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

This article was originally published at The Conversation. (opens in new tab) The publication contributed the article to Space.com’s Expert Voices: Op-Ed & Insights (opens in new tab).

Stacy Morford (opens in new tab), Associated Press national editor and state government reporter.

Fifty years ago, U.S. scientists launched a satellite that dramatically changed how we see the world.

It captured images of Earth‘s surface in minute detail, showing how wildfires burned landscapes, how farms erased forests, and many other ways humans were changing the face of the planet.

The first satellite in the Landsat series (opens in new tab) launched on July 23, 1972. Eight others followed, providing the same views so changes could be tracked over time, but with increasingly powerful instruments. Landsat 8 (opens in new tab) and Landsat 9 (opens in new tab) are orbiting the planet today, and NASA and the U.S. Geological Survey are planning a new Landsat mission (opens in new tab)

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

The images and data from these satellites are used to track deforestation and changing landscapes 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 from the ground.

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

Tracking changes in the Amazon

The Belo Monte Dam’s construction, shown here in 2012, flooded land and changed the river. (Image credit: Mario Tama/Getty Images) (opens in new tab)

When work began on the Belo Monte Dam project in the Brazilian Amazon in 2015, Indigenous tribes living along the Big Bend of the Xingu River started noticing changes in the river’s flow. The water they relied on for food and transportation was disappearing.

Upstream, a new channel would eventually divert as much as 80% of the water to the hydroelectric dam, bypassing the bend.

The consortium that runs the dam argued that there was no scientific proof that the change in water flow harmed fish.

But there is clear proof of the Belo Monte Dam project’s impact — from above, write Pritam Das (opens in new tab), Faisal Hossain (opens in new tab), Hörður Helgason (opens in new tab) and Shahzaib Khan (opens in new tab) at the University of Washington. Using satellite data from the Landsat program, the team showed how the dam dramatically altered (opens in new tab) the hydrology of the river.

Map of the Xingu River’s Big bend after the Belo Monte Project.  (Image credit: OpenStreetMap contributors) (opens in new tab)

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

The first satellite image shows the Big Bend of the Xingu River on May 26, 2000, before the Belo Monte Dam project began. The image then overlaid on top is the same region on July 20, 2017.  Gif made with juxtapose.knightlab.com. (Image credit: NASA) (opens in new tab)It’s hot in the city — and even hotter in some neighborhoods

A street fan provides relief on a hot summer day in New York City. (Image credit: Stephen Chernin/Getty Images) (opens in new tab)

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

“Cities are generally hotter than surrounding rural areas, but even within cities, some residential neighborhoods get dangerously warmer than others just a few miles away,” writes Daniel P. Johnson (opens in new tab), who uses satellites to study the urban heat island effect at Indiana University.

Neighborhoods with more pavement and buildings and fewer trees can be 10 degrees Fahrenheit (5.5 degrees Celsius) or more, warmer than leafier neighborhoods, Johnson writes. He found that the hottest neighborhoods tend to be low-income, have majority Black or Hispanic residents and had been subjected to redlining, the discriminatory practice once used to deny loans in racial and ethnic minority communities.

Comparing maps of New York City’s vegetation and temperature shows the cooling effect of parks and neighborhoods with more trees. (Image credit: NASA/USGS Landsat) (opens in new tab)

“Within these ‘micro-urban heat islands,’ communities can experience heat wave conditions well before officials declare a heat emergency,” Johnson writes.

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

The making of ghost forests

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

Satellites that scan the same areas year after year can be crucial for spotting changes in hard-to-reach regions. They can monitor snow and ice cover, and, along U.S. Atlantic coast, dying wetland forests.

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

Emily Ury (opens in new tab), an ecologist now at the University of Waterloo in Ontario, used Landsat data to spot wetland changes. She then zoomed in with high-resolution images from Google Earth — which includes Landsat images — to confirm that they were ghost forests.

“The results were shocking. We found that more than 10% of forested wetland (opens in new tab) within the Alligator River National Wildlife Refuge [in North Carolina] was lost over the past 35 years. This is federally protected land, with no other human activity that could be killing off the forest,” Ury writes.

Landsat’s view of the Alligator River and refuge shows signs of ghost forests on the east side of the river. (Image credit: NASA Earth Observatory) (opens in new tab)

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

Many more stories can be found in Landsat’s images, such as an overview of the war’s effects (opens in new tab) on Ukraine’s wheat crop, and how algae blooms have spread in Florida’s Lake Okeechobee (opens in new tab). Countless projects are using Landsat data to track global change and possibly find solutions to problems, from deforestation in the Amazon (opens in new tab) to the fires that have put Alaska on pace for another historic fire season (opens in new tab).

An artist’s rendering of Landsat 8. (Image credit: NASA/Goddard Space Flight Center Conceptual Image Lab) (opens in new tab)

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

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Source: space.com

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