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Climate crisis: Forests apparently store less CO₂ than assumed
🇩🇪 Germany /Environment & Climate

Climate crisis: Forests apparently store less CO₂ than assumed

From Der Spiegel · () German

Translated from German, summarized and contextualized by DistantNews.

At a glance

News Documents & data Context piece
  • Forests may store less carbon dioxide than previously assumed, according to new research.
  • A study found that tree growth and photosynthesis are not directly coupled, meaning increased photosynthesis doesn't automatically lead to more growth.
  • This decoupling means trees might not be as effective at long-term carbon sequestration as models predicted, impacting climate change mitigation efforts.

Forests play a crucial role in combating climate change by absorbing carbon dioxide through photosynthesis. During this process, trees convert CO2, sunlight, and water into glucose, releasing oxygen and storing carbon in their wood. However, new research suggests that the relationship between photosynthesis and tree growth is more complex than previously understood, potentially limiting forests' capacity for long-term carbon storage.

The understanding of this connection is crucial to understanding how forests store carbon in the long term.

— Mukund Palat RaoEco-climatologist at Columbia University, explaining the importance of the photosynthesis-growth link.

A study published in 'Science Advances' by researchers from Columbia University indicates that the assumption that increased photosynthesis directly translates to increased tree growth is flawed. "We found that this is not the case: more photosynthesis does not necessarily mean more tree growth in the future," stated lead researcher Mukund Palat Rao, an eco-climatologist.

The research team analyzed satellite imagery and used various measurement instruments on trees at 137 sites across the eastern United States and California. They tracked CO2 levels in tree canopies and the daily expansion and contraction of tree trunks over several years. Their findings revealed that in the eastern U.S., oak trees continued photosynthesis well into October, even after their growth phase concluded between May and July. Approximately 36 percent of carbon uptake occurred after the main growth period.

Most models currently assume that photosynthesis automatically leads to growth.

— Mukund Palat RaoDescribing the prevailing assumption in climate modeling.

Similarly, in California, where oaks grew from January to July, about 26 percent of carbon uptake happened post-growth. Rao explained that when drought and heat occur, growth nearly stops, while photosynthesis continues at a reduced intensity. The carbon absorbed during this later phase is used for forming new leaves or stimulating growth in the following year.

We found that this is not the case: more photosynthesis does not necessarily mean more tree growth in the future.

— Mukund Palat RaoPresenting the study's key finding about the decoupling of processes.

This decoupling of photosynthesis and growth means that current climate models, which often assume a direct link, may overestimate the amount of carbon forests can sequester. The researchers note that the extent of this decoupling likely varies among different tree species, ecosystems, and regions. Further investigation is needed to understand these variations and refine predictions about forests' future role in carbon storage.

As soon as drought and heat set in, growth stops almost immediately, while photosynthesis apparently continues with slightly reduced intensity.

— Mukund Palat RaoExplaining how environmental conditions affect tree processes.
DistantNews Editorial

Originally published by Der Spiegel in German. Translated, summarized, and contextualized by our editorial team with added local perspective. Read our editorial standards.

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