate, Crops, and Migration – South Africa

• Importance of South African agriculture

• Large projected changes in climate

• Projected shifts in regions suitable for agriculture

• Recently experienced large decreases in number offarmers – chance to measure relationships

Climate, Crops, and Migration – South Africa

• Africa’s most highly productive agricultural system

• Extensive maize, sugarcane, and wheat production

Maize harvested area Wheat harvested area(Monfreda et al., 2008)

Future Climate, Crops, and Migration – South Africa

• Significant changes in SA’s climate are likelyby 2100 over 1960-1990 baseline, A1B scenario:

• Average inland temp.s: increase by 4°C • Precipitation: 20% decrease

• Current extent of land suitable for maize cultivation is at risk of:

a) Shrinkingb) Shifting into PA

buffer zones

Bradley et al. (2012) Diversity Dist.

Past Crops, Climate, and Migration – South Africa

In SA, structural reforms in early 1990s led to:

Removal of heavy subsidies & protectionfrom global market

Planted area of important cereal crops

Production concentratedin high yielding areas

Maize harvested area & yield (FAOSTAT, 2013)

Crops, Climate, and Migration – South Africa

Total commercial farms:

1996: 60,9382007: 39,966

Whether changes in climate across space & time influenced crop production & off-farm migration future dynamics?

Changing climate and agricultural production

Q1.1. What climate stressors have farmers faced in recent history and how have they influenced crop production in different regions?

• Historical analysis of weather & crop yield data

Q1.2. Did climate influence the decline in SA’s planted area & the decision of farmers to migrate off farms?

• Using patterns in climate, production & migration across space and time

• National household migration survey data + population census statistics

• Empirical, statistical migration model (OLS, IV?)

Changing climate, human migration

Q2. What were the outcomes of those farmers who:1) Remained in operation 2) Stopped operating but did not move3) Stopped operating and moved

Mixed methods:

- Quantitative analysis, census statistics & survey data

- Qualitative, interview-basedmethods (early 2014)

Thank you!

Crops, Climate, and Migration – South Africa

Using historical relationships between climate, crop production and migration as a partial indicator:

How likely are people to move off cropland with reduced productive potential/yields in SA?

c. Carlos Gomes

Climate Change, Agriculture, Human Migration

• There is concern that the climate change will increase human migration flows.

• For example, a small but growing body of work:• Link between climate change, agricultural production,

human migration.

Actual wheat yields, circa 2000, tons / hectare (Monfreda et al., 2008)What is the maximum yield that these regions can achieve given their climate?How do the maximum potential yields compare with current yields?

Which regions could support higher crop yields?

Comparing yields across “agro-climatic zones”

Growing Degree-Days Soil Moisture Index

100agro-

climaticzones

How do climate and social factors drive crop yield gap patterns?

Wheat yield gap fraction

Licker et al., 2010, Global Ecology and Biogeography