climate change in africa impacts on agriculture

Climate Change in Africa: Impacts on Agriculture

Prof. John Prof. John Sweeney,Sweeney,

Department of Department of GeographyGeography

NUI MAYNOOTHOllscoil na Éireann Má Nuad

Food Security & Climate Change in Africa – A community solution. 20th May 2010

Thomas Malthus on Population and Resources

Malthusian Theory of PopulationMalthus argued that population increased geometrically while resources increased only arithmetically.

He predicted that, eventually, population growth would outstrip resources and calamities (starvation, diseases, wars) would produce a population crash which would bring population back to balance supply of resources.

The Green Revolution

First green revolution(developed countries)First green revolution(developed countries)

Second green revolution(developing countries)

Second green revolution(developing countries)

Major International agricultural research centres and seed banksMajor International agricultural research centres and seed banks

Heavier heads required:more fertilizer, water, hybrids with shorter stalks (to prevent lodging)

Higher density plantings required:more fertilizer, constant water, hybrids with smaller root system

More plantings per year required:more fertilizer, year round water, pesticides

2,000

1,500

1,000

500

0

Gra

in p

rod

uct

ion

(mill

ion

s o

f to

ns)

1950 1960 1970 1980 1990 2000 2010

Total World Grain Production

400

350

300

250

150

Per

cap

ita

gra

in p

rod

uct

ion

(kilo

gra

ms

per

per

son

)

1950 1960 1970 1980 1990 2000 2010

Per Capita World Grain Production

200

Population Growth2000-2080

Source: Lutz et al., 2001

Africa by 2050 will have a population equivalent to that of Europe, Australasia and the Americas

combined

Global Food production

• Yields still increasing but rate declining• 800 million undernourished (hungry) with

no money to buy available food• 3 billion malnourished• Many countries not self-sufficient in food• Total calorie production has kept pace

with population growth thanks to oil crops, but…

• per capita grain production has fallen for past two decades (380 to 330 kgs/person)

Compounding Impacts of Climate Variability

Climate variability has huge impacts on poverty & livelihoods

Correlation between Rainfall and Real GDP growth in Zimbabwe

-10.0

-5.0

0.0

5.0

10.0

15.0

20.0

25.0

Years

-4.0

-3.0

-2.0

-1.0

0.0

1.0

2.0

3.0

4.0

Real GDP growth (%)

Variability in Rainfall (Meter)

Relationship holds even in diverse middle income economies with substantial water storage infrastructure e.g. Morocco

(Source: Le Houérou et al, 2006)

Rainfall trends in the Sahel

1950-1959 (mm)

1970-1984 (mm)

Atbara 92 54

Khartoum 178 116

Agadez 210 97

Tombouctou 241 147

Global Food production needs to double to meet the needs of an additional 3 billion people in the next 30 years

Climate change is projected to decrease agricultural productivity in Africa for almost any amount of warming

Assessing Agricultural Impacts requires two sometimes contradictory effects to

be considered

• The (Direct) beneficial effect to most plants of having more CO2 in the atmosphere to aid photosynthesis

• The (Indirect) effect, positive or negative, which a particular change of climate may have on the productive capacity of the plant itself.

C3 and C4 Plants• C3 Plants

– Wheat, Rice, Barley, Oats, Pea, Bean,Potato– Soya Bean, Coconut, Banana, Cassava, Sugar

Beet

• C4 Plants– Maize, sorghum, Millet,Sugar cane– Most grasses

C3 crops outperform C4 crops with higher CO2 concentrations

Crop yield response to temperature change

IPCC WG-II (2007)

Without adaptationWith adaptation

Cereal production in developed and developing countries

Projected changes in crop yields

Suitability for rainfed cereals 1961-90

Suitability for rainfed cereals 2080’s A1FI

Suitability for coffee in Uganda

IPCC WG-I (2007)

Indirect Effects

• As well as stimulating the crop directly, the increases in CO2 will also stimulate weed growth.

• Many weeds are C3 plants

Indirect Effects

• Temperature increases may extend the range of some pests currently limited by temperature, especially at high latitudes

• No of generations per year may increase

• Earlier appearance in the growing season

Vulnerability to climate change (A2) in 2050

Without adaptation

With adaptation

0

20

40

60

80

80 100 120 140 160 180 200

Index of Food Supply / Food Required

% u

nd

ern

ou

rish

ed

0

200

400

600

800

1000

1969-71 1979-81 1990-92 1997-99

mill

ion

peo

ple

Latin America &Carribean

South Asia

East Asia

Near East & North Africa

Sub-Saharan Africa

The State of Food

Insecurity

(Source: FAO, 2001)

0

100

200

300

400

500

600

2000 2010 2020 2030 2040 2050 2060 2070 2080

Po

eple

at

Ris

k o

f H

un

ger

(m

illi

on

s)

A2

B2

B1

A1

0

50

100

150

200

250

300

350

2000 2010 2020 2030 2040 2050 2060 2070 2080

Po

eple

at

Ris

k o

f H

un

ger

(m

illi

on

s)

A2

B2

B1

A1

Source: Fischer et al., 2002

Number of People at Risk

of Hunger

projected for different IPCC

economic development paths

AFRICA

SOUTH, SOUTHEAST and

EAST ASIA

What needs to be done

• Improve our understanding of the effects of climate change on specific cropping systems and the possibilities for adapting to change

• Improve institutional capacities (research, advisory systems, on-farm experimentation, farmer education)

• Investment in the development of improved seeds and cultivars in terms of tolerance to high temperatures and drought

• Improved strategies to tackle biological constraints including those pertaining to pests and diseases

• Improve efficiency of irrigation systems• Improve strategies for soil and land use management systems to make them

more resilient to flooding and droughts• Ensure that sufficient financial and human capital is available to make timely

investments in adaptation and overcome recognised socio-economic-constraints.

Climate effects on crop yields

Yield

ClimateTemperature + Rainfall

Growthduration

Wateravailability

Resource useefficiencies

SoilWeeds,Pests, diseasesFreshwater

Adaptation

Yield

ClimateTemperature + Rainfall

Growthduration

Wateravailability

Resource useefficiencies

SoilWeeds,Pests, diseasesFreshwater

Microclimatemodification

Changecrops Irrigation Soil

managementCropping systemdiversity

Teleconnections in Sahel

Greenhouse gas emissions

-50

-25

0

25

50

75

100

125

150

0.01 0.1 1 10

CO2 emissions per capita (tons Carbon; logarithmic scale)

% c

han

ge

pro

du

ctio

n p

ote

nti

al

Developing

Developed

Transition

Climate Change Impacts and Carbon Dioxide EmissionsECHAM4, 2080s

Fairness and Equity?

Greenhouse gas emissions since 1950:

75% from developed countries, 25% from developing countries

Pro

bab

ility

of

occ

urr

ence

Average HotCold Very Hot

More record hot

weather

More record hot

weather

More record hot

weatherMore

record cold weather

- “mean” effect

- “variance” effectcombined “mean + variance”

Climate change effects on extreme temperatures

Current climateFuture climate

After Timbal,B and McAvaney, B.