Little Changes, Big Problems? Why Phenology Matters


California Lilac, Ceanothus thyrsiflorus

With an unseasonably warm and dry winter, spring appears to have come early for many Bay Area flowers. While these displays are beautiful, their early arrival may indicate significant changes in climate or long-term weather patterns. The study of phenology holds the key to unmasking the consequences that climate change may have on the ecology of natural events like annual blooming.


Phenology studies the timing of biological events in relation to climate variation. The occurrences of biological events are responses to variations in three major environmental factors: temperature, precipitation, and sunlight. Plants are cued to flower in the presence of warm temperatures, sufficient precipitation, and abundant sunlight. These environmental factors are characteristic of spring, a season innately associated with flowers. The timing of biological events can shift earlier or later each year depending on the weather, and ecosystems are resilient enough for normal phenological variations.

If we continue to see this drought pattern for several years, it can cause a major shift in the timing of biological events and may indicate a shift in climate. And because all life is interconnected, phonological shifts can give rise to larger problems. For instance, if flowers bloom too early, there may be fewer nectar sources for late-arriving hummingbirds and butterflies. Furthermore, early blooms may mean an earlier fruit production, which typically leads to a yield of poor-quality fruit. Both of these events affect migratory-bird food sources. One shift in plant phenology has the potential to change entire food webs.

With the recent rains, more and more life will be visible in the parks and in your own backyard. Take a moment to check out new plants and study them for signs of seasonal changes over time. Remember that all changes affect other plants and animals. If we start taking notice of these small things, we can start working on big changes as our climate shifts!  

By Ruby Kwan, Diana Feldmann, and Robin Binaoro
Park Stewardship

For more information on phenology, check out the National Phenology Network’s website

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