There are fewer than 3,500 wild tigers left in the world. But researchers studying satellite data reveal that enough wild forest habitat exists for tigers to double their population by 2022. The findings are published in Science Advances this week.
In the last century, tigers (Panthera tigris) have become locally extinct in over 90 percent of their original range. The remaining tigers are still being threatened by poaching, habitat loss from logging and agriculture, and infrastructure development. Because of the solitary nature of Asia’s largest apex predator, large territorial spaces exceeding 30 square kilometers (11.6 square miles) are required. In 2010, government officials convened in St. Petersburg and agreed on a global recovery goal: a commitment to double the wild tiger population by 2022. It was dubbed the “Tx2” goal.
To estimate progress towards this objective, a team led by University of Minnesota’s Anup Joshi used Google Earth and a satellite-based monitoring system called Global Forest Watch (pictured below) to analyze tree cover loss between 2001 and 2014 in 76 so-called Tiger Conservation Landscapes (TCLs) spanning 13 countries where tigers live. These landscapes represent less than 7 percent of the tigers' historic range, and they measure between 278 and 269,983 square kilometers (107 and 104,241 square miles).
Turns out, forest loss was far less than the researchers expected: 79,597 square kilometers (30,733 square miles), or 7.7 percent of the remaining habitat over the 14-year study period. That means there’s enough wild habitat remaining to support a doubling of the world’s tiger population by 2022. And that’s despite an overall decline in habitat during those years; not to mention, tiger-harboring countries are some of the fastest growing economies in the world.
"We want to appreciate work done by conservation managers and state governments to protect the tiger. The expectedly low loss in priority TCLs is very exciting," Joshi told IFLScience over email. "On the other hand, we lost habitat that could have supported an estimated 400 tigers. We still have more work to do." According to the researchers, several actions would help further tiger population gains: restoring corridors in deforested areas, preventing erosion in key spots, implementing smart green infrastructure, and reintroducing recovered tigers.
Just 10 of the landscapes accounted for more than 98 percent, or 57,392 square kilometers (22,159 square miles), of habitat loss. And three of these – Taman Negara–Belum in Peninsular Malaysia and Kerinci Seblat and Bukit Tigapuluh in Sumatra – experienced the biggest reduction in forest cover.
While satellite imagery can’t detect poaching for tiger body parts, prey availability, or disturbances underneath the canopy, the findings suggest that habitat monitoring could be useful between on-the-ground surveys, since these are labor-intensive and less frequently conducted.
This Indonesian park is surrounded by tree cover loss (pink) that’s now creeping into the park boundaries. Global Forest Watch/World Resources Institute