We are in a period of relatively rapid climate change. This poses challenges for individual species and threatens the ecosystem services that humanity relies upon. Temperature is a key stressor. In a warming climate, individual organisms may be able to shift their thermal optima through phenotypic plasticity. However, such plasticity is unlikely to be sufficient over the coming centuries. Resilience to warming will also depend on how fast the distribution of traits that define a species can adapt through other methods, in particular through redistribution of the abundance of variants within the population and through genetic evolution. In this paper, we use a simple theoretical ‘trait diffusion’ model to explore how the resilience of a given species to climate change depends on the initial trait diversity (biodiversity), the trait diffusion rate (mutation rate), and the lifetime of the organism. We estimate theoretical dangerous rates of continuous global warming that would exceed the ability of a species to adapt through trait diffusion, and therefore lead to a collapse in the overall productivity of the species. As the rate of adaptation through intraspecies competition and genetic evolution decreases with species lifetime, we find critical rates of change that also depend fundamentally on lifetime. Dangerous rates of warming vary from 1°C per lifetime (at low trait diffusion rate) to 8°C per lifetime (at high trait diffusion rate). We conclude that rapid climate change is liable to favour short-lived organisms (e.g. microbes) rather than longer-lived organisms (e.g. trees).
Ocean warming is already causing widespread changes to coral reef ecosystems worldwide. Warming is having direct and indirect impacts on food webs, but their interaction is unclear. Warming directly affects fishes and invertebrates by increasing their metabolic rate, resulting in changes to demographic processes such as growth rates. Indirect effects involve a loss of reef habitat quality as coral bleaching reduces the availability of refuges. We used a size‐structured dynamic energy budget model of fishes and invertebrates, coupled to a spatially explicit model of coral and algae, to explore potential changes to ecosystem function with warming. Modeled changes in biomass for +3°C of warming were found to be controlled predominantly by the direct effects of warming on growth rates, rather than by indirect effects via the changed coral habitat. Crucially for fisheries, the biomass of predators decreased by at least 50% with +3°C of warming, and productivity of predators decreased by at least 60%.
<p>Microbial respiration in soils controls a key flux in the global carbon cycle, yet its sensitivity to warming remains uncertain. Respiration rates increase exponentially with rapid warming, but the response is dampened over time. Several possible mechanisms have been suggested to explain the response: taxon-level adaptation, changes to community composition and changes to community biomass. However, the role played by each mechanism has not been resolved. Here, we separate the relative importance of these mechanisms, finding that taxon-level adaptation has a larger role in controlling the dampening of the temperature sensitivity of community respiration rather than changes to community composition. We used a novel dataset of five taxa incubated simultaneously in monoculture and as a community across a range of temperatures in a controlled laboratory environment, which showed the expected dampening of community respiration. Taxon-level adaptation, changes to community composition and changes to community biomass were all observed, with a new mathematical model of taxon-level adaptation revealing that the dampening of taxon-level respiration was due to changes in maintenance respiration and cell mass. The importance of taxon-level adaptation in the dampening of community respiration response to temperature reconciles disagreement from previous studies and provides evidence for a robust representation of microbial processes in carbon cycle models.</p>
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