The broad footprint of climate change from genes to biomes to people

Most ecological processes now show responses to anthropogenic climate change. In terrestrial, freshwater, and marine ecosystems, species are changing genetically, physiologically, morphologically, and phenologically and are shifting their distributions, which affects food webs and results in new interactions. Disruptions scale from the gene to the ecosystem and have documented consequences for people, including unpredictable fisheries and crop yields, loss of genetic diversity in wild crop varieties, and increasing impacts of pests and diseases. In addition to the more easily observed changes, such as shifts in flowering phenology, we argue that many hidden dynamics, such as genetic changes, are also taking place. Understanding shifts in ecological processes can guide human adaptation strategies. In addition to reducing greenhouse gases, climate action and policy must therefore focus equally on strategies that safeguard biodiversity and ecosystems. 

The impacts of climate change on marine fisheries have major consequences for human so- cieties because these currently provide ~17% of the global protein for people. Impacts on plant genetics and physiology are influencing human agricultural systems. For example, yields in rice, maize, and coffee have declined in response to the combined effects of rising temperatures and increasing precipita- tion variability over past decades. Pollination is a key process linked to yields for a large number of crops. The short-lived, highly mobile insect species that provide pollination ser- vices to numerous crops have responded rapidly to changing climates by shifting their ranges throughout North America and Europe. Several native insect species from North America, with no prior records of severe infestation, have recently emerged as severe pathogens of forest resources because of changes in population dynamics. We must also recognize the role that intact natural ecosystems, particularly large areas, play in overcoming the challenges that climate change presents, not only as important reposi- tories for carbon but also because of their ability to buffer and regulate local climate regimes and help human populations adapt to climate change.