Science

Landsat 50: How satellites revolutionized the way we see and protect the natural world

This article was originally published in The Conversation. (will open in a new tab) The publication published an article in Expert Voices: Op-Ed & Insights on Space.com. (will open in a new tab).

Stacey Morford (will open in a new tab)Associated Press national editor and state government reporter.

Fifty years ago, American scientists launched a satellite that radically changed our vision of the world.

He captured images of the Earth’s surface in great detail, showing how wildfires burned landscapes, how farms destroyed forests and much more, how people changed the face of the planet.

The first satellite of the Landsat series. (will open in a new tab) launched July 23, 1972. It was followed by eight others that provide the same views so you can track changes over time, but with increasingly powerful tools. Landsat 8 (will open in a new tab) and Landsat 9 (will open in a new tab) today revolve around the planet, and NASA and the USGS are planning a new Landsat mission (will open in a new tab)

Related: Celebrate 50 years of Landsat with these stunning images (gallery)

Images and data from these satellites are being used to track deforestation and landscape change around the world, locate urban heat islands and understand the impact of new river dams, among many other projects. Often the results help communities respond to risks that may not be obvious on the ground.

Here are three examples of Landsat in action from The Conversation archive.

Track Changes at Amazon

The construction of the Belo Monte Dam, shown here in 2012, flooded the land and changed the course of the river. (Image credit: Mario Tama/Getty Images) (will open in a new tab)

When work began on the Belo Monte Dam project in the Brazilian Amazon in 2015, indigenous tribes living along the Great Bend of the Xingu River began to notice changes in the flow of the river. The water they used for food and transportation was disappearing.

Upstream, the new canal will eventually divert up to 80% of the water to the hydroelectric dam, bypassing the bend.

The consortium that runs the dam has argued that there is no scientific evidence that the change in water flow has harmed the fish.

But there is clear evidence of the impact of the Belo Monte Dam project from above, writes Pritam Das. (will open in a new tab)Faisal Hossain (will open in a new tab)Herdur Helgason (will open in a new tab) and Shahzaib Khan (will open in a new tab) at the University of Washington. Using satellite data from the Landsat program, the team showed how dramatically the dam had changed. (will open in a new tab) river hydrology.

Map of the Great Bend of the Xingu River after the Belo Monte Project. (Image courtesy of OpenStreetMap contributors) (will open in a new tab)

“As scientists working with remote sensing, we believe that satellite observations can empower people around the world who face threats to their resources,” write Das and his colleagues.

The first satellite image shows the Great Bend of the Xingu River taken on May 26, 2000, before construction of the Belo Monte Dam began. The image overlaid on top is from the same region on July 20, 2017. The gif was made using juxtapose.knightlab.com. (Image credit: NASA) (will open in a new tab)

It’s hot in the city and hotter in some areas

A street cheerleader brings relief on a hot New York summer day. (Image credit: Steven Chernin/Getty Images) (will open in a new tab)

Landsat instruments can also measure surface temperatures, allowing scientists to map street by street of heat risk in cities as global temperatures rise.

“Cities tend to be warmer than the surrounding rural areas, but even in cities, some residential areas become dangerously warmer than others just a few miles away,” writes Daniel P. Johnson. (will open in a new tab)which uses satellites to study the urban heat island effect at Indiana University.

Johnson writes that areas with more sidewalks and buildings and fewer trees can be 10 degrees Fahrenheit (5.5 degrees Celsius) or more, which is warmer than greener areas. He found that the hottest neighborhoods tend to be low-income, majority black or Hispanic, and were subject to redlining, a discriminatory practice once used to deny credit to racial and ethnic minority communities.

A comparison of New York’s vegetation and temperature maps shows the cooling effect of parks and areas with lots of trees. (Image credit: NASA/USGS Landsat) (will open in a new tab)

“Within these micro-urban heat islands, communities could experience heat waves well before officials declare a state of emergency,” Johnson wrote.

Knowing which areas face the highest risks (will open in a new tab) allows cities to organize cooling centers and other programs to help residents manage heat.

Creation of ghostly forests

The white trunks of the ghost forest mark the coastal landscape of North Carolina. (Image credit: Emily Urey, CC BY-ND) (will open in a new tab)

Satellites that scan the same areas year after year can be critical to detecting changes in hard-to-reach regions. They can watch for snow and ice, and along the US Atlantic coast for dying wetlands.

These eerie landscapes of dead, often discolored tree trunks have earned the nickname “ghost forests”.

Emily Urey (will open in a new tab), an environmentalist now at the University of Waterloo in Ontario, used Landsat data to determine wetland changes. She then zoomed in on high-resolution images from Google Earth, including Landsat images, to confirm they were ghost forests.

“The results were shocking. We found that more than 10% of forested wetlands (will open in a new tab) in the Alligator River National Wildlife Refuge [in North Carolina] has been lost in the last 35 years. This is land protected by the state, and there is no other human activity that could destroy the forest,” Yury writes.

A Landsat image of the Alligator River and refuge shows signs of a ghost forest on the east side of the river. (Image credit: NASA Earth Observatory) (will open in a new tab)

As the planet warms and sea levels rise, more salt water reaches these areas, increasing the amount of salt in the soil of coastal forests from Maine to Florida. “Rapid sea level rise appears to be outpacing the ability of these forests to adapt to wetter, saltier conditions,” Urey writes.

Many more stories can be found in Landsat images, such as an overview of the aftermath of the war. (will open in a new tab) about the wheat harvest in Ukraine and how algae blooms spread to Lake Okeechobee in Florida (will open in a new tab). Countless projects use Landsat data to track global change and possibly find solutions to problems ranging from deforestation in the Amazon to (will open in a new tab) fires as Alaska braces for another historic fire season (will open in a new tab).

Artistic rendering of Landsat 8. (Image credit: NASA/Goddard Space Flight Center Conceptual Imaging Lab) (will open in a new tab)

This article is republished from The Conversation (will open in a new tab) under a Creative Commons license. Read original article (will open in a new tab).

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