Human activity fundamentally changes the distances the world’s animals need to live, hunt, and forage, according to a study examining the impact on more than 160 species on six continents.
All activities changed animal behavior, but the study found that destructive activities such as urbanization and logging affected animal movement less than sporadic efforts such as aircraft use, hunting, and recreation.
The changes not only have a profound impact on animals – such as reducing their ability to feed and reproduce – and “point to a global restructuring of animal movement” that could have profound implications, the study said. published today in Nature Ecology. and Evolution journal.
Dr. Tim Doherty, a wildlife ecologist at the University of Sydney, said it was already widely known that humans influenced animal movement, with thousands of studies tending to focus on a few species or activities, but the information was uneven and was not synthesized.
Doherty personally read the abstracts of 12,000 research articles from academic journals around the world, before working with his colleagues to retrieve 208 relevant studies with enough actionable data on how human activity had changed the distances traveled by 167 different species.
When human activities forced animals to move further, such as when animals fled hunters or had to bridge roads or avoid skiers or campers, they moved an average of 70% further in response.
“In Australia, the average person’s commute is about 16km, so 70% is like an extra 11km,” said Doherty.
“If animals don’t move naturally, there is a chance of wider consequences.”
The animals and effects studied included:
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Madagascar lemurs expanded their home ranges by more than half in response to logging
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Brushtailed possums in Victoria, Australia, traveled 57% further in areas interrupted by roads compared to large forests
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Elk in Sweden moved 33 times faster in the hour after being disturbed by cross-country skiers
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Texas tortoises traveled fewer distances in areas where livestock grazed
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Mountain lions in the US moved more slowly when they heard human voices, which in turn increased the distances rodents traveled in the same area
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New Zealand flying railbirds that help disperse seeds about a third less distance traveled in areas near campgrounds
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Reindeer in Canada move faster in response to noise from petroleum exploration.
The research says, “Even a small change in movement can have major consequences for an individual, and when these costs pile up across an entire population, reproductive rates and population viability can be compromised.”
Tracking movement changes was important because it showed how animals’ behavior was changed when they fled or traveled from humans or predators to find food, shelter, or partners.
Some activities tended to shorten distances traveled for animals, such as urbanization, which made food easier for some animals to find.
Doherty, who began the study while working at Deakin University, told the Guardian, “We found that about a third of the data we discovered reported a change in motion of 50% or more.
“That tells us that we as humans have a pretty big impact on animals, but these aren’t being addressed.”
Birds advanced 27% on average in response to human disturbances, with mammals farther 19% and insects 38%.
For mammals, roads, agriculture and airplanes had the greatest impact on distances traveled, with grazing and hunting tending to expand species’ habitat.
“Most of the Earth’s surface has been disturbed by humans, but there are places that have not and need to be protected,” said Doherty. “We need some places on Earth where animals can do their thing.”
Last year, a study found that wilderness areas were disappearing on a massive scale, converting an area the size of Mexico from virtually intact landscapes to areas greatly altered by humans in just 13 years.
Prof Corey Bradshaw, director of the Global Ecology Lab at Flinders University in South Australia, who was not involved in the latest research, said the study confirmed much of what was known, but it made a “useful summary”.
“That most species increase movement in response to disturbance provides an interesting hint as to the mechanism of anthropogenic pressures beyond the obvious, such as invasive predators, habitat loss, or direct exploitation.”
Bradshaw said the study also illustrated how difficult it was to predict how an animal’s habitat might change once human activities began.
He said a revealing aspect of the study was the finding that disturbance from recreation and hunting caused species to move more than habitat loss or fragmentation.
“It then suggests that even the so-called ‘non-invasive’ human presence could potentially be harmful.”