May 11: World Endangered Species Day

Céline Arétin, culture, women's issues and environment correspondent, May 11, 2025

Main causes of species extinction

Habitat destruction remains the leading cause of biodiversity loss, with agricultural expansion alone accounting for 70% of tropical deforestation. Next comes biological overexploitation: industrial fishing, poaching, and unsustainable harvesting of wood or medicinal plants. The introduction of invasive alien species is a further factor in ecological disruption; lacking natural predators, these species compete with, prey on, or transmit new diseases to native wildlife. Add to this chemical and plastic pollution: bioaccumulation of heavy metals in food webs and 11 million tonnes of plastic dumped into the ocean every year. Finally, climate change is altering temperature, acidity, and the phenology (biological calendar) of ecosystems faster than species' genetic capacity to adapt.

Animals threatened with extinction

Of the 169,420 species assessed by the IUCN as of April 2026, 47,187 (28%) are classified as threatened. In Africa, the black rhinoceros population has fallen to around 2,000 animals due to poaching for horn, despite a slight rebound thanks to canine anti-poaching units. Even more critical, the Gulf of California harbor porpoise, the vaquita, numbers fewer than 10 individuals. In Asia, the Amur leopard survives with fewer than 120 adults in the temperate forests of the Russian Far East and China, isolated by clear-cutting. In Europe, the Oltenia blind mole-rat now occupies only two steppe grasslands in Romania, threatened by intensive irrigation.

So-called "keystone" species

A keystone species is an organism whose influence on ecosystem function is disproportionate to its abundance. For example, the gray wolves of Yellowstone National Park, reintroduced in 1995, restored the herbivore-vegetation balance: by controlling elk populations, they allowed willows to regenerate, benefiting beavers and, ultimately, aquatic biodiversity. Along the Pacific coast, the sea otter keeps sea urchin populations at a level compatible with kelp forests. In West Africa, forest elephants create clearings and disperse, through endozoochory, more than 70 tree species. Reef-building corals, calcium "engineers," provide habitat, protection and nursery grounds for 25% of marine fish; their mass bleaching therefore threatens the entire reef.