With pollen production from ordinary plants amping up 300-500% over normative levels from increased atmospheric CO2, sending people running for their Claritin, one could (I suppose) have also predicted we'd eventually see the emergence of super weeds. Well, according to two recent stories in The Wall Street Journal (June 4, p A16, 'Superweeds Trigger New Arms Race'; June 21, p. D1, 'Least Welcome Sign of Summer') that time has more than arrived.
According to the first account, by the middle of this decade at least 40% of U.S. corn and coybean crops will "harbor Roundup resistant super weeds". Roundup, and especially Monsanto's Roundup -ready seeds, have been amongst the biggest "success stories" in the domain of weed control, primarily because of its primary constitutent - glyphosate- which is one of the least toxic around. As one farmer cited in the first article put it: If glyphosate isn't the safest herbicide, it's damned close".
Today Roundup and generic competitors are used on nearly 4 times as many acres as any other herbicide, but true to evolutionary dictates and principles - the weeds are adapting, and new, hardier variants are emerging resistant to the weedicide. Many believe that enhanced CO2 plays no small role in faciliating this adaptation, since stronger, larger weeds are the result.
Currently, nine species of weed have developed total immunity to it and spread to millions of acres in more than twenty states. In the article, one farmer from Osceola, AR is quoted who says he spends hundreds of thousands of dolalrs on herbicide, but can't control the pigweed which now runs rampant over his 8,600 acre field.
The variant of pigweed on his property grows to six feet in height on a stalk the width of a baseball bat's wide end. The weed is so tough, it damages mechanical parts of his cotton picking equipment and must be rooted out by hand. The farmer had to hire 20 labor hands to attack the weeds using hoes, even then breaking a number of them.
The emergence of these super weeds, especially as threats to farm productivity have convinced many farmers they must resort to much more toxic weedicides to get the job done. That includes using such infamous carcinogenic agents as: 2, 4- D, dicamba and paraquat. But critics have warned given the uncontrolled factors afoot, such as ever increasing CO2 concentrations (now tipping at nearly 400 ppm) all that will happen is that even more super weeds will emerge, resistant to even those arch-herbicides.
In the second story, attention is on the accelerative growth of poison ivy and the increased tribulations of people (mainly gardeners, but some hikers) coming in contact with its irritant chemical urushiol. Gardeners quoted in the article attest to "many more seedlings observed" in their gardens.
The article also references a study published in the journal Weed Science, in 2007, which indicates poison ivy is getting bigger and spreading faster, plus producing more urushiol as a result of increasing levels of carbon dioxide in the atmosphere.
Lead researcher, Lewis Ziska, a plant biologist at the U.S. Dept. of Agriculture, exposed poison ivy plants to different carbon dioxide concentrations- mirroring those that actually existed in the atmosphere at various times, over decades. He found that as one reached increased exposure levels bigger, hardier and more irritating plants were produced.
Will the weeds inherit the Earth if humans continue to punt in attending to global warming and the CO2 threat? Well, from looking at the rate at which "super dandelions" have taken over my front lawn, I wouldn't be too surprised. Generally, dandelions exhibit seed heads of maybe 4-5 cm diameter at most, before shooting out their parachute seeds. The ones now occupying my lawn have seeder heads in the vicinity of 7-8 cm in width.
Go figure. Or maybe not!