We're not talking about the overall greenhouse situation, but particular regions experiencing high wet-bulb temperatures, or intense heat waves, and acute plant

We're not talking about the overall greenhouse situation, but particular regions experiencing high wet-bulb temperatures, or intense heat waves, and acute plant resilience in relation to human survivability. I am very aware some plants can manage and adapt. But for example there is a difference between C3 and C4 plants in regard to heat tolerance and distribution. The question is, can all plants manage in a given region, in a given moment of time, with a shift in competitive advantage for certain organisms around? Geological or evolutionary time scales are irrelevant, here, since we're talking about the years to come - a human life time. A temporary disturbance of a single factor may kill an ecosystem. For example eutrophication in lakes may lead to algae bloom, killing all other plants, fish and animals around. Or the extermination of the wolf, or another top predator, leads to overgrowth of deer, or another important prey animal, which then will eat all the young trees, which leads to receding forests, leading to increased soil erosion by wind, and leading to decreased rainfall, which ultimately leads to desertification or aridification. An instant 10% increased fitness for some opportunistic fungi could wreak havoc in a particular ecosystem. 10% decreased fitness for a local tree species, too. A general loss of diversity may lead to bad adaptability for periodic stress events. But you won't find evidence of these isolated catastrophes in fossils or drill cores. You don't see the farewell messages from all those species who didn't make it.