Expanding human activity has been eating away at Earth’s forests and the disappearing woodlands are causing certain species of animals to vanish along with them, according to a new study.

The findings concluded 85 percent of animals living in forests are affected by fragmentation, which impacts all species and ecosystems, but each animal group is impacted differently.

“Tropical forests and the animals they harbor are being lost at alarming rates, but in order to protect them, we need to know exactly how fragmentation of the land is impacting on the animals that live there,” study co-author and Newcastle University scientist Marion Pfeifer said.

Currently, half of the world’s woodland habitats fall within 1,600 feet of a forest edge due to being broken up by roads under construction and other expansion-related human activity. The researchers say these edges contribute to global declines in biodiversity and the functions of ecosystems.

In order to study the impacts, the scientists looked at changes to the land surrounding the forests and mapped the numbers of 1,673 species of mammals, birds, reptiles and amphibians in 22 tropical regions of Asia, Africa and America.

They found species that were living in the center of forests and were more likely to be considered threatened by the International Union for Conservation of Nature (IUCN) reached their highest numbers more than 650 to 1,300 feet from the edges of the forest. This suggested that they depend on large, rolling forests in order to flourish.

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However, in no way do the researchers consider this good news. The study also finds that there are 46 percent fewer trees on Earth than there were before humans started the lengthy, but recently accelerating, process of deforestation.

“We can now say that there’s less trees than at any point in human civilization,” says Thomas Crowther, a postdoctoral researcher at the Yale School of Forestry and Environmental Studies who is the lead author on the research. “Since the spread of human influence, we’ve reduced the number almost by half, which is an astronomical thing.”

In fact, the paper estimates that humans and other causes, such as wildfires and pest outbreaks, are responsible for the loss of 15.3 billion trees each year — although the authors said at a press conference that perhaps 5 billion of those may grow back each year, so the net loss is more like 10 billion annually.

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Deforestation has a huge effect on climate change. Activities like slash-and-burn agriculture account for nearly 20 percent of greenhouse gas emissions, according to the UN. Trees, of course, also play a key role in slowing climate change by pulling CO2 out of the atmosphere.

Historically, deforestation has been an especially vexing problem for environmentalists, raising the concern of climate hawks and conservationists alike. This week’s agreement straightens out some key details of an initiative — called Reducing Emissions From Deforestation and Forest Degradation, or REDD+ — that negotiators hope will provide developing, forest-rich countries with incentives to slow and eventually halt logging of forested land.

The details of REDD+ had been held up for years as negotiators tried to deal with a number of thorny issues, including how to work with indigenous communities to make sure they retain the rights to their land, understand the program, and don’t lose their economic livelihoods through it.

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The new study found that fragmented habitats lose an average of half of their plant and animal species within twenty years, and that some continue to lose species for thirty years or more. In all of the cases examined, the worst losses occurred in the smallest habitat patches and closest to a habitat edge. The study also demonstrates, using a high-resolution map of global tree cover, that more than seventy per cent of the world’s forest now lies within one kilometer of such an edge.

The consequences of that forest loss, the researchers discovered, may be more profound than we’ve previously realized. Fragmented habitats, they found, can reduce plant and animal diversity by anywhere from 13 to 75 percent. Fragmented forests experienced a decline in their core ecosystem functions, as well: they were less able to sequester carbon dioxide, an important element of mitigating climate change, and displayed reduced productivity and pollination.

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