USDA: Increased ragweed pollen a “troubling” effect of higher CO2

Published November 1, 2000

If any of the Washington muckety-mucks should be ecstatic over increasing levels of carbon dioxide in the air, it should be the Secretary of Agriculture. After all, it is the USDA’s mission to “enhance the quality of life for the American people by supporting production of agriculture.”

Abundant research makes it absolutely clear that most agricultural crops grow like mad, and produce greater yields, when they’re fed high levels of carbon dioxide (CO2).

Yet this administration is not wont to rejoice over such good news, which accounts for Secretary Dan Glickman’s statement in an August 15 Department of Agriculture news release concerning the results of a new USDA study: “This research may help us better understand the troubling impact of high carbon dioxide levels on our environment and our health.”

Exactly what research has Glickman so “troubled”? Do the results show that increased levels of atmospheric CO2 are going to lead to a reduction in corn yields? Is the nation’s wheat crop going to fail? Are we all going to go hungry?

It turns out to be nothing of the kind. Instead, a USDA study by Lewis Ziska has found that ragweed pollen is increasing because of higher CO2 levels. That’s right, rising levels of ragweed pollen have the U.S. Secretary of Agriculture concerned about carbon dioxide levels. That is like receiving a $20 million lottery prize and complaining they forgot to give you your free ticket.

Sylvan Wittwer, chairman emeritus of the National Research Council’s Board on Agriculture and pioneering researcher into the effects of carbon dioxide and crop production, has written, “Globally, it is estimated that the overall crop productivity has already been increased by 10 percent because of [elevated levels] of CO2.”

How many hundreds of millions of people across the world have benefitted from that increased food supply? Yet Glickman is “troubled” by extra ragweed pollen.

It’s not that the USDA results are wrong. It shouldn’t be surprising to anyone who’s taken introductory plant biology that happy, healthy plants (such as those grown under elevated CO2 levels) produce lots of pollen—reproduction is one thing that happy plants (and animals) are very keen to do.

Is Glickman serious? Does he believe we should move to significantly reduce carbon dioxide levels, lower crop production, and reduce the quality of life across the planet because he gets the sniffles for a few weeks every September?

What’s more, that ragweed-CO2 connection is not quite so simple. The ragweed plant’s niche is ecological disturbances—old pastures, vacant lots, and wastelands not already occupied by trees, shrubs, or other species. With forests and shrubs thriving under higher CO2 levels, why should we assume there will be more “disturbed” land for ragweed to infest? And if there is, what in D.C. does that have to do with global warming?

Of course, that’s a rhetorical question. When political hay can be made by coughing up some new government study every few weeks about the evils of CO2 to a press willing to gag any opposing views, there is no down side.

Not yet, anyway. CO2’s benefits the biosphere, especially in the way it will help feed the world’s ever growing population. It is becoming increasingly obvious that the positive effects of rising atmospheric CO2 levels will far outweigh the negatives. And that, despite Glickman’s protests, is nothing to sneeze at.

Robert E. Davis, Ph.D., is an associate professor of environmental science at the University of Virginia.


Global Warming’s High Carbon Dioxide Levels May Exacerbate Ragweed Allergies.