City dwellers rejoice: spring greening comes earlier for urban plants


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The first signs of spring occur earlier in cities than surrounding rural areas, new research found (via Creative Commons).

Julia Poska | February 27, 2020

Vegetation starts turning green earlier in cities than surrounding rural areas, but urban plants are less sensitive to unseasonable warmth, new Iowa State University-led research found. The authors attribute the difference to the urban “heat island” effect.

Cities typically have somewhat higher temperatures than surrounding rural areas because materials like asphalt and brick absorb heat more readily than natural landscapes. For example, New York City is about 7 degrees Fahrenheit warmer than surrounding areas in summer, according to NASA’s Climate Kids site.

Researchers found this “heat island” phenomenon causes urban vegetation to perceive the start of spring and begin greening an average of six days earlier than surrounding rural plants.

As climate change progresses, however, plants in both rural and urban areas are responding to unseasonably warm temperatures by beginning growth earlier and earlier over time. Pollinators and last frosts have failed to keep up, which has damaged the early bloomers’ ability to survive and reproduce.

The study found that rural vegetation is more sensitive to early spring weather than urban vegetation, perhaps due to the urban heat island effect as well.

ISU Ph.D. student Ling Meng led the research team, which included CGRER member Yuyu Zhou, an ISU geological and atmospheric scientist, among others. The study, published this month in Proceedings of the National Academy of Sciences, was based on satellite images from 85 large U.S. cities from 2001 to 2014.

Zhou told the Iowa State News Service that this sort of research can help predict how plants will respond to climate change and urbanization.

Climate change and wild spring weather


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The Greenland block is a high pressure atmospheric block that hangs above Greenland and affects weather moving down to lower latitudes. (flickr/Stig Nygaard)

Jenna Ladd | April 18, 2018

By-in-large, spring weather has been arriving earlier each year in the United States. For instance, the frost-free season was 10 days longer between 1991 and 2011 than it was from 1901 to 1960.

This may come as a shock to Midwesterners, who saw several inches of snow fall this Sunday, April 15th. So what’s going on?

Among some other factors, the Greenland Block has a lot to do with the snowy spring of 2018, according to Dr. David Mechem of the University of Kansas. Mechem, a professor of geography and atmospheric science, explained that there is a persistent atmospheric area of high pressure above Greenland which funnels cold air from the poles straight into the mid-latitudes of North America. He told KCUR that the block was in place throughout February and March and is finally starting to break down, which would bring long-awaited warmer temperatures to the midwest.

Further research is needed to establish exactly what kind of effect climate change has on spring weather, but scientists are noticing some changes. Winter storms (even if they happen in April) have increased in frequency and intensity in the Northern hemisphere since 1950 according to the National Climate Assessment. Nor’easter winter storms plague the eastern U.S. and are caused by the the cold air from the Arctic and warm air from the Atlantic interplaying. This year, that region of the U.S. saw several Nor’easters in very quick succession, which is unusual. A recent study in the journal Nature Communications found that as the Arctic’s climate continues to warm at an alarming rate, winter storms becoming more likely in the eastern U.S.

The good news is that as the Greenland block continues to break down, residents of the mid-latitudes can expect spring to finally arrive. The bad news is that unpredictable spring weather can be expected to continue coming years as the climate continues to change.

Earlier spring could threaten bees


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The new study looked at three bee species in the Rocky Mountain region. (CL Baker/flickr)
Jenna Ladd | October 5, 2017

A new study has found that longer spring seasons associated with climate change may be harmful to certain bee populations.

Researchers focused on a region in the Colorado Rocky mountain range and three species of bees. Using 40 years of climate and flower data collected by David Inouye, a professor emeritus at the University of Maryland, College Park, the report concludes that mountain snow in the area is melting earlier than it used to, resulting in longer spring seasons with longer growing seasons for flowers. Somewhat surprisingly, there has been an increase of total number of days with low flower availability since spring began getting longer.

One of the study’s co-authors, Rebecca Irwin of North Carolina State University, said to the Scientific American, “Years that have a lot of days with low floral abundance seem to be years that have really low snowfall and early snowmelt.”

The study points out that when flowers emerge too early, they are susceptible to early spring frosts which can kill some of them off. Additionally, if snow melt begins flowing down mountain sides too early in the spring, there can be drought conditions later in the summer when it runs out.

It was found that years with a lot of low floral abundance days also had lower bee populations. The scientists write, “Our study suggests that climate-driven alterations in floral resource phenology can play a critical role in governing bee population responses to global change.”

On the Radio: Warmest March on record alters Iowa’s environment


Photo by Kenneth Ristau, Flickr.

Listen to this week’s radio segment here or read the transcript below. This week’s episode discusses the effects of an unusually warm March on Iowa’s agricultural community.

Are you curious how the warmest March on record affected Iowa’s farming?

This is the Iowa Environmental Focus.

Continue reading

Warm weather presents dilemma for corn farmers


Photo by brandoncripps, Flickr.

Iowa’s warm weather is tempting farmers to start planting corn early.

Conditions are ideal for planting right now, but many farmers worry that a freeze may still come. If corn is planted within the next couple of weeks, it would face a high risk of damage from a May freeze.

The incentive for planting early is that corn delivered in September receives a 50-cents per bushel premium over the corn delivered in October.

Read a Press-Citizen article about the farmers’ dilemma here.

Read about how the warm weather affects Iowa’s fruit farms here.

Read about what the warm weather means for Iowa’s pests here.