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Tropical mountain forests as carbon stocks of underestimated potential

Professor Christine Schmitt, geographer at the University of Passau, is part of an international research team that proves - in a "Nature" article - that tropical African mountain forests store more carbon than previously thought.

The picture above shows the view from a mountain massif of the Taita Hills in southern Kenya: Data that Professor Schmitt collected here in 2018 was included in the "Nature" study. Photo: Schmitt

Tropical rainforests function as gigantic carbon stocks. However, the contribution of tropical mountain forests to climate protection has been underestimated to date. This has been confirmed by a broad, international study that was recently published in the renowned British science magazine "Nature". 

Due to the altitude, research had assumed that tropical mountain forests were less productive than lowland rainforests. In its reports, the Intergovernmental Panel on Climate Change (IPCC) gave Africa an average storage value of 89.3 tonnes of carbon per hectare.

But the international study reveals that this figure is, in actuality, two-thirds higher on the African continent. In fact, a patch of forest in Africa's tropical mountain forests can store an average of roughly 149.4 tonnes of carbon per hectare - roughly equivalent to the carbon storage of Africa's lowland rainforests and well above that of South America's lowland and mountain forests. The reality is that African rainforests are generally characterised by a fairly low tree density, but many large trees. The reasons for this are not yet fully understood. The study authors suggest that the presence of large herbivores - such as forest elephants - could play a role, affecting forest structure; in addition, large-scale disturbances (such as cyclones) are quite rare and the African mountains are not as steep as the Andes, for example.

Professor Christine Schmitt, Chair of Physical Geography with a focus on human-environment research at the University of Passau. Photo: ZEF, University of Bonn

Professor Christine Schmitt, Chair of Physical Geography with a focus on human-environment research at the University of Passau. Photo: ZEF, University of Bonn

Passau geographer provides data from Ethiopia and Kenya

Professor Christine Schmitt, Chair of Physical Geography with a focus on human-environment research at the University of Passau, contributed data from Ethiopia and Kenya to the broad-based "Nature" study. Overall, 72,336 trees were measured on 226 plots, which were spread over 44 regions in 12 African countries. Lead author Dr. Aida Cuni-Sanchez, an environmental geographer at the Norwegian University of Environmental and Life Sciences (NMBU) and the UK's University of York, compiled the work of 101 colleagues who independently conducted field studies in tropical mountain forests.

"With the help of this overarching work effort, we can demonstrate just what potential Africa's tropical mountain forests have for climate protection," says Passau geographer Professor Schmitt, who has been working in this field of research for several years. Rapidly advancing deforestation endangers this potential. Schmitt cites Ethiopia as an example, where forest areas that she had studied as part of her doctoral thesis from 2003 to 2005 may no longer exist. "The forests are being cleared to create land for agriculture," the scientist describes. For many people, this is the only way to get food. The current conflicts gripping the country are exacerbating the situation.

How agriculture and forest intertwine: In south-west Ethiopia, Professor Christine Schmitt collected data on tropical mountain forests for her doctoral thesis. Photo: Schmitt

Concern for Kenya's biodiversity

In Kenya, too, the situation appears critical for the mountain rainforests, where Professor Schmitt has been active with field studies since 2016. Together with German and Kenyan students, she collected data on biodiversity and forest structure in the Taita Hills in southern Kenya as part of a DAAD-funded research project. The data she collected as part of the project in 2018 was included in the "Nature" study. Although deforestation has decreased in the Taita Hills, there are only very few forest fragments left. "We are, therefore, concerned that the areas are too small to maintain biodiversity in the long term," says Professor Schmitt, who is currently continuing her research in Ethiopia and Kenya with the DAAD-funded BioCult project.

With the help of this overarching work effort, we can demonstrate just what potential Africa's tropical mountain forests have for climate protection.

Professor Christine Schmitt, University of Passau

She hopes that the "Nature" study will sensitise the international community to the importance of Africa's tropical mountain forests for climate protection. "International mechanisms and agreements can create incentives for forest protection and help finance measures. On the ground, however, forest protection can only be achieved together with the local population, for example, through educational work and the creation of alternative income opportunities," says the Passau researcher.

Professor Schmitt has held the Chair of Physical Geography with a focus on human-environment research at the University of Passau since April 2021. She is a landscape ecologist with a specialisation in vegetation geography and experience in international policy advice. In particular, she investigates how changes in climate and land use affect the biodiversity and ecosystem services of tropical and temperate forests and forest landscapes. The geographical focus of her research is Europe and East Africa.

Text: Kathrin Haimerl

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