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NASA/USGS NASA/USGS

In the late 1980s, China’s Pearl River Delta was as bucolic as the name implies—a verdant, littoral expanse populated with rice paddies, orchards, and about 10 million mostly rural residents. Fast-forward three decades and it’s now a sprawling maze of development that, with a population of 42 million, is said to be the biggest urbanized region on the planet.

Today NASA is highlighting the delta’s unreal growth spurt with an eye-opening duo of satellite images. The first was taken in 1988 by the Landsat 5 craft and shows vast zones of forests and crops (in green), with moderately sized cities like Shenzhen and Zhongshan appearing as white-and-gray nebulae:

And here’s a Landsat 8 image of the delta in 2014, when the cities had completely metastasized into one giant carpet of concrete and steel:

The space agency, which has included an image-comparison slider that makes the transformation even more stark, notes the delta’s population is now larger than Canada and the entirety of Australia. Here’s more:

If taken as one entity, the Pearl River Delta region has overtaken Tokyo as the world’s largest urban area—by size and population—according to an analysis of satellite and demographic data published by the World Bank. Between 2000 and 2010, the Pearl River Delta’s urban spaces—defined as areas where the built environment covered more than 50 percent of the landscape in a given pixel—had expanded from 4,500 square kilometers to 7,000 square kilometers. (In 2010, Tokyo had a population of about 32 million people and covered about 5,600 square kilometers.) ... The Pearl River Delta region has a very different pattern of growth compared to other fast-growing cities in China. “Vast and multinucleate with no clear center, its form arose from its unique economic origins in the 1980s and 1990s, as the geographic center of the market reforms that subsequently transformed the Chinese economy, particularly the Shenzhen Special Economic Zone,” the World Bank authors noted. “This region thus has a very different, and more recent, urban growth trajectory than those of Beijing and Shanghai, which, despite their explosive recent growth, have grown around well-defined historic urban centers.”