A satellite-based study in Nature Climate Change finds forests with more tree species draw down more carbon. It warns that biodiversity loss could cost up to 35.7 petagrams of carbon uptake by 2050.
The link between biodiversity and climate has often been treated as two separate problems. New research suggests they are closely tied. A peer-reviewed study in Nature Climate Change finds that forests holding a wider range of tree species pull carbon dioxide from the air more strongly, and that they respond more vigorously as CO2 levels rise. The finding gives policymakers a concrete reason to fold species protection into climate strategy, because losing diversity means losing carbon uptake.
The researchers combined satellite measurements of photosynthesis with tree species records from forest plots around the world. Their approach used sun-induced chlorophyll fluorescence, a faint glow that green plants emit as they photosynthesise, as a proxy for how much carbon a forest fixes. Where species richness was higher, that signal tended to be stronger.
How the study measured forest carbon
The team matched richness data against the fluorescence signal across a range of climates and latitudes. At the global scale, species richness and photosynthesis moved together. The relationship was strongest in tropical forests, where diversity is greatest, and weaker at high latitudes, where fewer species grow and colder conditions limit growth.
Richer forests also showed a steeper rise in photosynthesis over time. That matters because it points to a stronger CO2-fertilisation effect, the process by which extra atmospheric carbon dioxide can boost plant growth. Diverse forests are better sinks today, and they may capture a larger share of future emissions.
What biodiversity loss could cost
The study then projected what happens if diversity falls. Under scenarios of biodiversity decline to 2050, driven by climate change and land use, the authors estimate a cumulative loss of forest photosynthesis of between 4.4 and 35.7 petagrams of carbon. A petagram is a billion tonnes, so the upper end represents a large dent in the land carbon sink that models often assume will keep absorbing emissions.
That range is wide, and the authors are clear about the uncertainty. Even so, the direction is consistent. As forests lose species, they lose some of their capacity to soak up carbon, and the loss compounds over time.
Why it matters for climate policy
Most national carbon accounts and integrated climate models treat forests mainly as a function of area and climate. Diversity rarely enters the calculation. If a richer forest is a stronger sink, then plantations of a single species may bank less carbon than mixed natural forests of the same size, a distinction with direct consequences for offset schemes and reforestation targets.
For carbon markets, the implication is sharper still. Credits generated by monoculture planting could overstate the climate benefit if they ignore the diversity premium the study describes. Folding biodiversity into how removals are measured would tighten that gap. As countries prepare stronger 2035 climate pledges, the research adds weight to the case for protecting existing forests rather than banking on new ones to compensate.
