Environmental Valuation & Cost-Benefit News

Link: http://www.nytimes.com/2008/06/29/magazine/29weeds-t.html?ref=science

Lewis Ziska, a weed ecologist with the Agriculture Research Service of the U.S. Department of Agriculture, determined that temperatures in Baltimore run 3 to 4 degrees Fahrenheit warmer on average than those of the surrounding countryside, and the concentration of CO2 in the local atmosphere (440 to 450 p.p.m., or parts per million by volume) is well above the current global average. This, coincidentally, matched almost exactly what the panel on climate change predicted for the planet as a whole 30 to 50 years in the future in its “B2 scenario,” a middle-of-the-road projection that envisions continuing greenhouse gas increases but also some success in abatement programs.

By comparing three sites — an organic farm in western Maryland, a park in a Baltimore suburb and the one by the inner harbor — Ziska [ found that ] ... not only did the weeds grow much larger in hotter, CO2-enriched plots — a weed called lambs-quarters, or Chenopodium album, grew to an impressive 6 to 8 feet on the farm but to a frightening 10 to 12 feet in the city — but the urban, futuristic weeds also produced more pollen. Even more alarming was the way that the increased heat and CO2 accelerated and perverted the succession of species within the plots.
...
As someone who has spent his career battling weeds, he was frightened by the implications. Weeds already cost U.S. farmers about 12 percent of their harvest, exacting an estimated annual loss of $33 billion. What would be the additional cost in the future
...
Tests with common agricultural weeds like Canada thistle and quack grass found them more resistant to herbicides when grown in higher concentrations of CO2, making them harder to control. Ziska hypothesizes that this may be a result of faster growth; the weeds mature more rapidly, leaving behind more quickly the seedling stage during which they are most vulnerable. This promises to be an expensive problem for farmers, who will have to spend more on chemicals and other anti-weed measures to protect their crops. (Herbicides already cost farmers more than $10 billion annually worldwide.)
...
When he grew ragweed plants in an atmosphere with 600 p.p.m. of CO2 (the level projected for the end of this century in that same climate-change panel “B2 scenario”), they produced twice as much pollen as plants grown in an atmosphere with 370 p.p.m. (the ambient level in the year 1998). This is bad news for allergy sufferers, especially since the pollen harvested from the CO2-enriched chamber proved far richer in the protein that causes the allergic reaction.

Environmental Protection Agency has labeled [invasive plants] as the second-greatest threat to the continent’s biodiversity, exceeded in their impact only by outright destruction of habitat. Major resources have been devoted to the spraying and rooting-out of invasive plants in the belief that their removal would enable an ecological revival. Roughly $45 million, for example, is spent every year in the unsuccessful attempt to stop the spread of a single European wetland weed, purple loosestrife (Lythrum salicaria).
...
With the challenges, [Ziska believes], come opportunities. Kudzu, for instance: Ziska has been seeking financing to study its potential as a source of biofuel. Kudzu roots, as much as 50 percent starch by weight, seem ideal for ethanol production, while the plant’s supercharged vines, which can grow a foot a day, would be an abundant source of alternative energy. This would be win-win: we develop an alternative to fossil fuels and, at the same time, create a financial incentive to root out a particularly troublesome weed.

Developing techniques for managing weeds in a time of global climate change will be essential to the world’s agricultural future, and the U.S.D.A. researchers, though they have been starved of essential financing, lead the world in this field. (There is one exception, Ziska admits; his Web searches have revealed that marijuana growers have an amazingly detailed knowledge of how CO2 enrichment affects their crop. But as Ziska points out, they don’t publish in scientific journals.) Possession of this expertise could be a great economic asset to the United States, both for the protection it could provide to our own harvests and as an intellectual export that is sure to be much in demand in other countries.

Ziska says that he worries about mankind’s ability to feed itself in a fast-changing future. Paradoxically, it is weeds, he says, that can provide solutions. They have helped us deal with lesser crises in the past. When diseases and pests overwhelmed our domesticated food crops, it was to their wild relatives — plants that mankind has been battling for millennia — that plant breeders turned. Because weeds have more diverse genomes, it is easier to find one with the proper genetic resistance to a given threat — and then to create a new hybrid by breeding it with existing crops. An answer to the Irish potato blight of 1845-6 was eventually found among the potato’s wild and weedy relatives; a wild oat found in Israel in the 1960s helped spawn a more robust, disease-resistant strain of domesticated oats.

Weedy ancestors of our food crops, Ziska predicts, will cope far better with coming climatic changes than their domesticated descendants.
...
by Tom Christopher
FOR FULL STORY GO TO:
http://www.nytimes.com/2008/06/29/magazine/29weeds-t.html?ref=science
The New York Times www.NYTimes.com
June 29, 2008