Robust Negative Impacts of Climate Change on African Agriculture

Sub-Saharan Africa (SSA) has the highest proportion of malnourished people in the world, even though its economy is dependant on agriculture production. A major question for the region is how crops in SSA will endure climate change; as to date there have been very limited scientific findings on the topic.  Schlenker and Lobell (2010) use historical crop production and weather data to create a model detailing the crop yield response to the expected change in climate.  The study found that climate change is expected to negatively impact crops in SSA, and substantial investments will be necessary for sufficient agricultural production.—Whitney Dawson 

Schlenker, W., Lobell, D., 2010. Robust negative impacts of climate change on African agriculture. Environmental Research Letters 5, 014010.

          Schlenker and Lobell have created an assortment of models using panel analysis to demonstrate the extent to which SSA agricultural production responds to climate change.  In past studies, availability of reliable data has been a problem, and ‘best-guess’ estimates with large uncertainties have been used.  The models that Schlenker and Lobell designed incorporate historical data of both crop production and weather, and are applied to the staple African crops: maize, sorghum, millet, groundnuts and cassava.  These are thought to be key sources of protein, fat, and calories in the region. Schlenker and Lobell’s use of a data series of historical weather patterns, rather than averaging conditions is advantageous, because infrequent extreme weather events are accounted for.  Their panel data set is preferable to past studies’ methods because it is an observational study, measuring how various constraints affect farmers’ reactions to weather shocks.  The disadvantage to the panel model is that responses to weather shocks may differ from responses to a permanent climate shift.
          The regression model is able to examine how climate change affects the crop yields while keeping all other variables unchanged.  However, farmers in this area tend to use production technologies that are suboptimal due to a lack of resources, and fertilizer is underused in many countries.  Zimbabwe and South Africa have higher fertilizer use, and therefore higher yields, but, as a result are also more susceptible to damage from temperature increases.  Schlenker and Lobell fit separate models for countries that use higher and lower amounts of fertilizer since the responses would be varied.  Although lower fertilizer use results in less of an impact from climate change, the countries using higher amounts of fertilizer still produce higher yields, underlining the importance of sufficient fertilizer use.
The predicted changes in climate were evaluated under 16 climate change models and 1000 randomly drawn years.  Almost all models had significant improvement when the weather variable was excluded from the equation altogether, and predicted negative impacts of warming when it was included, with the exception of the cassava crop, a root crop with a highly variable growing season.  The mean estimates of total changes in production for maize, sorghum, millet, groundnut, and cassava are –22, –17, –17, –18 and –8%, respectively.   
It was found that temperature changes have a significantly stronger impact on crop yields than precipitation changes.  The study omits the possible changes in the distribution of rainfall during growing seasons, which could potentially be important.  Increasing the precision of the climate change forecasts would allow a more confident analysis.  A more regionalized set of data may also prove to be beneficial, however, the broader scale of data analysis can be useful for decision making on the national level.
According to this study, major improvements in agricultural productivity are necessary to combat the substantial poverty problems in SSA.  The study suggests that the challenge of increasing productivity will become more difficult with time due to the warming climate.  The authors suggest that this should be seen as incentive for significant investments in production renovations that will be sustained in the future.  Important investments recommended are crop varieties with greater tolerance to heat and draught, improvement of irrigation systems, disaster relief, and insurance programs to help SSA reach a more sustainable agriculture system.  

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