As the air's CO2 content continues to rise, what can we expect of herbivores? Will their appetites and numbers increase? Or will plants become more resistant to them? Reviews of the scientific literature suggest that the fraction of plant production that is consumed by herbivores in a CO2-enriched world will likely remain about the same as it is now or slightly decrease, and that the frequency and severity of pest outbreaks that are detrimental to agriculture may decrease as well.
But even if herbivore-induced damage happened to increase - for some strange reason in some situations - in a future CO2-enriched world, it need not spell disaster for Earth's plants. Several studies have shown, for example, that in a high-CO2 world of the future, most plants should be more capable of tolerating severe defoliation events, which in the lower-CO2 world of the present have been implicated in widespread plant growth declines.
All in all, therefore, it would appear that Earth's plants will fare much better in the future with respect to the periodic assaults of leaf-damaging herbivores, as the air's CO2 content continues its upward climb.
** For additional peer-reviewed scientific references and an in-depth discussion of the science supporting our position, please visit Climate Change Reconsidered: The Report of the Nongovernmental Planel on Climate Change (www.climatechangereconsidered.org), or CO2 Science (www.co2science.org).