How does rising atmospheric CO2 affect marine organisms?

Click to locate material archived on our website by topic


CO2 and Poison Ivy
Reference
Mohan, J.E., Ziska, L.H., Schlesinger, W.H., Thomas, R.B., Sicher, R.C., George, K. and Clark, J.S. 2006. Biomass and toxicity responses of poison ivy (Toxicodendron radicans) to elevated atmospheric CO2. Proceedings of the National Academy of Sciences, USA: 103: 9086-9089.

What was done
The authors studied the effects of an extra 200 ppm of atmospheric CO2 on the growth and development of poison ivy (Toxicodendron radicans (L.) Kuntze), as well as its effect on the plant's toxicity, over a period of six years at the Duke Forest FACE facility, where the noxious vine grew naturally in a loblolly pine plantation's understory, except for being surrounded by 4-cm plastic-mesh exclosures to protect them from damage by indigenous white-tailed deer.

What was learned
Mohan et al. report that CO2 enrichment increased poison ivy photosynthesis by 77%, while boosting its water use efficiency by 51%. They also note that at the end of the study's sixth year (2004), the aboveground biomass of poison ivy plants in the CO2-enriched plots was 62% greater than that of plants in the ambient-treatment plots. In addition, they report that high-CO2-grown plants produced "a more allergenic form of urushiol," which is the substance that produces the plant's allergic reaction in humans.

What it means
In the words of the seven scientists involved in the research, "our findings indicate that under future levels of atmospheric CO2, T. radicans may grow larger and become more noxious than it is today." And so it may. At the same time, however, a multitude of studies have indicated that the health-promoting properties of many food and medicinal plants will likewise be enhanced by the ongoing rise in the air's CO2 concentration (see Health Effects (CO2) in our Subject Index). Hence, it is our feeling - and we believe it will be yours as well after perusing these materials - that the many beneficial impacts of elevated atmospheric CO2 concentrations on food and medicinal plants will far outweigh the negative health implications arising from CO2-induced increases in the growth of plants that may induce human allergies (such as poison ivy and ragweed). It is a fact of life that "the wheat and the tares" - the good and the bad - will always grow together; but it would appear that the ongoing rise in the air's CO2 content is shifting the balance in favor of the good.

Reviewed 21 June 2006