Six of Africa’s 11 vulture species are now at risk of extinction, according to a new report released Thursday by a top conservation group. The large scavenger birds are vanishing, and it could impact human health and livestock on the world’s poorest continent.

The assessment was conducted by conservation group BirdLife International for the International Union for Conservation of Nature’s “Red List of Threatened Species,” which is deemed the most authoritative estimate of wild bird and animal populations. The group found that the main causes of the drop in African vulture populations are threefold. Primarily, the big birds have fallen victim to indiscriminate poisonings by alleged poachers. At least 62 wild elephants in western Zimbabwe have died from cyanide poisoning in the past month, and the lethal chemical has killed vultures and other animals who feed off the carcasses.

Vulture body parts are popular in traditional medicine, which is thought to be widespread in West Africa as well as southern Africa. A recent scientific paper found that 29 percent of the vulture deaths recorded continentwide could be attributed to this practice.

African vultures are also deliberately targeted by poachers, who kill the birds to stop them from circling the carcasses of illegally slain animals and thus alerting authorities. Africa’s elephant and rhino populations are being increasingly poached for their ivory tusks and horns to meet growing demand in the Asian markets.

“As well as robbing the African skies of one of their most iconic and spectacular groups of birds, the rapid decline of the continent’s vultures has profound consequences for its people – as vultures help stop the spread of diseases by cleaning up rotting carcasses,” said Julius Arinaitwe, BirdLife International’s Africa program director.

Vultures play a crucial role in maintaining healthy ecosystems, and their decline can have a serious effect on other species, including humans, since populations of other scavengers like rats and jackals could increase as a result.

"Vultures are important. They come in, they clean up and they leave," Ross Wanless of BirdLife South Africa told Reuters. "Other scavengers like rats and jackals will eat a carcass and then will go after livestock or become a pest to humans. And if vultures are removed, their numbers can increase."