CO2, Global Warming, and Pollen-Allergies
Thomas Ogren
The benefits of added organic matter to the soil have long beenknown and are usually attributed to increased nitrogen, greaterwater-holding capacity and an increase in activity of soilearthworms and microbes. But experiments have shown that theincrease in carbon dioxide (CO2) release that accompanies addedorganic matter is certainly one of the main reasons why addingorganic matter to the soil increases plant growth. Greenhouseowners have long understood that plants consume CO2 and releaseoxygen. In a greenhouse packed full of plants, through theprocess of photosynthesis, the plants can quickly use up most ofthe available CO2 and then their growth slows down or stops. Tocompensate for this, old time growers used to place boxes orflats of fresh manure underneath their greenhouse benches. Asthe manure decomposed it released CO2 into the greenhouse airand the plants grew faster as a result. In today’s moderngreenhouses, especially those with concrete floors, lack of CO2is always a concern. Most of the newer greenhouse ranges are nowequipped with automatic CO2 regulators that monitor the amountof CO2 in the air inside the greenhouse and then release more asneeded. In these greenhouses with their gas growth CO2generators the plants don’t just grow bigger-- they also matureearlier.
So, what has all this to do with global warming and allergies?
As we become more and more reliant on burning petroleum productsand as our global temperatures continue to rise, carbon dioxidelevels in our air are rising. Before the last election we in theUS had assumed, incorrectly, that no matter which candidate wonthe election, new controls were going to be placed on CO2emissions. We know better now. The US with its huge consumptionof fossil fuels, (the U.S. produces nearly 25 percent ofman-made carbon dioxide emissions worldwide). also isexperiencing the greatest increase in CO2. Actually, CO2accounts for 80-85 percent of the heat trapping (greenhouse)gases contributing to global warming. The idea that is nowcalled the “Greening Theory” holds that all this extra CO2 isgood. It will result in increased plant growth and thus inresulting increases in food supplies. There is some merit tothis theory but there are numerous downsides too.
Pollen-Allergies There are many negative effects from globalwarming but let’s just consider one here, pollen production andit’s affect on allergies. Since 1959 allergies have dramaticallyincreased in the US from 2 to 5 percent of the populationaffected, to a whopping 38 percent now. Largely because of thehuge horticultural “success” of the much over-simplified theoryof “litter-free” landscaping we already have vast urbanlandscapes that are heavily loaded with wind-pollinateddioecious male cultivars (clones) of trees and shrubs. Thesemodern landscape trees result in surrounding air withunnaturally large amounts of allergenic pollen. Because the“messy” urban female trees are now so rare, almost none of thispollen is now trapped, removed from the air and turned intoseed. (Female trees produce no pollen, ever, but they do makeseeds, pods, and fruit.) We have tidy sidewalks butpollen-filled air. Under normal carbon dioxide levels these malecloned trees will always produce abundant amounts of pollen.Under increased levels of carbon dioxide, they produceconsiderably more. The increase in temperature itself alsoresults in increased pollen production, and in pollen productionthat starts earlier in the spring and lasts further into thefall. There is research that shows that under stress conditionsmale plants are able to take up more water than are females.Under stress conditions, such as drought, male trees are alsoable to hold onto the water they already have better than arefemale plants. Where there are abundant water and soil nutrientsources the increases in carbon dioxide levels in our air willresult in larger urban trees, which if they’re allergy trees,will be capable of producing ever more pollen. Increases incarbon dioxide increase plant growth but only if there is enoughavailable extra water and nitrogen in the soil to support thisadditional growth. When the supplies of water and nutrients arenot adequate to support this added CO2-induced growthinteresting physiological things happen in plants. Foremost, itis an added stress on the plants and stress often results in anincrease in unusual reproduction factors.
A stressed lemon tree, for example, will often produce a hugecrop of tiny, very seedy lemons. This is simply the lemon tree’sway of preparing for it’s own imminent demise and also it’s ownlegacy of possible seedlings. Another stress example: In dailypollen collections taken by biology professor Dr. Lee Parker andhis students from the top of the Fisher Science Building at CalPoly, San Luis Obispo, California, taken during the middle of asevere seven year drought, all-time record oak pollen countlevels were recorded. In the past twenty years in particularthere has been a huge increase in this planting of male clonedstreet trees. These trees can not produce pollen until theymature but with the increases in CO2 levels, we can predict thatthey will mature earlier than expected. Shannon L. LaDeau, aresearcher at Duke University found that pine trees grown withelevated levels of CO2 produced three times the normal amount ofseeds and also matured prematurely. Lewis H Ziska, Ph.D., a USDAresearcher, recently found that increased CO2 resulted in hugeincreases in the pollen production of ragweed and other weeds.David Karowe, a researcher at the University of Michigan, foundanother interesting factor about increased CO2 levels andplants: their leaves contain fewer nutrients than normal. NancyTuchman, biology professor at Loyola University in Chicago, isalso researching the feed value of CO2 enhanced leaves onmicroorganisms and insects. She found that they all grow slowerwhen fed these “enhanced” leaves. “If all the plants are alteredon a global level, then it’s certainly going to affect all theorganisms on Earth,” she said. “No one is going to escape.”Compounding all of this is that excessive burning of fossilfuels and the resulting pollution may well be compromising ourvery endocrine and immune systems. Theo Colburn explored thiswell in the very interesting book, “Our Stolen Future.” Greatincreases in the already excessively high rates of urban pollen,combined with further compromised immune systems, may well bethe recipe for allergies of true epidemic proportions in the nottoo distant future. Dr. Robert C. Stebbins, renowned biologistfrom UC Berkeley, told me recently in a phone conversation, thatthe planting of all these cloned male dioecious and compromisedmonoecious trees, “is a classic example of how they just didn’tthink about the ecology involved.” If we don’t start payingcloser attention to how we landscape our cities, and we don’tstart getting serious about alternative clean energy sources,rampant allergies and other pollen-related illnesses may well bethe end result.
This article first appeared in New Scientist Magazine, inLondon.
About the author:Thomas Ogren is the author of Allergy-Free Gardening, Ten SpeedPress. Tom does consulting work on landscape and allergies forthe USDA, county asthma coalitions, and the Canadian andAmerican Lung Associations. He has appeared on HGTV and TheDiscovery Channel. His book, Safe Sex in the Garden, waspublished in 2003. In 2004 Time Warner Books published hislatest book: What the Experts May NOT Tell You About: Growingthe Perfect Lawn. His website: www.allergyfree-gardening.com
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