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Abstract

Carbon stocks in vegetation have a key role in the climate system1–4.
However, the magnitude, patterns and uncertainties of carbon stocks
and the effect of land use on the stocks remain poorly quantified. Here
we show, using state-of-the-art datasets, that vegetation currently
stores around 450 petagrams of carbon. In the hypothetical absence
of land use, potential vegetation would store around 916 petagrams of
carbon, under current climate conditions. This difference highlights
the massive effect of land use on biomass stocks. Deforestation and
other land-cover changes are responsible for 53–58% of the difference
between current and potential biomass stocks. Land management
effects (the biomass stock changes induced by land use within the
same land cover) contribute 42–47%, but have been underestimated
in the literature. Therefore, avoiding deforestation is necessary but
not sufficient for mitigation of climate change. Our results imply
that trade-offs exist between conserving carbon stocks on managed
land and raising the contribution of biomass to raw material and
energy supply for the mitigation of climate change. Efforts to raise
biomass stocks are currently verifiable only in temperate forests,
where their potential is limited. By contrast, large uncertainties
hinder verification in the tropical forest, where the largest potential
is located, pointing to challenges for the upcoming stocktaking
exercises under the Paris agreement.