This collapse of biodiversity is unprecedented in both history and pre-history and can be directly attributed to human activity.
The Atlantic Forest, or what’s left of it, sprawls along Brazil’s east coast and reaches inland towards the Amazon. It’s one of the world’s most ecologically diverse regions that is home to numerous species of rare and endangered animals: birds, mammals, reptiles and amphibians.
Jaguars prowl in the woods, golden lion tamarins shimmy up on trees, woolly spider monkeys cavort in the foliage, maned three-toed sloths hang from branches and red-tailed parrots add dashes of color to their surroundings. The forest is also home to some 20,000 species of plants. Within just a single hectare as many as 450 species of tree have been identified.
Yet since Europeans began colonizing the area in the 16th century, Brazil’s Atlantic Forest, which is second only to the Amazon’s forest in their grandeur, has been slashed down from more than 1.1 million square kilometers to just 0.143 square kilometers. And along with the loss of trees has come a drastic decline in the numbers of most resident mammalian species, scientists have found.
More than half of the local assemblages of co-existing species of medium-sized and large mammals have been driven into extinction in a massive loss of biodiversity. The culprits have been humans.
The scientists, who published their findings in a study (aptly titled “Wish you were here: How defaunated is the Atlantic Forest biome of its medium- to large-bodied mammal fauna?”), compared inventories of large and medium-sized mammals from the past three decades. Their baseline data derived from as far back in time as the early colonial period in Brazil’s history some 500 years ago.
The hardest-hit species, they concluded, have included apex predators such as jaguars and pumas, but large herbivores like tapirs have also fallen on hard times. These iconic mammals have been hunted mercilessly while they have also been losing most of their natural habitats to logging and agricultural settlements.
“These habitats are now often severely incomplete, restricted to insufficiently large forest remnants, and trapped in an open-ended extinction vortex,” said Carlos Peres, a biologist at the University of East Anglia who was a lead author on the study. “This collapse is unprecedented in both history and pre-history and can be directly attributed to human activity.”
In fact, laments Juliano Bogoni, a postdoctoral researcher at the University of São Paulo, who also participated in the study, “[t]he mammalian diversity of the once majestic Atlantic Forest has been largely reduced to a pale shadow of its former self.”
Nor is Brazil’s Atlantic Forest alone in the dramatic loss of its wildlife. Across the tropics from the Amazon to the Mekong, forests have been felled extensively with their populations of mammals hunted and poached endlessly. “Mammals represent the largest-bodied elements of the world’s surviving megafauna and provide several key ecosystems services, yet their populations are often under steep decline throughout the tropics,” the researchers note.