Arctic greening won’t save the climate – here’s why

A map of North America showing green areas in the far north.

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Satellite images show that the Arctic has been becoming greener due to rising temperatures in the far northern region. Three times fasterIt is higher than the global average.

Some theories suggest that this “Arctic greening” will help counteract climate change. Because plants absorb carbon dioxide as they grow, increasing temperatures will result in Arctic vegetation absorbing more carbon dioxide from the atmosphere. This will reduce the greenhouse gases that are warming our planet.

But is that actually happening?

I am a Biologist who studies the response of ecosystems to climate changes, including tundra ecosystems.. My students, colleagues, and I have been tracking the changes in Arctic vegetation for five years.

You have to brave bears in order to find evidence on the tundra

The Arctic tundra is a vast area of mostly treeless land that stretches across North America and Eurasia. The soil below the surface is covered in frozen permafrost. However, the top layer blooms with grasses, low shrubs, and other vegetation during the short summer months.

Satellite studies have been conducted over the past decade to track changes in Arctic greening by measuring the visible light reflected by vegetation. Healthy green vegetation absorbs visible sunlight but reflects the near infrared light. Scientists can use this data to estimate plant growth over large areas.

But satellites don’t measure the plants’ carbon dioxide uptake.

Satellite images of the Arctic greening. NASA Goddard Space Institute.

Field studies that could verify how much carbon dioxide Arctic plants were absorbing were not available until recently. This prevented scientists from testing the hypothesis of earlier snow melt and its effect on plants helping to control carbon dioxide in our atmosphere.

For Our studyScientists Braved bear territoryDuring the cold summer nights, we collected extensive carbon dioxide measurements near soil and plants in 11 Arctic tundra ecosystems. These include Alaska, Canada Siberia, Greenland, and Alaska. We focused our attention on the Arctic areas that are most understudied, and those that are located above continuous permafrost.

A slower pace of late-season growth but earlier growth

Arctic plants only have three months to grow and reproduce before it gets too cold.

We wanted to see if earlier starts to the growing season had an effect on the amount of carbon dioxide taken up each summer by vegetation. We were surprised by the results: Despite the obvious greening, the overall carbon dioxide uptake did not increase or decreased in any significant way.

We were able to see the reasons behind the shifts in productivity from week to week when we looked closely. While the earlier snowmelt was stimulating plants’ productivity in June, that productivity began to taper off in July – normally their peak season for photosynthesis. By August, productivity was significantly lower than normal.

The Arctic’s dominant shrubs, sedgesOther wetland plants weren’t storing any more carbon late in this season. It was like getting up earlier and being ready for bed at night.

We are still unsure if the widely used index of plant growth based upon changes in visible or infrared light is correct. Known as NDVIA higher uptake of carbon dioxide is clearly associated with the Arctic ecosystems. Some Arctic ecosystems have shown Strong correlationsBetween NDVI and carbon dioxide absorption Others have not. We didn’t find evidence that plants were affected by water limitations in the late season.

Tundra ecosystems may not be able to continue taking in carbon dioxide into the later seasons, and the expected increase in carbon sequestration may not occur.

And there’s another problem. There’s another problem. Tundra plants normally store more carbon through photosynthetic than tundra releases. carbon sink. The long, cold winters slow plants’ decomposition and lock them in the frozen ground. This and other organic matter is released more greenhouse gases into the atmosphere when permafrost holds them.

Illustration of plant growth by month for early and later snowmelt shows the growing period shift from July-August to June-July. — This infographic shows the variations in plant growth for each month. Plants begin to decompose earlier if snow melts earlier in the year.
Donatella Zona

The local impact extends beyond carbon.

This isn’t just a story about plants and the climate. Changes in vegetation can have broad-ranging impacts on other components of ecosystems such as animals and humans.

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The Intergovernmental Panel on Climate Change is the United Nations body responsible for assessing climate science. It has already estimated that snow cover changes have already been impacted. Water and food security in affected areas. Many local communities rely on hunting, trapping, and fishing. Early vegetation development can have an impact on the delicate balance of complex Arctic systems.

If Arctic greening is only shifting seasons and isn’t increasing the overall carbon dioxide level as previously believed, that could also mean the models currently used to evaluate and predict the overall impact of climate change are missing an important piece of information. The result could be that a process we assumed would slow or mitigate climate change isn’t actually working as expected.

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