Spicing Things Up

By Robert C. Balling Jr., Ph.D.
Arizona State University

We review the effects of elevated carbon dioxide on as many members of the biosphere as possible, but our favorites usually deal with crops that are most important in feeding humans, especially staple crops such as wheat and rice.

Again and again, we find new studies among the hundreds that have been conducted confirming that an increase in atmospheric carbon dioxide levels stimulates plant growth and yield. We see plants coping better in times of drought, resisting the effects of pests, and more.

Until now, however, we have not had the chance to look at what you might think of as "accent" foods, those flavorings that give the food we eat a little punch. No doubt chefs are wondering: What does global warming mean for herbs?

After all, pumped-up wheat, bean, and rice crops are great, and a better peach or orange crop is terrific. But what about our mint juleps in springtime? Our Thanksgiving stuffing in the fall? Great food is about nuance, right?

Never fear. A team of scientists from the U.S. Department of Agriculture in Illinois grew mint and thyme shoots in tubes with atmospheric carbon dioxide concentrations ranging from ambient (350 parts per million, or ppm) to highly elevated (10,000 ppm) levels. Tisserat and colleagues found that the elevated carbon dioxide caused the fresh weights of the mint to increase by over 300 percent while the weights of the thyme increased by nearly 600 percent. Parsley, sage, and rosemary will hopefully be next!

Ongoing human population growth will yield billions of additional mouths to feed the world over, and the biological response to elevated carbon dioxide will certainly be a blessing in producing the food necessary to meet the future demand. (Indeed, we wonder how the United Nations can be so concerned about feeding the world yet equally eager to slow the growth of atmospheric CO2.)

But isn't it great to know that your kitchen garden, overgrown with mint, punctuated by thyme, will fare well in future years as well?

Reference:

Tisserat, B., S.F. Vaughn, and R. Silman, R. 2002. Influence of modified oxygen and carbon dioxide atmospheres on mint and thyme plant growth, morphogenesis and secondary metabolism in vitro. Plant Cell Reports, 20, 912916.