Fifty years ago, American scientists launched a satellite that drastically changed the way we see the world.
He captured images of the Earth’s surface in detail, showing how forest fires burned landscapes, how farms cleared forests, and many other ways in which humans were changing the face of the planet.
The first satellite in the Landsat series was launched on July 23, 1972. Eight others followed, providing the same views so that changes could be tracked over time, but with increasingly powerful instruments. Landsat 8 and Landsat 9 are orbiting the planet today, and NASA and the U.S. Geological Survey are planning a new Landsat mission.
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 up.
Here are three examples of Landsat in action, from The Conversation archive.
Track changes in the Amazon
The construction of the Belo Monte Dam, shown here in 2012, flooded the land and changed the river. Mario Tama / Getty Images
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 began to notice changes in the river’s flow. The water on which they depended for food and transportation was disappearing.
Upstream, a new canal would eventually divert up to 80% of the water to the hydroelectric dam, avoiding the bend.
The consortium managing the dam argued that there was no scientific evidence that the change in water flow harmed the fish.
But there is clear evidence of the impact of the Belo Monte Dam project: from above, Pritam Das, Faisal Hossain, Hörður Helgason and Shahzaib Khan write at the University of Washington. Using satellite data from the Landsat program, the team showed how the dam drastically altered the river’s hydrology.
The front satellite image shows the Big Bend of the Xingu River on May 26, 2000, before the Belo Monte Dam project began. Move the slider to the left to see the same region on July 20, 2017.
“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 colleagues.
Read more: Satellites on the Amazon capture the suffocation of the “house of God” at the Belo Monte dam; they can also help find solutions
It’s hot in the city, and even more so in some neighborhoods
A fan on the street provides relief on a hot summer day in New York City. Stephen Chernin / Getty Images
Landsat instruments can also measure surface temperatures, allowing scientists to map street-by-street heat risk within cities as global temperatures rise.
“Cities are generally warmer than the surrounding rural areas, but even within cities, some residential neighborhoods heat up dangerously than others a few miles away,” writes Daniel P. Johnson, who uses satellite. beds to study the urban heat island effect at Indiana University.
Johnson writes that neighborhoods with more pavement and buildings and fewer trees can be 10 degrees Fahrenheit (5.5 C) or warmer than greener neighborhoods. He found that the most popular neighborhoods tend to be low-income, have mostly black or Hispanic residents, and had been subjected to a red line, the discriminatory practice previously used to deny loans to racial and ethnic minority communities.
Comparison of New York City vegetation and temperature maps shows the cooling effect of parks and neighborhoods with more trees. NASA / USGS Landsat
“Within these‘ microurban heat islands ’, communities can experience heat wave conditions long before officials declare a heat emergency,” Johnson writes.
Knowing which neighborhoods face the highest risks allows cities to organize cooling centers and other programs to help residents manage heat.
More information: Landsat approaches the hottest neighborhoods in cities to help combat the urban heat island effect
The creation of ghost forests
The white trunks of a ghost forest mark a coastal landscape of North Carolina. Emily Ury, CC BY-ND
Satellites scanning the same areas year after year can be crucial in detecting changes in hard-to-reach regions. They can control snow and ice cover and, along the U.S. Atlantic coast, dying wetland forests.
These strange landscapes of dead tree trunks, often bleached, have earned the nickname “ghost forests”.
Emily Ury, now an ecologist at the University of Waterloo in Ontario, used Landsat data to detect changes in wetlands. He then zoomed in with high-resolution images from Google Earth, which includes images from Landsat, to confirm that they were ghost forests.
“The results were shocking. We found that more than 10% of the forest wetlands within the Alligator River National Wildlife Refuge [in North Carolina] has been lost for the past 35 years. This is federally protected land, with no other human activity that can kill the forest, ”Ury writes.
The view of Landsat over the Alligator River and the refuge shows signs of ghost forests on the east side of the river. NASA Earth Observatory
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,” Ury writes.
Many more stories can be found in Landsat’s images, such as an overview of the effects of the war on Ukraine’s wheat harvest and how algae blooms have spread to Florida’s Okeechobee Lake. Countless projects are using Landsat data to track global change and possibly find solutions to problems, from deforestation in the Amazon to fires that have set Alaska ready for another historic fire season.
Representation of a Landsat artist 8. NASA / Goddard Space Flight Center Conceptual Imaging Laboratory
Read more: Sea level rise is killing trees on the Atlantic coast, creating “ghost forests” that are visible from space