For half a century, Landsat satellites have been photographing the Earth from all angles. Photographs illustrating landscape changes, particularly those related to human activities and climate change.
It offers “an unbiased look at climate change”. Jointly managed by NASA and the US Geological Survey (USGS), the Landsat space program was launched 50 years ago, in July 1972. Since then, eight satellites have been launched, three of which are still in orbit, reports Vice. This is the first civilian Earth observation space program.
“For 50 years, the mission has collected data on our planet’s forests, farms, urban areas and freshwater, producing the longest continuous record of its kind,” writes NASA.
Through these thousands of snapshots, the Landsat program has created a bird’s eye view mosaic of our planet, making it possible to illustrate the changes associated with human activities over the past half century.
The shrinking Aral Sea
In the 1960s, the Aral Sea formed the fourth largest lake area in the world. In 2000, this area was already halved. This drying up is due to the Soviet Union diverting the two rivers for mass production of cotton.
These images, taken by Landsat satellites in 2000 and then in 2018, show the shrinking of the Aral Sea. “As the Aral Sea dried up, fishermen and other communities that depended on it collapsed,” writes NASA.
“The increasingly saline water was contaminated with fertilizers and pesticides. The dust contaminated with agricultural chemicals has become a public health hazard,” the agency continues.
Retreating glaciers and expanding lakes in Tibet
Scientists often refer to the Tibetan Plateau and its many mountain ranges as the “Third Pole” because they contain the world’s largest freshwater reserves outside of the polar regions. Much of this water is stored in tens of thousands of glaciers scattered across the region. However, rising temperatures are accelerating the melting of these ice sheets.
These images of lakes west of the Tanggula Mountains in 1987 and then in 2021 provide a glimpse of changes caused by glacial retreat. Therefore, the lakes have grown over time.
The melting ice in Alaska
The Columbia is a large coastal glacier in Alaska, USA, that flows directly into the sea. It has started to retreat since the 1980s: its end has retreated 20 km and it has lost more than half its thickness and total volume.
Captured by Landsat satellites, these false-color images show how the glacier and surrounding landscape have changed since 1986 compared to 2019. Snow and ice appear in light cyan, vegetation in green, clouds in white or light orange, and open water in dark blue.
“The receding Columbia Glacier is contributing to global sea level rise, primarily through the calving of icebergs,” NASA said.
Deforestation in the Amazon
The state of Rondônia in western Brazil, which was once home to 208,000 square kilometers of forest — an area slightly smaller than the US state of Kansas — has become one of the most heavily deforested areas in Amazonia.
All major rainforests are disappearing, primarily to make way for human food production, including livestock and crops.
“Although deforestation in the tropics meets certain human needs, it also has profound, sometimes devastating consequences, such as social conflict and human rights abuses, plant and animal extinction, and climate change,” NASA explains.
Urban expansion in Shanghai
In 1960, about 110 million Chinese – or 16% of the population – lived in cities. In 2018, those numbers grew to 820 million and 59%. Urbanization began in the 1980s when the Chinese government opened the country to foreign trade and investment. This series of Landsat images shows the growth of Shanghai between 1984 and 2019.
In 1984, the heart of the city lay on the west bank of the Huangpu River, an artificial tributary of the Yangtze River. Since then, Shanghai has expanded in all directions over mostly farmland.
The replacement of forests and farmland with concrete has raised the city’s temperature. Chinese researchers working with thermal sensors on Landsat have shown that temperatures in some areas of Shanghai increased by 81% between 1984 and 2014.
The Exploitation of Oil in Canada
Beneath Canada’s boreal forest lies one of the world’s largest oil reserves. These Landsat satellite images show the growth of open pit mining over the Athabasca Oil Sands between 1984 and 2016, a trend expected to continue as mine expansion permits have been granted in the region.
Only 20% of the oil sands are near the surface where they can be easily mined. The rest of the oil sands are buried more than 75 meters underground and are extracted by injecting hot water into a well that liquifies the oil to pump it out.
This exploitation has a significant impact on the environment. First, the forests must be cleared for exploitation. It also releases a number of toxins that can leak into groundwater or directly into the Athabasca River.
Also, because extracting and separating oil from the sands requires energy, the oil sands emit more greenhouse gases than other forms of oil extraction.