Background

As global warming progresses at an unprecedented rate, the question of how flora and fauna will respond to changing habitat environments has become a major topic in ecology. There are three primary pathways for biological populations to survive in rapidly changing environments: migration to higher latitudes or altitudes, expression of individual-level phenotypic plasticity, and genetic evolution adapting to unfavorable environments across generations.

Traditional conservation biology research has relied heavily on climate envelope models that combine only climate models and species geographic distribution information. This approach has faced continuous criticism for overestimating or underestimating extinction risks because it fails to reflect genetic variation within biological populations, environmental adaptation capacity, or intergenerational demographic dynamics. Some have raised optimistic expectations that rapid evolutionary rescue via natural selection could mitigate the impacts of warming. However, there has been a lack of precise numerical verification regarding whether long-lived perennial trees or large vertebrates, which have long generation intervals, can evolve fast enough to keep up with the pace of climate change triggered by human activities.

Key Findings

The researchers established an integrated eco-evolutionary forecasting framework that combines quantitative genetics (QG), population statistics, and climate variability projection scenarios. This framework was designed to track the interactions between dielectric constant, phenotypic selection intensity, environmental carrying capacity, and reproductive rates through individual-based simulations. Long-lived tree communities with generation periods spanning decades were selected as the study subjects, with temperature rise rates and extreme weather frequency according to greenhouse gas emission pathways entered as environmental variables.

Analysis revealed that the level of genetic variation and the rate of adaptation in the studied species were far insufficient to keep pace with the rate of warming. Under the high-emission scenario (SSP5-8.5), where greenhouse gas reduction efforts are delayed, the optimal phenotypic adaptation rate of the population remained at only 30% of the climate velocity. This is because it takes a long time for new alleles to become fixed within a population for organisms with long generation periods. As phenotypic adaptation lagged, the average fitness of the population decreased sharply, directly leading to decreased birth rates and increased mortality rates.

Even populations with relatively abundant genetic variation could not avoid demographic collapse once the temperature rise exceeded a critical threshold. A vicious cycle was observed where population decline occurred during the process of adaptive evolution, causing the effective population size to plummet, which in turn accelerated inbreeding and genetic drift, thereby eroding adaptive potential. In essence, the speed of the collapse of the climate system is far outpacing the limits of biological mutation and recombination for evolutionary rescue to function.

Implications and Outlook

The vague hope that living organisms will overcome the climate crisis through evolution has lost its scientific basis. This analysis clearly demonstrates how devastating the policy negligence of delaying greenhouse gas reductions or neglecting habitat destruction can be, based solely on reliance on genetic adaptive capacity. It implies that as long as the root cause of climate change is not controlled, the biological mechanism of natural selection alone cannot stop the wave of mass extinction.

A significant shift in artificial conservation strategies is inevitable. It is time to identify vulnerable species with slow adaptation rates and consider interventions such as assisted migration or restoration ecology to actively facilitate gene flow before genetic diversity is depleted. In terms of modeling, follow-up work remains to further incorporate multi-gene interactions, epigenetic factors, and interspecies interaction networks. This study strongly argues that when discussing ecosystem resilience, the priority should be placed on braking the warming itself rather than on the speed of evolution.