A new study highlighted the severe impact of deforestation on Africa’s tropical montane forests, revealing that tree loss has caused a dramatic rise in temperatures and cloud base height (CBH) — effects surpassing those of climate change alone.
The research underscored the urgent need to address deforestation in these critical ecosystems, pointing out threats to biodiversity and water supply in the region. Tropical montane forests are fragile but valuable ecosystems found in high-altitude mountainous areas. They act as water towers, trapping water from fog and clouds and supplying high-quality fresh water to millions of people in Africa’s lowlands.
Conducted by a team of researchers from Finland, Germany, South Africa and Ethiopia, the study was published in journal Nature Communications. The team presented observational evidence demonstrating the response of air temperature and CBH to deforestation in the African forests over the last two decades. CBH is the altitude of the cloud’s lowest visible part.
The paper found that deforestation has accelerated warming and cloud level increases in the highlands of Kenya, Tanzania, Ethiopia, and South Africa. Between 2003 and 2022, about 18 per cent of Africa’s montane forests were lost, resulting in a two-fold increase in maximum temperature and cloud level rise compared to climate impact.
Over the last two decades, the air temperature has risen by 1.4 degrees Celsius and the cloud base height has increased by 230 metres, the researchers found.
The study discovered that rising cloud levels reduce water harvesting because when the cloud touches the forest canopy, fog (water) is deposited on plant and land surfaces. If the cloud base is higher, this phenomenon does not take place. The researchers also looked at the effects of deforestation and climate change on CBH at various elevations.
Large-scale deforestation can counteract the cooling effect of elevation, and similar warming can be induced at higher elevations in African montane forests, the paper found. In addition to its impact on water supply, deforestation is a major contributor to biodiversity loss in the tropics.
Raising CBH also has an impact on biodiversity by affecting humidity, light conditions, and water availability, all of which are necessary for organism survival.
These findings indicate that large-scale deforestation in montane forests is especially harmful. The main driver of montane deforestation in Africa was attributed to small-scale cropland expansion, with other factors (urbanisation, large-scale commodity crops and forest fires) playing a lesser role.
The scientists used air and dew point temperature data from local weather stations in montane forests in Ethiopia (Bale Mountain), Kenya (Taita Hills), and Tanzania (Kilimanjaro Mountain) to independently validate the model.
The research group included scientists from University of Helsinki, University of Marburg and University of Bayreuth in Germany, Finnish Meteorological Institute, Addis Abeba University in Ethiopia, and North-West University in South Africa
