Antarctica Has Gotten 10 Times Greener in 35 Years

Our satellites are dispassionate observers of Earth’s climate change. From their vantage point they watch as pack ice slowly loses its hold on polar oceans, ice shelfs break apart, and previously frozen parts of the planet turn green with vegetation.

Now, scientists have compiled 35 years of satellite data showing that Antarctica is slowly, yet perceptibly, becoming greener.

NASA and the United States Geological Survey sent the first Landsat into space in 1975. Since then, they’ve launched eight more Landsats, with Landsat 9 being the most recent launch in 2021. Landsat data is a unique treasure trove of data about Earth and the changes it goes through, including millions of images.

Landsats have watched as forest fires burn, as urban regions expand, as glaciers melt, and as Earth goes through many other changes.

Recent research published in Nature Geoscience used 35 years of Landsat data, from Landsat 5 through Landsat 8, to measure the spread of vegetation into Antarctica. It’s titled “Sustained greening of the Antarctic Peninsula observed from satellites.” The research was co-led by Thomas Roland, an environmental scientist University of Exeter, and by remote sensing expert Olly Bartlett of the University of Hertfordshire.

“This study aimed to assess vegetation response to climate change on the AP <Antarctic Peninsula> over the past 35 years by quantifying rates of change in the spatial extent and ‘direction’ (greening versus browning), which have not yet been quantified,” the paper states.

The research shows that the amount of land covered in vegetation on the Antarctic Peninsula has increased by more than 10x since 1986. The area of vegetated land rose from 0.86 sq. km. (0.33 sq. mi.) in 1986 to 11.95 sq. km (4.61 sq. mi.) in 2021. The coverage is restricted to the warmer edges of the peninsula, but it still indicates a shift in the region’s ecology, driven by our carbon emissions.

This vegetative colonization of Earth’s coldest region begins with mosses and lichens. Mosses are pioneer species, the first organisms to move into a newly-available habitat. These non-vascular plants are tough and hardy, and can grow on bare rock in low-nutrient environments. They create a foundation for the plants that follow them by secreting acid that breaks down rock and by providing organic material when they die.

The map makes the results of the research clear. Each of the four panels show the amount of green vegetation on the Antarctic Peninsula’s ice-free land below 300 meters (1000 ft) altitude. Each hexagon is shaded depending on how many sq. km. of it are covered in vegetation. That’s determined by the satellite-based Normalized Difference Vegetation Index (NDVI). The NDVI is based on spectrometric data gathered by the Landsat satellites during cloud-free days every March, the end of the growing season in Antarctica.

Mosses dominate the green areas, growing in carpets and banks. In previous research, Roland and co-researchers collected carbon-dated core samples from moss banks on the western side of the AP. Those showed that moss had accumulated more rapidly in the past 50 years and that there’s been a boost in biological activity. That led them to their current research, where they wanted to determine if moss was not only growing upward to higher elevations, but outward, too.

“Based on the core samples, we expected to see some greening,” Roland said, “but I don’t think we were expecting it on the scale that we reported here.”

“When we first ran the numbers, we were in disbelief,” Bartlett said. “The rate itself is quite striking, especially in the last few years.”

The Western Antarctica Peninsula is warming up faster than other parts of Earth. Not only are its glaciers receding, but the extent of the sea ice is shrinking and there’s more open water. The authors point out that changing wind patterns due to GHG emissions could be contributing.

What will happen as the ice continues to retreat and pioneer species colonize more of Antarctica? The continent has hundreds of native species, mostly mosses, lichens, liverworts, and fungi. The continent has only two species of flowering plants, Antarctic Hair Grass and Antarctic Pearlwort. What does it mean for them?

“The narrative in these places has been dominated by glacial retreat,” Roland said. “We’re starting to think about what comes next, after ice recession.”

After moss gains a foothold in a region, soil is created where there was none. That provides an opening for other organisms, both native and non-native. The risk is that the inherent biodiversity will be undermined. Tourism and other human activity can inadvertently introduce new species, and wind-borne seeds and spores can do the same. If robust organisms arrive, they can outcompete the native species. There are already a few documented instances of this happening.

The carbon-core and Landsat data is just the beginning for Roland, Bartlett, and their fellow researchers. Up-close fieldwork is the next step. “We’re at the point that we’ve said the best we can say with the Landsat archives,” Roland said. “We need to go to these places where we’re seeing the most distinctive changes and see what’s happening on the ground.”

The researches want to know what types of plant communities are establishing themselves, and what shifts are playing out in the environment.