Tigers Still Have Enough Habitat to Bounce Back

When the 20th century began, about 100,000 wild tigers still roamed across wooded swaths of Asia. Fewer than 3,500 of the iconic cats exist today, living in fragments of forest that only add up to about 7 percent of the species' historic range.

Tigers may never regain their former glory, but that doesn't mean they're doomed. In fact, a new study suggests Earth still has enough natural tiger habitat for the iconic cats to double — or even triple — their wild population within the next six years.

Such a big rebound could help tigers claw back from the brink of extinction, so this is obviously good news. But there is a caveat: Wild tigers can only recover if humans stop degrading and disconnecting their habitats. Not only do tigers rely on large tracts of forest to survive, but they need those tracts to be linked. That's partly for genetic diversity and access to prey, but also to prevent a more direct danger.

"Male tigers can't stay in the home range of their fathers, or they will be killed," says study co-author Eric Dinerstein, director of biodiversity and wildlife solutions at RESOLVE. "So having forest corridors connecting reserves is vital."

Room to roam

The long-term decline of wild tigers spurred an urgent meeting of global leaders in 2010, the Year of the Tiger in the Chinese zodiac. Held in St. Petersburg, Russia, the summit led to an international goal of doubling wild tiger numbers by the next Year of the Tiger in 2022 — a target dubbed "Tx2." And according to the new study, published in the journal Science Advances, that goal is still well within reach.

Under the right conditions, tiger populations can bounce back surprisingly quickly, the study's authors note. In Nepal and India, the species has seen respective increases of 61 and 31 percent — a resurgence attributed partly to reduced poaching, but also to a network of wildlife corridors known as the Terai Arc Landscape.

The researchers used medium- and high-resolution satellite imagery to assess the global decline of tiger habitat from 2000 to 2014, the first time that's been done across all tiger habitats. "We've tried to do this kind of study twice before," Dinerstein says, but those efforts were limited by technology of the time. Thanks to modern conveniences like Google Earth Engine and cloud computing, however, the once-daunting task turned into a few days of data processing.

Covering 76 landscapes across the 13 countries where wild tigers still exist, the study found forest loss was not as severe as expected, with less than 8 percent of forested area in those landscapes having disappeared since 2000.

"There is enough habitat available to allow not only a doubling, but a tripling of the tiger population if we simply do the right things," Dinerstein tells MNN. "We would've expected much more clearing and conversion in the habitat than we saw. In fact, of the 76 landscapes, 29 are considered absolutely crucial to achieve the doubling of the population. And in 20 of those 29 landscapes, we saw virtually no change at all in the amount of habitat. Which means that over 90 percent of the habitat conversion occurred in just nine landscapes, but 20 others were mostly unchanged."

This map shows loss of forest habitat in Sumatra's Bukit Tigapuluh ecosystem from 2001 to 2014. (Image: RESOLVE)

Earning stripes

This is rare good news for tigers, but the study also highlights how fragile the species' survival still is. Deforestation since 2000 has erased habitat that could have held 400 adult tigers, the researchers estimate — about 11 percent of Earth's wild population. The worst forest loss was in parts of Malaysia and Indonesia with heavy palm-oil development, like Sumatra's Bukit Tigapuluh ecosystem, where 67 percent forest loss since 2001 wiped out habitat that could have supported 51 tigers. In Indonesia overall, an area five times the size of New York City has been allocated for oil palms.

Yet tigers are capable of co-existing with oil-palm plantations and other agricultural endeavors, Dinerstein points out, as long as the land is managed the right way.

"There is enough degraded land in those countries that you could shift any expansion in oil palm or paper production to degraded lands, with some soil amendment, without cutting down any further tiger habitat," he says. "And sometimes tigers will even hunt in the plantations, if they're not huge monocultures. Wild boar might come in to eat the palm oil nuts, and the tigers will hunt them there."

For the most part, however, wildlife does not thrive in areas with extensive oil-palm plantations, Dinerstein adds. And given the additional pressure tigers face from poaching and shrinking prey populations, that's why it's so important to halt habitat loss before it's too late. The new study helps us visualize and quantify the problem, and it might even help us enforce habitat protections more efficiently.

"The reason this study is revolutionary is the scale of information we have. A single pixel, the finest resolution used in this scale, is 30 meters on each side," Dinerstein says. "If there's a change of even one pixel in tiger habitat, a park manager could get an alert that says 'something is going on there; you should check it out.' We'll have 30-meter-resolution alerts available weekly. It's not real-time, but near real-time."

To see the data for yourself, check out this interactive map from Global Forest Watch.