79. Rice farming: Yaayaa adopts new methods and gets a bountiful harvest

W

or

ki

ng

P

ap

er

Climate change impacts

on African crop

production

Working Paper No. 119

CGIAR Research Program on Climate Change,

Agriculture and Food Security (CCAFS)

Julian Ramirez-Villegas

Philip K Thornton

1

Climate change impacts on

African crop production

Working Paper No. 119

CGIAR Research Program on Climate Change,

Agriculture and Food Security (CCAFS)

Julian Ramirez-Villegas

Philip K. Thornton

2

Correct citation:

J Ramirez-Villegas, Thornton PK 2015. Climate change impacts on African crop production. CCAFS

Working Paper no. 119. CGIAR Research Program on Climate Change, Agriculture and Food Security

(CCAFS). Copenhagen, Denmark. Available online at: www.ccafs.cgiar.org

Titles in this Working Paper series aim to disseminate interim climate change, agriculture and food

security research and practices and stimulate feedback from the scientific community.

The CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS) is a

strategic partnership of CGIAR and Future Earth, led by the International Center for Tropical

Agriculture (CIAT). The Program is carried out with funding by CGIAR Fund Donors, the Danish

International Development Agency (DANIDA), Australian Government (ACIAR), Irish Aid,

Environment Canada, Ministry of Foreign Affairs for the Netherlands, Swiss Agency for Development

and Cooperation (SDC), Instituto de Investigação Científica Tropical (IICT), UK Aid, Government of

Russia, the European Union (EU), New Zealand Ministry of Foreign Affairs and Trade, with technical

support from the International Fund for Agricultural Development (IFAD).

Contact:

CCAFS Coordinating Unit - Faculty of Science, Department of Plant and Environmental Sciences,

University of Copenhagen, Rolighedsvej 21, DK-1958 Frederiksberg C, Denmark. Tel: +45 35331046;

Email: ccafs@cgiar.org

Creative Commons License

This Working Paper is licensed under a Creative Commons Attribution – NonCommercial–NoDerivs

3.0 Unported License.

Articles appearing in this publication may be freely quoted and reproduced provided the source is

acknowledged. No use of this publication may be made for resale or other commercial purposes.

© 2015 CGIAR Research Program on Climate Change, Agriculture and Food Security (CCAFS).

CCAFS Working Paper no. 119

DISCLAIMER:

This Working Paper has been prepared as an output for Flagship 4 and CCAFS Coordinating Unit

under the CCAFS program and has not been peer reviewed. Any opinions stated herein are those of the

author(s) and do not necessarily reflect the policies or opinions of CCAFS, donor agencies, or partners.

All images remain the sole property of their source and may not be used for any purpose without

written permission of the source.

3

Abstract

According to the most recent IPCC report, changes in climates over the last 30 years

have already reduced global agricultural production in the range 1-5 % per decade

globally, with particularly negative effects for tropical cereal crops such as maize and

rice (Porter et al., 2014). In addition, there is now mounting evidence suggesting that

even at low (+2 ºC) levels of warming, agricultural productivity is likely to decline

across the globe, but particularly across tropical areas (Challinor et al., 2014). This

Working Paper provides an overview of projected climate change impacts on crop

production and suitability across Africa, using a combination of literature review,

models and new data analysis

Keywords

Climate impacts, Africa, Crops, Agriculture Production, Climate Change

4

About the authors

Julien Ramirez-Villegas works as a researcher at the International Center for Tropical

Agriculture (CIAT) and is affiliated with the School of Earth and Environment,

University of Leeds, UK.

Philip K Thornton works as Flagship Leader at the CGIAR Research Program on

Climate Change, Agriculture and Food Security (CCAFS) and as a researcher at the

International Livestock Research Institute (ILRI).

5

Contents

Introduction .................................................................................................................... 6

 

Summary of Impacts ...................................................................................................... 8

Developing heat-toleant common beans in East Africa ............................................... 19

 

Methods........................................................................................................................ 21

 

References .................................................................................................................... 23

 

6

Introduction

According to the most recent IPCC report, changes in climates over the last 30 years

have already reduced global agricultural production in the range 1-5 % per decade

globally, with particularly negative effects for tropical cereal crops such as maize and

rice (Porter et al., 2014). In addition, there is now mounting evidence suggesting that

even at low (+2 ºC) levels of warming, agricultural productivity is likely to decline

across the globe, but particularly across tropical areas (Challinor et al., 2014).

Significantly greater are projected at higher levels of warming (i.e. where no

mitigation policies are enforced) as critical crop physiological thresholds related to

reproductive capacity and/or acceleration of senescence are exceeded (Gourdji et al.,

2013; Teixeira et al., 2013).

This Working Paper provides an overview of projected climate change impacts on

crop production and suitability across Africa, using a combination of literature review,

models and new data analysis. The paper focuses on the biophysical impacts of nine

agronomic crops critical for food security: maize, common bean, cassava, sorghum,

yam, finger millet, pearl millet, groundnut, and banana, as well as on one cash crop:

coffee, and provides insights as to the countries and crops in Africa that are projected

to be most negatively impacted. The Working Paper also reviews some potential

avenues for adaptation. All analyses focus on rainfed agriculture.

7

Paper’s key messages:

• Geographically, the majority (~90 %) of currently cropped maize area is projected

to experience negative impacts, with production reductions in the range 12-40 %.

• Common bean yield is highly sensitive to climate: small changes in yield within

±5 % of current yield levels can be expected in less than 2% of the agricultural

area of the continent.

• Sorghum, cassava, yam, and pearl millet show either little area loss or even gains

in suitable area, whereas common bean, maize, banana and finger millet are

projected to reduce their suitable areas significantly (30-50 %).

• Suitability projections also suggest that opportunities may arise from expanding

cropping areas in certain countries and regions (e.g. cassava towards more

temperate regions in Southern Africa, or yam outside West Africa).

• Climate change will reduce area suitable for coffee, on average across emission

scenarios, by about 50 %, with arabica coffee being most negatively impacted.

Two phenomena will likely be observed for coffee in East Africa: (1) an overall

reduction in arabica growing areas accompanied by migration and hence

concentration towards higher altitudes, and (2) a replacement of heat-stressed

arabica areas (

8

Summary of Impacts

For tropical areas, model-based estimates indicate that if no adaptation actions are

taken, on average, maize productivity could decrease by 5-10%, whereas rice

productivity could decrease by 2-5 % by every degree of warming during the 21st

century (Fig. 1). Adaptation can counter some of these negative impacts, but it is

critical that measures are implemented early, as impacts are already taking place in a

number of cases or are likely to be observed in the next 10-20 years.

For Africa, previous work on climate change impacts indicates that maize (-5 %),

sorghum (-14.5 %) and millet (-9.6 %) yields are set to decline significantly, whereas

rice and cassava yields are projected to not be significantly impacted during the 21st

century (Knox et al., 2012). Maize, in particular, contributes the greatest calories

(mean contribution of 16 %, range: 0-60 %) and is grown across the greatest area.

During the 21st century, total maize output is projected to decrease at a rate of 3-5

tonnnes per decade from historical levels as a result of climate change (Fig. 2).

According to these projections, if no adaptation occurs, by the end of the 21st century,

in the best scenario, total maize production in Africa would have decreased from ~42

to ~37 million ton per year (12%), whereas in the worst-case scenario maize

production could be as low as 25 million ton per year (40% reduction) (Fig. 2A).

9

Figure 1: Percentage yield change as a function of temperature for rice and maize across tropical

regions. Taken from Challinor et al. (2014).’

Geographically, the majority (~90 %) of currently cropped maize area is projected to

experience negative impacts. Humid and West African countries (including those

across the Sahel) are amongst the most negatively impacted, with mean production

losses between 20 and 40 % by 2050s [RCP8.5] –equivalent to +2 ºC above pre-

industrial temperatures (see Fig. 2B). Crop yield losses in these areas are mostly

mediated through shortened cropping seasons and heat stress during the crop’s

reproductive period (Thornton et al., 2009; Cairns et al., 2012). These projections are

robust, thus suggesting that adaptation of maize production should be a priority for

many African countries, but particularly for those in the Sahel.

Areas unlikely to exhibit neither significant positive or negative impacts from climate

change on maize production occur mostly in Southern Africa (Namibia and Botswana,

Zimbabwe, Lesotho and northern South Africa) and some areas of Eastern Africa

(eastern Kenya). In southeastern Namibia and Lesotho, in particular, crop production

is expected to increase significantly (>50 %), whereas in Zimbabwe, northern South

Africa, and eastern Kenya production tends to change much less, often with changes

10

within ±5 % (Fig. 2B). As climate change intensifies, however, areas with production

gains or stable production tend to reduce their size and/or may disappear completely.

Figure 2: Projected changes in maize production. (A) Future projected African maize total production

during the 21st century and two future emissions pathways: intermediate (RCP4.5) and high-end

(RCP8.5); and (B) spatial distribution of percentage change in production by 2050s and RCP8.5 (high-

end emissions) in relation to the mean production of 1971-2000. This figure was constructed using the

outputs of the Agricultural Model Intercomparison and Improvement Project (AgMIP) [see Rosenzweig

et al. (2014), freely available at http://esg.pik-potsdam.de/esgf-web-fe/].

Common bean (Phaselous vulgaris L.) is of considerable importance to the nutrition

and food security of many people in Africa. Substantial yield losses for bean in most

11

of sub-Saharan Africa have been projected for a range of different scenarios for the

current century (Lobell et al., 2008; Thornton et al., 2009, 2011). Results of some

new bean model simulations are shown in Fig. 3. Continent-wide production

decreases (relative to mean production for the period 1971-2000) are shown in Fig.

3A for RCP4.5 and RCP8.5 for two time periods centered on 2050 and 2080.

These results may be compared directly with those of maize presented above [based

on Rosenzweig et al., (2014)], in that the same soils data and daily weather data from

five climate models were used, although only one crop model was used. Fig. 3B

shows the distribution of percentage changes in production by the 2050s for RCP8.5.

Production and yield decreases of 40% and more are projected over large areas of the

Sahel, east and Central Africa and southern Africa. Some yield increases are projected

in parts of the East African highlands, western regions of southern Africa, and some

of the coastal areas of North Africa. The results highlight that bean yield is highly

sensitive to climate: small changes in yield within ±5% of current yield levels can be

expected in less than 2% of the agricultural area of the continent. Much larger yield

changes can be expected, in general.

12

Figure 3: Projected changes in dry bean production. (A) Future projected African bean production

during the 21st century and two future emissions pathways: intermediate (RCP4.5) and high-end

(RCP8.5), relative to 1971-2000; and (B) spatial distribution of percentage change in production by

2050s and RCP8.5 (high-end emissions) in relation to the mean production of 1971-2000. These

results were generated using weather data from the Agricultural Model Intercomparison and

Improvement Project (AgMIP) (Rosenzweig et al., 2014), soils data from the Harmonized World Soil

Database (FAO/IIASA/ISRIC/ISS-CAS/JRC, 2012) clustered using methods in Jones and Thornton

(2015), and the DSSAT cropping system model (Jones et al., 2003).

As stated above, for the entire set of crops suitability simulations were produced with

the EcoCrop model. Relative to historical (1971-2000) climate, these simulations

indicate that impacts vary substantially by crop and region, with sorghum, cassava,

13

yam, and pearl millet showing, on average, either little area loss or even gains in area

in most regions (Fig. 4). Conversely, common bean, maize, banana and finger millet

are projected to reduce their suitable areas significantly (30-50 %) in many regions.

Maize, in particular, shows large decreases in suitable area across the Sahel (in

agreement with previously described production projections, see Fig. 2), particularly

in Senegal, Mali, Burkina Faso, and Niger, and to some extent also in humid West

Africa (Nigeria, Togo, Benin and Ghana, also see Fig. 5). Suitable area reductions for

maize are less severe elsewhere, though Kenya, Mozambique and Botswana show

some reduction in area. Most of these reductions result from temperatures that exceed

the optimal and marginal maximum temperatures at which the crops can grow, and in

a few cases (e.g. pearl millet, sorghum and yam) decreases in precipitation.

(a) Northern Africa

(b) Sahel

(c) Western Africa

(d) Central Africa

(e) Eastern Africa

(f) Southern Africa





Projected change in suitable area [2040−2069] (%)

−100 0 100 200 300 400 500

Maize

Bean

Sorghum

P. millet

● ●





● ●





Projected change in suitable area [2040−2069] (%)

−100 −50 0 25 50 75 100

Yam

Sorghum

P. millet

Cassava

Groundnut

F. millet

Banana

Maize

Bean









Projected change in suitable area [2040−2069] (%)

−100 −50 0 25 50 75 100

Cassava

P. millet

Sorghum

Yam

Groundnut

F. millet

Maize

Banana

Bean







Projected change in suitable area [2040−2069] (%)

−100 −50 0 25 50 75 100

Yam

P. millet

Groundnut

Sorghum

Cassava

F. millet

Maize

Banana

Bean



●●



Projected change in suitable area [2040−2069] (%)

−100 −50 0 25 50 75 100

Banana

Cassava

P. millet

Groundnut

Sorghum

F. millet

Maize

Bean





●●







Projected change in suitable area [2040−2069] (%)

−100 −50 0 25 50 75 100

Banana

Yam

P. millet

Sorghum

Groundnut

Cassava

F. millet

Maize

Bean

14

Figure 4: Projected climate change impacts by 2050s (RCP8.5) and associated uncertainties for six

different regions of Africa. Countries are associated only to one region following Lobell et al. (2008)

as follows: Northern Africa: Mauritania, Morocco, Algeria, Tunisia, Libya, Egypt, and Eritrea; Sahel:

Mali, Burkina Faso, Niger, Chad, Sudan and South Sudan; West Africa: Senegal, Ivory Coast, Guinea,

Guinea-Bissau, Gambia, Liberia, Nigeria, Benin, Togo, Ghana and Sierra Leone; Central Africa:

Cameroon, Central African Republic, Congo, Democratic Republic of the Congo, Equatorial Guinea

and Gabon; East Africa: Tanzania, Uganda, Kenya, Ethiopia, Eritrea, Somalia, Rwanda, and Burundi;

and Southern Africa: Zimbabwe, South Africa, Botswana, Lesotho, Swaziland, Mozambique, Zambia,

Malawi, Angola and Namibia. Variation for each region is a result of using 5 GCMs for the EcoCrop

simulations.

(a) Banana

(B) Common bean

(C) Cassava

(D) Finger millet

(E) Groundnut

(F) Maize

(G) Pearl millet (H) Sorghum (I) Yam

−20

0

20

40

−20 0 20 40

−100

−50

0

50

100

150

−20

0

20

40

−20 0 20 40

−100

−50

0

50

100

150

−20

0

20

40

−20 0 20 40

−100

−50

0

50

100

150

−20

0

20

40

−20 0 20 40

−100

−50

0

50

100

150

−20

0

20

40

−20 0 20 40

−100

−50

0

50

100

150

−20

0

20

40

−20 0 20 40

−100

−50

0

50

100

150

−20

0

20

40

−20 0 20 40

−100

−50

0

50

100

150

15

Figure 5: Projected median changes in percentage area suitable for 9 key crops for 2050s for RCP8.5

(high-end emissions). Changes in area suitable are calculated as the percentage of area suitable in the

future relative to the area suitable in the historical period. Note that this scenario and time period

(2050s, RCP8.5) is equivalent to a global mean temperature of +2 ºC above preindustrial levels.

Suitability projections, however, also suggest that opportunities may arise from

expanding cropping areas in certain countries and regions. A clear example of this

situation is cassava, for which there could be opportunities beyond the geographical

limits where it is currently cultivated, particularly towards higher elevation areas in

East Africa, and towards more temperate regions in Southern Africa. A similar

situation can be seen for yams in East Africa, where projections indicate large

increases in cropping area. Additionally, in East Africa, there could be further

opportunities for bananas, groundnuts and millets (Fig. 4). The studies of Zabel et al.

(2014) and Lane and Jarvis (2007) also support the finding that geographic shifts in

suitable areas for crops are likely under climate change. For Africa, this means that

complex systemic and transformational changes in farming systems accompanied by a

combination of improved trade policies and shifts in diets will be needed in order to

capitalize on geographic shifts in suitable areas.

−20

0

20

40

−20 0 20 40

−100

−50

0

50

100

150

−20

0

20

40

−20 0 20 40

−100

−50

0

50

100

150

−20

0

20

40

−20 0 20 40

−100

−50

0

50

100

150

16

At the country level, Sahelian countries are projected to be the most negatively

impacted. In particular, Mali, Senegal, Burkina Faso and Niger, are projected to

decrease their suitable areas for 70 % or more than of the crops (Fig. 5). In these

countries, currently, agricultural yields are low and agriculturally suitable areas are

limited (Licker et al., 2010; Zabel et al., 2014), which implies that unless appropriate

adaptation strategies (e.g. livelihood diversification through agroforestry, breeding

climate-smart varieties, improved crop management through site-specific or precision

agriculture) are developed, many of the crops analyzed here can no longer be grown

in these countries (or at least in a