A warming climate has extended the wildflower season in the Rocky Mountains by 35 days since the 1970s, according to a 39-year study of more than two million blooms. The bloom season, which used to run from late May to early September, now lasts from late April to late
September, the researchers say. Previous, less extensive studies seemed to indicate most wildflowers simply shift their bloom cycles to earlier in the year, but new findings published in the Proceedings of the National Academy of Sciences show that the changes are more complex, with the flowers reaching peak bloom sooner and flowering later in the year. The shift in the timing of blooms could have a major impact on pollinating insects and migratory birds. For example, hummingbirds that summer in the Rocky Mountains time their nesting so that their eggs hatch at peak bloom, when there is plenty of flower nectar for hungry chicks. As the bloom season lengthens, the plants are not producing more flowers. The same number of blooms is spread out over more days, so at peak bloom there may be fewer flowers and less food for hummingbirds, the researchers say.