Land use change (LUC) and climate are significant threats to terrestrial ecosystems. As these impacts are expected to worsen in the future, it is important to understand how LUC affects vegetation cover and its relationship with regional climate. Using Earth system large ensemble simulations, our research found that abrupt decreases in the Leaf Area Index (LAI) mainly result from cropland expansion. These reductions are also strongly influenced by climate. In areas where LUC occurs, a negative relationship between LAI and surface temperature creates a positive feedback that further decreases LAI and increases warming. Additionally, regionally prolonged dry conditions and a shift toward drier climates can exacerbate the negative effects of LUC on LAI. The impacts of climate change vary by region, with western South America experiencing the most significant LAI decline under the SSP3-7.0 scenario. Our results improve the understanding of the combined effects of LUC and climate change, which could lead to abrupt decreases in vegetation cover in the future.