#storm frequency

We know that forests are crucial to fighting global climate change, but another important and perhaps less appreciated aspect is the way they affect the climate on a much more local scale. Our research shows that deforestation in west Africa has made storms more frequent and thus increased the risk of disastrous flash flooding in the region’s coastal cities.

Much of west Africa was deforested throughout the 20th century, a process driven by agriculture, international trade in goods like cocoa, and the displacement of people by conflict. The rapid growth of cities, particularly along the coast, is also leading to deforestation in the surrounding regions.

With the increasing availability of satellites in recent decades, we can see how many of the pockets of remaining forest have disappeared in the space of just a few years. We analysed satellite images of clouds every 30 minutes since the 1990s to calculate trends in the frequency of storms.

In this humid, tropical region, rain is a near-daily occurrence in the wet season. We weren’t looking for this sort of rain, though. The storms we analysed are less frequent but produce deluges of several inches of rain in an hour or two, enough to flood low-lying areas and trigger torrents of water to run down particularly exposed catchments.