Satellite Images, Track ‘Greening’ of Forest Amid Climate Change

Researchers from North Carolina State University used satellite imagery and field sensors to estimate global changes in plant leaf growth caused by global warming.

The researchers discovered that changes in "greening," or the number of leaves plants can produce, have a significant impact on how much carbon dioxide plants capture and store.

Using Satellites To Track Earth 'Greening' Amid Climate Change

(Photo : Jes Aznar/Getty Images)

"As we work to predict the future climate, one big question is: What will happen to vegetation, one of the largest carbon stores on the planet?" said study co-author Josh Gray, associate professor of forestry and environmental resources at NC State, as per ScienceDaily.

They know that temperatures will rise and the growing season will lengthen in most places, but there are many unknowns about how this will affect how carbon is cycled between plants and the atmosphere; Gray's new findings give them more confidence about what those changes will be.

According to the study's first author, Xiaojie Gao, a graduate student in NC State's Center for Geospatial Analytics, an earlier spring may be beneficial to plant productivity because it allows for a longer period of carbon uptake.

Longer autumn, on the other hand, could exacerbate the situation. Plants tend to emit carbon in the autumn.

Researchers wanted to understand the role of growing season length and the number of leaves plants produce in carbon uptake in the study published in Global Biogeochemical Cycles.

They measured plant leaf biomass using satellite measurements of infrared light taken between 2000 and 2014.

Because plants cannot use infrared light for photosynthesis, it is reflected.

Because healthy green leaves act as infrared mirrors, they appear extremely "bright" to satellites operating at these wavelengths.

Gray calculates an index that is a combination of how bright a place is in infrared and red wavelengths and corresponds to how many leaves are in a place using a few tricks.

Furthermore, researchers used sensors on field towers to measure the exchange of carbon dioxide between plants and air in order to calculate how much carbon plants remove from the atmosphere each year through photosynthesis.

They discovered that the amount of leaf biomass, or the number of leaves produced by plants in a year, has a greater impact on net carbon uptake than changes in growing season length.

Gray stated that there are some areas with more leaves than others, particularly at higher latitudes.

There are also some areas where spring arrives early and fall arrives late.

All of these changes affect the amount of photosynthesis that occurs, but the number of leaves produced by plants has a stronger relationship with carbon uptake than changes in growing season length.

In other words, they discovered that greening trends were more important for carbon uptake than extending the growing season.

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What Is The State Of The World's Forests?

The Food and Agriculture Organization of the United Nations' 2022 State of the World's Forests report is packed with the most recent data on deforestation and reforestation, tree cover, and the benefits of trees.

Forests cover 31% of the Earth's land surface, but that area is shrinking - we lost 420 million hectares of forest between 1990 and 2020 alone due to deforestation.

Although the rate of deforestation is decreasing, forests are still being lost at a rate of 10 million hectares per year between 2015 and 2020.

Between 2000 and 2020, 47 million hectares of primary forest were lost.

Planted forests cover 294 million hectares or 7% of the global forest area.

Between 2015 and 2020, this area increased by nearly 1% per year, compared to a 1.4% increase per year between 2010 and 2015.

Gray's findings also suggest that satellite imagery could be a useful tool for tracking changes in plant growth and the carbon cycle as the climate changes.

Furthermore, their findings should help to inform future predictions of plants' roles in carbon capture.

The total area of non-forest land defined as woodland decreased by nearly 1% between 2000 and 2020, while the area of land with tree cover (urban trees, tree orchards, palms, and agroforestry landscapes) increased by more than a third.

Agroforestry is becoming more popular, with at least 45 million hectares of land currently dedicated to the practice.

Forests are home to 80% of amphibian species, 75% of bird species, and 68% of mammal species, and tropical forests contain approximately 60% of all vascular plant species.

Over 700 million hectares of forest (or only 18% of the global forest area) are legally protected.

Forests play a variety of roles, including the storage of 662 billion tonnes of carbon, which accounts for more than half of the global carbon stock in soils and vegetation.