Tree Species Diversity Linked to Long-Term Rise in Forest Photosynthesis

A new analysis suggests that forests with richer tree species not only produce more photosynthesis today, but also show faster gains in carbon uptake over time—an effect that could shape how well the land can buffer climate change in the coming decades. Using a high-resolution map of tree species richness across forests, researchers paired biodiversity patterns with satellite-derived photosynthesis proxies spanning 2001–2020.

The study’s core finding is a long-term relationship: locations with higher species richness correlate with both higher current photosynthesis levels and steeper positive trends through the two decades. In other words, biodiversity appears to enhance not just ecosystem productivity at a single point in time, but the trajectory of photosynthetic recovery and strengthening under environmental change.

To interpret why this happens, the authors focus on the CO₂ fertilization effect (CFE)—the tendency for rising atmospheric carbon dioxide to boost plant carbon assimilation. Their results indicate that species-rich forests exhibit an amplified CFE, meaning the same increase in CO₂ translates into a larger photosynthesis increase in diverse stands than in less diverse forests.

The paper also points toward mechanisms that could amplify this boost. Diverse forests may be better positioned to withstand water and nutrient limitations, reducing the likelihood that constraints on growth and photosynthesis blunt the response to CO₂. When limitations ease across multiple species and functional traits, the canopy can sustain higher photosynthetic performance for longer.

Because satellites can capture broad, consistent signals, this approach offers a rare window into long-term ecosystem change at continental scales. The analysis integrates biodiversity mapping with time-evolving photosynthesis proxies, enabling trend comparisons rather than static correlations.

Looking ahead, the authors warn that biodiversity loss could weaken the land carbon sink. Projections suggest that by 2050, declining species richness may reduce photosynthesis trends by 3–17%, corresponding to a cumulative forest photosynthesis loss of 4.4–35.7 PgC.

The implication is clear: protecting biodiversity may not be only an ecological goal, but a climate mitigation strategy. If diverse forests respond more strongly to CO₂ and better maintain photosynthesis under stress, losing that diversity could undermine one of the most important natural levers for drawing down atmospheric carbon.

In a warming world, the study argues that future climate models and mitigation plans should account for biodiversity as an active driver of how effectively ecosystems convert CO₂ into biomass.