Humans are in the process of planting the world's largest animals right over the brink of extinction, and the main driving force is our unsatisfied appetite for meat.
It's a tough warning, and it comes from the first analysis to look at how people have affected world's "megafauna".
Bringing together over 300 species of unusually large vertebrates – including polar bears, blue whales, hippos, saltwater crocodiles, ostriches – the findings illustrate a woeful future for our shared environment.
All told, at least 200 megafauna species are dwindling in number, and more than 150 are pushed under the shadow of extinction.
"Our results suggest that we are in the process of eating megafauna to extinction," says lead author William Ripple, an ecology expert at the Oregon State University.
"In the future, 70 percent will experience further population decline and 60 percent of the species could become extinct or very rare."
If people choose to continue on this path, the loss could jeopardize the planet as we know it. Biodiversity is essentially the variety of life that holds up all the ecosystems in the world, but after millennia of unchecked actions, people are now facing environmental crisis.
Imagine it like a game of Jenga. The more pieces we remove, the more unstable the entire system becomes, only increasing the threat of collapse.
"Maintaining biodiversity is crucial for the ecosystem structure and function, but it is compromised by population declines and geographic range losses that have left roughly one fifth of the world's species of vertebrate threatened with extinction," the authors write.
The problem has been building up for a while now.
Ever since the late Pleistocene, over a hundred thousand years ago, humans have wreaked havoc on the world's biodiversity, sending large vertebrates after the large vertebrate into the abyss of extinction, at a rate not seen in the previous 65 million years.
But in the past 500 years or so, things have started to speed up, and it's got scientists worrying. Today, every single class of megafauna is most at risk from human hunting.
In fact, of all the threatened megafauna species, 98 percent were at risk from "direct harvesting for human consumption of meat or body parts."
Not only do these large creatures hold more meat and possibly more glory, they are also less abundant than smaller species and they reproduce much slower.
This leaves large vertebrates for exceptional risk of extinction, not just from hunting, but also from the degradation of their habit.
"Megafauna species are more threatened and have a higher percentage of declining populations than all the rest of the vertebrate species together," explains Ripple.
So even though megafauna has a small, collective biomass, their ongoing loss is already changing the structure and function of our ecosystems, in ways that we are still discovering.
In the past 250 years, we know that nine megafauna species have either gone extinct completely, or gone extinct in the wild. The animals with the greatest threat are those on the land.
This is no doubt because people can reach them easier. For example, in 2012, two species of giant tortoise disappeared, and two species of deer.
Marine creatures have it marginally better. Only 27 percent of the species are assessed as threatened, but there are also more than two dozen that we just do not know enough about to say.
Bony fish, like sharks, skates and rays are at the top of the list, more at risk than any other marine group.
Yet in the end, it was those large creatures that frequent both the land and the sea that saw the worst outcomes. Of all the mega amphibians, only one species remains on Earth.
Weighing in at 40 kilograms and stretching up to 1.8 meters, the Chinese Giant Salamander (Andrias davidianus) is sometimes called a living fossil, one of the few survivors in a family that dates back to 170 million years.
Considered a delicacy in Asia, it is now critically endangered and scientists say it is only a matter of time before it also disappears.
Afraid that more creatures are headed in the same way, the authors urge that "our heightened abilities as hunters" be matched by "the sober ability to consider, criticize, and adjust our behaviors."
Otherwise, we may end up eating the last of our planet's megafauna.
"Preserving the remaining megafauna will be difficult and complicated," says Ripple.
"If we do not consider, criticize and adjust our behaviors, our increased abilities as hunters can lead us to consume much of the last of Earth's megafauna. "
This study was published in Conservation Letters.