GlobalWarming & ClimateChange News Desk – Satellite images show human activity is reducing Arctic vegetation greenness, partly offsetting the gains linked to warmer temperatures according to Earth News report
The Arctic is getting greener, but human activity is reversing the trend
Across much of the Arctic, plants have grown greener as the region warms. Around mines, roads, and towns, people are changing that picture.
A new study found that land disturbed by development lost greenness between 2000 and 2020, while nearby land without recorded disturbance generally grew greener.
Both changes happened within the same areas, so a broad view of the region can hide damage on the ground.
Chong Liu and Xiao Cheng of Sun Yat-sen University in China led the research. Their team used satellite images to track how green the land looked each summer, rather than measuring plants on the ground.
Satellites have recorded increasing plant growth across the Arctic since the early 1980s.
The region has also warmed nearly four times faster than the world overall since 1979, according to a 2022 study.
Mapping where people build
Scientists had already documented development harming Arctic plants, but only one place at a time.
Gas development on Russia’s Yamal Peninsula changed which shrubs grew and reduced lichen cover, while roads and pipelines on Alaska’s North Slope damaged the vegetation beside them.
Liu and Cheng’s team set out to see the whole picture at once. Their Arctic was a broad one, reaching as far south as the Siberian city of Krasnoyarsk.
To find where people live and work, the researchers started with satellite maps of nighttime lights.
Many Arctic mines give off little light after dark, though, so the team added two global mining maps to catch them.
That search turned up 2,221 areas of human activity covering about 8,300 square miles (21,400 square kilometers), a little less than the size of New Jersey.
Nearly 7,000 of those square miles were in Russia, and most of the areas were in boreal forests, where forestry, mining, and energy development are concentrated.
Next, the researchers broke Landsat images of each area into squares about 98 feet (30 meters) across, roughly the length of a basketball court.
Every square got a greenness score each year based on the light it reflected, and the score generally runs higher where leafy plant cover is denser.
Disturbed land turned browner
Over those 20 years, disturbed and stable land moved in opposite directions. Disturbed ground lost greenness about three times as fast as stable ground within the same areas gained it.
The difference became clear around 2011. Before then, disturbed land had been greener on average; afterward, stable land remained greener.
Areas with little disturbance often continued to green, but browning became more common as the disturbed share increased.
The disturbed portions lost greenness in 58.7% of the mapped areas, while stable portions gained it in 67.7%.
That means a single area could contain both trends. Browning was especially common in the southern parts of the study region, including southern Siberia, Sweden, and parts of the Canadian Arctic.
Separating the two influences
Plants can lose greenness without anyone clearing the ground, for example when soil dries out or permafrost thaws.
Inside the mapped areas, though, the researchers traced 93.7% of the recorded land disturbance to direct human activity such as construction, farming, and urban management.
Disturbed land still warms along with everything around it, so the team had to work out what climate alone was doing.
They compared each disturbed square with stable land no more than 3.7 miles (6 kilometers) away and within about 1,640 feet (500 meters) of the same elevation.
Those nearby squares shared the same weather but had no recorded disturbance, so their trend showed how the plants might have changed if the ground had been left alone.
Comparing the two let the researchers estimate how much of each disturbed square’s trend came from climate and how much came from disturbance.
Climate was linked to greening in 76.3% of the vegetated squares, and disturbance to browning in 68.9%. Overall, disturbance explained 16.1% of the variation in greenness.
That’s a larger share than earlier estimates made with coarser satellite images, which may blur small damaged patches into the wider trend.
Mining areas lost more
Across 50.3% of the mapped area, climate supported greening while disturbance pushed vegetation toward browning.
Climate still explained most of the overall variation, but human activity was working against some of those gains.
“Arctic vegetation change cannot be characterized by a uniform ‘greening’ phenomenon,” the authors wrote.
Disturbance-related browning was strongest in western Russia, northern Fennoscandia, which includes Norway, Sweden, and Finland, and major mining areas in Canada and Siberia. It also appeared along roads and pipelines.
Sites with fewer than 200 residents browned more than towns did.
The researchers suggested that mining and other extraction activities at these sites remove vegetation more intensively and keep it from returning for longer.
Local views reveal damage
The team took a closer look at three places: the Mirny diamond mine in Siberia, the city of Yellowknife in Canada, and the Fort Knox gold mine in Alaska.
At all three, disturbed ground had weaker greenness trends than stable ground.
Within those sites, greening tended to cluster in urban centers, while browning showed up at the edges, along transport routes, and near industrial sites.
Those local differences can get lost in a regional average, which is why a single greening trend can’t describe every part of the landscape.
To see whether the browning reached beyond each site, the researchers checked rings of land roughly 6 to 19 miles (10 to 30 kilometers) outside every mapped area.
More heavily disturbed areas didn’t have browner surroundings, which suggests the browning stayed close to the disturbance itself.
Recovery can take generations
Above about 65 degrees north, roughly the latitude of Fairbanks, Alaska, climate-related greening became stronger. The influence of disturbance declined farther north, especially in Russia.
The authors linked that pattern to the difficulty and expense of building in remote places with harsh conditions. Those obstacles limit large development projects in the high Arctic.
Once people disturb the soil, plants may struggle to return. Arctic growing seasons usually last just 60 to 90 days, and soils contain few nutrients.
Earlier studies cited by the team found that vegetation can take decades to centuries to recover after physical soil damage.
Plants may never return to their previous abundance if the disturbance permanently changes how water moves through the ground.
The researchers therefore suggested that some brown patches could represent lasting damage.
They warned that expanding development could increasingly offset warming-related vegetation gains and weaken the Arctic’s ability to store carbon on land.
What satellites cannot show
The maps may miss small developments and underground activity that nighttime lights and mining records cannot detect.
Human disturbance could therefore extend beyond the areas the team identified.
Greenness also tells only part of the story about vegetation.
The analysis grouped temperature, rainfall, and other climate influences together, and it could not separate the effects of roads from those of mines.
The study did not establish whether vegetation recovers after work stops.
Future research could combine radar, more detailed climate information, and better disturbance records with measurements of carbon storage and biodiversity.
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