A new international study published in the journal PLOS One reveals that land-use change caused by rapid population growth, not climate change, was the primary direct cause of the loss of 76 per cent of natural plant species on the lower slopes of Mount Kilimanjaro between 1911 and 2022.
The findings, which mark one of the most detailed long-term ecological studies in the region, highlight a severe and accelerating threat to the biodiversity of Africa’s tallest free-standing mountain, located in Tanzania.
The Role of Population and Land Use
Researchers analyzed historical maps, census data, satellite imagery, and a high-resolution dataset of nearly 3,000 plant species over the 111-year period. The analysis conclusively showed that the expansion of urban areas and the conversion of natural savanna habitats to agricultural land were the main drivers of plant biodiversity decline.
This land-use change was directly linked to massive demographic shifts on the mountain’s lower slopes, where population density surged from approximately 30 to 430 people per square kilometre between 1913 and 2022. The intense human-related pressures have significantly threatened the savanna ecosystems, which are crucial for maintaining plant species diversity, including traditional medicinal plants relied upon by millions living in the area.
A visible consequence of this growth is the loss of an ecological corridor of sub-montane forest that once connected Kilimanjaro and Mt. Meru, now largely replaced by human settlements and agriculture.
Climate Change Not the Main Direct Driver
While the glaciers atop Mount Kilimanjaro are visibly shrinking due to climate warming, the study provided a crucial distinction regarding the lower slopes where the majority of species loss occurred.
The analysis showed that climate change was not a significant direct cause of the severe biodiversity loss in the mountain’s lowlands. In these lower parts, rainfall has remained largely unchanged and warming has been slow. Instead, researchers found that the most severe biodiversity loss occurred specifically where people had cleared land for farming and used the land more intensively.
The study is the first to directly link human population densities with plant species densities at a one square kilometre scale in a tropical region, providing a powerful, high-resolution correlation between socio-economic factors and ecological degradation. The researchers hope their findings will directly guide policies aimed at mitigating biodiversity loss by focusing on sustainable land management and conservation planning in human-dominated landscapes.