Human activity is fundamentally altering the distances the world’s animals need to move to live, hunt and forage, according to a study that examined the impact on more than 160 species across six continents.
All activities changed the behaviour of animals, but the study found destructive activities such as urbanisation and logging affected the movement of animals less than sporadic endeavours such as using aircraft, hunting and recreation.
As well as having a profound impact on the animals – like reducing their ability to feed and breed – the changes “point to a global restructuring of animal movement” that could have profound knock-on effects, says the study published today in the Nature Ecology and Evolution journal.
Dr Tim Doherty, a wildlife ecologist at the University of Sydney, said it was already well known that humans affected the movement of animals, with thousands of studies tending to focus on single species or activities, but the information was disparate and hadn’t been synthesised.
Doherty personally read the summaries of 12,000 research articles extracted from academic journals around the world, before joining colleagues to pull out 208 relevant studies with enough useful data on how human activity had altered the distances that 167 different species moved.
When human activities forced animals to move further, such as when animals fled hunters or had to negotiate roads or avoid skiers or campers, they moved an average of 70% further in response.
“In Australia, an average person’s commute is about 16km, so 70% is like travelling an extra 11 km,” Doherty said.
“If animals aren’t moving around in a natural way, then there’s potential for broader impacts.”
The animals and impacts examined included:
Madagascan lemurs extending their home range by more than half in response to logging
Brushtailed possums in Victoria, Australia, moved 57% further in areas broken up with roads compared with large forests
Moose in Sweden moved 33 times faster in the hour after being disturbed by cross-country skiers
Texas tortoises covered less distances in areas with livestock grazing
Mountain lions in the US moved more slowly if they heard human voices, which in turn increased the distances moved by rodents in the same area
Flightless rail birds in New Zealand that help disperse seeds covered about a third less distance in areas near campgrounds
Reindeer in Canada move faster in response to noise from petroleum exploration.
The research says: “Even a small change in movement can have big impacts on an individual, and when these costs accumulate across an entire population, reproductive rates and population viability may be compromised.”
Tracking changes in movement was important, because that showed how animals’ behaviour was being altered as they fled humans, predators or travelled to find food, shelter or mates.
Some activities tended to shorten the distances travelled for animals, such as urbanisation, which makes food easier to find for some animals.
Doherty, who started the research while at Deakin University, told the Guardian: “We found about a third of the data we uncovered reported a change in movement of 50% or more.
“That tells us that we as humans have a pretty wide impact on animals, but these are going unaddressed.”
Birds moved an average 27% further in response to human disturbances, with mammals going 19% further and bugs 38%.
For mammals, roads, agriculture and aircraft had the greatest affect on distances travelled, with grazing and hunting tending to extend the home range of species.
“Most of the earth’s surface has been disturbed by humans, but there are some places that haven’t and they should be protected,” said Doherty. “We need some places on earth where animals can be left to do their thing.”
Last year a study found wilderness places were disappearing on a massive scale, with an area the size of Mexico being converted in just 13 years from virtually intact landscapes to areas heavily modified by humans.
Prof Corey Bradshaw, director of the Global Ecology Lab at Flinders University in South Australia, and who was not involved in the latest research, said the study confirmed much of what was known, but it formed a “useful synopsis”.
“That most species increase movement in response to disturbance gives an interesting hint regarding the mechanism of anthropogenic pressures beyond the obvious, such as invasive predators, habitat loss or direct exploitation.”
Bradshaw said the study also illustrated how hard it was to predict how an animal’s home range could change once human activities started.
He said one revealing aspect of the study was a finding that disturbance from recreation and hunting made species move more than habitat loss or fragmentation.
“It suggests then that even so-called ‘non-invasive’ human presence can be potentially detrimental.”