Deforestation and climate change

• 1. Introduction

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  Deforestation and climate change are locked in a feedback loop that scientists describe as self-amplifying. Every year, 75,700 square kilometers of forest disappear from the planet. That is roughly the size of a small country, gone in twelve months. And the consequences do not stay local. They travel upward into the atmosphere and ripple outward across rainfall patterns, fire seasons, and global temperatures.

  Forests currently cover 31% of all land on Earth. When they grow, they act as carbon sinks, pulling carbon dioxide out of the air and storing it in wood, roots, and soil. But when they are cut, burned, or left to decompose, that stored carbon floods back into the atmosphere. Land use change driven by deforestation is now the second largest source of human-caused carbon dioxide emissions, surpassed only by the burning of fossil fuels. Globally, deforestation accounts for roughly 11% of all greenhouse gas emissions.

  What makes this especially alarming is the direction the trend is moving. Carbon emissions from tropical deforestation are accelerating. Between 2019 and 2020 alone, the loss of primary tropical forests increased by 12%. And somewhere in the Amazon, nearly 20% of the rainforest has already been clear cut. The questions that follow are stark: at what point does forest loss become irreversible? And what happens to the planet's climate systems when that threshold is crossed?

• 2. The Feedback Machine

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  Modeling studies have identified two specific thresholds that could push the Amazon toward catastrophic collapse. A temperature rise of 4 degrees Celsius or deforestation reaching 40% of the forest cover are the two crucial moments researchers flag as triggers for devastating, potentially unstoppable change.

  The relationship between deforestation and climate change is what scientists call a positive feedback. Not positive in the sense of helpful, but in the sense that each effect amplifies the other. Removing trees accelerates warming; warming then accelerates tree loss through drought, pest outbreaks, and fire. The cycle tightens with each pass.

  The Amazon rainforest once absorbed one-fourth of all carbon dioxide emissions on Earth. Today, that absorption capacity has dropped by 30% compared to the 1990s, a direct consequence of deforestation. What was a planetary buffer is slowly becoming a diminished one, and the downstream effects extend far beyond the forest itself. Irreversible deforestation, according to research, would result in a permanent rise in global surface temperatures. Standing tropical forests, by contrast, help cool the average global temperature by more than 1 degree Celsius.

• 3. Fire and Tipping Points

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  Statistics from the Brazilian Amazon during the early 2000s showed a direct correlation between fire and deforestation. High deforestation rates led to frequent fires, with the air pollution from those fires mirroring the spatial patterns of forest clearing across the region.

  The Amazon faces fires inside the forest and wildfires on its outer edges. Wetlands, too, have seen an increase in forest fires. Rising temperatures have made the climate around forests warmer and drier, creating exactly the conditions fire needs to spread. A study in the tropical peatland forests of Borneo reached a similar conclusion, finding that deforestation raises fire risk there as well.

  Under unmitigated climate change, research projects that by the end of this century, 21% of the Amazon would be vulnerable to post-fire grass invasion. In 3% of the Amazon, fire is already returning faster than the canopy can recover, creating a high risk of permanent shifts toward a degraded, fire-maintained grassy state. The south-eastern region of the Amazon carries the highest current risk of this kind of irreversible degradation. Once grass establishes itself in place of forest, the canopy cannot reclaim the ground, and the land's ability to store carbon or sustain rainfall is permanently reduced.

• 4. Rain, Albedo, and Distant Costs

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  A 2023 study found that tropical deforestation has already produced a measurable decrease in observed precipitation. By the year 2100, researchers anticipate that deforestation in the Congo alone could reduce regional rainfall by up to 8-10%.

  The mechanism runs through evapotranspiration. Trees pull water from the soil and release it into the atmosphere, feeding the moisture cycles that produce rainfall. When the trees are removed, that process stops. Precipitation drops, the climate grows hotter and drier, and dry seasons lengthen. These shifts increase the frequency and severity of fires and disrupt the pollination cycles that sustain plant reproduction. The effects do not stay within the deforested zone; they spread outward.

  Deforestation also changes the reflectivity of the land surface, a property called albedo. Forests are darker than bare ground. When forest is removed, more sunlight bounces back as heat rather than being absorbed by vegetation, which enhances warming. Intriguingly, research since the early 1990s has shown that large-scale deforestation above 50 degrees north latitude actually produces net global cooling because the exposed high-latitude ground reflects far more sunlight than the forest it replaced. Tropical deforestation, by contrast, produces substantial warming. Carbon-centric metrics alone cannot capture this distinction, because the biophysical mechanisms at high latitudes work differently than they do near the equator.

• 5. Land Use After Clearing

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  Not all deforestation is equal in its climate impact. When cleared forest is converted to pasture for livestock grazing, the ecological damage is greater than when it is converted to cropland. The type of land use that follows clearing shapes how much carbon is released and how severely local ecosystems are disrupted.

  The causes of deforestation are multiple: agricultural clearcutting, livestock grazing, logging for timber, and wildfires all contribute. Each driver interacts differently with the remaining forest, the soil, and the regional water cycle. In the Amazon, deforestation affects not only carbon levels in the atmosphere but also water sources and soil health across a vast interconnected region.

  Some effects of climate change circle back to cause more forest loss. More intense wildfires, the spread of invasive species, and increasingly extreme weather events all reduce forest cover, which in turn releases more carbon and feeds further warming. The tipping point scenarios modeled for the Amazon, where temperature rise of 4 degrees Celsius and 40% deforestation converge, reflect the worst-case version of this cycle running uninterrupted.

• 6. Global Responses

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  The Bali Action Plan was developed in December 2007 in Bali, Indonesia, as a direct outcome of the Kyoto Protocol of December 1997. Its core commitment was to mobilize member countries to create policy approaches that incentivize emissions reductions from deforestation and forest degradation in the developing world. It also emphasized sustainable forest management and conservation as tools for mitigating climate change, and it linked carbon stock protection to additional resource flows for developing countries.

  On the reforestation side, the United Nations Environment Programme launched the Billion Tree Campaign in 2006, initially targeting the planting of one billion trees in 2007. By 2008, that target had been raised to 7 billion trees, timed to the climate conference in Copenhagen, Denmark, in December 2009. Three months before that conference, the 7 billion mark had already been surpassed. In December 2011, after more than 12 billion trees had been planted, UNEP handed management of the program to the not-for-profit Plant-for-the-Planet initiative, based in Munich, Germany. The campaign was subsequently rebranded as the Trillion Tree Campaign, a name that reflects how dramatically the ambition expanded in just a few years.