Climate Change Affects Phenology and Alters Ecological Relationships.

Climate change is altering the phenology of biological systems—which in turn alters ecosystem processes, forestry, agriculture, and human economies and cultures—and these changes will continue in coming decades. In temperate regions, spring phenology is often strongly controlled by temperature, and a warming climate results in earlier germination, growth, and flowering of most plants. Most insects similarly emerge and become active earlier in warmer springs, while the dates that migratory bird species arrive on their breeding grounds are less responsive to spring temperatures. Migratory bird populations may decline if they become mismatched with their insect food sources. At the same time, populations of many pest insects and invasive plants species could grow rapidly if they can take greater advantage of milder winters and earlier springs than native species. In contrast to spring, autumn has been neglected in climate change research, but major shifts in ecological relationships are almost certainly happening at this time of year as well. For example, many migratory birds are remaining on their breeding grounds longer due to milder autumn temperatures. These birds may increasingly feed on the late-ripening fruits of invasive plant species, facilitating the spread of their seeds. These changes in ecological relationships, which are occurring in summer and winter as well, challenge our ability to understand, manage, and protect natural and human-dominated ecosystems. Adapting to these changes may be difficult or even impossible in certain parts of the world.