African Mountain Forests Store More Carbon Than We Thought But They're Vanishing Fast

Although the attention given to the Amazon rainforest and the jungles in southeast Asia receives less than the tropical forests of Africa, it doesn't diminish their importance in the global carbon cycle.
Recent research shows that the highest mountain forests of Africa can store far more carbon per hectare, than the Amazon. This is far more than what we thought.

"The results are astonishing because the climate in mountainous areas would be expected to lead low carbon forests," said Aida Cuni Sanchez, a tropical forest ecologist from the University of York (UK) and the Norwegian University of Life Sciences.

"The cooler temperatures and longer periods of cloud cover should slow down tree growth. Strong winds and unstable slopes may limit the size of trees before they die."

Africa has trees that are unlike any other continent. Researchers found that many trees grew to over 70 cm in diameter (28 in) even in harsh mountainous environments. They store as much carbon in Africa as in Borneo and in Africa.

These same old-growth forests are often the ones that are being cut down for logging and mining and other farming operations, as well as political unrest. At least 0.8 million hectares of mountain forests have been lost since the turn of the century. Most of these were in the Democratic Republic of the Congo and Uganda.

Researchers calculated that this would be equivalent to emitting more than 450 million tonnes of CO2 into the atmosphere.

If we don't do anything to stop deforestation, Africa could lose 0.5million hectares in the next ten years.

Researchers write that it is crucial to better understand montane carbon stocks for many African countries, especially in eastern Africa, where montane forests make up the majority of the remaining evergreen old-growth forest.

For estimating the national carbon loss from deforestation or forest degradation, it is crucial to quantify carbon stocks in these ecosystems. The quantification of carbon stocks in montane forests old-growth helps to limit potential carbon uptake from restored natural forests.

Yet, there has been very little research on African forests' ability to store carbon. The authors state that data from African mountain areas is "exceptionally scarce."

In a 2019 update of the 2006 Intergovernmental Panel on Climate Change report (IPCC), old-growth forests in Africa's mountains were given the same carbon-storing potential that secondary forests in high-altitude areas, approximately 89 tons per hectare.

This could however be an underestimation. Researchers analyzed 44 old-growth forests from a dozen African countries to find a carbon-storing potential that was nearly twice as high as the IPCC report.

This is pretty comparable to lowland forests in Africa. Both landscapes also had low stem density and high numbers of larger trees. This indicates that Africa's forests are not affected by higher elevations as much as other parts of the world.

The authors did not find any variation in carbon storage between mountain forest forests. However, they found no correlation with elevation.

The authors actually found that the carbon content of Africa's tropical mountain forests was 70% higher than the average for other mountain forests in the tropics.

Cuni-Sanchez explains, "While we know what makes African forest special, we don’t yet know why."

It is possible that elephants in Africa play an important role in mountain forest ecology. These large herbivores eat small trees and disperse nutrients. However, further research is needed.

14 African countries have signed the Bonn Challenge today, which aims to restore 350 million hectares deforested land before 2030 in order to combat biodiversity loss, poverty and climate change.

These new results indicate that forests must be preserved at all levels of the continent in order to reach this lofty goal.

Nature published the study.