Global terrestrial biodiversity hotspots are among the most ecologically important regions on Earth. These 36 regions, which occupy only 2.5% of the planet's land surface, support nearly half of all plant species and more than one-third of terrestrial vertebrates.

However, their current condition contrasts sharply with this ecological importance. Most hotspots have lost more than 85% of their original vegetation, and human land use pressures within these regions continue to intensify. With accelerating global land use changes, achieving zero net land degradation in these regions has become increasingly challenging.

In this context, a research team led by Prof. CHEN Yaning from the Xinjiang Institute of Ecology and Geography of the Chinese Academy of Sciences has assessed land-use changes in global terrestrial biodiversity hotspots within the framework of the United Nations' 2015 Land Degradation Neutrality (LDN) policy.

To quantify both historical land-use legacies and recent policy impacts, the researchers developed a Land Use Balance Approach (LUBA). Using this method, the researchers measured net land-use change across these hotspots from 1992 to 2022. They used the period from 2000 to 2015 as the pre-LDN baseline and the period from 2016 to 2022 as the monitoring period.

Their analysis revealed that land use has impacted approximately 9.4% of global biodiversity hotspots since 1992. Although restoration and revegetation efforts increased after 2015, they were insufficient to offset ongoing degradation. This resulted in a global land-use debt of 29.1 million hectares (about 0.9% of the total hotspot area), indicating that, globally, degradation continues to outweigh restoration.

Hotspots in Asia and the Americas accounted for most of the global land-use debt due to continued deforestation and agricultural expansion, while Africa showed a modest land-use credit. Importantly, the researchers identified a "vegetation greenness paradox," in which structural greening after LDN adoption masks declines in key ecosystem functions, such as carbon storage and habitat quality, in areas with significant land-use debt.

"Effective land restoration must go beyond land surface greening," said Prof. CHEN Yaning. "Reversing land-use debt will require locally tailored policies that emphasize functional recovery alongside visible greening to ensure that LDN efforts deliver effective ecological integrity in biodiversity hotspots."