Nature’s “clean-up crew” is vanishing – and it’s bad news for human health | More than a third of large animals that feast on dead animals are struggling to survive, their downfall could present a serious risk to human life, with an uptick in zoonotic disease spread as a result.

From the article: Stanford University researchers analyzed the data on 1,376 vertebrate scavenger species, and found that 36% are now considered threatened or declining. And the decline is disproportionately higher for apex scavengers – larger animals that primarily eat carrion, or decaying animal remains.

This means that without those efficient high-food-chain scavengers that act as the animal kingdom’s clean-up crew, we’re likely to see a rise in the type and frequency of zoonotic diseases that cross over to humans.

“The evidence we found is very clear,” said senior author Rodolfo Dirzo, a professor of biology at Stanford’s School of Humanities and Sciences. “Scavengers are in decline, but it’s not homogeneous. It is particularly the large and specialized ones. At the same time, this allows space for the smaller scavengers, which are problematic because they are themselves sources of zoonotic diseases. They are also not capable of compensating as they cannot consume as much carrion.”

The “specialized” scavengers are known as obligate scavengers, like vultures, which have a diet primarily consisting of carrion (while facultative scavengers, like some corvids and gulls, supplement their foraging with it). Without the larger obligate scavengers around, smaller animals like rats and feral dogs thrive – and they’re more convenient vectors for zoonotic disease transmission.

What’s more, how we view scavengers – as dirty, diseased, ugly and a pest around livestock – has played a big part in their downfall. Vulture populations are being decimated through poisoning to keep birds from farms and to prevent alerting authorities to illegal poaching activities.

Much like how the eradication of wolves in Yellowstone National Park saw mule deer numbers explode, which then stripped vegetation and saw the loss of many species including beavers, knocking out apex scavengers upsets a balanced ecosystem. (The reintroduction of wolves has now seen beavers return to the national park.) Most biodiversity studies focus on categories of animals such as birds, or the decline of a specific species. Stanford biologists stress that rapid decrease in a “functional group” – aka large scavenging species – could be even more detrimental.

But all the hunters say we need to kill the deer because there is so many deer. If we dont kill them first, then nature might play its part!! We can’t have that apperently.