Kudzu vines have become a wide-spread but unwelcome sight throughout much of the southeastern United States. The noxious weed – native to Asia and once planted to prevent soil erosion – has spread rapidly, smothering native species in its wake. But the vine may be wreaking atmospheric havoc as well.
In a paper in Proceedings of the National Academy of Sciences, Jonathan Hickman of Stony Brook University and colleagues find that invasion of the vine more than doubles nitric oxide emissions and increases ozone pollution.
Kudzu is a legume, and like all legumes, its roots are associated with a host of microbes that cycle nitrogen. Based on experiments in infested areas of Georgia and subsequent biogeochemical modeling, Hickman’s team found that the end result of these microbial communities springing up is an average 127% increase in soil nitric oxide (NO) emissions in invaded areas. Emissions of nitrous oxide (N2O), a greenhouse gas, could also rise, although the result was not clearly significant.
Though not a greenhouse gas itself, NO is a precursor to ozone, which when formed in the lower atmosphere, is a greenhouse gas and major pollutant. What’s more, kudzu is also a prolific emitter of the biological hydrocarbon isoprene, another chemical implicated in ozone production.
With hot, humid summers, the southeast is a particular hotspot for ozone formation. Hickman’s team finds that an extreme invasion of kudzu could actually increase the number of days with dangerously high levels of ozone. The team warns that warmer winters and higher atmospheric CO2 concentrations could drive a northward expansion of the vine, with localized outbreaks already reported in New York, Maine and Ontario.
Image: Untreat Kudzu vines JEREMY MCDONALD/USDA FOREST SERVICE