If you look at satellite images of the world over just the last five years, some of the changes are striking: Massive swaths of forest burned in Australia, Russia, and California. In Egypt, urban sprawl in Cairo edged out to the pyramids at Giza. The fastest-growing city in the world—Gwagwalada, Nigeria—also spread into nature, in a pattern of urban growth that was repeated around the planet. In South America, millions of acres of rain forest were lost in the Amazon.
Land cover change 2017 to 2021, showing Cairo’s recent urban sprawl. [Image: courtesy Esri]In a new global map based on the European Space Agency’s Sentinel-2 satellite data from 2017-2021, the mapping company Esri has created a detailed rendering of the current state of the planet that anyone can explore. In the past, land use mapping has been slow, because it’s done pixel-by-pixel and requires a long process of review.
Recent urban sprawl in and around Gwagwalada, Nigeria. [Image: courtesy Ersi]“We’re always looking at something almost two years late,” says Sean Breyer, who manages Esri’s Living Atlas of the World, where the map will be available and updated annually. “That’s what prompted this whole conversation with one of our business partners, Impact Observatory, and ourselves, to say, could we reinvent the way we build land cover mapping to be much faster and easier to reproduce?”
This map shows the impact of recent Northern California wildfires. [Image: courtesy Esri]Esri and Impact Observatory used artificial intelligence and machine learning to quickly crunch through the satellite data, which has 26 pictures of every point on the planet throughout the year. (Microsoft donated the use of its servers to run the program.) Data that might have taken months or a year to process in the past can now be processed in around a week.
Effects on the landscape of the construction of the Grand Ethiopian Renaissance Dam. [Image: courtesy Esri]Impact Observatory plans to use the system to give some organizations daily updates on changes. At a national park in Africa that covers a large area, for example, where there may be few people on staff, the system could help quickly alert the team to visit a particular area when changes start to appear. Governments can also use the maps to plan land use. While others have illustrated changes on the planet with before-and-after satellite images, these maps offer more detail; it’s possible to measure exactly how much a city has grown or how much a forest has shrunk.
Deforestation bordering protected areas in Itaituba, Brazil. [Image: courtesy Esri]From the beginning, the partners knew that they wanted to make the maps freely accessible. “There’s so much change, and so much need in the world for this kind of information,” Breyer says. “A lot of large countries don’t have access to an annual land cover map at the rate that we’ve got right now. So making this publicly available just makes it easier for everyone to get access and start to make more informed decisions on what’s happened in the last five years.”
Bark beetle deforestation can be seen in the Harz Mountains in Germany. [Image: courtesy Esri]“It also helps them define a trajectory for the future,” he says. “Once you start to understand where your change is actually happening, you can do a better job of managing it, building policies to protect it if that’s what you need, or manage the way it’s growing.”
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