In this age of climate change, we naturally train our attention on all the fossil fuels being combusted for human use — but scientists have long known that what’s happening is also all about the land.
Just as buried fossil fuels are filled with carbon from ancient plant and animal life, so too are living trees and vegetation on Earth’s surface today. Razing forests or plowing grasslands puts carbon in the atmosphere just like burning fossil fuels does.
Now, new research provides a surprisingly large estimate of just how consequential our treatment of land surfaces and vegetation has been for the planet and its atmosphere. If true, it’s a finding that could shape not only our response to climate change, but our understanding of ourselves as agents of planetary transformation….
….Using a series of detailed maps derived from satellite information and other types of ecological measurements, Erb and his colleagues estimated how much carbon is contained in Earth’s current vegetation. The number is massive: 450 billion tons of carbon, which, if it were to somehow arrive in the atmosphere as carbon dioxide, would amount to over a trillion tons of the gas. (The mass is greater due to the addition of oxygen molecules.)
But the study also presented an even larger and perhaps more consequential number: 916 billion tons. That’s the amount of carbon, the research calculated, that could reside in the world’s vegetation — so not in the atmosphere — if humans somehow entirely ceased all uses of land and allowed it to return to its natural state. The inference is that current human use of land is responsible for roughly halving the potential storage of carbon by that land….
…the impact calculation is so large because humans have done far more than just bring about deforestation, which Erb said accounts for about half of the loss of potential vegetation. … “But the other half, in most studies, is completely missing.”…
…The study found that there are two far-less-recognized components of how humans have subtracted from Earth’s potential vegetation — and that in combination they are just as substantial as deforestation. Those are large-scale grazing and other uses of grasslands, as well as forest “management.” With the latter, many trees and other types of vegetation are subtracted from forests — often the larger and older trees due to logging — but the forests as a whole don’t disappear. They’re just highly thinned out.
“This effect is quite massive, more massive than we expected actually,” Erb said….
….The research means that so-called degraded land — not fully deforested but not “natural” or whole, either — is a phenomenon to be reckoned with.
“It suggests that the amount of carbon released to the atmosphere from land use is approximately equal to the amount still retained,” said Tom Lovejoy, an ecologist at George Mason University who was not involved in the work. “That means the restoration agenda is even more important than previously thought and highlights the enormous amount of degraded land in the world.”…
….“Scenarios that limit global warming to 1.5 or 2 degrees [Celsius] require not only rapid cessation of greenhouse gas emissions but also removal of somewhere between about 100 and 300 billion tons of carbon [or 370 to 1110 billion tons (Gt) of CO2e] from the atmosphere,” Phil Duffy, president of the Woods Hole Research Center, said in an email.
“This paper suggests that restoring vegetation around the world could in principle achieve that,” Duffy continued, noting that if all the potential vegetation were restored it would offset some 50 years of global carbon emissions. While “the full theoretical potential will never be realized in practice … this paper indicates that restoring vegetation could make an extremely important contribution to controlling global climate change.”