A new scientific study says that the rapid expansion of farmland across tropical Africa is having mixed effects on local temperatures, cooling the land at night while either cooling or warming it during the day, depending on regional conditions.
The paper published in Communications, Earth and Environment, based on 17 years of satellite data, examined how converting natural grasslands into cropland affects land surface temperatures across the continent. The findings show a consistent pattern at night: farmland tends to have lower temperatures compared to nearby grasslands.
“Croplands consistently cool the surface at night relative to surrounding grasslands,” the study says.
Scientists attribute this nighttime cooling to changes in how crops release heat and moisture into the atmosphere after sunset.
However, the situation during the day is more complex and varies depending on how dry or wet a region is. In drier areas, such as semi-arid regions, farmland tends to cool the surface during daylight hours. In contrast, in wetter regions, cropland can actually increase daytime temperatures.
Researchers explain that these differences are driven by how crops interact with the environment. Crops can release water into the air through a process similar to sweating, which helps cool the land. They also change how sunlight is absorbed or reflected and how heat moves between the ground and the atmosphere. The balance of these processes differs between dry and wet regions, leading to opposite temperature effects.
The study also identifies vegetation density–how leafy or dense the crops are–as a key factor. In dry regions, crops often have more vegetation than the natural grassland they replace, which enhances cooling. In wetter regions, this effect is weaker or reversed, contributing to warming.
While some cooling effects may seem beneficial, especially in hot and dry areas, the findings raise concerns about the broader impact of agricultural expansion. In particular, scientists warn that continued conversion of land to farmland in wetter regions could worsen heat during the day.
This could have implications for human health, water resources, and crop productivity, especially as climate change continues to increase temperatures across Africa.
The research shows that agriculture plays a more complex role in climate than previously understood. Rather than simply contributing to global climate change through greenhouse gas emissions, farming also directly alters local temperatures through physical changes to the land.
The paper underscores the importance of considering local environmental conditions when planning agricultural expansion. As Africa continues to increase food production to meet growing demand, understanding these climate impacts will be critical for sustainable land management.
Photo from Foodtank