It’s the biggest forest in the world, the “lungs of the Earth”. But huge swathes of it are burning. Brazil’s space research agency INPE has counted more than 72,800 fires in the Brazilian Amazon in 2019 so far. For this time of year, that’s thought to be a new, harrowing, record.
The blazes are threatening indigenous communities, destroying precious wildlife habitats and sending gigantic plumes of pollution skyward. The burning of the Amazon is a “tragic” moment, says Pieter Tans at the US National Oceanic and Atmospheric Administration (NOAA).
But how bad are the fires for the Earth’s climate, particularly in terms of CO2 released?
The first indications seem dire. A measurement of how much CO2 has been emitted by Amazonian fires so far this month has been calculated by the European Centre for Medium-Range Weather Forecasts (ECMWF). By August 20, the fires had already spewed out around 23 million tonnes of CO2 – more than in any previous August going back to 2003. For comparison, in 2018 the entire UK energy industry pumped 98 million tonnes of CO2 – or its equivalent – into the atmosphere.
However, estimating the total amount of CO2 that will be emitted in 2019 by Amazonian fires is tricky because it depends on how much of the forest has burned and will continue to burn. There are only approximate estimates of that. CNN notes that, at the current rate of burning, one and a half football pitches are being destroyed every day. Back in 2010, another bad year for fires in the Amazon, 64,000 square kilometres were lost in total.
It’s impossible to know what 2019’s sobering tally will be, but the Amazon is particularly prone to producing CO2 when it burns. Tans explains that this is because the rainforest is extremely dense. About four times as dense as the average US forest, in fact. Burning therefore emits much more CO2 per square kilometre.
But here’s the truly terrifying part. In comparison to global CO2 emissions from fossil fuels, the Amazon fires will pale in comparison. Perhaps just a few per cent of the total emitted this year, explains Tans: “The impact on the global budget is remarkably small even though when you see these fires they look huge.”
You could look at the situation another way, he adds: the amount of CO2 humanity emits globally is “remarkably large”. Christine Wiedinmyer at the University of Colorado Boulder, agrees. “[For the] global carbon cycle it’s important but it’s not earth-shattering. But regionally on an air quality impact it’s huge.”
There are caveats. For one thing, trees killed by fires will decompose, releasing yet more CO2 over many years. In general, living trees in the Amazon absorb more CO2 than is emitted by dead trees, but the degree to which this is true can obviously fluctuate when an especially large number of trees are killed by fire.
The rainforest is not just a place that can release carbon – it is a potentially vast store of the stuff as well. So how do the fires affect the Amazon’s capacity to soak up carbon in its 390 billion trees, for example?
That’s where things get even trickier. The great hope in the aftermath of any forest fire is that new trees will take the place of burned ones, sucking up CO2 as they spring to life. This is often the case and it’s worth noting that young trees acquire CO2 at a faster rate than established old ones.
But if burned forest is claimed as agricultural land or for urban development, regrowth will obviously be prevented in those places. Even those areas left to nature will have their work cut out. Dominique Bachelet at Oregon State University explains that because big fires fill the air with particulate, the amount of sunlight reaching new and surviving trees can be reduced.
Photosynthesis is stymied as a result and the trees take up less CO2 than they otherwise would. Bachelet also points to a recent paper that found just how devastating repeated fires in the same patches of forest can be to above-ground carbon stores. “Forests with a history of one, two, and three or more fires retained only 54.4 per cent, 25.2 per cent, and 7.6 per cent of intact [above-ground carbon density], respectively, when measured after a year of regrowth,” the authors write. In other words, the more often a forest has been ravaged by fire, the longer we must wait before it removes the same volume of carbon from the atmosphere again.
And the scale of this year’s Amazonian fires also means that the rainforest is being pushed closer and closer to a “biophysical tipping point”, says Jim Randerson at the University of California, Irvine. As the forest shrinks, total rainfall decreases, potentially triggering a downward spiral of declining plant growth.
“Once the rainfall declines, it will be difficult for the forests to regrow, even if we have policies in place to allow for reforestation,” he says. “Many modelling simulations suggest we [are] getting closer to this tipping point.”
The Amazon rainforest is, like so many other things on our planet, part of a connected system. The 2019 fires are devastating. Even if they don’t in themselves overshadow anthropogenic CO2 emissions, deforestation begets deforestation and ultimately weakens the Amazon’s ability to store carbon. It’s a situation we can ill-afford in these climatologically troubled times.
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