Australia’s Tropical Forests Turn from Carbon Sinks to Emitters, Raising Alarm Ahead of COP30

A new study reveals that Australia’s tropical forests have become net emitters of carbon dioxide for the first time in recorded history. As world leaders prepare for COP30 in Brazil, experts warn this alarming shift could reshape global climate negotiations.

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Introduction: A Global Environmental Alarm

Australia’s lush tropical forests, once among the planet’s most reliable natural carbon absorbers, have crossed a dangerous threshold. According to groundbreaking research published in Nature on October 16, these forests are now emitting more carbon dioxide (CO₂) than they absorb — a troubling sign that could accelerate global warming and reshape climate strategies worldwide.

This finding arrives just weeks before the United Nations Climate Change Conference (COP30), set to begin on November 10, 2025, in Belém, Brazil — at the heart of the Amazon rainforest. The discovery adds urgency to an already tense global dialogue about deforestation, ecosystem decline, and the failure of international climate commitments.

The Study That Changed Everything

The study, led by Hannah Carle, an ecophysiologist at Western Sydney University, analyzed nearly five decades of data (1971–2019) from Australia’s tropical and subtropical rainforests. The findings were stark: since the early 2000s, the forests’ woody biomass — the trunks and branches that store carbon — has been shrinking.

Tree deaths have soared, driven by rising temperatures, prolonged droughts, and increasingly destructive tropical cyclones. As these trees die, the carbon they once locked away is released back into the atmosphere, transforming the forests from carbon sinks into carbon sources.

“This is the first time we’ve seen a tropical forest system tip from absorbing carbon to releasing it,” Carle said. “It’s a signal that even the most resilient ecosystems are reaching their limits.”

Why It Matters: Forests as Earth’s Carbon Regulators

Forests play a crucial role in regulating the global climate by capturing CO₂ during photosynthesis and storing it in their biomass. For decades, scientists viewed tropical forests as powerful buffers against climate change — absorbing as much as one-third of all human-produced carbon emissions annually.

Australia’s tropical forests, concentrated in Queensland and northern New South Wales, were long considered among the most stable of these ecosystems. Their shift into net emitters could mark a tipping point for global carbon balance.

If other tropical forests follow suit — particularly the Amazon and Congo basins — the world’s ability to naturally offset greenhouse gas emissions could collapse, making climate targets far harder to achieve.

Climate Stress and Tree Mortality

The study attributes rising tree mortality to several overlapping human-induced factors:

Rising global temperatures: Persistent heat waves have increased forest stress, making trees more vulnerable to disease and pests.
Extended droughts: Decreased rainfall has reduced soil moisture, limiting trees’ ability to photosynthesize and recover from damage.
Extreme weather events: Tropical cyclones and bushfires have become more frequent and intense, directly destroying vegetation and accelerating forest degradation.

Ecologist David Bauman, co-author of the study and researcher at the French National Research Institute for Sustainable Development, warned that these combined pressures are pushing ecosystems beyond recovery.

“Our findings underscore the urgency for global climate action,” Bauman said. “Ambitious efforts must be made to slow down climate change — and that includes protecting tropical forests before they stop protecting us.”

The Carbon Feedback Loop

The shift of tropical forests from carbon absorbers to emitters could create what scientists call a carbon feedback loop — a self-reinforcing cycle where warming triggers more emissions, which in turn cause further warming.

As more trees die, less carbon is stored in biomass, while decomposition releases more CO₂. This additional greenhouse gas traps heat in the atmosphere, further stressing forests and increasing mortality.

The concern is not just theoretical. Climate models now suggest that if these trends continue, forests worldwide could become net carbon emitters by mid-century, potentially adding billions of tons of CO₂ annually.

Nutrient Limits and Stalled Growth

One of the study’s most surprising discoveries was that extra CO₂ in the atmosphere — which scientists once believed would stimulate more plant growth — is no longer compensating for tree loss.

This unexpected result may be linked to nutrient limitations, particularly phosphorus, a mineral essential for plant growth. In tropical soils, phosphorus is often scarce, limiting how much additional CO₂ plants can absorb.

“The idea that plants would just grow faster with more CO₂ was overly simplistic,” Bauman explained. “Without enough nutrients, especially phosphorus, forests can’t respond as strongly as we once thought.”

This finding challenges some of the optimistic climate models that assumed forest growth would continue to offset rising emissions.

A Warning for COP30 Delegates

As world leaders prepare to convene for COP30 in Belém, the new data from Australia serves as a chilling reminder that the world’s natural defenses are weakening.

The conference, hosted in the Amazon region — another ecosystem under severe stress — is expected to focus heavily on forest protection, biodiversity loss, and carbon finance.

COP30 will also review progress (or lack thereof) on the Glasgow Declaration of 2021, where nearly 140 nations pledged to halt and reverse forest loss by 2030. So far, progress has been dismal.

According to the United Nations Environment Programme (UNEP), roughly 291 million hectares of tropical forest — nearly 20% of the global total — are at high risk of destruction. To meet current goals, the UNEP says global climate finance for forest protection must triple to $300 billion by 2030.

The Amazon: The Next Domino?

The Amazon rainforest, the planet’s largest and most biodiverse tropical forest, could soon face a fate similar to Australia’s.

Recent reports show that the Amazon, which currently absorbs about 25% of global land-based CO₂, is nearing a tipping point. Deforestation, record-breaking droughts, and wildfires have already reduced its carbon storage capacity.

In 2024, the Amazon experienced its worst drought in recorded history, drying major tributaries and triggering massive forest fires. Deforestation now affects nearly 17% of its total area — close to the threshold at which scientists predict “dieback” could occur, converting vast areas of rainforest into savannah.

If this transformation takes place, the Amazon could release over 90 billion tons of carbon, accelerating global warming far beyond current projections.

The Global Pattern: Congo Basin and Southeast Asia

Australia’s findings fit into a troubling global trend. Long-term studies have shown that other tropical forests — in Africa’s Congo Basin and Southeast Asia — are also losing their carbon absorption power.

In Africa, research led by Wannes Hubau of Ghent University indicates that even intact forests — those not directly logged or fragmented — began showing higher tree mortality around 2010.

Meanwhile, in Southeast Asia, forest fragmentation from urban sprawl, palm oil plantations, and infrastructure projects has severely weakened carbon storage capacity. A 2017 study warned that Southeast Asia’s forest carbon sink could vanish entirely if deforestation continues at current rates.

“It’s quite alarming,” Hubau said. “African tropical forests seem to be the last man standing, but even they are now showing cracks.”

The Human Cost of a Failing Forest System

The collapse of tropical forest health is not just an ecological tragedy — it’s a human crisis.

Tropical forests provide:

Food and water for over 1 billion people.
Rainfall regulation that supports global agriculture.
Natural flood and storm protection for vulnerable communities.
Medicinal plants that form the basis of many modern drugs.

As forests degrade, communities that depend on them — particularly Indigenous peoples — face increased poverty, food insecurity, and displacement.

Economist Sara Wallace Goodman, who studies climate adaptation policy, warns that without large-scale investment, forest-dependent populations will bear the brunt of climate inaction.

“Protecting forests is not just an environmental issue,” Goodman said. “It’s a human rights issue — one that determines food systems, water security, and social stability.”

The Financial Equation: How Much Will It Take?

According to the UNEP’s October 2025 Forest Finance Report, global investment in sustainable forest protection must reach:

$300 billion annually by 2030 (triple current levels)
$498 billion annually by 2050 (sixfold increase)

These funds would go toward:

Promoting sustainable agriculture that reduces land conversion.
Developing supply chains free of deforestation.
Strengthening forest law enforcement and monitoring systems.
Supporting Indigenous land rights and community-led conservation.

The report notes that every $1 invested in forest protection generates an estimated $9 in climate and social benefits, making it one of the most cost-effective climate strategies available.

Can COP30 Deliver a Turning Point?

The world’s attention will soon turn to Belém, Brazil, where COP30 is expected to serve as a reckoning for global forest commitments.

The key question for negotiators: Can countries move beyond promises and deliver binding financial and conservation mechanisms?

Experts suggest several potential outcomes that could emerge from COP30:

A Global Forest Fund: A dedicated financing mechanism for tropical forest nations.
Expanded Carbon Credit Frameworks: Ensuring fair compensation for verified forest preservation.
Stronger Deforestation Regulations: Especially targeting industries like palm oil, beef, and soy.
Indigenous Leadership Inclusion: Prioritizing the role of native communities as guardians of the forests.

Still, skepticism remains high. “We’ve seen bold declarations before,” said policy expert Clara D’Souza. “The challenge is implementation, not inspiration.”

A Planet at the Crossroads

Australia’s rainforest reversal underscores a larger truth: climate systems are unraveling faster than political systems can respond.

If tropical forests continue to emit rather than absorb carbon, humanity’s window to limit global warming below 1.5°C could close within a decade.

“The message from nature couldn’t be clearer,” Bauman said. “Forests have always protected us. Now it’s our turn to protect them.”

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