Issued on: 25/08/2021 -
Paris (AFP)
Africa's mountain forests may store up to two-thirds more carbon than previously thought, according to research published Wednesday that highlights the role the threatened ecosystems can play in battling climate change.
Traditionally, forests at higher altitudes are thought to contain less carbon than lowland forests due to factors such as soil and climactic changes that affect growth and thus the amount of carbon the trees can absorb.
To more accurately estimate the carbon stored in these so-called montane forests, an international team analysed data on carbon stored in trees across 44 highland sites in 12 African countries.
They measured the height and diameter of more than 72,000 trees to calculate the wood's density and logged the species in each plot.
From that they were able to calculate the amount of carbon stored per unit of forested area.
Writing in Nature, the team found that Africa's montane forests contain an average of 149.4 tonnes of carbon per hectare -- roughly equivalent to the carbon storage rates seen in African lowland forests.
Notably, this is two-thirds higher than estimated by the Intergovernmental Panel on Climate Change (IPCC) -- some 89.3 tonnes of carbon per hectare.
Yet montane forests are under threat from logging, mining and land clearance for farming.
The study found for example that Mozambique had lost nearly a third of its 18,000 hectares (44,500 acres) of high-altitude forests since 2000.
In the Democratic Republic of Congo, around half a million hectares of montane forest have been lost this century, accounting for most of the roughly 800,000 hectares lost across Africa in that time.
"African montane forests are immensely valuable. They store vast amounts of carbon, and thereby have a key role in tackling climate change," Nicolas Barbier, from the University of Montpellier and France's Nature Centre for Scientific Research, said in a linked comment article.
"Of course, this immense intrinsic value does not preclude human exploitation of these ecosystems."
The authors said the research had a range of policy implications, including the use of "carbon finance" -- inducements to conserve forests rather than cut them down.
Past underestimates by the IPCC of the carbon storage potential of African high-altitude forests may have given governments little incentive to preserve them, they said.
Barbier said that setting a fair price on preserving carbon stores such as montane forests could help check the "flood of damage" and stimulate African economies.
"The aim is to reward African countries... for their conservation endeavours, and for renouncing efforts to access the timber and ore in these ecosystems, even when such resources are otherwise desperately lacking," he wrote.
© 2021 AFP
Tropical forests in Africa’s mountains store more carbon than previously thought – but are disappearing fast
Scientists studying tropical forests in Africa’s mountains were surprised to uncover how much carbon they store, and how fast some of these forests are being cleared.
IMAGE: MONTANE FOREST IN CAMEROON view more
CREDIT: JIRI DOLEZAL
Scientists studying tropical forests in Africa’s mountains were surprised to uncover how much carbon they store, and how fast some of these forests are being cleared.
The international study reported today in Nature, found that intact tropical mountain (or montane) forests in Africa store around 150 tonnes of carbon per hectare. This means that keeping a hectare of forest standing saves CO2 emissions equivalent to powering 100 homes with electricity for one year.
The study found that African mountain forests store more carbon per unit area than the Amazon rainforest and are similar in structure to lowland forests in Africa. Existing guidelines for African mountain forests – which assume 89 tonnes of carbon per hectare – greatly underestimate their role in global climate regulation.
The international team also investigated how much tropical mountain forest had been lost from the African continent in the past 20 years. They found that 0.8 million hectares have been lost, mostly in the Democratic Republic of the Congo, Uganda and Ethiopia, emitting over 450 million tonnes of CO22 into the atmosphere. If current deforestation rates continue, a further 0.5 million hectares of these forests would be lost by 2030.
Lead author Dr Aida Cuni-Sanchez, from the University of York’s Department of Environment and Geography and at Norwegian University of Life Sciences, said: “The results are surprising because the climate in mountains would be expected to lead to low carbon forests.
“The lower temperatures of mountains and the long periods they are covered by clouds should slow tree growth, while strong winds and steep unstable slopes might limit how big trees can get before they fall over and die.
“But unlike other continents, in Africa we found the same carbon store per unit area in lowland and mountain forests. Contrary to what we expected, large trees remain abundant in mountain forests, and these large trees (defined as having diameters over 70 cm) store a lot of carbon.”
Scientists measured 72,000 trees in 44 mountain sites in 12 African countries, from Guinea to Ethiopia, and south to Mozambique. In each mountain site they established plots where they recorded the diameter, height and species of every tree.
Researchers said that better knowledge about how much carbon mountain forests store is especially important for the ten African nations where the only tropical forests they have are those found on mountains.
“While we know what makes African forests special, we don’t yet know why they are different. It is possible that in Africa, the presence of large herbivores such as elephants plays an important role in mountain forest ecology, as these large animals disperse seeds and nutrients, and eat small trees creating space for others to grow larger, but this requires further investigation,” Dr Cuni-Sanchez added.
CAPTION
Tropical forest in Africa's mountains
CREDIT
Dr Aida Cuni-Sanchez, University of York
Co-author Dr Phil Platts, from York’s Department of Environment and Geography and the IUCN’s Climate Change Specialist Group, said: “About five per cent of Africa’s tropical mountain forests have been cleared since 2000, and in some countries the rate exceeds 20 per cent. Besides their importance for climate regulation, these forests are habitats for many rare and endangered species, and they provide very important water services to millions of people downstream”.
Most African nations have committed large amounts of land to forest restoration under the Bonn Challenge. Although forest restoration is important to mitigate climate change, avoiding deforestation is a greater priority.
Co-author Dr Martin Sullivan, at the Department of Natural Sciences, Manchester Metropolitan University, added: “Previous carbon estimates for tropical mountain forests in Africa were much lower than the values we report in our study.
“We hope that these new data will encourage carbon finance mechanisms towards avoided deforestation in tropical mountains. As outlined in the Paris Agreement, reducing tropical deforestation in both lowland and mountain forests must be a priority.”
Co-author Dr Gerard Imani, at the Department of Biology, Université Oficielle de Bukavu in DR Congo, added: “Carbon finance mechanisms could help improve conservation interventions on the ground – even within protected areas, deforestation, forest degradation and defaunation remain a challenge.”
Note to Editors
The forest inventory data is part of AfriMont and AfriTRON plot networks, covering 13 countries in Africa, www.afritron.org . The data are curated at www.forestplots.net .
The research was funded by Marie Skłodowska-Curie Actions and National Geographic amongst other funders. All funders are listed in the acknowledgements of the paper.
ENDS
JOURNAL
Nature
SUBJECT OF RESEARCH
Not applicable
ARTICLE PUBLICATION DATE
24-Aug-2021
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