Vegetation cover change as a growing driver of global leaf area index dynamics.

Abstract

The ongoing four-decade increase in global leaf area index (LAI), inferred from satellite observations, suggests enhanced carbon sequestration and evaporative cooling with potential benefits that may help mitigate climate warming. However, the role of vegetation cover change in driving these trends remains debated, raising concerns about the potential effects of reforestation and deforestation on ecosystem-climate interactions. Here, we develop a data-driven framework combining satellite-based observations to quantify the contributions of vegetation cover change to LAI dynamics across space and time. We find that vegetation cover change explains 18.1 ± 5.9% of the observed LAI increase since the 1980s, with pronounced contribution from increased tree cover primarily occurring in the northern hemisphere (33.8 ± 3.6%), partially offset by deforestation mainly taking place in the southern hemisphere (-15.7 ± 3.1%). Increases are most prominent in forestation regions such as China and Europe, while the sensitivity, defined as LAI change per unit percentage of tree cover gain, is lower than declines induced by deforestation in tropical areas. Our findings reveal that vegetation cover change is already, and increasingly, shaping global LAI dynamics to a greater extent than previously recognized, with important implications for future LAI trajectory projections, model development, and climate mitigation policies.