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How can the climate be warming when it’s -9 degrees Fahrenheit outside? Why do some plants stay green in the fall?

by Belle Bergner

Honestly, when I woke up sometime in early February and it was as cold in Riverwest as it was in Anchorage, I asked the same question — but only for a second. Because I know the question is actually misplaced. The fact that it’s -9 degrees F outside has nothing to do with whether the climate is warming or cooling. Neither does the mid-summer day when it is a desperate 99 degrees. In fact, the climate is the long-term, annual, or decadal average of weather patterns. Weather is what happens on a short-term, daily, or weekly basis. So if you read any of the multitudinous “climate-change-is-happening” articles coming out in prestigious, peer-reviewed journals such as Nature or Science while trying to warm your nearly frostbitten toes one evening, remember this: you can’t be the judge of whether the climate is warming. But the long-term data can. In one of the more recent “climate-change-is-happening-and-here’s-why” articles in the January 8, 2004, issue of the journal Nature, more than a dozen scientists published their results of a computer-modeled test of the effect of climate change on species extinctions. They looked at the area of land that species require, which determines the number of individuals and species that can live on that land. Then they modeled the effect that climate change will have on that land. And lo and behold, when you raise temperatures or change precipitation rates faster than species can adapt, they die. The craziest part about this study is that the highest extinction rates are predicted to occur right here, in temperate Wisconsin and other mid-latitude regions. Yes, you read correctly. In this coldest of cold climates, even Milwaukee’s -9 F days can’t combat the larger picture of the increasing average temperatures and lengthening of the growing season. Not only that, but species that would otherwise be doing just fine are not only being threatened by the growing conversion of native land to human development, but our development’s effect on the climate as well. The recent Butler’s Gardner Snake controversy here in Milwaukee that stopped a new development dead in its tracks points to a need for developers to understand the importance of rare or threatened species. Why would Wisconsin be the place where the most species are threatened? In part, because we don’t have the huge, genetically diverse pool that the tropics have. We also have species that are strictly bounded by cold weather extremes that the mid-west and mid-latitudes are famous for. Any change in those boundaries forces species that are already at the edge of their climate range to jump off that northern-most cliff. Why you should care is simply that diversity is the fundamental unit upon which evolution occurs. When you lower the diversity of a species’ gene pool, you reduce the ability of species to adapt. If species can’t adapt, they won’t survive. Reduced species diversity can also cause ecosystem functioning to decline — essential nutrients are leached, and with fewer plants, there are fewer potential cures for currently untreatable diseases. What can we do about it? The major culprit of climate warming is carbon dioxide (CO2). According to the latest Intergovernmental Panel on Climate Change report, one-third of all man-made CO2 emissions come from personal vehicle use. Take the bus to work at least once per week, and ride your bike when the weather permits. In the words of E.O. Wilson, the internationally renowned Harvard Biologist and Pulitzer Prize-winner, it is now an ethical choice rather than a scientific question. What will we decide? And how many species will be left when our grandchildren want to learn about them? Q: Why do some plants stay green in the fall when every other tree and shrub has lost their leaves? A: Those green machines are most likely invasive plants. Invasive, or non-native plants are what ecologists call plants that evolved in a different region of the country or globe. They made their way to their new home on the backs or shoe-bottoms of human travelers or the vessels that carried them. Around Milwaukee, the biggest invaders are Buckthorn (Rhamnus catharsis) and Garlic mustard (Alliaria petiolata); see pictures above. These visitors come to us by way of Europe and Asia. They can often be seen churning their sunlight-capturing, photosynthetic machinery weeks past the first frost! What should you do? Seek out these bad boys in a park near you and pull them up! Pull the tall garlic mustards rather than the rosettes that stay close to the ground, and yank the small- to medium-sized buckthorn seedlings to give some space for native Oak and Maple seedlings to grow. The Urban Ecology Center in Riverside Park has a “Burdock Brigade” that cleans up Riverside park. Right now, they are cleaning seeds to help ensure the germination success of native plants. Go to www.urbanecologycenter.org for dates and times. Belle Bergner received her M.S. in Ecology from the University of Pennsylvania. She has published her research in the primary literature and is currently Program Director for Keep Greater Milwaukee Beautiful, Inc., a non-profit environmental organization in Milwaukee.
by Belle Bergner