Researchers have discovered that deforestation over the past twenty years has led to a greater increase in temperatures and cloud levels than climate change alone. This situation poses risks to the biodiversity and water resources of Africa’s montane forests.
Montane forests are typically shrouded in clouds, cool, and moist, found on isolated mountains across Africa. They boast a rich diversity of species and serve as important water reservoirs by capturing moisture from fog and clouds, supplying high-quality fresh water to millions residing in the lowland regions of Africa.
In the last two decades, approximately 18% of Africa’s montane forests have been lost due to deforestation. This loss has caused a temperature increase and rise in cloud levels that are double what has been attributed to climate change. Research indicates that air temperature has elevated by 1.4 degrees Celsius, while the elevation of clouds has increased by 230 meters in the past twenty years.
“This has significant repercussions for water resources and biodiversity,” notes Professor Dirk Zeuss from the University of Marburg.
The findings are detailed in a study published in Nature Communications.
Increased cloud level hinders water collection
The elevated cloud levels impede water collection because when clouds come into contact with the forest canopy, the fog (water) gets deposited onto trees and the ground. If the clouds are at a higher altitude, this process won’t occur, explains Professor Petri Pellikka, director of Taita Research Station.
This process also relies on having forested mountain tops as they expand the area covered by vegetation, allowing better storage of water in trees and soil compared to open areas.
The research took place in the highland areas of Kenya, Tanzania, Ethiopia, and South Africa. It is one of the outcomes from the Taita Research Station, maintained by the University of Helsinki since 2009. Contributions from the University of Helsinki were provided by the Earth Change Observation Laboratory in the Department of Geosciences and Geography.
“In our studies in Taita Hills, it was found that annually, 20% more water accumulated on the ground in forested mountain tops compared to open lands. This is mainly due to fog collecting on trees and dripping onto the ground, adding to rainfall. If the clouds do not reach the forests, this process ceases to happen,” Pellikka explains.
Numerous small forested mountain tops exist in the Taita Hills. Key water sources in Kenya include Mt. Kenya, the Mau Forest, the Aberdare Mountains, Mt. Elgon, the Cherangani Hills, and Mt. Kilimanjaro, which, despite being in Tanzania, also supports water availability on the Kenyan side.
“Since 1880, 50% of the forest around Africa’s tallest mountain, Kilimanjaro in Tanzania, has been lost,” states Dr. Andreas Hemp from the University of Bayreuth, who has conducted research on Kilimanjaro for three decades.
Inverse relationship between temperature and elevation
The research also uncovered that the negative correlation between temperature and elevation indicates that deforestation’s warming effects could lessen at higher altitudes. However, significant deforestation (where tree cover loss exceeds 70% in a 1 km x 1 km area) can counteract the cooling benefits associated with higher elevations, leading to similar warming effects even at elevated locations in African montane forests.
“The findings emphasize the urgent need for action, as montane deforestation driven by agricultural expansion and logging poses critical threats to biodiversity and ecosystem services, such as water supply in Africa,” states Temesgen Abera, a visiting scholar from the University of Helsinki and postdoctoral researcher at Philipps University of Marburg (Germany), supported by the Alexander von Humboldt foundation.
The study employed a data-driven methodology utilizing satellite observations, reanalysis data, ensemble learning, empirical methods, and independent onsite temperature and cloud base height measurements for validation.
The research team consisted of scientists from the University of Helsinki, the University of Marburg, and the University of Bayreuth in Germany, the Finnish Meteorological Institute, Addis Ababa University in Ethiopia, and North-West University in South Africa. This research was part of the ESSA project (Earth observation and environmental sensing for climate-smart sustainable agropastoral ecosystem transformation in East Africa) funded by the European Commission.
