Species-rich forests improve faster; biodiversity loss may cut gains 17%

A new study published in Nature Climate Change reveals that forests with greater tree species diversity appear to improve their photosynthesis rates faster over time, according to researchers. By analyzing satellite data from 2001 to 2020, the study found that forests with higher species richness exhibited not only stronger photosynthesis levels but also more substantial increases in photosynthesis over time.

This suggests that biodiversity plays a crucial role in helping forests adapt to changing environmental conditions, enhancing their ability to absorb carbon dioxide from the atmosphere. Photosynthesis is a vital process that powers forest growth and carbon uptake, making it an essential natural buffer against climate change.

The researchers combined high-resolution maps of tree species richness with satellite-based photosynthesis data to make their findings. Their analysis showed that forests with more tree species were not only more productive at a single point in time but also improved their photosynthesis rates at a faster pace, indicating that biodiversity may contribute to forests' better adaptation to environmental changes.

The study points to an amplified CO2 fertilization effect in species-rich forests, meaning that these forests can convert rising atmospheric carbon dioxide levels into stronger photosynthetic gains compared to less diverse forests. This finding aligns with previous research suggesting that diverse forests tend to capture light more effectively and distribute it more evenly throughout the canopy.

The relationship between tree species richness and photosynthesis was particularly strong in tropical forests, which are already critical carbon sinks and face significant threats from deforestation, warming, and habitat fragmentation. In these ecosystems, richer species mixtures seem to capture sunlight more efficiently and support higher photosynthetic capacity overall.

By 2050, if biodiversity continues to decline, the researchers estimate that forest photosynthesis trends could weaken by 3% to 17%, resulting in a cumulative loss of 4.4 to 35.7 petagrams of carbon from forest photosynthesis. This weakening of forest photosynthesis could hinder nature's ability to absorb human-produced emissions, making it more challenging for the global carbon cycle to regulate climate change.

The study's findings extend beyond conservation efforts, emphasizing the functional value of biodiversity. More diverse forests can provide greater stability under climate variability, maintaining their photosynthetic capacity throughout heatwaves, droughts, and other stressors. Protecting species-rich forests, especially in the tropics, may be one of the most practical ways to preserve natural carbon uptake at a global scale.

In summary, the headline finding is clear and impactful: biodiversity enhances forest performance, and the loss of biodiversity could weaken this capacity in the future. As the world seeks climate solutions, the study underscores that healthy, diverse forests are not only biologically important but also more effective in mitigating climate change.