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A study published in the journal Science shows that naturally recovering tropical forests can regain up to 80% of their soil fertility within 20 years.
Good news for the protection of ecosystems. A recent study published in the prestigious journal Science conducted in Côte d’Ivoire by 80 scientists from around the world, including three Ivorian researchers and two scientists from CIRAD (the French Agricultural Research Centre for International Development), shows that tropical forests that revitalise without human intervention can recover up to 80% of their soil fertility, structure and plant diversity in just 20 years.
The survey goes even further, arguing that natural restoration of tropical forests is the optimal choice to allow abandoned farmland to return to its initial state, before the clearing of primary forest. These areas, considered secondary forests, already cover thousands of hectares across Africa, contributing to the overall restoration of ecosystems, protection of biodiversity, improvement of soil and water quality, and carbon sequestration.
A revival with conditions
This unexpected discovery does not call into question the critical need to halt deforestation. Indeed, the results of the study in Côte d’Ivoire concern land that has not been subjected to intensive agriculture. In this case, seed banks are still present in the soil, allowing flora to grow quickly after the return of a plot to its wild state. The situation is much more complex for soils that have been rendered almost sterile by excessive ploughing and chemical inputs.
In addition, the warm and humid tropical climate is favourable to plant growth. In other, drier or colder regions of the world, the conditions for natural regeneration are not so easily met. Furthermore, while soils can recover quickly, animal diversity can take up to 60 years to return to its pre-clearing state. The maintenance and protection of primary forests therefore remains an important environmental objective.
Nevertheless, the study published in Science provides a new perspective on future mass reforestation campaigns, focusing on areas hardest hit by ecosystem and soil degradation. This passive restoration could be accompanied by other techniques such as assisted natural regeneration, agroforestry and forest plantations.