Lewis Ziska, a lanky, sandy-haired weed ecologist with the Agriculture Research Service of the U.S. Department of Agriculture, matches a dry sense of humor with tired eyes. The humor is essential to Ziska’s exploration of what global climate change could do to mankind’s relationship with weeds; there are many days, he confesses, when his goal becomes nothing more than not ending up in a fetal position beneath his battleship gray, government-issue desk. Yet he speaks of weeds with admiration as well as apprehension, and even with hope.
It is easy to share the admiration and apprehension when you consider the site that Ziska planted with weeds in downtown Baltimore in the spring of 2002. Tucked in next to the city’s inner harbor, the site is part of a barren expanse of turf rolled out over a reclaimed industrial landscape. This unfertile scrap seems an unlikely choice for growing anything, but Ziska saw in it, ominously perhaps, a model of where the global habitat as a whole is headed.
“Ingenuity,” Ziska says, “may be the mother of invention, but poverty is definitely the father.” For some time, he had wanted to create in a laboratory setting the elevated temperatures and increased concentrations of atmospheric CO2 predicted for the mid-21st century by the Intergovernmental Panel on Climate Change, the leading international scientific authority on the subject. Carbon dioxide has received a lot of attention as a greenhouse gas, a major cause of global warming. But it is also, along with water, light and nutrients, one of the four essential resources for plant growth. The effect that boosting this gas’s concentration in the atmosphere will have on plants is very poorly understood.