Home Science Satellites have changed the way we see the world

Satellites have changed the way we see the world

Satellites have changed the way we see the world

Fifty years ago, American scientists launched the first of thousands of satellites, dramatically changing the way we see the world.

He captured images of the Earth’s surface in detail, showing how wildfires scorched landscapes, how farms cleared forests, and many other ways humans were changing the face of the planet.

The first Landsat series satellite was launched on July 23, 1972. Eight more followed, providing the same views so that changes over time could be tracked, but with increasingly powerful instruments. Landsat 8 and Landsat 9 are orbiting the planet today, and NASA and the US Geological Survey are planning a new Landsat mission.

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 dams on rivers, among many other projects. The results often help communities respond to risks that may not be apparent on the ground.

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

Satellites track changes in the Amazon

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

Upstream, a new channel would end up diverting up to 80% of the water to the hydroelectric plant, bypassing the curve.

The consortium that manages 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, write Pritam Das, Faisal Hossain, Hörður Helgason and Shahzaib Khan of the University of Washington. Using data provided by satellites from the Landsat program, the team showed how the dam dramatically altered the river’s hydrology.

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

It’s hot in the city, and even hotter in some neighborhoods.

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

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

Neighborhoods with more floors and buildings and fewer trees can be 10 degrees Fahrenheit (5.5 C) or higher than more leafy neighborhoods, Johnson writes. The most attractive neighborhoods were found to tend to be low-income, have a majority of black or Hispanic residents, and have been the target of redlining, the discriminatory practice used to deny loans in racial and ethnic minority communities.

“Within these ‘urban micro heat islands,’ communities can experience heat waves long before authorities declare a heat emergency,” writes Johnson.

Knowing which neighborhoods face the greatest risks allows cities to organize cooling centers and other programs to help residents manage heat.

The creation of ghost forests

Satellites scanning the same areas year after year can be crucial for detecting changes in hard-to-reach regions. They can monitor snow and ice cover and, along the US Atlantic coast, dying rainforests.

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

Emily Ury, an ecologist now at the University of Waterloo in Ontario, used Landsat data to detect changes in wetlands. She then zoomed in on high-resolution Google Earth images, including Landsat images, to confirm they were ghost forests.

“The results were shocking. We found that more than 10% of the forested wetlands within the Alligator River National Wildlife Refuge [en Carolina del Norte] has been lost in the last 35 years. This is federally protected land, with no other human activity that could be killing the forest,” Ury writes.

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

Many other stories can be found in the Landsat footage, such as an overview of the effects of the war on Ukraine’s wheat crop and how algae blooms spread in Florida’s Lake Okeechobee. Countless projects are using Landsat data to track global changes and possibly find solutions to problems ranging from deforestation in the Amazon to the wildfires that put Alaska on track for another historic fire season.

This article was written by Stacy Morford, who interviewed several experts for this. It is republished from The Conversation under a Creative Commons license.. Article in English

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