Ecosystem structure change: increasing risk of large-scale changes in ecosystem structure. Ecosystem structural change with most information derived for tropical forests, boreal forests, savannas and tundra for both observations and future projections. The transition from non-detectable risk to moderate risk is based on detected changes attributable to climate change or to interactions between changing disturbance regime, climate and rising CO2. These changes have already been observed at 0.5℃ above pre-industrial levels, with shifts initially detected in boreal forests, tundra and tropical grassy ecosystems. The transition from moderate risk to high risk is centred around 1.5℃, based on widespread global observations  that agree with projected future impacts with at least 10% area of key ecosystems being affected . Overall, there is medium confidence in projections. This is based on existing observations and some projections that have a high confidence of risk for several ecosystems, but data and projections are not available for all biomes, thus lowering overall confidence to medium confidence. The transition from high risk to very high risk occurs when >50% of multiple ecosystems are projected to experience shifts in structure. 
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report