The new battle on climate change is being waged in our nation’s forests. Nonnative, invasive species are changing the face of natural ecosystems across the country by reducing biodiversity or wiping out large areas of natural vegetation completely. Climate change is helping to fuel this transformation. Warmer temperatures and variations in precipitation are allowing the spread of invasive species by providing a larger range of idealistic conditions. Since invasive species are competitive and adaptable by nature, they are better suited to alter their annual activities. In a study performed by Charles Davis from Harvard’s Department of Organismic and Evolutionary Biology, it was found that nonnatives were more successful in altering their flowering times by as much as three weeks in order to take advantage of earlier spring thaws as a result of an upward trend of average annual temperatures. Native species, on the other hand, are often suited to particular conditions and are less likely to adapt to rapid variations in climate change. These differences in adaptability could transform entire ecosystems as native species perish and invasives thrive.
The Kudzu vine (Pueraria montana) is one such example of a nonnative that has taken advantage of its new-found environment in the southeast and is quickly spreading to other regions of the nation due to climate change. Kudzu is a native vine of China and Japan. It was introduced in the United States at the 1876 Philadelphia Centennial Exposition as an ornamental and forage crop. It wasn’t until the 1930’s that the vine was put into use as a method to control soil erosion. The warm, wet summers and mild winters of the southeast were an ideal habitat for Kudzu, and it quickly took off. By the 1950’s it was classified as a pest weed, and its agricultural use was discontinued. However, Kudzu was able to adapt to varying soil types and conditions. At the rate of a foot per day, it continued to spread by covering and killing all vegetation in its path eventually earning itself the nickname “the vine that ate the south.” As climate change has pushed warmer weather farther north, the Kudzu vine has followed and can now be found as far north as Massachusetts.
Unlike other invasive species, Kudzu is having a twofold impact on the environment. Not only is it helping to facilitate the eradication of native species, it is also a contributor to climate change itself. Kudzu emits isoprene and nitric oxide which react with nitrogen in the atmosphere to form ozone in the troposphere, the lowest of Earth’s atmospheres. Ozone in this region is an air pollutant and greenhouse gas. In a joint study between professors at Stony Brook University, Harvard University, and the University of Virginia, Kudzu emissions and its effects on air quality were examined at three sites in Georgia. The vine was found to be responsible for a 50% increase in the number of days each year in which ozone exceeds unhealthy levels according to the EPA. This new finding negates the ozone reductions made from stricter legislation concerning automobile emissions. With Kudzu covering nearly seven million acres in the United States already and growing at the rate of 150,000 acres annually, it will soon become a major player in greenhouse gas emissions.
Alternate uses of Kudzu are being evaluated as methods to control the vine’s spread and environmental effects. It may be used as a foraging crop for grazing animals; as a food source due to its high content of starch in the roots; in the cosmetic industry as an ingredient in soaps and lotions; as a dietary supplement used to lower blood pressure, cholesterol, and insulin levels; as a source of biofuel; in the medical field as a treatment for alcohol cravings, cancer prevention, and in the treatment of migraines among other uses. The eradication of Kudzu is also being considered with the use of a biological herbicide. In field experiments, the fungus Myrothecium verrucaria attacked and killed 100% of seedlings and 90% of established Kudzu growth with little to no damage to neighboring vegetation.
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