Climate change
as a threat to native tree species across Central Africa

Every year, around three million hectares of forest – an area roughly the size of Belgium - are lost across Africa. In total, about 65% of African land is currently degraded.

This reduction in natural productivity creates pressures on smallholder farming and biodiversity. Under the African Forest Landscape Restoration Initiative, countries across the continent have pledged to restore almost 128 million hectares of degraded land by 2030—an area the size of Egypt. Through a mass tree-planting initiative, the aim is to regenerate the degraded land, to secure and improve food security, fight rural poverty through the generation of new jobs, and to build climate change resilience, while mitigating the existing impacts. By maintaining and improving tree biodiversity, this has a positive and reinforcing effect on the biodiversity of all animal and plant life in the ecosystem.

But climate change is altering the habitats in which the native trees are being planted, and the composition of the forests is shifting. Bioversity International, a research organisation working on agricultural and tree biodiversity in Central and West Africa, joined up with VITO supported by the Copernicus Climate Change Service (C3S) to access the high-quality data needed to create an accurate picture of how the climate will change over central Africa. Having this information, they could then decide which tree species to plant which would thrive in the changing climate for years to come.

Central African rainforests hold more carbon per hectare than the Amazon, and trees grow in greater densities than on any other continent. This is thought to be due to interactions with the diverse range of herbivores that live among the forests. Scientists are increasingly worried about the threats that climate change poses to these rainforest ecosystems, and as so much forested land has already been lost, policymakers are racing to restore as much as possible.

Investments in ecological restoration are happening around the world at pace. But there has been little analysis about the effects future climate change will have on tree restoration plantings. There is growing concern that the germplasm currently used in forest landscape projects in the region may not be well suited to future local environments. If the trees do not adapt well, the restoration efforts may fail.

Getting the right mix of tree species is key to restoration success. By understanding how tree germplasm will function under changing climates, researchers and stakeholders can build informed strategies for planting that will benefit from the already existing genetic diversity in the landscape, and improve the ecosystem’s ability to adapt to future climates.

But, central to the case study was to make predictions about how each species would react to potential future conditions: under the impacts of climate change, would they survive, thrive or die. The team needed to understand how a range of climate variables, such as temperature and humidity, would change in the region.

Climate change is also impacting the frequency and intensity of extreme weather events. Prolonged droughts or heavy precipitation which result in flooding can adversely effect native trees, so Bioversity International also needed to analyse this type of data.

Data harnessed from these online resources was then added to key climate variables freely available the CDS. Spatial variables on temperature, precipitation, cloud cover and climatic extremes, as well as further variables on soil and terrain, were used to understand the conditions under which species were growing. Research organisations such as Bioversity International can pick and choose from high quality C3S datasets to create customized analysis in this way.

The Bioversity International team wanted to assess how the future climate would change in the region. To do so, they used 51 climate, soil and terrain variables. The majority of the information came from the CDS, from which the analysis took into account 19 climate variables, five variables of cloud cover, and 12 variables of climatic extremes, such as droughts or heavy rains.

Climate extremes were vital to include, as these will influence the long-term survival of native tree species, particularly those less resistant to events such as drought.

Climate data were retrieved from from two datasets covering bioclimatic indicators accessible in the CDS: ‘Downscaled bioclimatic indicators for selected regions from 1950 to 2100 derived from CMIP5 climate projections’ and ‘Downscaled bioclimatic indicators for selected regions from 1979 to 2018 derived from ERA5 reanalysis’.

These vital climate data were then joined with information on terrain and soil.

SDG 13 - Climate action

Native tree species provide a range of benefits to the climate, both local and global. By promoting the restoration of native trees, the project is supporting a healthy balanced ecosystem, which regulates not just environmental resources like water and soils, but also helps to regulate pests and diseases.

Landscape restoration projects are climate smart policies, which can mitigate the effects of climate change at country-wide level.

Increasing tree density in the Central African rainforests will boost the carbon that can be sequestered from the atmosphere and stored within the trees, as well as in the plants and soils alongside them.

In these ways, the project contributes to SDG 13, by taking action to combat climate change and its impacts.

SDG 15 - Life on Land

By ensuring the germplasm of native trees will survive and thrive for decades, the project is supporting the restoration and creation of climate-resilient forest ecosystems.

The tree species chosen offer a range of benefits to local rural populations, including food security, economic progress, raw materials and increased biodiversity.

This contributes directly to SDG 15 Life on Land, by protecting and restoring the sustainable use of terrestrial ecosystems.

SDG 2 - Zero Hunger

Native tree species were selected for their ecosystem services, including nutrition and their ability to regulate local environments needed to sustainably grow food. This includes preventing and reducing desertification, and regenerating degraded soils. Certain species offer a direct source of food for rural populations, such as Irvingia gabonensis (the wild mango tree) and Vitellaria paradoxa (the shea tree). Secondary products can also be used to generate economic revenue.

By offering a direct source of food and contributing to the creation of other agricultural products, the project contributes directly to SDG 2.