IB Biology Topic D4.3.10: Disruption to the Synchrony of Phenological Events by Climate Change Notes

Phenological synchrony: when partner species advance at different rates, climate change pulls them out of step

Phenology is the study of the timing of recurring biological events such as flowering, breeding, and migration.

1. Phenological synchrony is the coordinated timing of the life-cycle events of interacting species, so that each event happens when the other species needs it.
   1. For example, spring plant growth often lines up with the arrival of migratory animals that feed on those plants.
2. Synchrony matters because many species interactions, such as feeding young or pollination, only work if two events overlap in time.
3. When that overlap breaks, the result is a phenological mismatch that harms one or both species and can ripple through the food web.

Mismatch arises because different cues advance at different rates under warming

1. Temperature-cued events shift earlier as the climate warms, so plant growth and many animal breeding and emergence events advance.
2. Photoperiod-cued events stay fixed because day length does not change with temperature, so events triggered by day length do not advance.
3. Because partner species can use different cues, one advances while the other holds still, and the two slip out of synchrony.

Reindeer example: photoperiod-fixed migration falls behind temperature-driven plant green-up

1. In the Arctic, spring plant green-up and the arrival of migrating reindeer, Rangifer tarandus, have traditionally been timed to coincide.
2. Plant green-up is temperature-cued, so warming advances it and the vegetation greens up earlier each year.