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What was claimed

A new Nature study shows average tree size in the Amazon increasing 3.2% per decade due to rising CO2, adding 11-17 gigatons of biomass yearly in southwest Amazonia. CO2 isn't killing the forest, it's feeding it. The Amazon is stronger, bigger and more resilient than a generation ago.

Our verdict

Needs Caution

The Nature Plants paper and institutional summaries discuss increases in tree size and biomass but do not report a figure of 11–17 gigatons of biomass added per year in southwest Amazonia or anywhere else. Global and regional carbon and biomass flux estimates for the Amazon are far smaller than such a number; no credible source associated with this study reports or supports this specific annual biomass range. The study and expert commentary emphasize that elevated CO2 is acting as a fertilizer that increases tree growth and size, but they explicitly caution that this does not mean CO2 is simply “good for the forest.” Authors note ongoing vulnerability to drought, heat, lightning, fire, and deforestation, and state the findings show resilience, not relief, so framing CO2 as not killing but feeding the forest oversimplifies and contradicts these cautions.

All 3 AI systems agree9 sources citedChecked Jul 7, 2026

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Key findings

The study shows the Amazon is adding 11–17 gigatons of biomass yearly in southwest Amazonia

Incorrect90%
2 of 3 AIs agree·Claude: Can’t verify

CO2 isn't killing the forest, it's feeding it.

Misleading85%
All 3 AIs agree

The Amazon is stronger, bigger and more resilient than a generation ago.

Misleading85%
1 of 3 AIs agree·Claude: Incorrect, ChatGPT: Can’t verify

A new Nature study shows average tree size in the Amazon increasing 3.2% per decade due to rising CO2

Verified95%
3 of 4 AIs agree·ChatGPT: Misleading

Verified against 9 sources

nature.comnbcnews.comphys.orgconservation.cam.ac.ukeos.orgbirmingham.ac.ukindianexpress.comfacebook.comreddit.com

Detailed Analysis

The response mixes one accurate, well-supported result from a recent Nature Plants study with several claims that are either numerically unsupported or interpret the findings in a misleadingly optimistic way. The statement about biomass added per year and the sweeping conclusions about the Amazon’s overall health and resilience cannot be verified and conflict with expert interpretations of the same study.

Why this verdict

  • The response mixes one accurate, well-supported result from a recent Nature Plants study with several claims that are either numerically unsupported or interpret the findings in a misleadingly optimistic way.
  • The statement about biomass added per year and the sweeping conclusions about the Amazon’s overall health and resilience cannot be verified and conflict with expert interpretations of the same study.

Claims checked

The study shows the Amazon is adding 11–17 gigatons of biomass yearly in southwest Amazonia

Incorrect90%
The Nature Plants paper and institutional summaries discuss increases in tree size and biomass but do not report a figure of 11–17 gigatons of biomass added per year in southwest Amazonia or anywhere else.[1] [3] [4] [6] Global and regional carbon and biomass flux estimates for the Amazon are far smaller than such a number; no credible source associated with this study reports or supports this specific annual biomass range.[1] [3] [4] [6]

This claim may mislead readers without added context.

The Amazon is stronger, bigger and more resilient than a generation ago

Misleading85%
The study finds the forest’s trees have become bigger on average and that large trees are growing and not yet dying off faster, which indicates a degree of resilience in intact forest plots.[1] [2] [3] [4] [5] [6] However, researchers and reports stress that this represents the forest “holding on” in monitored areas, not that the Amazon overall is unequivocally stronger and more resilient; they highlight serious ongoing threats from climate extremes and deforestation, so the claim overgeneralizes the result to the whole Amazon system.[2] [5] [4]

This claim may mislead readers without added context.

CO2 isn't killing the forest, it's feeding it

Misleading90%
The study and expert commentary emphasize that elevated CO2 is acting as a fertilizer that increases tree growth and size, but they explicitly caution that this does not mean CO2 is simply “good for the forest.”[1] [3] [4] [5] [6] Authors note ongoing vulnerability to drought, heat, lightning, fire, and deforestation, and state the findings show resilience, not relief, so framing CO2 as not killing but feeding the forest oversimplifies and contradicts these cautions.[2] [5]

This claim may mislead readers without added context.

What other AI think

The statement contains accurate data about tree growth from the Nature study but makes misleading interpretations. The 3.2% per decade increase is verified, but the claim that "CO2 isn't killing the forest, it's feeding it" and that the Amazon is "stronger, bigger and more resilient than a generation ago" contradicts recent evidence of severe degradation, fire damage, and declining resilience. The biomass figure cannot be verified from available sources.

Why this verdict

  • The statement contains accurate data about tree growth from the Nature study but makes misleading interpretations.
  • The 3.2% per decade increase is verified, but the claim that "CO2 isn't killing the forest, it's feeding it" and that the Amazon is "stronger, bigger and more resilient than a generation ago" contradicts recent evidence of severe degradation, fire damage, and declining resilience.
  • The biomass figure cannot be verified from available sources.

Claims checked

The Amazon is stronger, bigger and more resilient than a generation ago

Incorrect90%
Recent data contradicts this. The Amazon has lost 17% of intact humid forest since 1990. Forest degradation increased 163% from 2022-2024. The forest is approaching a tipping point, with declining resilience documented since the early 2000s. Deforestation and fires have severely weakened the ecosystem.

This claim may mislead readers without added context.

CO2 isn't killing the forest, it's feeding it

Misleading85%
While CO2 fertilization is stimulating tree growth in intact forests, the statement oversimplifies. Study authors explicitly note that deforestation is a 'huge threat-multiplier' and that the forest faces climate threats. The forest's resilience is described as temporary ('at least for now').

This claim may mislead readers without added context.

Adding 11-17 gigatons of biomass yearly in southwest Amazonia

Can’t verify40%
This specific figure for southwest Amazonia biomass accumulation does not appear in the search results from the Nature study or related coverage. The claim cannot be verified from available sources.
The statement mixes an accurate, well-supported numerical result with unverified or incorrect quantitative and interpretive claims. The 3.2% per decade increase in average tree size matches a 2025 Nature Plants analysis, but the 11–17 gigatons/year biomass figure and broad claims about CO2 'feeding' and the Amazon being overall 'stronger' are unsupported or misleading.

Why this verdict

  • The statement mixes an accurate, well-supported numerical result with unverified or incorrect quantitative and interpretive claims.
  • The 3.2% per decade increase in average tree size matches a 2025 Nature Plants analysis, but the 11–17 gigatons/year biomass figure and broad claims about CO2 'feeding' and the Amazon being overall 'stronger' are unsupported or misleading.

Claims checked

Adding 11–17 gigatons of biomass yearly in southwest Amazonia.

Incorrect90%
I found no reputable source reporting an 11–17 Gt yr⁻¹ biomass increase for southwest Amazonia; that magnitude is implausibly large compared with published regional and global carbon flux estimates.

This claim may mislead readers without added context.

This increase is due to rising CO2.

Misleading75%
The study finds patterns consistent with CO2 fertilization as a likely contributor, but it does not conclusively prove causation and notes other factors and future limitations.

This claim may mislead readers without added context.

CO2 isn't killing the forest, it's feeding it.

Misleading80%
While elevated CO2 can stimulate tree growth, CO2-driven climate impacts (heat, drought, fire) and other stressors can harm forests, so the blanket claim oversimplifies complex, opposing effects.

This claim may mislead readers without added context.

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