The world’s population of mammals is in constant decline, and at least one fourth of them are on the verge of extinction, the International Union for Conservation of Nature (IUCN) revealed. The organization explained during its World Conservation Congress held in Barcelona, Spain that at least 1,141 of the 5,487 species of mammals have entered an extinction crisis.

IUCN’s Red List of Threatened Species made public at the beginning of this week drew alarm signals that almost one in four mammal species are at risk of disappearing forever. The worst part is that people are responsible for the mammals’ loss and degradation of habitat, which affects 40 percent of the species worldwide.

The situation has worsened in Central and South Africa, West, East and Central Africa, Madagascar, and in South and Southeast Asia, where over-harvesting is slowly wiping out the mammals. And while IUCN warned one in four mammals is at risk of extinction, the situation could be much worse.

“The reality is that the number of threatened mammals could be as high as 36 percent,” Jan Schipper of Conservation International, who will also publish an article on the subject in the journal Nature, pointed out. This huge difference could be explained through an addition of 836 mammals that have been listed as Data Deficient.

This suggests that in the future, research, doubled by conservation actions, should become a priority not only for a more efficient evaluation of endangered or poorly known species, but also as a way of investigating means of recovering threatened species and populations, Schipper explained.

Further investigation and conservation is especially important, researchers pointed out, simply because mammal populations on the verge of extinction can be revived through conservation measures. To support that stands the 5 percent of currently threatened animals that are showing signs of recovery in their natural habitat.

The Red List shows 188 species of mammals in the Critically Endangered category, including the Iberian Lynx, whose current population counts 84-143 adults. IUCN conservationists explained that the steep decline continued due to a shortage of its primary prey, the European Rabbit, whose population in turn declined due to habitat loss and over-hunting.

The Père David’s Deer lives in China and had been listed as Extinct in the Wild. The deer is now known to only live in captivity. However, the captive and semi-captive populations appear to have increased in the past years, and conservationists hope to soon see the wild populations re-established.

But that’s a fortunate case, IUCN explained. As many as 29 species have been flagged as Critically Endangered Possibly Extinct, and for these species, it is probably too late to hope something can be done. Other 450 species of mammals are considered Endangered, including the Tasmanian Devil, whose population declined by over 60 percent in the last decade due to an infectious facial cancer.

Another mammal, the Fishing Cat, is no longer considered Vulnerable, but Endangered, due to a massive habitat loss in wetlands, IUCN said. Another feline, the Caspian Cat, has sufferer an incredible 90 percent loss in population in the last century due to over-hunting and habitat degradation.

“Within our lifetime hundreds of species could be lost as a result of our own actions, a frightening sign of what is happening to the ecosystems where they live,” Julia Marton- Lefèvre, IUCN Director General, explained. “We must now set clear targets for the future to reverse this trend to ensure that our enduring legacy is not to wipe out many of our closest relatives.”