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Home » Key Findings » Overall changes in phenology
Overall changes in phenology
As well as changes in the abundance of butterflies, transect data is invaluable for assessing changes in the timing of appearance. Measures of phenology have become important indicators of the effects of climate change, and we have calculated the mean date of almost 47,000 flight periods recorded by the BMS. Since 1976, there has been a significant trend towards earlier appearance of butterflies in both spring (including 1 st generations of bi- or multi-voltine species) and summer (including 2 nd generations).
Trends towards earlier appearance in both spring and summer generations of bi- and multivoltine butterfly species.
The rate of change is more marked for spring species than those flying later in the season with the mean date of flight periods being 5 days and 3¼ days per decade earlier, respectively. The effects of temperature on rates of development of immature stages of butterflies and the resulting timing of adult emergence are well established. These trends in the phenology of British butterflies are consistent with trends found in a range of taxonomic groups (birds, flowers, trees) from many regions in the northern temperature zone that suggest that climate warming is having a profound effect on the timing of naturally recurring events.
