Land purification for agriculture, especially cattle grazing, is one of the major causes of habitat loss and declining animals worldwide.
But according to new research, our taste for meat has a much more direct impact on the world's largest animals.
Megafauna – big animals like elephants, gorillas and even Chinese giant salamanders, are under strong pressure from hunting.
Research published in Conservation Letters today says that direct hunting of the world's largest human food for meat and body parts is the single largest killer of these animals, and more than 150 species are threatened as a result.
While the habitat course certainly affects many smaller species, hunters seek larger animals because they provide more meat per year. Kill, according to co-author Matthew Hayward of the University of Newcastle.
"There are about 150 species that are threatened and 200 that fall and it looks like direct human hunting, which is basically for food, is the main reason for killing the big animals," said Professor Hayward.
Animals like elephants, gorillas and the Somali ostrich are targeted at Africa, which is a hotspot for illegal bushmeat, according to Dr. Hayward.
"[But] a lot of it is quite discriminatory. A lot of [developing]-world hunting activities are wire snares that tend to get a leg, and then they go back and kill the animal, "he said.
"So that leads to how we rectify this. It's easy to just say that we want to improve the law, but many of these sites already have a rather strict law – these are illegal activities going on.
"It's really about poverty reduction and education, I think it will improve the situation for some of these species."
Habitat loss still a bigger fish to roast
The researchers categorized megafauna as mammals, redfish and cartilage fish (sharks and rays) over 100 kg, and amphibians, birds and reptiles over 40 kg.
They then took conservation status and threats for each from the International Union for Conservation of Nature (IUCN) data.
IUCN is widely regarded as the global authority on the status of the natural world and provides a periodically updated "red list" documenting the changed conservation status of animals and plant species.
The researchers identified a total of 362 live megafauna species that fell into their defined categories, and there were enough data to analyze 292 of them.
Of these 292 animals, 70 percent decreased in number, and 59 percent threatened with extinction, with hunting being the biggest threat for each category.
But hunting is not only done for shrubs. Commercial operators targeting creatures such as bluefin tuna are also guilty, according to James Watson of the University of Queensland.
"When talking about fish, it's industrial, it's nations that go shopping," said Professor Watson.
And while hunting can be a visible pressure on large animals, other activities are far more insidious, he said
"Let's be clear here, stopping exploitation is difficult but achievable, but the destruction of habitat is worse because habitat destruction is irreversible," says Professor Watson.
"We need to be cautious about focusing on just those numbers, even though the numbers are alarming.
"We need to keep an eye on the bigger game that stops the conversion of the Amazon forest, clearing the savannahs to agriculture, bottom trawling in the sea. There are bigger threats."
Real numbers probably higher for endangered species
Road construction is also an insidious threat.
In Sumatra, legal and illegal routes to log and infrastructure projects are pushed through the Leuser ecosystem – the last place on earth where orangutans, elephants, tigers, rhinoceros, and sun bears still exist.
Research has shown that hunting and poaching are facilitated and concentrated around these roads.
And roads also act as invasion corridors for game pests, Professor Watson said.
"In Australia, it's one of the reasons we worry a lot about fracking. [The wells] does not look like a big threat because they are a small hole in the ground, but when you see the roads coming in, you see other threats coming in like invasive species and changing fire regimes, "he said.
Australian species on the list of falling megafauna include dugong, green turtle, plain tuna and Australian sea lion.
Other animals on the list include whale shark, pygmy hippopotamus, North Atlantic right whale and tiger.
However, there were 70 species that were excluded from analysis due to lack of data.
It is likely that the inclusion of these species would push the total number of falling megafauna, according to dr. Hayward.
"It can be much worse than what we are talking about here. So we need more research to look at the status of some of these cryptic species that we don't know much about," he said.