Ive here. I must admit missed this. I can’t believe “Arctic Greening” is considered a reasonable idea, at least a plus in the climate change category. Granted, after the 2007-2008 International Polar Year, I had the pleasure of watching a few days of presentations at the Explorers Club, where every 10 years a large number of scientists and a few adventurers’ assistants travel to the North Pole to make measurements and observations. For a group of professional realists For example, they are very terrified of how much has changed since last year’s polar year.

By Donatella Zona, associate professor of biology at San Diego State University.Originally Posted in conversation

Satellite images show Arctic getting greener as temperatures rise in the far north three times fasterhigher than the global average.

Some theories suggest that this “Arctic greening” will help combat climate change. The idea is that because plants absorb carbon dioxide as they grow, rising temperatures will mean that Arctic vegetation will absorb more carbon dioxide from the atmosphere, ultimately reducing the greenhouse gas that warms the planet.

But does this really happen?

I am a Biologist, focusing on ecosystem responses to climate change, including tundra ecosystemsFor the past five years, my colleagues, students and I have been tracking vegetation changes in remote Arctic regions to find out.

Brave bears gather evidence on the tundra

The Arctic tundra is a vast, almost treeless region that spans the northernmost parts of North America and Eurasia. A few feet below its surface, most of the soil is permafrost, but during the short summer months, the top layer is overgrown with grass and low shrubs.

Satellite studies over the past decade have tracked changes in Arctic greenery by measuring visible and near-infrared light reflected by vegetation. Healthy green vegetation absorbs visible light but reflects near-infrared light. Scientists can use the data to estimate plant growth over a wide area.

But satellites cannot measure carbon dioxide uptake by plants.

Satellite image of Arctic greening. NASA’s Goddard Institute for Space Studies.

Until recently, there were few field studies that could potentially test how much carbon dioxide Arctic plants take up, leaving scientists unable to test the hypothesis that early snowmelt and its effects on plants helped control carbon dioxide in the atmosphere.

for our researchscientists Brave Bear Territory and cold summer nights to collect extensive CO2 measurements near plants and soils in 11 Arctic tundra ecosystems, including Alaska, Canada, Siberia, and Greenland. We focus on the least studied Arctic regions, which lie above continuous permafrost.

Early growth, but later slowdown

Arctic plants currently only have about three months to grow and reproduce before temperatures get too cold.

When we started this study, we wanted to understand how an earlier start of the growing season affects the total amount of carbon dioxide absorbed by vegetation each summer. The results surprised us: despite the obvious greenery, there was either no significant or only a small increase in overall CO2 uptake.

When we took a closer look and compared the weekly changes, we discovered why. While earlier snowmelt stimulated plant productivity in June, that productivity began to taper off in July—usually the peak season for photosynthesis. By August, productivity was well below normal.

the main shrub of the arctic, sedge and other wetland plants no longer absorb more carbon later in the season. It’s like waking up early in the morning and getting ready to go to bed early at night.

We still have many questions, including why plants respond in this way, and whether the widely used plant growth index is based on changes in visible and infrared light, called NDVI, certainly associated with higher carbon dioxide uptake.Some Arctic ecosystems have shown Strong correlationrelationship between NDVI and carbon dioxide uptake, while no one else. We found no evidence that plants were affected by water limitation in the late season.

If the tundra ecosystem cannot continue to absorb carbon dioxide later in the season, the projected increase in the number of carbon sequestering plants may not materialize.

There is another problem.Generally, plants on the tundra store more carbon through photosynthesis than the tundra releases, making it a huge carbon sink. The long, cold winter slows the decomposition of plants and locks them to the frozen ground. However, when permafrost containing this and other organic matter thaws, it releases more greenhouse gases into the atmosphere.

Local impacts go beyond carbon

It’s not just a story about plants and climate. Vegetation changes can have widespread impacts on other components of the ecosystem, including animals and people.

The UN’s Intergovernmental Panel on Climate Change, which assesses science related to climate change, estimates that changes in snow Affecting food and water security. Many local indigenous communities rely on hunting, trapping and fishing, and early vegetation development can affect the delicate balance of complex Arctic systems.

If Arctic greening simply changes the seasons and doesn’t increase overall carbon dioxide levels as previously thought, it could also mean that current models used to assess and predict the overall impact of climate change are missing an important piece of information. The result may be that the processes we thought would slow or mitigate climate change are not actually working as expected.