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What is phenology?

Phenology is nature’s calendar—when cherry trees bloom, when a robin builds its nest and when leaves turn color in the fall.

Phenology is a key to understanding life on earth. Many birds time their nesting so their eggs hatch when insects are available to feed nestlings. Likewise, insect emergence is often synchronized with the time a host plant starts to grow leaves.

Phenology influences the abundance and distribution of organisms, ecosystem services, food webs, and global cycles of water and carbon. In turn, phenology may be altered by changes in temperature and precipitation.


Changes in phenological events like flowering and animal migration are among the most sensitive biological responses to climate change. Across the world, many spring events are occurring earlier—and fall events are happening later—than they did in the past.


However, not all species are changing at the same rate or direction, leading to mismatches. Understanding how plants and animals respond to changes in climate can help us predict whether their populations will grow or shrink – making phenology a “leading indicator” of climate change impacts.

For people, earlier flowering means earlier allergies. Farmers and gardeners need to know the schedule of plant and insect development to decide when to apply fertilizers and pesticides and when to plant to avoid frosts. Knowing when mosquitos lay their eggs can help reduce populations and prevent the spread of human disease. Understanding how dry seasons impact wildfires can protect people and homes from tragedy.

But scientists can't do it alone! Gathering enough observations of the natural world is only made possible by people like you!

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What is a phenophase?

A phenophase a stage in the life cycle of a plant or animal. The stage must have a beginning and end, for example the time when a flower blooms or when a bird builds a nest. Watch the video to learn more about identifying phenophases.

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