Human activity is fundamentally altering the distances that animals in the world need to travel to live, hunt and feed, according to a study that examined the impact on more than 160 species on six continents.
All activities changed the behavior of animals, but the study found that destructive activities, such as urbanization and logging, affected the movement of animals less than sporadic efforts, such as aircraft use, hunting and recreation.
In addition to having a profound impact on animals – how to reduce their ability to feed and reproduce – the changes “point to a global restructuring of the animal movement” that can have profound side effects, says the study published today in Nature Ecology and newspaper Evolution.
Dr. Tim Doherty, a wildlife ecologist at the University of Sydney, said it was already well known that humans affected animal movement, with thousands of studies tending to focus on a single species or activity, but the information was disparate and had not been synthesized.
Doherty personally read the abstracts of 12,000 research articles extracted from academic journals around the world, before joining colleagues to draw 208 relevant studies with sufficient useful data on how human activity altered the distances that 167 different species moved.
When human activities forced animals to move further, such as when animals ran away from hunters or had to cross roads or avoid skiers or campers, they moved on average 70% further in response.
“In Australia, the average person’s journey is about 16 km, so 70% is like traveling an extra 11 km,” said Doherty.
“If animals don’t move naturally, there is potential for wider impacts.”
The animals and impacts examined included:
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Lemurs of Madagascar expanding their living area by more than half in response to logging
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Opossums in Victoria, Australia, advanced 57% in areas destroyed by roads compared to large forests
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Sweden’s Moose moved 33 times faster in the hour after being bothered by cross-country skiers
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Texas turtles covered less distances in areas with cattle grazing
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Mountain lions in the USA moved more slowly if they heard human voices, which in turn increased the distances traveled by rodents in the same area
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Railway birds that do not fly in New Zealand that help disperse seeds covered about a third less in areas close to the camps
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The reindeer in Canada move faster in response to noise from oil exploration.
The research says: “Even a small change in movement can have major impacts on an individual and, when these costs accumulate across an entire population, reproductive rates and the viability of the population can be compromised.”
Tracking changes in movement was important because it showed how the animals’ behavior was changing as they fled humans, predators or traveled to find food, shelter or companions.
Some activities tend to shorten the distances traveled by animals, such as urbanization, which makes it easier to find food for some animals.
Doherty, who started the research while at Deakin University, told the Guardian: “We found about a third of the data we discovered reporting a change in movement of 50% or more.
“It tells us that we, as humans, have a very broad impact on animals, but that is not being addressed.”
Birds advanced an average of 27% in response to human disturbances, with mammals going 19% further and insects 38%.
For mammals, roads, agriculture and aircraft had the greatest effect on the distances covered, with pasture and hunting tending to extend the species’ range of life.
“Most of the Earth’s surface has been disturbed by humans, but there are some places that have not been and 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 that wild places were disappearing on a large scale, with an area the size of Mexico being converted into just 13 years of virtually intact landscapes to areas heavily modified by humans.
Professor Corey Bradshaw, director of the Global Ecology Laboratory 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 formed a “useful synopsis”.
“The fact that most species increase their movement in response to the disturbance gives an interesting clue about the mechanism of anthropic pressures beyond the obvious, such as invasive predators, habitat loss or direct exploitation.”
Bradshaw said the study also illustrated how difficult it is to predict how an animal’s home range might change after human activities begin.
He said a revealing aspect of the study was the discovery that disturbances caused by recreation and hunting caused species to move more than habitat loss or fragmentation.
“This then suggests that even the so-called ‘non-invasive’ human presence can be potentially harmful.”