A first of its kind NASA-backed study has demonstrated that the Amazon rainforest may actually be helping us in the fight against global warming by virtue of the amount of carbon dioxide it is able to hold onto.
The highly technical study, which was carried out over seven years and involved a number of universities from across the globe, is the first to measure Amazon tree deaths that were caused by natural processes, and is also the first to give a true glimpse into the Amazon’s carbon dioxide intake.
Over its lifetime, a tree will take carbon dioxide out of the air as it grows. That carbon is then stored within the tree, and this is why trees are known as carbon traps or “sinks.” When the tree decomposes, though, the greenhouse gas is then released back into the air.
The precise balance of the total level of carbon dioxide taken in compared to that which is released by decay hasn’t been fully understood as, until now, scientists have only been able to work with so-called test plots, small scale and heavily-studied tree areas. These aren’t ideal as while they may offer some insight, the numbers from these kinds of observations can’t simply be scaled up to represent the probable input and output of the massive Amazon forest due to the fact that so many things in those forests can happen, for instance a large band of trees might die all at once.
Yet with this new research, the scientists have finally been able to glimpse the Amazon forest’s most intimate life cycle. The study, published this month in Nature Communications, saw researchers use a variety of indicators for finding dead trees, including using aerial images to spot where fallen trees had left a gap in the tree canopy, and using satellite images to map for the color change of dead wood.
In this way, researchers could calculate the rate at which trees were dying and, estimating an average carbon dioxide output per tree, calculate the total output of the forest per year. They found that each year Amazonian trees emit about 1.9 billion tons of carbon into the atmosphere. Given how notorious carbon dioxide is as an insulating gas — that is to say, how it stays in our atmosphere and traps heat — that figure might be alarming, so it was important for the researchers to then understand how much carbon the Amazon actually takes in out of the air.
To do this, the researchers used a variety of methods, including but not limited to census data on new growth as well as more hi-tech methods like airborne lidar (laser surface imagery). By examining the data, they found that the Amazon rainforest may absorb as much as 2.2 billion tons of carbon dioxide, significantly more than it gives out. It is not overstating things, then, to say that the Amazon is acting at least in part to help reduce the amount of global warming causing CO2 in our atmosphere — though of course what effect that ultimately has on overall CO2 numbers isn’t clear.
Another important finding in this research was that the number of Amazon forest trees dying of so-called blowdowns is only about 0.1%. There had been some scientific debate over just how large an effect blowdowns have after observations made in the early 1990s showed that large swathes of the forest could be toppled in a short space of time. Now, the scientists know that these blowdowns probably have very little effect on the carbon cycle of the Amazon, though of course this says nothing about the real-life problems that species of plants and animals might face as a result of such events.
You may have already realized the stumbling block in this remarkable study: the researchers were only looking at natural causes for tree death.
Based on data from 2012 (the most recent we have until new data this July), research suggests that the area of the Amazon suffering deforestation is 5,843 sq km (2,255 sq miles). That figure rose in 2012 for the first time in years. To put the massive scale of loss into perspective, researchers have previously said that between 2000 and 2012, we lost an area equal to 50 football pitches every single minute. While a third of that has been replaced by reforestation efforts, that’s still a mindblowing loss. The amount of carbon dioxide released by that deforestation isn’t precisely known, but unfortunately its likely to put a sizable dent in the Amazon’s ability to hold on to more than it emits.
This perhaps underscores yet another reason why it is imperative that global powers take steps to combat and begin to reverse this forest loss, as scientists have shown yet another way the Amazon rainforest is integral to the survival of so much life on our planet.
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