The distribution of living species on Earth follows a surprisingly simple logic. An international study reveals that biodiversity systematically organizes itself around rich central zones before gradually declining.
This discovery, published in
Nature Ecology & Evolution, is based on the analysis of over 30,000 species, from amphibians to trees and marine rays. Researchers have identified a recurring pattern: regardless of the ecosystem, the majority of species concentrate in restricted geographic cores.
A concentric circle structure
Each biogeographic region has a core where diversity reaches its peak. These central zones, often stable and resource-rich, host endemic and generalist species. Moving away from this core, the number of species decreases, giving way to more hostile or fragmented environments.
Researchers have mapped seven types of zones, from dense cores to transitional margins. This hierarchy is found equally in tropical forests and coral reefs. Species adapted to local conditions dominate the cores, while generalists colonize the peripheries.
The study confirms the key role of environmental filtering. Only organisms tolerant of specific constraints—heat, drought, salinity—persist in each zone. This mechanism explains why biodiversity gradually declines from the central cores.
Implications for conservation
Protecting biodiverse cores is crucial, as they ensure the survival of the majority of species. These zones, sometimes tiny, constitute irreplaceable reservoirs. The authors emphasize that their preservation must be a priority, even if the margins host rare species adapted to extreme niches.
This universal rule also provides a tool to anticipate the effects of climate change. By identifying the most resilient cores, scientists can better target conservation efforts. Current models thus gain in accuracy.
Finally, the study challenges the idea of disordered biodiversity. The same environmental forces seem to structure life everywhere on the planet. This unexpected regularity opens new avenues for understanding ecosystem evolution.
Article author: Cédric DEPOND