Spring is coming earlier, and it is bringing warmer temperatures and earlier blooming trees and flowers. The USA National Phenology Network tracks these factors and has documented an early spring across the southeast. Reporter Tegan Wendland talked with director Theresa Crimmins about so-called “false springs” and the implications for plants and animals.
Q: It seems like we are seeing warmer springs here in the south and across the country. What can you tell us about what trends we are seeing nationwide?
On a nationwide basis, over the long period, the last 70 years or so, there definitely is a trend toward warmer temperatures, especially in the spring. However, when you start to break it down by region, it doesn't always tell a real clear story. And especially in the southeast, there's so much variability from year to year. And we actually fall into something that's been referred to as a warming hole where there's been a pretty clear increase in the average temperatures. It's not actually as apparent over the long term in the Southeast.
Q: It certainly feels warmer this season and we're seeing lots of trees budding early and flowers coming up. What are the implications of these warming trends, if they are trends?
Absolutely, you're right. The spring is coming earlier this year to the southeast and absolutely it's been warmer than average. And the warmer than average temperatures that we've been experiencing in January and February so far is what's driving early leaf-out and flowering in a lot of species.
Q: And why is that bad?
Well, it's interesting. Not all species respond to warmer than average temperatures. So when we have anomalous conditions like this, some species are very responsive and are able to leaf out earlier or put on their buds earlier, but others may not be as responsive. And that can lead to mismatches where species that depend on each other aren't all undergoing these things that they're supposed to do at the same time of the year. It can also have implications for migratory species. If there are birds or other species that are migrating from the south or the southern hemisphere, they may be arriving at the same time every year. But if they're getting here after their food sources that they depend on in the spring, upon their arrival are at their peak, then that can really be a problematic situation for them with an inability to find sufficient food.
Q: And what are some examples of some species we might see flowering or leafing out early in the Southeast?
The real classic early spring plants like daffodils, we're seeing a lot of reports of those coming up and opening their flowers way ahead of schedule. All across the south and even up into some of the Midwestern states. Silver maple also flowers earlier in the season. Same thing for forsythia - and even magnolias are starting to bud out as well.
Q: What kind of trends do you expect going forward?
There's definitely a pattern where we are seeing an earlier start to spring more regularly in recent years. We've definitely had a sequence where we've had earlier springs in rapid sequence. And there has been some research that has come out in the last few years, too, that is projecting earlier springs will become almost the norm - something that we might see in, say, one out of every three or five years. But without clear change in the concentration of CO2 in the atmosphere and other things that are causing the temperatures to increase, then that may be what we might be looking forward to in the coming decades.
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