Substantial changes in vegetation structure and ecosystem processes are already happening . Many of these observations have already been projected to take place as early as at least IPCC AR3 , and can they now be increasingly tested for their robustness with observational evidence. These multiple changes in response to warming  are further expected for already relatively small additional temperature increases. In particular, in cold  regions, as well as in dry regions , alterations of 2-47% of the areal extent of terrestrial ecosystems in scenarios of <2℃ warming above pre-industrial levels have been projected, increasing drastically with higher-warming scenarios . More recent work, applying also probabilistic methods, confirm the risk of drastic changes in vegetation cover  at the end of the 21st century even for approximately 2℃ warming scenarios, especially in tundra, and also in tropical forest and savannah regions, with more subtle changes  likely to occur in all regions . Model studies have found 5-20% of terrestrial ecosystems affected by warming of around 2°C-3ºC, increasing to above one-third at a warming of 4°C-5℃ .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report