The Earth is getting greener and it’s all down to increased carbon dioxide production.
Nearly half of Earth’s vegetation has grown more green in color over the last 35 years. A new study claims this is due to rising levels of atmospheric carbon dioxide.
An international team of 32 authors from 24 institutions in eight countries led the effort. They consulted satellite data from NASA’s Moderate Resolution Imaging Spectrometer and the National Oceanic and Atmospheric Administration’s Advanced Very High Resolution Radiometer to help determine the leaf area index in areas of vegetation. The data shows an increase in leaves on plants including trees equivalent in area to twice the size of the USA.
Green leaves use energy from sunlight through photosynthesis to chemically combine carbon dioxide drawn in from the air with water and nutrients tapped from the ground to produce sugars, which are the main source of food, fiber and fuel for life on Earth.
Studies demonstrate that increased concentrations of carbon dioxide increase photosynthesis, spurring on plant growth. However, carbon dioxide fertilization isn’t the only cause of these greener areas; nitrogen, land cover change, and climate change have all contributed.
To determine the extent of carbon dioxide’s contribution, researchers ran specific data relating to carbon dioxide in isolation.
Results showed that carbon dioxide fertilization explains 70 percent of the greening effect, said co-author Dr. Ranga Myneni, a professor in the Department of Earth and Environment at Boston University. “The second most important driver is nitrogen, at 9 percent. So we see what an outsized role CO2 plays in this process.”
About 85 percent of Earth’s ice-free lands is covered by vegetation. The area covered by all the green leaves on Earth is equal to, on average, 32 percent of Earth’s total surface area – oceans, lands and permanent ice sheets combined. The extent of the greening over the past 35 years “has the ability to fundamentally change the cycling of water and carbon in the climate system,” said lead author Dr. Zaichun Zhu, a researcher from Peking University, China.
Every year, about half of the 10 billion tons of carbon emitted into the atmosphere from human activities remains temporarily stored, in about equal parts, in the oceans and plants. “While our study did not address the connection between greening and carbon storage in plants, other studies have reported an increasing carbon sink on land since the 1980s, which is entirely consistent with the idea of a greening Earth,” said co-author Shilong Piao of the College of Urban and Environmental Sciences at Peking University.
While these high carbon dioxide concentrations can be great for plants, they’re also the biggest suspect of climate change.
CO2 traps heat in our atmosphere which has been increasing since the industrial revolution, growing to reach concentrations not seen in at least 500,000 years. Climate change has caused global warming, rising sea levels, melting glaciers and sea ice, and severe weather events.
The beneficial impacts seen among plants could also be limited.
Study co-author Dr. Philippe Ciais, associate director of the Laboratory of Climate and Environmental Sciences in Gif-sur-Yvette, France said, “Studies have shown that plants acclimatize, or adjust, to rising carbon dioxide concentration and the fertilization effect diminishes over time.”