It's hard to deny that humanity has played a pretty big role in changing nature for the worse. That's why many environmental groups have advocated showcasing the world's natural grandeur, reminding everyday citizens what is worth protecting. The bad news, however, is that this so-called 'eco-tourism' may cause its own problems for Mother Earth.

That's at least according to a report recently publisher in the journal Trends in Ecology & Evolution, which details how most interaction between animals and nature-friendly tourists may actually tip the delicate balance between predator and prey.

"Recent data showed that protected areas around the globe receive 8 billion visitors per year; that's like each human on Earth visited a protected area once a year, and then some," Daniel Blumstein, a researcher with the University of California, explained in a recent statement. "This massive amount of nature-based and eco-tourism can be added to the long list of drivers of human-induced rapid environmental change."

Eco-tourism is clearly a booming business, but it's often marked off as something that helps nature. Not only do activates like bison-watching in Yellowstone National Park or snorkeling off the Australian coast help people better understand why conservationists do their good work, but the tourism also often helps fund continued protections. (Scroll to read on...)

The United Nations, for instance, has even started a migratory bird-watching campaign called Project Destination Flyaways. A joint project with the Convention on the Conservation of Migratory Species of Wild Animals (CMS) and the African-Eurasian Migratory Waterbird Agreement (AEWA), the project will reportedly be self-sustaining, establishing new and protected rest-stops for declining migratory species while simultaneously using those stops as tourism posts for enthusiastic (and paying) birdwatchers.

"The end result hopefully will be a classic win-win situation -- good for the birds' habitats and the birds themselves and advantageous also for the tourists, the tour operators and local communities," Bert Lenten, the Executive Secretary of the AEWA said in a statement.

Unfortunately, Blumstein and his colleagues are finding that there are some unforeseen consequences to these 'nature-friendly' tourism projects.

"When animals interact in 'benign' ways with humans, they may let down their guard," Blumstein said.

According to the report, regular exposure to human tourists can often make animals more bold than they would be in a humanless world. This may be because a human presence makes local predators cautious. However, if new genrations of prey learns to be bold around apex predators like humans, they may mistakenly act equally bold with real threats. (Scroll to read on...)

"Then they will suffer higher mortality when they encounter real predators," Blumstein explained.

Animal behavior experts call this phenomenon 'habitualization,' and it is already rampant among animals like pigeons, squirrels, and even fish. The difference with these creatures, however, is that they live alongside humans year-round, using us like a ward against predation.

However, eco-tourism is often seasonal. While vervet monkeys, for instance, have fewer run-ins with leopards when humans are in their jungles, they wind up having to break lazy habits fast when tours end.

"We know that humans are able to drive rapid phenotypic change in other species," the researchers wrote. "If individuals selectively habituate to humans -- particularly tourists -- and if invasive tourism practices enhance this habituation, we might be selecting for or creating traits or syndromes that have unintended consequences, such as increased predation risk."

So what's to be done? Blumstein and his colleagues stress that the more we know, the better.

Experts determined last year, for instance, that Antarctic eco-tourism risks spreading disease to penguins. As a result, actions have been taken to prevent potential exposure.

It will "now be essential," Blumstein said, "to develop a more comprehensive understanding of how different species and species in different situations respond to human visitation and under what precise conditions human exposure might put them at risk."

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