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International audience; Climate warming is considered to be among the most serious of anthropogenic stresses to the environment, because it not only has direct effects on biodiversity, but it also exacerbates the harmful effects of other human-mediated threats. The associated consequences are potentially severe, particularly in terms of threats to species preservation, as well as in the preservation of an array of ecosystem services provided by biodiversity. Among the most affected groups of animals are insects—central components of many ecosystems—for which climate change has pervasive effects from individuals to communities. In this contribution to the scientists' warning series, we summarize the effect of the gradual global surface temperature increase on insects, in terms of physiology, behavior, phenology, distribution, and species interactions, as well as the effect of increased frequency and duration of extreme events such as hot and cold spells, fires, droughts, and floods on these parameters. We warn that, if no action is taken to better understand and reduce the action of climate change on insects, we will drastically reduce our ability to build a sustainable future based on healthy, functional ecosystems. We discuss perspectives on relevant ways to conserve insects in the face of climate change, and we offer several key recommendations on management approaches that can be adopted, on policies that should be pursued, and on the involvement of the general public in the protection effort.

Contains fulltext : 292642.pdf (Publisher’s version ) (Open Access) 10 maart 2023

Oxygen bioavailability is declining in aquatic systems worldwide as a result of climate change and other anthropogenic stressors. For aquatic organisms, the consequences are poorly known but are likely to reflect both direct effects of declining oxygen bioavailability and interactions between oxygen and other stressors, including two—warming and acidification— that have received substantial attention in recent decades and that typically accompany oxygen changes. Drawing on the collected papers in this symposium volume (“An Oxygen Perspective on Climate Change”), we outline the causes and consequences of declining oxygen bioavailability. First, we discuss the scope of natural and predicted anthropogenic changes in aquatic oxygen levels. Although modern organisms are the result of long evolutionary histories during which they were exposed to natural oxygen regimes, anthropogenic change is now exposing them to more extreme conditions and novel combinations of low oxygen with other stressors. Second, we identify behavioral and physiological mechanisms that underlie the interactive effects of oxygen with other stressors, and we assess the range of potential organismal responses to oxygen limitation that occur across levels of biological organization and over multiple timescales. We argue that metabolism and energetics provide a powerful and unifying framework for understanding organism-oxygen interactions. Third, we conclude by out-lining a set of approaches for maximizing the effectiveness of future work, including focusing on long-term experiments using biologically realistic variation in experimental factors and taking truly cross-disciplinary and integrative approaches to understanding and predicting future effects.

Rising temperatures are associated with reduced body size in many marine species, but the biological cause and generality of the phenomenon is debated. We derive a predictive model for body size responses to temperature and oxygen (O 2 ) changes based on thermal and geometric constraints on organismal O 2 supply and demand across the size spectrum. The model reproduces three key aspects of the observed patterns of intergenerational size reductions measured in laboratory warming experiments of diverse aquatic ectotherms (i.e., the “temperature-size rule” [TSR]). First, the interspecific mean and variability of the TSR is predicted from species’ temperature sensitivities of hypoxia tolerance, whose nonlinearity with temperature also explains the second TSR pattern—its amplification as temperatures rise. Third, as body size increases across the tree of life, the impact of growth on O 2 demand declines while its benefit to O 2 supply rises, decreasing the size dependence of hypoxia tolerance and requiring larger animals to contract by a larger fraction to compensate for a thermally driven rise in metabolism. Together our results support O 2 limitation as the mechanism underlying the TSR, and they provide a physiological basis for projecting ectotherm body size responses to climate change from microbes to macrofauna. For small species unable to rapidly migrate or evolve greater hypoxia tolerance, ocean warming and O 2 loss in this century are projected to induce >20% reductions in body mass. Size reductions at higher trophic levels could be even stronger and more variable, compounding the direct impact of human harvesting on size-structured ocean food webs.