action is not effective if the unique and threatened systems in question reach a hard limit to adaptation  . Furthermore, adaptation benefits deriving from restoration rapidly diminish with increasing temperature . One study quantifies how land management  might reduce extinctions in biodiversity hotspots or globally significant terrestrial biodiversity areas more generally . While the latter suggests that substantial benefits can result globally in terrestrial systems, allowing less unique systems to persist at higher levels of warming but only under a high adaptation scenario in which globally applied terrestrial ecosystem restoration and protected area expansion takes place, this is less likely for many of the unique and threatened terrestrial systems which are more vulnerable than the globally significant biodiversity areas treated in that study . Such high levels of adaptation globally are likely infeasible owing to competition for land use with food production . Novel targeted adaptation interventions for coral reefs such as artificial upwelling and local radiation management show some promise for reducing the adverse effects of thermal stress and resulting coral bleaching , but are far from implementation . Larger benefits in this RFC could theoretically accrue only if adaptation action became ubiquitous and extensive, which experts considered infeasible at the scales required. Small island communities are confronted by socio-ecological limits to adaptation well before 2100, especially those reliant on coral reef systems for their livelihoods, even for a low-emissions pathway  . At warming levels beyond 1.5ºC, the potential to reach biophysical limits to adaptation due to limited water resources are reported for small islands  and unique systems dependent on glaciers and snowmelt  .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report