Esri Map of Nighttime Lights
Blue represents increase in lighting between 2012 and 2016 while pink indicates a decrease. Esri

In four short years, urbanization, economics, and war have changed a satellite’s view of the Earth at night.

A lot can happen in four years. To get a sense of just how much, look no further than a set of maps from NASA showing the Earth’s lights at night.

Comparing two satellite images—one from 2012, the other from 2016— it’s apparent that some areas have lit up, indicating urban development and electrification. In other places, the lights have dimmed or been extinguished altogether, which could be a sign of war, economic downturn, or a concerted effort to reduce light pollution.

The NASA maps are dubbed Black Marble, reflecting a globe that’s, for the most part, covered in dark blue, with bursts of light where humans have settled into lively cities. Toggling from one map to the other, Esri product engineer John Nelson said he was amazed, and he wanted to see the changes in clearer detail. “I tried to detect the change [on my own], whether it's twinkling on over here or turning off over there,” he says. “But what if we could get a robot to do this visualization work and detect the change for me?"

So, feeding the underlying data from NASA into Esri’s ArcGIS program, Nelson overlaid the two maps, using blue to indicate areas that grew brighter over the four years, and pink to indicate areas that got darker. Overall, the project, called “Lights On Light Out,” shows that much of the globe remained more or less the same—but certain areas are striking. Cities in India light up in blue, as do their neighbors in South East Asia. In the Middle East, Syria and parts of Iraq have become seas of pink, standing in stark contrast to Lebanon and the northern half of Israel. Meanwhile, cities in the U.S. and throughout Europe show a little of both.

Nelson admits that he doesn’t have the answers as to why certain areas changed the way they did, but he says the best part of the project is inviting people to talk about it. "I’m just comparing two images, and the software itself doesn’t know what those images are, and so a lot of it is still a mystery to me,” he says. “I make maps not because I'm an expert, but to start conversations. I like the fact that it gets people asking questions.”

Here are three areas that have seen noticeable changes over the past four years.

India

Esri

The striking blue across India is the result of the country’s rural electrification efforts, which started in the 1950s when only a handful of villages had access to power. By the end of the first decade of the 21st century, a little over half of India’s 600,000 villages had electricity. In 2012, almost a quarter of the entire population—304 million of about 1.3 billion—lacked access to electricity. By 2016, when NASA updated its Black Marble map, the government declared that only 18,500 villages remained unelectrified (“electrified” is defined here as providing electricity to public places and at least 10 percent of all households in the village).

So far, according to the government, only 4,300 villages still need electricity—and the plan is to connect them all by the end of the year. Under Prime Minister Narendra Modi’s grand vision, all households would be connected to the grid by 2019. But local reports say despite the progress, the efforts have been implemented unevenly, and the numbers may be misleading. The Hindu, for example, found that more than 300 villages marked as electrified were in fact dark. Meanwhile, data journalists reported at the end of 2016 that 92 percent of at least 10,000 newly electrified villages still had homes that lack electricity.

The Middle East

Esri

The Syrian civil war had already begun by the time NASA took its initial nighttime snapshot of the country, but soon afterwards, the bombings began. Damascus, once the country’s bustling capital with busy markets and historic monuments, was left in rubble, as was Aleppo, and the cities in between. By 2016, the satellite images reflected a region where airstrikes have taken their toll on the people, economy, and built environment, effectively sending the western edge of the country into darkness.

In between, ISIS militants swept into northern Iraq in the summer of 2014, taking control of Mosul and Raqqa. The pink patches in Esri’s map mirror not only the bombings as Iraqi forces tried to take back the cities, but also the accounts of a grim life under the terrorist organization’s rule, as described in The Guardian:

Electricity and water has deteriorated significantly. Before Isis came, Mosul had about 20 hours a day of electricity from the national grid. Within four months of Isis taking over, it dropped to six [to] eight hours. For the past three months it has fallen to two hours a day. Each neighbourhood has water once a week at different times to fill up their tanks. In Raqqa, electricity is sporadic, dependent on how happy the militants are with the people’s adherence to their rules.

Venezuela & Puerto Rico

Esri

Both Venezuela and Puerto Rico saw a concentrated reduction in lighting, but for two very different reasons. In Venezuela, an economic recession eventually spiraled into a desperate crisis, which left the government unable to provide its citizens with the most basic needs. That includes electricity, which, generated through water, became scarce as a result to both drought and political mismanagement. To save power, the country endured several planned and unplanned power outages.

Puerto Rico, on the other hand, is colored pink in large part because of the island’s efforts and need to reduce energy consumption and light pollution, according to NASA. Houses have installed LED lights because of the high cost of energy there, and some roads remain dark as the local governments can’t afford to light them. When it comes to light pollution, Puerto Rico—which calls itself the Shining Star of the Caribbean—is among the worst offenders in the region despite being one of more than a dozen U.S. states and territories to have enacted “dark skies” legislation. Nevertheless, residents there take lightly the fact that artificial lights fill up the night skies in the state’s commercial centers. To combat that, the government created a special task force to raise public awareness about the consequences of light pollution, among other things

Credit

As more cities transition to LED lighting—those in the U.S. and across Europe have certainly started the transition—it’s an open question as to whether night-time maps will remain effective measures of the human footprint and economic activity. Adam Storeygard, an economist at Tufts University who studies satellite imagery, says it might make the interpretation harder in the future, but not obsolete. “You can look at changes in light over time, and there it might be problematic, but some of my other work just looks at the level [of light] across places,” he tells CityLab. “It's unlikely to me that those [light pollution laws] would be so effective that a large city will not be more lit than a national park. So it will still be able to help us to tell use where people live.”

See the project here and explore the interactive map at the end.

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