It's sometimes a challenge for scientists to articulate just how extensively certain ecosystems in sensitive areas around the world are being threatened. There's nothing ambiguous about the term "extinction vortex," however.

That's what one of the world's most important forests — Brazil's Atlantic Forest — is now being called. It's difficult to fathom just how much this once-expansive rainforest has been transformed. Since colonization in the 16th century, the forest has been reduced from over 1.1 million square kilometers (420,000 square miles) to a measly 0.143 square kilometers (0.06 square miles). And there's no doubt as to the cause of this destruction: human activities, mostly from farming and logging.

Now a new assessment of the region's biodiversity has reached some equally startling results. More than half of the subtropical forest's local mammal species have been wiped out, reports Business Insider.

"These habitats are now often severely incomplete, restricted to insufficiently large forest remnants, and trapped in an open-ended extinction vortex. This collapse is unprecedented in both history and pre-history and can be directly attributed to human activity," said Carlos Peres, a biologist at the University of East Anglia and a lead author of the report.

A place transformed by humans

The study found that apex predators, like jaguars and pumas, as well as large-bodied herbivores like tapirs, were the most devastated. But when you're talking about ecological destruction this extensive, everything takes a hit.

To reach their conclusions, researchers compared inventories of large- and medium-sized mammals in the forest from the past 30 years. Baseline records came from those taken when the area was first colonized by Europeans in the 16th century. This was a region that left European naturalists in utter awe when it was first discovered, with its lushness and with the amount of creature diversity.

The health of the forest's mammals is seen as an important indicator because mammals are most instrumental in helping plants disperse their seeds, and also in regulating prey populations.

"The mammalian diversity of the once majestic Atlantic Forest has been largely reduced to a pale shadow of its former self," said Peres.

A Brazilian rainforest is now being called an 'extinction vortex'
Brazil's once-expansive Atlantic Forest has now almost completely disappeared.