Trees May Release Less Carbon Than Feared

A May 2025 study in Science, led by Tsinghua University, reveals that trees may release less CO2 through stem respiration than previously thought, challenging climate model assumptions. Analyzing thousands of measurements from 100+ tree species across tropical, temperate, arid, and boreal zones, researchers found that trees adapt to long-term warming via thermal acclimation, reducing respiration rates over months to decades. Unlike short-term experiments showing sharp CO2 spikes, this suggests forests could dampen positive climate feedbacks, with global ecosystems potentially absorbing 10-20% less carbon emissions than modeled. As Earth exceeds 1.5°C warming, can this resilience aid climate stability, or will human emissions overwhelm nature’s buffer?

Key Findings

• Thermal Acclimation: Trees adjust respiration over long timescales, cutting CO2 release by 15-25% compared to short-term heat responses.

• Global Dataset: Includes Australian savannas, Amazon rainforests, and boreal forests, covering 80% of global forest types, collected over 10 years.

• Model Impact: Current models overestimate respiration by 10-30% at 2°C warming, inflating atmospheric CO2 projections by 5-10 Gt/year by 2100.

• Ecosystem Resilience: Forests could slow warming by storing 20% more carbon than predicted, especially in tropics (50% of global forest carbon).

“Long-term responses differ from short-term spikes,” said Wright. “This dampens climate feedbacks.”

READ MORE: Earth’s Tipping Points Near Collapse as Warming Exceeds 1.5°C

Why It Matters

Forests absorb 30% of global CO2 emissions (11 Gt/year), balancing photosynthesis (120 Gt absorbed) and respiration (60 Gt released). Models assuming rapid respiration increases at 2.6°C by 2100 amplify warming forecasts. The study suggests:

• Lower Feedback: Reduced respiration cuts positive feedback loops, aligning with Amazon tipping point concerns.

• Refined Models: Updating models could lower 2100 warming estimates by 0.1-0.2°C.

• Policy Impact: Supports nature-based solutions, like Meta’s Olympic Rainforest credits, enhancing forest carbon sinks.

Strategic Context

Aligns with climate efforts:

• IFRS S2 Disclosures: Accurate forest carbon data improves Scope 3 reporting.

• EU’s 54% Emissions Cut: Forestry strengthens land sector carbon removal.

• Swiss Glacier Collapse: Highlights urgency of ecosystem resilience amid warming.

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Challenges and Risks

• Data Gaps: Only 20% of tropical species are sampled; scaling findings risks errors.

• Deforestation: 10M hectares lost yearly (FAO) offsets gains, releasing 5 Gt CO2.

• Limits: Acclimation weakens above 3°C, with 40% of forests at risk.

• Policy Risks: U.S. deregulation (e.g., $1.5B Army Corps cuts) may reduce reforestation funding.

What’s Next?

Researchers plan a 2026 global forest respiration database, covering 90% of species, costing $10M. Updated models, integrating acclimation, could guide $100B in reforestation by 2030, per UNEP. Tropical forests, storing 50% of terrestrial carbon, are priority targets.

“Ecosystems may slow warming,” said Wright.

With 36 Gt CO2 emitted in 2024, trees offer cautious hope. Will refined models spur action, or will deforestation and emissions outpace nature’s resilience?

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