Spring Flowers and Climate Change

Apr 11, 2014

Credit Richard Barrett-Small / Flickr Creative Commons

Climate change is already being felt by natural systems around the world – and locally. We can see how flowers react to temperatures as they first emerge in the spring. And now, we have a specific record for our area. For more than three decades, one avid local gardener has been keeping a diary of the first-flowering date of many species in her yard, like snowdrops, crocuses, bleeding hearts and crab apples.

 A few years ago she let a few of us at the University of Dayton see her observations. We had a hypothesis: we’d look through the diary, and not find any patterns over time. To our surprise, it became clear that many flower species are blossoming earlier over time. Using local temperature data over the same time period, we saw something else as well.

First, although temperatures fluctuate, there was a small but significant upward trend over time. More importantly, there was a clear correlation between higher winter temperatures and spring blossoming. According to the gardener’s diary, crocuses were up and flowering nearly a month earlier in 2005 than in the 1970s.

Many of us would be happy to have a few extra days of early spring. The catch is that the changes we’re seeing are happening as much as ten times faster than normal natural rates of temperature change. It’s not normal in any way. And there’s a chain reaction.

Once flowers start blossoming and trees start budding earlier, the cycles of insects and animals get out of synch as well - a ripple effect through the ecosystem. The earlier flowering times can be a problem for other creatures with life-cycles triggered by lighting changes in the spring. Think about this, when oak tree buds appear earlier in the season, giving food for caterpillars, birds that hatch at their normal times are out of luck because their food source is already past its peak.

Ecosystems will eventually adapt to climate change, as they always have. That’s part of a natural cycle, but the changing climate now is the result of humans increasing carbon dioxide levels in the atmosphere. Unfortunately, we don’t always know what is going to happen when we disrupt these natural systems. We don’t get several trials – and we may not always like the unintended consequences of the one chance we do have.

Bob Brecha is a professor of physics and renewable and clean energy. He is the coordinator of the Sustainability, Energy and The Environment program at the University of Dayton.