Image source: The American Physiological Society.
I just read an amazing review article written by George Somero from the Department of Biology at Stanford University on how the field of comparative physiology may be used as a crystal ball to predict how different species will respond to global changes. Some changes that may impact species include temperature, salinity, pH, and oxygen levels. For these studies, scientists often examine closely related species that are adapted to different environments to see how they differ physiologically and behaviorally.
Changes in biogeographic patterning occur when animals move locations in response to changing environments. Dr. Somero refers to studies showing that by 2080, 20% of lizard species will be extinct. This is because these animals are ectotherms and therefore are greatly impacted by rising global temperatures. Plankton has also been moving northward which impacts any fish reliant on this source of food.
The most heat tolerant species are in the greatest danger of extinction because they are already living close to their maximum tolerable temperatures. Sometimes, you simply cannot climb a mountain to cool off or move north fast enough.
Direct effects of global warming on an animal’s physiology include altered cardiac function and changes in gene expression, to name just two examples. Changes in cardiac function has an immediate impact on the survival of species. Changes in gene expression (increased or decreased expression) impacts not only living animals, but also their offspring as alterations in gene expression may be passed on.
For most species, the impact of increasing temperatures will produce changes that will impact the ability of species to survive over generations. Some animals may move to different locations impacting the new as well as old ecosystems. Some animals may be larger or smaller over time. Reproduction may also be impacted since animals may change how often they reproduce, where they reproduce, the number of offspring, etc. All of these changes have the possibility of impacting the number of animals over time and may result in extinctions. On the other hand, some animals may thrive with global warming and out-compete the weaker species resulting in dramatic changes in the ecosystem.
What Dr. Somero has shown so effectively is the need for more comparative physiology research to understand the effects of global change on animals and ecosystems.
Somero GN. Comparative physiology: a “crystal ball” for predicting consequences
of global change. Am J Physiol Regul Integr Comp Physiol 301: R1-R14,
Wang T, Overgaard J. The Heartbreak of Adapting to Global Warming. Science 315(5808), 49-50, 2007.