The increasingly urgent climate crisis has led to a boom in commercial tree plantations in an attempt to offset excess carbon emissions. However, authors argue that these carbon-offset plantations might come with costs for biodiversity and other ecosystem functions. Instead, the authors say we should prioritize conserving and restoring intact ecosystems.
"Despite the broad range of ecosystem functions and services provided by tropical ecosystems, society has reduced value of these ecosystems to just one metric -- carbon," write the authors, led by Jesús Aguirre-Gutiérrez of the Environmental Change Institute at the University of Oxford. "Current and new policy should not promote ecosystem degradation via tree plantations with a narrow view on carbon capture."
Tropical ecosystems, which include forests, grasslands, and savannahs, are attractive sites for tree plantations because their climate and physical features promote rapid tree growth (and rapid tree growth means rapid carbon capture). Although some tree plantations involve reforestation of degraded land, in many cases they involve afforestation -- planting forests in undegraded and previously unforested regions such as grasslands.
It's often assumed that tree planting for carbon capture also benefits biodiversity and enhances socioeconomic benefits, but the authors argue that this is usually not the case. Tropical ecosystems are highly biodiverse, and they provide multiple ecosystem services, such as maintaining water quality, soil health, and pollination. In comparison, carbon-capture plantations are usually monocultures and are dominated globally by just five tree species -- teak, mahogany, cedar, silk oak, and black wattle -- that are grown for timber, pulp, or agroforestry.