Organisms from primary producers to top predators are shrinking in size in response to climate change, according to a Perspective published online this week in Nature Climate Change.
It is well established that species are shifting their distributions to higher elevations and latitudes in response to warming, and that key life events such as migration are happening earlier in the year. What is less appreciated is that many species are also becoming smaller, as an ecological and metabolic response to increased temperatures and variability in precipitation. If this trend continues, it could have profound implications for food security and the stability of ecosystems.
David Bickford and Jennifer Sheridan look at the evidence from fossil records, experimental and geographic comparisons, and recent studies implicating current climate change in the shrinking size of both warm- and cold-blooded organisms. Highlighting the changes in organism size that are most likely as a result of climate change and increased carbon dioxide levels, they theorize on reasons for the observed patterns of size declines and discuss notable exceptions to the size-reduction trend.
Bickford and Sheridan argue that the size reduction trend will become much more pervasive in the future, negatively impacting both the crop plants and protein sources that are important for human nutrition. They say that research should focus on quantifying size trends more broadly, and identifying the drivers of size declines.