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Land use, climate increasingly restrict wildlife home ranges
Throughout the world, the average wildlife species has lost 18% of its natural range due to land use and climate change, researchers found. About 16% of species worldwide have lost more than half of their historical range, and that number may go up to 26% over the next century.
“We are aware that at this point in time, about 40% of the Earth’s ice-free land is covered with agricultural and urban areas,” said Robert Beyer, a Research Associate at Cambridge University and lead author of the study published in Nature Communications. The magnitude of land conversion in recent decades — even the past few centuries — likely had a strong impact on the ranges of the world’s species, he said.
Beyer and his colleagues decided to look at range size because it is a strong predictor of a species’ vulnerability to extinction. Species that already have small ranges can be even more vulnerable.
The researchers had access to home range data for 16,919 mammal, amphibian and bird species, and land use and climate reconstructions dating back to 1700. “It’s quite amazing. Literally every single mammal, amphibian and bird has spatial data on where the species are distributed today,” Beyer said. He and his colleagues overlaid this data with reconstructions of past and predictions of future land use changes and climate.
The researchers found that on average, the species they studied lost 18% of their range compared to the range they would have had without human encroachment. That includes Bengal tigers (Panthera tigris tigris) which have lost 20% of their home range; jaguars (Panthera onca), which have lost 21%; and red deer (Cervus elaphus), which have lost 22%.
For many species, though, the situation is much more severe. Sixteen percent of the species the studied lost about half of their natural home range, including the black rhinoceros (Diceros bicornis), which has lost 53%. In another 80 years, as many as 26% may see their ranges cut by more than half, Beyer said. “That’s the most alarming finding,” he said.
The team found tropical areas are seeing the largest impacts of land use change as rainforests and other natural areas are increasingly being cleared for large-scale agriculture, like palm oil plantations. This is a concern especially because these areas usually have high biodiversity, and many species there already have small home ranges.
Overall, Beyer said, land use change is having a bigger impact than climate change, because its effects on wildlife are often immediate. “But climate change is increasingly a strong driver,” he said. “The main finding here was, the more emissions we have, the more warming we have and the worse it is for species, on average.”
Beyer said, things can be done to minimize areas needed for agricultural production and increase maximum yield in productive areas. More people shifting to more vegetarian diets would also help, he said.
Beyer plans to continue the research by looking even further back — to the very beginning of agriculture 12,000 years ago — to see how early land use changes affected wildlife.