Crops and Range Shifts

A cowpea farm in Namibia (Southern Africa) [18]. Farmers may want to switch from maize to cowpea because it performs well under hot, dry conditions.

Overall crop yields are expected to fall in in most of Africa by 2050. But how will individual crop species respond to warming temperatures? To answer that question, it’s important to note that many factors may influence a given plant’s response, including (1) whether or not the plant is a habitat specialist, (2) how sensitive they are to increased temperatures during various life stages, and (3) the extent to which they are affected by interspecies interactions, such as attacks by pests [4]. 

One way plants respond to warming temperatures is by timing life events earlier. One study found that the spring advancement of herbs and grasses has been occurring earlier worldwide, by 1.1 days per decade on average [5]. Another major way plants adapt to climate change is by shifting range to a cooler region, such as an area at higher elevation or a more northern latitude. One study found that during recent years, terrestrial organisms have moved to higher elevations at a rate of 11 meters per decade, and to more northern latitudes at a rate of 16.9 kilometers per decade [4].

Crops have one built-in advantage over other plants. When crops begin to experience too much thermal stress, they don’t need to rely on slow natural migration to find a more suitable habitat (for example, via wind dispersal of seeds). Theoretically, as temperatures increase, farmers can simply plant new crop species that are known to tolerate heat and drought better than previous crops did. For example, maize (corn) yields are projected to decline in much of Africa, so farmers may want to switch to a crop like cowpeas (black-eyed peas), which perform well under dry, hot conditions. Drought-resistant crop varieties have been developed, including drought resistant maize, but obtaining such seeds can be difficult and prohibitively expensive, especially for poorer, rural farmers [15]. Farmers may also benefit from planting crops earlier, which many are already doing [3].