Specific examples of climate change-driven range shifts of tropical deciduous forests upslope into alpine grasslands have been documented in the Americas  and Asia . However, tree line behaviours are diverse. A study in Nepal recorded that the tree line fomed by Abies spectabilis had been stable for more than a century, while the upper limit of large shrubs  had been advancing . In both the Andes  and Himalayas , most tree lines have been stable, leading  to postulate a 'grass ceiling' that has been difficult for trees to penetrate. The tree line shifts that have occurred are probably driven by interactions between changing land use  and climate changes such as increased rainfall, warming and elevated CO2   .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report