You may have seen images like this all over social media. The Amazon rainforest is burning, and these images have, understandably, caused international alarm, with media outlets, NGO’s and politicians all weighing in on the conversation about the value of one of the most unique and biodiverse ecosystems on the planet. Amidst all the discussion, one particular claim has stood out: that the forests of the Amazon are the lungs of the Earth, producing 20% of the world’s oxygen. But, that’s not exactly right. Now, the Amazon is the world’s largest remaining rainforest, covering between 6-8 million square km of land, holding millions of species, from plants to insects, birds, and mammals, many of which are yet to be discovered by researchers. However, it’s an ecosystem that is compromised. This year more than 74,000 fires have been recorded in Brazil, most of which are in the Amazon region. And because of this, many are wondering if the deforestation taking place in the Amazon will have a negative impact on our global oxygen supply, which in turn, has led to the claim that the Amazon produces 20% of the world’s oxygen. So where exactly did this figure come from? “This misunderstanding arises from the fact that the Amazon accounts for roughly 20% of the land surface photosynthesis on the planet, and photosynthesis produces oxygen and takes our carbon dioxide from the atmosphere. But the bigger issue is that it misunderstands what happens to that oxygen, and where our long term oxygen resource comes from. And the key thing to understand is that most ecosystems consume as much oxygen as they produce.” In other words, we can assume that the Amazon probably consumes the same amount of oxygen that it creates. “We estimate that about 60% of the oxygen produced by plants is consumed by plants as well for their metabolism. And the remainder is consumed by microbes, in particular, as they’re consuming dead organic material, and we estimate that’s somewhere around 40%. So overall, in terms of oxygen supply, the Amazon and almost any other biome on Earth is pretty close to zero, in the net amount of oxygen it provides.” The biggest contributor to Earth’s oxygen supply is actually within our oceans: around half of Earth’s oxygen is generated from marine organisms through photosynthesis. Phytoplankton are one of the primary producers, using carbon dioxide, water, and solar energy to create their food and produce oxygen as a byproduct. Okay, so you might be wondering if we did lose the Amazon completely, what would happen to Earth’s atmosphere? Unlike carbon dioxide, which has quite a low concentration in the atmosphere, with carbon dioxide at around 400 parts per million, oxygen is 21% of the atmosphere, so the atmosphere is awash in oxygen. So, if the Amazon was entirely disappear in flames, the concentration of oxygen in the atmosphere would dip by just a tiny fraction of a percent. However, the Amazon still remains a crucial part of our global ecosystem. It regulates regional rainfall and by extension, the global climate, through deep tree roots that can access water and recirculate it back to the atmosphere, generating moisture that can produce clouds and rainfall. Most importantly, it acts as a carbon sink thanks to the process of photosynthesis, and that would be the biggest threat we’d face if we lost this rainforest. “So if the entire Amazon rainforest were to disappear, atmospheric CO2 concentrations would increase by around 10%, which may sound like a small number, and it is, compared to our fossil fuel emissions. But if this were to happen, our chances of stabilizing atmospheric CO2 concentrations at a level that we can say within a safe climate zone would be much, much more challenging.” So, all this is to say, that as the world considers how to protect the Amazon, it’s important to make sure that we’re equipped with the right facts when having these discussions. “I think this relates to the idea of the lungs of the Earth, which I think is a fine metaphor, if you just use it as a poetic metaphor of how important Amazon is. I prefer to think of as a global cooling system or a global pump. I think that there are plenty of strong scientific reasons to to protect the Amazon to value the Amazon. And it’s good to make the case for the Amazon based on where the science is strong. It’s dangerous to make a case of something that actually is a flawed scientific concept.” If you liked this episode, let us know in the comments below, and check out this video on what a cloudless world would look like. Make sure to subscribe, and thanks for watching.