Bats in December. Bluebonnets in January. Butterflies in February. These are a few of the unseasonal appearances Austinites noticed this warm winter. And, experts say, people should get used to such sights.
The first two months of winter in Austin were the second warmest in 122 years of records. The city returned to more seasonal norms in February, but experts say the winter will still likely fall somewhere in the top 10 hottest ever recorded.
December and January were 4.7 degrees warmer than the 30-year average, according to Victor Murphy, climate service program manager with the National Weather Service. Those two months brought only one day, Dec. 19, when the thermometer dipped down to freezing.
“That’s quite a bit of warmth spread over quite a few days,” he said. “It’s pretty significant.”
It also fits with long-term warming trends caused by climate change and urbanization, which can lead to the so-called "heat island effect" in built-up areas. The average temperature of Austin winters rose almost 4 degrees from 1970 to 2018.
That kind of warmth can upset the rhythms of the natural world.
The climate shift also allows migrating monarch butterflies to survive in Texas later than usual.
"In cold winters, they'll have two or three sightings along the Gulf," Chip Taylor, director of Monarch Watch, said. In a warm year, "you'll get butterflies that are sighted from Florida all the way to over to the middle of Texas and even into the San Antonio, Austin area."
The great migration of monarchs to Mexico already faces many pressures. Taylor said he thinks continued warming may one day help end it altogether, leaving small "islands" of nonmigrating butterflies around the Gulf Coast.
Then there are the Mexican free-tailed bats. Their emergence from under the Congress Avenue bridge in downtown Austin is a nightly tourist attraction during summer. But most of them either migrate to Mexico or become inactive in the fall. This season they remained visible through the winter.
“They shouldn’t be here,” city wildlife officer Sarah Whitson said, and more of them have stuck around longer the last several winters.
“It’s great if there’s food sources here throughout the winter,” she said. But she worries about what could become of the bats if a sudden cold snap kills off the bugs.
That happening would be an example of what scientists refer to as a “mismatch” –when one species becomes active while another species it relies on is dormant, said Norma Fowler, a biology Professor at UT Austin.
Fowler said researchers are noticing more “mismatches” as a result of climate change.
“You can get plants that bloom before the pollinators are available,” she said. “You can get birds that come north before the insects are out for them to eat.”
Changes like these also threaten agriculture. Some scientists expect the shifting migration patterns in Texas could hurt crops that are linked to the seasonal arrival of bats, birds and bugs to pollinate and fertilize their crops.
Got a tip? Email Mose Buchele at firstname.lastname@example.org. Follow him on Twitter @mosebuchele.
If you found the reporting above valuable, please consider making a donation to support it. Your gift pays for everything you find on KUT.org. Thanks for donating today.