September 20, 2013
By: Deborah Lawson
In January 2012 the United States Department of Agriculture released new plant hardiness zones for the United States. Plant hardiness zones are based on the average annual lowest winter temperatures, which have shifted to the north and northwest over the past 20 years. After release of the new maps, many questioned why no link was made by the USDA to the warming trends affecting the planet generally. I would assume the USDA chose to avoid the global warming debate.
Regardless of public opinion and controversy, science and the data collected support the fact that our planet is warming beyond what might occur with various cyclical trends. People who have lived in North Florida their whole lives know – it used to be colder. The National Oceanic and Atmospheric Administration’s (NOAA’s) Climate Extreme Index, which tracks the last 100 years, shows a marked reduction in extremes of cold and substantial spikes in extreme heat occurring since the 1980’s. This year is no exception, with a very mild winter and an extremely long, hot summer.
With milder winter temperatures we have seen more tropical plants that did not previously survive our winters, do so — particularly if they are in a space that provides some protection. Conversely, do we risk losing some of our most beloved trees due to warming? Dogwood decline has been well documented throughout the southeastern United States. Although the decline has been largely attributed to dogwood anthracnose, a fungal infection, warmer temperatures and stressful conditions provide an ideal situation for the fungus to spread. In our area, we see many more dead and declining dogwoods than healthy ones. Thirty years ago, that was not the case. The dogwood population has decreased by fifty percent.
If our winters continue to be mild, will we lose trees that require some chilling to grow such as Japanese maples? We are on the edge of their southernmost growing area, so even incremental change to our climate could eliminate them from our area. Certainly apple and peach trees that require a number of chilling hours would be at risk.
A July special edition of the American Journal of Botany explores global biological change. Plants not only help regulate climate by absorption of carbon dioxide, but are also dramatically affected by climate change. The series of articles explores these effects, the increase in invasive species, and a host of other issues. Stephen Weller (University of California, Irvine) who was a collaborator on the project emphasizes, “Many people are familiar with the impact of rising temperatures and greater intensity of storms on humans, but have less understanding of the effects of these and other global changes on the foundation of our biological ecosystem – plants.”
Most certainly these issues are a growing priority for our research universities and the subject of a great deal of study. A wealth of information can be found on the University of Florida IFAS website alone, including a discussion of the role of Extension as our climate continues to warm. IFAS is a member of the Southeast Climate Consortium (SECC), one of eight Regional Integrated Science Assessment Centers sponsored by NOAA and comprised of the Southeast’s seven agricultural research universities. Over the past 10 years SECC has become a recognized leader in adaptive research, and Extension forms the link between the research and those who must develop local adaptation and mitigation strategies for responding to climate change.
Deborah Lawson is owner of Rejuvenation, LLC landscaping and design, and is a Certified Master Gardener Volunteer with the University of Florida IFAS Extension in Leon County. http://leon.ifas.ufl.edu
Photo by Deborah Lawson: Declining Dogwood
Additional Possible Graphic: NOAA’s Climate Extreme Index