Since 2000, the world has lost about 100 square miles of forest every day. Deforestation in the Amazon, where cattle ranchers and soybean farmers have slashed through woodlands to make way for pastures and fields, has slowed recently, but Indonesia has emerged as a new hot spot. Palm oil plantations and logging operations have cleared about 23,000 square miles of forest there in the last 15 years. Given that 40 percent of this loss has occurred in areas that officially restrict logging, it's clear that regulations aren't enough to protect the trees. So conservationists are turning to high-tech surveillance gear.

The World Resources Institute's project Global Forest Watch keeps an eye on forests from above. Sophisticated software analyzes images from U.S. government satellites that pass over the globe's tropical zones every 16 days, examining the landscape in minute detail. The automated system notes the color and infrared signature of each pixel, which corresponds to an area of forest slightly smaller than an Olympic swimming pool. The software detects changes that can't be accounted for by seasonal cycles, such as the clearing of an illegal logging road. Next, an alert goes out to government officials and activists, so illegal logging operations can be shut down before they cause significant damage.  

Rainforest Connection employs old smartphones to listen for trouble. The group attaches solar-powered phones to trees and uses their microphones to detect logging activity. When a phone picks up the distinctive buzz of chainsaws within its one-square-mile range, it sends an alert to a remote server, which in turn notifies local authorities of the exact location of the illegal logging. The group has tested its system on the Indonesian island of Sumatra and is also rolling out projects in the Amazon and equatorial Africa.