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By Vivek Saini
A well-known climate change contrarian, Steve Milloy, recently posted a series of statements on X (formerly Twitter) regarding the Amazon rainforest’s environmental role. In his tweet, Milloy disputed the commonly held idea that the Amazon is the “lungs of the planet,” minimised its contribution to the Earth’s carbon cycle, criticised scientific methods, downplayed its contribution to the Earth’s carbon cycle, and questioned the validity of scientific methods used to study it. His assertions, however, reflect a misunderstanding or oversimplification of the Amazon’s critical role in the global climate system.
X Post:
Claim 1: The Amazon jungle is not the “lungs of the planet.”
Fact: True, but misleading. The forest’s net contribution to global oxygen levels is nearly zero because it consumes the oxygen the trees produce through respiration and decomposition. However, its role as the most significant land-based carbon sink makes it crucial for climate regulation. Milloy’s statement that the Amazon rainforest is not the “lungs of the planet” refers to a common metaphor used to describe the Amazon’s role in global oxygen production. He argues that this characterisation is “lame green romanticism,” implying that the Amazon’s significance to the planet’s oxygen levels has been overstated or fabricated. This claim has some factual basis but misses the larger picture.
The Amazon rainforest absorbs large amounts of carbon dioxide (CO₂) during photosynthesis, releasing oxygen as a byproduct. However, Professor Yadvinder Malhi of the University of Oxford pointed out that the ecosystem almost entirely consumes the oxygen the Amazon produces through respiration and the decomposition of organic matter. Essentially, the Amazon’s net contribution to atmospheric oxygen is negligible, as the oxygen it generates is balanced by the oxygen used by plants, animals, and microorganisms in the forest.
This process helps mitigate climate change by storing carbon that would otherwise contribute to global warming. While Milloy’s claim that the Amazon isn’t a significant oxygen producer is technically valid, his argument ignores the forest’s essential contribution to carbon sequestration. The ‘lungs’ metaphor may not be entirely accurate in this context, but Milloy’s dismissal overlooks Amazon’s crucial role in the global climate system. The actual value of the Amazon lies not in its oxygen production but in its role as a massive carbon sink, absorbing around 2 billion tons of CO₂ annually.
This process helps mitigate climate change by storing carbon that would otherwise contribute to global warming. While Milloy’s claim that the Amazon isn’t a significant oxygen producer is technically valid, his argument ignores the forest’s essential contribution to carbon sequestration, which is crucial in regulating the Earth’s climate.
Claim 2: The Amazon jungle might be 2% or so of the Earth’s carbon cycle.
Fact: False. While the Amazon covers only a tiny portion of the Earth’s surface, it plays a disproportionately large role in the global carbon cycle. In his tweet, Milloy suggests that the Amazon represents only “2% or so” of the Earth’s carbon cycle, implying its relatively minor role in global carbon fluxes. This claim dramatically understates the Amazon’s true significance.
The Amazon, covering 2.5 million square miles, makes up about 1.2% of the Earth’s total land area, but its impact on the carbon cycle is far more substantial than Milloy indicates. Even though the Amazon rainforest is extensive, it’s still essential for regulating carbon levels on Earth—tropical forests like the Amazon account for about one-third of the carbon stored in land-based ecosystems. More specifically, the Amazon is the largest tropical rainforest in the world. It is the most important terrestrial carbon sink, storing 150–200 billion tons of carbon in its trees, soil, and vegetation.
The forest’s ability to absorb CO₂ has profound implications for climate regulation. Research shows that forests like the Amazon help offset human-caused carbon emissions by sequestering carbon in their biomass. Without the Amazon’s critical carbon storage, the atmospheric concentration of CO₂ would be significantly higher, contributing to accelerated global warming. Deforestation and environmental degradation threaten to transform the Amazon from a carbon sink into a carbon source, releasing the stored carbon into the atmosphere and exacerbating the climate crisis.
Therefore, while the Amazon may cover a small percentage of the Earth’s surface, its contribution to the carbon cycle and climate regulation is disproportionately large. Milloy’s assertion that it accounts for only 2% of the carbon cycle is not supported by the broader body of scientific evidence, highlighting the Amazon as a critical component in mitigating climate change.
Claim 3: Measuring tree circumference won’t yield more accurate estimates or useful climate information.
Fact: False. Measuring tree circumference is a critical scientific method for understanding forest growth, carbon storage, and the effects of climate change on forests. Milloy criticises measuring tree circumference, suggesting that this method won’t produce meaningful climate data or improve estimates of the Amazon’s role in the carbon cycle. This statement disregards well-established scientific practices foundational in forest ecology and climate research for decades.
Measuring tree circumference, or tree girth, is one of the most direct ways to monitor forest biomass growth. By tracking how much trees grow over time, researchers can estimate how much carbon these trees store and how effectively they sequester CO₂ from the atmosphere. When aggregated across large areas like the Amazon, such measurements provide critical data for modelling the forest’s carbon absorption capacity and tracking changes in forest health due to deforestation or climate change. This method is a cornerstone of scientific research and provides valuable insights into the health of our forests and their role in climate regulation.
These tree measurements also help scientists monitor the broader carbon fluxes in ecosystems, allowing them to assess how forests contribute to the global carbon cycle and how they may be affected by rising temperatures, changing precipitation patterns, and human activities like logging. Without these measurements, scientists would lack the detailed, ground-level data to refine global climate models and inform policies to reduce carbon emissions and protect vital ecosystems like the Amazon.
Furthermore, studies have shown that the Amazon is already approaching a critical tipping point, beyond which it could transition from a carbon sink to a carbon source due to deforestation and the impacts of climate change. Understanding forest growth and carbon storage dynamics is essential for predicting and preventing this shift. Thus, Milloy’s dismissal of tree circumference measurements as useless or inaccurate reflects a misunderstanding of their value in scientific research and climate policy.
References:
https://journals.plos.org/climate/article?id=10.1371/journal.pclm.0000054
http://www.yadvindermalhi.org/blog/does-the-amazon-provide-20-of-our-oxygen
https://www.wwf.org.uk/where-we-work/amazon
https://www.sciencedirect.com/science/article/abs/pii/S2352550923001641
https://www.nature.com/articles/s41586-021-03629-6
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6439692
‘Unprecedented’ stress in up to half of the Amazon may lead to tipping point by 2050
Banner image: Photo by Juan Orestes on Unsplash
