The Sahel: Weather data insights to adapt rainfed agriculture to climate change

The Sahel: Weather data insights to adapt rainfed agriculture to climate change

Precipitation patterns are changing and with high resolution observed rainfall surfaces, crop production systems can be more effectively managed to reduce the risk of food insecurity.  Detailed weather data is needed to optimize watersheds and deliver agricultural advisories to empower farmers to be more profitable and increase resilience in the face of climate change. This analysis offers a quick look into changes during the main crop growing season (July-September from 2006-2019) for the Sahel.

Sahel cropping season from July to September 2006-2019: Average P/PET

Precipitation divided by Potential Evapotranspiration (P/PET) is an excellent indicator of water availability to support crop production. All across the Sahel (Senegal, Mali, Burkina Faso, Niger, and northern Nigeria) the mean seasonal P/PET is less than 1.0 during the main rainy season (refer to map above).  Maize, for example, will be ‘at risk’ of drought due to seasonal fluctuations and in-season rainfall distribution. P/PET below 0.80 indicates that farmers might consider  transitioning to sorghum (more drought tolerant than maize) and pearl millet for even drier areas. P/PET below 0.65 is too risky for grain crops and so forage crops to support livestock are important down to a P/PET of 0.45, below this value, even forage grasses will struggle 

sWith rainfall variability increasing in the Sahel, regions colored red-to-yellow in the map above are at risk of crop failure.  For the Sahel, rainfall drives agriculture and food security. Rainfall distribution within the season and between seasons will define the success in realizing food security and profitability for farmers. Mean 3-month P/PET indicates where water stress and food insecurity are likely to occur.  Orange areas (P/PET <0.8) are home to over 25 million people, all of whom are continually at risk of agricultural drought or yield impacting water stress during the growing season. 

The coefficient of variation (CV =  standard deviation / mean) is a useful statistic to describe the variability ‘around the mean’.  Thus a P/PET mean of 0.90 with a CV of 15% is more predictable for farmers to manage than a CV of 45% where a crop of maize is frequently at risk of drought or even water logging. It is the increase in variability that is posing the greatest risk to rainfed agriculture in the Sahel. The charts below illustrate the variability for a few locations across the Sahel.  Note that with aWhere’s contiguous weather surfaces, these charts and therefore the trends can be examined for any location.

Sahel Trends in Moisture Availability

Total population continues to increase in West Africa against the backdrop of warmer temperatures and more variable rainfall and this puts more people at risk of food insecurity. Monitoring observed rainfall in ‘real-time’ and leveraging 15 days of hourly forecast enables agronomic information services to empower farmers to become more resilient to climate change. Historical observed weather data offers insights into weather trends to  inform policy makers one strategic infrastructure investments to help avert famine due to increasing weather variability and extremes. 

The 2020 population for the region as depicted below is just above 120 million people (WorldPop, UK 2019 estimation). More than half (58%) of this population lives in areas where P/PET < 1.2.  This population of 70 million people is often under the threat of drought during their single growing season and with the dryness and the variability, they are challenged to achieve food security. 

Total Population per aWhere grid cell (9km). Source: WorldPop UK

The ability to monitor both short and long-term trends in P/PET with aWhere’s weather data allows decision-makers to anticipate where to invest in infrastructure for irrigation or where to deploy resources to at-risk populations.Data-driven decisions to adapt to climate change is the need of the hour for rainfed agriculture in West Africa to realize the aspirations of governments to fast-track rural development and ensure nutritional security.