Mount Kilimanjaro lost 75% of its plant species over last 100 years

By Stephen Beech

Africa's highest mountain has lost 75% of its natural plant species over the last 100 years, according to new research.

But climate change "had no measurable effect" on the trend, say scientists.

Instead, they believe human-driven land use change is likely the primary cause of biodiversity loss on Mount Kilimanjaro’s lower slopes.

Standing at around 19,340 feet (5,895 metres). Kilimanjaro is located in Tanzania and is also the world's tallest free-standing mountain, meaning it is not part of a mountain range.

The new study, by an international research team, suggests that, between 1911 and 2022, land-use change was the primary direct cause of the loss of three-in-four natural plant species on Kilimanjaro's lower slopes.

Study lead author Dr. Andreas Hemp, of the University of Bayreuth, Germany, said: "Kilimanjaro is a dormant tropical volcano in Tanzania and Africa’s tallest mountain.

"Millions of people living in the area rely on Kilimanjaro’s diverse ecosystems for such benefits as timber, food, and water regulation.

"But the variety of species found in these ecosystems - their biodiversity - is declining as a result of human-related pressures, such as climate change, pollution, introduction of invasive species, resource extraction, and land-use change.

Understanding which human activities are the main drivers of declining biodiversity on Kilimanjaro and other tropical mountains is necessary to inform mitigation efforts.

"However, most prior research has focused on climate change, without considering other drivers, and has typically explored the effects instead of the causes of environmental change."

To help clarify the main drivers behind Kilimanjaro’s decreasing biodiversity, Dr. Hemp and his colleagues analysed historical maps, census data, satellite imagery, and a high-spatial-resolution dataset of nearly 3,000 plant species found in different parts of the region.

The team focused on plant biodiversity, as it is closely related to the overall biodiversity of an ecosystem.

The analysis revealed that land-use change - for example, expanding urban areas or converting savannah habitats to agricultural land - was the main cause of plant biodiversity loss between 1911 and 2022.

The lower slopes of Kilimanjaro saw a loss of 75% of natural plant species per square kilometre during the study period, according to the findings published in the journal PLOS One.

Land-use change stemmed from rapid population growth and economic development, with population density rising from 30 to 430 people per square kilometre between 1913 and 2022.

But the analysis also showed that climate change was not a significant direct cause of biodiversity loss on Kilimanjaro.

The researchers say their findings could help guide policies to mitigate biodiversity loss.

As examples, they highlight specific locations in the Kilimanjaro region that have benefited from sustainable traditional agricultural practices and the establishment of protected areas.

Dr. Hemp said: “Our research reveals that land-use change driven by rapid population growth - not climate change - was the primary direct driver of biodiversity loss on Mount Kilimanjaro over the past century, with up to 75% of natural species per km² lost on the lower slopes.

"Encouragingly, traditional agroforestry and protected areas emerged as promising strategies for mitigation.

“Investigating a century of ecological change on Kilimanjaro allowed us to disentangle complex human and environmental impacts.

"This study was the first, to our knowledge, to link human population densities with plant species densities at a one km² scale in a tropical region - made possible by combining remote sensing with extensive ground-based species data.

"The process required cleaning and verifying ecological field data across diverse vegetation types, highlighting the critical role of biological collections and the taxonomic expertise of herbaria worldwide.”

He added: “It was striking to find that, contrary to common narratives, climate change had no measurable effect on local biodiversity trends - emphasising the urgent need to address socio-economic drivers like land use in conservation policy.”