Published on April 21, 2021 in the journal Nature, an international study coordinated by researchers from IRD and CIRAD, identifies for the first time the forest areas most exposed to the increasing climate and human pressures expected in the coming decades.
Cameroon, Gabon, the Republic of the Congo, the Democratic Republic of the Congo and the Central African Republic. Five Central African countries where one of the largest reservoirs for biodiversity extends, the second largest tropical forest in the world. A region with many distinct forests, each of which reacts differently to the climate press and to those exercised by humans, explains Maxime Réjou-Méchain, an ecologist at the Institute for Research for Development (IRD) and first author of the study.
This study updates the first transnational survey of forest types in the region. Impressive quantitative work, available online on the website of the Center for International Cooperation in Agricultural Research for Development (CIRAD). It is based on a huge dataset with almost 6 million trees. To realize the extent of the resources used, “it is estimated that if an individual reproduced this amount of data, it would take 1000 years of fieldwork,” specifies Maxime Réjou-Méchain. The aim of this research is to combine these data with future climatic and anthropogenic scenarios to understand which forests are most likely to be affected.
However, vulnerability, taking into account the climate scenarios of the Intergovernmental Panel on Climate Change (IPCC) and the UN population forecasts expected at the end of the century, is far from homogeneous. The Democratic Republic of the Congo, the Atlantic Forest in Gabon and in the Southern Republic of the Congo, the forest margins, especially in Cameroon, are regions that are more sensitive than others to climate and demographic change.
For Maxime Réjou-Méchain, the effort is clear on the Democratic Republic of Congo (DRC): “The country is home to half of the tropical forests in Central Africa and combines both anthropogenic and climatic pressures. There is an exploding demographic. It is estimated that the population of Congo between 2000 and 2085 will be multiplied by seven. Potentially until 2085, there may not be much left in the Democratic Republic of Congo if nothing is done today, he says.
Slash-and-burn, the leading cause of deforestation
If industrial agriculture, mainly for export, develops, in particular with oil palm, cocoa, cassava, rubber or maize, “slash-and-burn agriculture, linked to the population explosion, remains the main cause of deforestation in Central Africa”, Maxime continues Réjou-Méchain. Slash-and-burn is an agricultural method that has been practiced for at least 2000 years and consists of clearing fireplaces (often in forests where the soil is richer), which is used for subsistence cultivation before it is left fallow. “With the demographic pressure, the fragility times are getting shorter and shorter and more and more areas are being used,” the researcher adds. He also claims that there are still alternative energy sources to replace coal, still from tropical forests to supply large cities like Kinshasa.
Prevent isolation of forest islands to preserve biodiversity
Do not fragment the forest, maintain the connection between protected areas for the movement of animal and plant species and to preserve biodiversity. Researchers insist on this important aspect. “We want to encourage the establishment of permanent contacts, thanks to preserved or reconstructed corridors, between the large forest areas that are considered the least vulnerable,” explains Sylvie Gourlet-Fleury, forest ecologist at CIRAD, in the Forests and Societies research unit. . This would make it possible to maintain the flow of genes between these different zones (especially thanks to the maintenance of the circulation of the fauna, which spreads seeds from a large part of the species present) and thus preserve the diversity. It is imperative to maintain these corridors, to recreate them by replanting natural forest species or to allow them to regenerate. ”
For Maxime Réjou-Méchain “a good impact of this study would be to see our maps of vulnerability and floristic composition for policy makers, researchers and foresters to decide on strategies that ensure a future for the tropical forests of Central Africa.” The researcher plans to transfer this work for certain political leaders in the region, which he considers to be “decision-making tools”.
Once the file is on the decision maker’s desk, the ball will be in their court. The stakes are high. Between 2010 and 2020, 1.5 to 2 million hectares of forest disappeared each year in Central and West Africa. “One of the concerns is that the forests in some regions of Central Africa, in Cameroon and in particular in the Congo, are suffering the same fate as in West Africa, where the dense moist tropical forests have almost disappeared,” warns Sylvie Gourlet. -Fleury.
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