Impacts of climate change on cropping patterns in a tropical, sub-humid watershed

<div><p>In recent decades, there have been substantial increases in crop production in sub-Saharan Africa (SSA) as a result of higher yields, increased cropping intensity, expansion of irrigated cropping systems, and rainfed cropland expansion. Yet, to date much of the research focus of the impact of climate change on crop production in the coming decades has been on crop yield responses. In this study, we analyse the impact of climate change on the potential for increasing rainfed cropping intensity through sequential cropping and irrigation expansion in central Benin. Our approach combines hydrological modelling and scenario analysis involving two Representative Concentration Pathways (RCPs), two water-use scenarios for the watershed based on the Shared Socioeconomic Pathways (SSPs), and environmental water requirements leading to sustained streamflow. Our analyses show that in Benin, warmer temperatures will severely limit crop production increases achieved through the expansion of sequential cropping. Depending on the climate change scenario, between 50% and 95% of cultivated areas that can currently support sequential cropping or will need to revert to single cropping. The results also show that the irrigation potential of the watershed will be at least halved by mid-century in all scenario combinations. Given the urgent need to increase crop production to meet the demands of a growing population in SSA, our study outlines challenges and the need for planned development that need to be overcome to improve food security in the coming decades.</p></div

The cropping zones in the watershed under baseline climatic conditions and RCP scenarios.

<p>Sequential cropping zones have been disaggregated into full double cropping and relay cropping zones. These zones indicate the areas where water availability is sufficient to permit different cropping systems.</p

Land cover of the Upper Ouémé watershed showing current cropland areas.

<p>Land cover of the Upper Ouémé watershed showing current cropland areas.</p

Contour plots showing severity-duration-frequency relationships of streamflow droughts in the Upper Ouémé watershed under baseline climatic conditions (2003–2012) and two RCP scenarios.

<p>Contour plots were derived using daily streamflow simulated at the watershed outlet.</p

Probability density plots of 6-month and 12-month Standardized Precipitation Evapotranspiration Index (SPEI) derived under baseline climate conditions (2003–2012) and under two future climate scenarios.

<p>SPEI values < 0 represent meteorological drought and the greater the absolute value, the higher the severity. SPEI values > 0 represent wetter than normal conditions.</p

Probability density plots of 6-month and 12-month Standardized Streamflow Index (SSI) derived under baseline climatic conditions and under RCP scenarios.

<p>SSI values < 0 represent streamflow drought and the greater the absolute value, the higher the severity. SSI values > 0 represent higher streamflow.</p

Criteria for delineation of potential rainfed sequential cropping zones under rainfed conditions [61].

<p>Sequential cropping zones are disaggregated into relay and double cropping zones.</p

Irrigation potential (ha) in the Upper Ouémé watershed under current and future climate and water-use scenarios.

<p>Superscript ^a indicates that irrigation potential estimates represent the 2040s under the SSPs and baseline climate. For 2090s, irrigation potential under baseline climate and SSP1 was 36,100 ha whereas it was 26,900 ha under baseline climate and SSP3.</p

Characterization of water-use scenarios in line with the qualitative storylines of the Shared Socioeconomic Pathways (SSPs).

<p>Current population in the watershed is about 510,000 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192642#pone.0192642.ref026" target="_blank">26</a>]. Values of irrigation efficiency are based on [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192642#pone.0192642.ref052" target="_blank">52</a>].</p

Changes in annual precipitation totals and average temperature in future climate scenarios compared to baseline scenario.

<p>The average temperature in baseline is 27.4°C.</p