Steve Running: Approximately 25 to 30 percent of that emitted CO2 is taken back up by land vegetation. Another 20 to 25 percent is absorbed by the oceans. And the remaining about 40 percent stays in the atmosphere.
Ecologist Steve Running of the University of Montana studies how Earth’s trees and plants absorb carbon dioxide or CO2, a greenhouse gas known to contribute to global warming. Some say that as Earth warms, more plants will grow and absorb more CO2 – and counteract Earth’s warming. But Dr. Running disagrees.
Steve Running: We really don’t see evidence that global vegetation can be a savior for carbon emissions.
Dr. Running uses NASA’s Terra satellite to create daily maps of plant photosynthesis. He says Earth’s northern latitudes are ‘greening’ – vegetation is now growing there more abundantly than when he began this work in the early 90s. But, while Earth’s plants might slow down global warming by removing CO2 from the air, Running said, he doesn’t think plants offer a long-term solution to global warming.
Steve Running: The only solution that adds up on a global scale is reduced emissions, because the land surface can’t absorb dramatically more than what it’s absorbing now. And we may actually lose some of the carbon uptake potential as areas, large regions, become water stressed with rising temperatures. And so we can’t count on vegetation CO2 uptake as a comprehensive solution at all to the imbalanced global carbon cycle.
That’s true, he said, because while plant growth is increasing, there are also increased destructive factors at work.
Steve Running: Vegetation productivity in the boreal and temperate regions appears to be increasing by maybe 45 to 46 percent over twenty years. The counterpoint is that we’re now quantifying that forest clearing, wildfires, deforestation, on a global basis is now a major part of the CO2 emissions every year. They are actually about 20 percent of what fossil fuel emissions are. So on the one hand, we have vegetation growing better in temperate and boreal forests, but on the other hand we have accelerating disturbance, deforestation, and fire emissions that are actually increasing the CO2 emissions from the terrestrial landscape.
Some see a flourishing of plant life in certain areas as a good thing. Dr. Running shared his thoughts.
Steve Running: We try to just speak with our facts as scientists here, and there’s certainly no doubt in our minds that as global warming proceeds, there are going to be parts of the world that in many ways are better off, and other parts of the world that will definitely be losers. And when it comes to the terrestrial biosphere, particularly the very high cold latitude areas will be warming, and their vegetation flourishing to some extent. The permafrost will also melt, and so we try not to put value judgments on these facts. We try to just state them as just the measurements as we see.
To read more about Dr. Running, see Why the Earth Observing System matters to all of us on the Earth Observatory.