DEFORESTATION is hard to stop. It often happens in remote areas where law enforcement is weak; and by the time anyone finds out about it, the trees are long gone—transformed into garden furniture or burned to make way for agriculture. Governments interested in tracking deforestation in something close to real time rely on satellite imagery provided by NASA and others.

But this has its problems. Tropical forests are often covered by cloud, so the images the satellites beam back are incomplete. One way around this is to mount almost constant surveillance—as happens from NASA's Modis satellites, which orbit the earth a couple of times each day. This is not the only source of images of deforestation. Brazil's government has its own, run by INPE, the country's space agency. And the University of Maryland produces a dataset that allows people to examine forests in great detail, but only once a year.

How then to bring the data together and make them more useful? For the past five years the World Resources Institute has worked with Google to make all this information available to the public in a digestible form. The map they have come up with makes it easy to compare datasets, and to see in detail how forest cover has changed over the past decade. It also charts forest fires that are burning, with a slight delay. You can interact with it here.