D4.3.10 Disruption to the synchrony of phenological events by climate change (HL) Notes

Disruption to the Synchrony of Phenological Events by Climate Change

1. Phenological synchrony refers to the timing of biological events (such as flowering, breeding, or migration) within an ecosystem, where different species' life cycles are typically coordinated.
2. For example, the timing of spring growth in plants often aligns with the arrival of migratory animals that rely on these plants for food.
3. Climate change, however, is disrupting this synchrony, with consequences for species interactions and ecosystems as a whole.

Why Does Synchrony Matter?

1. Many species rely on cues like temperature or photoperiod (day length) to time their life events.
2. When these cues fall out of sync, it can lead to mismatches between species that depend on each other.

Key Factors Disrupting Synchrony

1. Temperature: For some species, temperature is the key cue that triggers biological events. Warmer temperatures are advancing the timing of seasonal events such as growth in plants and breeding in animals.
2. Photoperiod: For other species, the length of daylight (photoperiod) is the critical factor. This is particularly evident in species that use the seasonal change in day length to regulate timing, such as migrating birds or deciduous trees that rely on changing light to mark the onset of spring.

Arctic Mouse-ear Chickweed (Cerastium arcticum) and Migrating Reindeer (Rangifer tarandus)

1. In the Arctic, the spring growth of the Arctic mouse-ear chickweed and the arrival of migrating reindeer are two critical biological events that have traditionally been synchronized.
2. However, climate change is causing shifts in both events, creating a mismatch.

Arctic Mouse-ear Chickweed

1. This small herbaceous plant grows in the Arctic tundra, and its spring growth is primarily influenced by temperature.
2. As temperatures rise, the plant begins to bloom earlier in the season.
3. However, this earlier bloom could create issues for other species that rely on it for food.

Migrating Reindeer

1. Reindeer typically migrate seasonally, timed to match the availability of fresh vegetation in the spring.
2. They rely on the availability of spring growth like that of chickweed as an essential food source.
3. If the chickweed blooms earlier than usual due to rising temperatures, the reindeer may arrive too late to take advantage of it, leading to food shortages and potentially affecting their reproductive success.

Breeding of the Great Tit (Parus major) and Peak Biomass of Caterpillars

1. In northern European forests, the breeding of the great tit and the peak biomass of caterpillars are key events that have traditionally been in synchrony.
2. The great tit is a small bird that relies on the abundance of caterpillars to feed its young during the breeding season.
3. However, climate change is altering both the timing of caterpillar emergence and the breeding of the great tit, leading to a phenological mismatch.

Great Tit Breeding

1. The great tit's breeding cycle is heavily influenced by photoperiod, with the birds typically breeding when the days are longest, usually in early spring.
2. As temperatures rise, however, the birds may begin breeding earlier, but this earlier breeding does not always match up with the availability of caterpillars.

Peak Biomass of Caterpillars

1. Caterpillar populations also respond to temperature cues, and with warmer temperatures, they can emerge earlier in the season.
2. However, if the great tit breeds earlier than usual, the caterpillars may not be at their peak biomass when the chicks hatch.
3. This leads to insufficient food for the young birds and can negatively affect nestling survival and overall reproductive success.

Local Example: Flowering Plants and Pollinators

1. In many ecosystems, flowering plants rely on temperature to bloom, while pollinators like bees use photoperiod to emerge.
2. If plants flower earlier due to warming, pollinators may miss their window to collect nectar and pollen, disrupting both plant reproduction and pollinator survival.

Why Is This Important?

1. Ecosystem Stability: Mismatches can disrupt food webs, affecting multiple species.
2. Biodiversity Loss: Species unable to adapt may decline or go extinct.
3. Human Impact: These changes can affect resources we rely on, such as fisheries and agriculture.