Broadly, we are seeing steadily earlier occurrence of plant spring phenology across much of the world (especially in the Northern Hemisphere), in step with warming trends in these regions
For the fall/autumn, changes are lot more ambiguous. Plants during this season are less sensitive to climate, and more reliant on photoperiod or day length clues to tell them they need to start shutting down for the winter
In some cases, we can also see shifts in animal phenology as well (changes in migration, hibernation, etc). Data for animal phenology, unfortunately, is not quite as good, and the sensitivity of these events to climate is also less well understood
Phenology isn't just useful for its own sake, however. It is also an important trait that can affect lots of ecological processes
For example, earlier leafing or flowering can increase the exposure of plants to damaging frost or freeze events
This can affect their productivity for the rest of the growing season: phys.org/news/2018-08-g…
This can be a big problem for people when the plants we're talking about are crops. Some farmers in Georgia, for example, lost up to 80% of their peach crop in 2017 following a warm winter and late spring freeze: ajc.com/news/state--re…
Ecologically, shifts in phenology can also change species interactions if two species respond differently.
For example, some birds have adapted to time breeding during periods of greatest food availability. But if the food (e.g., caterpillars) is shifting in time and the birds are not, this can present a big problem: nature.com/scitable/blog/…
By changing interactions between species and other species, or species and their environments, climate change on phenology thus represents one of the most clear indicators we have to date for how climate change will impact ecosystems
