diversity will increase. And as herbivores that feed upon the plants follow them into new areas, herbivore biodiversity also increases. And then carnivores that eat the herbivores follow along. Across the globe many of the ecosystems will experience an increase in biodiversity.

So, in conclusion, I just want to summarize again that carbon dioxide is vital for life on the Earth. Plants do respond favorably when atmospheric carbon dioxide levels increase; they do produce much more yield and fiber. Hence, there is more agronomic production to allow for feeding and clothing-and timber production-to provide fuel and shelter to the increasing population of humanity. So I would recommend to the chairmen and the panel today that they do whatever they can within their legislative powers to ensure that carbon dioxide levels are not restricted, and that the amount of carbon dioxide in the atmosphere be allowed to continue to increase to provide for the benefit of all humanity and biodiversity as well. Thank you.

[The prepared statement of Mr. Idso follows:]

Testimony of

Keith E. Idso, Ph.D.

Vice President

Center for the Study of Carbon Dioxide and Global Change

Before the

United States House of Representatives Subcommittees on

National Economic Growth, Natural Resources and Regulatory Affairs

and

Science Subcommittee on Energy and the Environment

October 6, 1999

Introduction

I want to thank both Chairmen and the distinguished Members of the two Subcommittees for inviting me to testify about carbon dioxide (CO2) and the positive effects that its rising atmospheric concentration has on plant growth and ecosystem biodiversity. Contrary to what certain people would have you believe, CO2 is not a pollutant. In fact, it is the absolute antithesis of a pollutant; for this colorless, odorless gas is one of the primary raw materials (the other being H20) out of which plants construct their tissues. Hence, CO2 functions as one of the twin pillars of earth's biosphere, which is vital for supporting nearly all life that exists.

Plant responses to elevated CO2

Plants respond directly to increasing atmospheric CO2 concentrations. Kimball (1983a, b) conducted two of the earliest analyses of the peer-reviewed scientific literature dealing with this subject. From reported results of 770 individual plant responses, he determined that a 300 ppm rise in the air's CO2 content boosts the productivity of most herbaceous plants by approximately 33%. Other reviews conducted by Cure and Acock (1986), Mortensen (1987) and Allen (1990) have produced similar results. In a more detailed study, Poorter (1993) found the average growth stimulation of a 300 ppm increase in atmospheric CO2 concentration to be 41% for 130 different C3 plants, 22% for nine C4 species, and 15% for six different CAM plants. In addition, Poorter (1993), Ceulemans and Mousseau (1994), and Wullschleger et al. (1995, 1997) report the results

of 176 experiments on trees and other woody plants that reveal a mean growth enhancement of 48% for a 300 ppm increase in the air's CO2 content.

Perhaps the largest such review ever conducted was that of Idso (1992), which utilized papers published subsequent to the reviews of Kimball, in which a total of 1,087 observations of plant responses to atmospheric CO2 enrichment were compiled and analyzed. Of this number, 93% of the responses to CO2 were positive, 5% were negligible, and only 2% were negative.

data used to generate this figure were derived from 342 peer-reviewed scientific journal articles authored by 484 scientists residing in 27 foreign countries and 27 American states, representing 24 universities, 30 American government research organizations and 88 foreign institutions. In viewing these comprehensive results, one simple fact stands out clear and unmistakable: the science of atmospheric CO2 enrichment demonstrates that plants grow better with more CO2 in the air.

Plant responses to elevated CO2 when environmental constraints restrict their growth

It is often stated, in cursory reviews of the subject, that plants may not be able to reap the many benefits resulting from an increase in atmospheric CO2 if they are simultaneously experiencing less-than-optimal growing conditions brought about by environmental stresses or resource limitations. In evaluating this possibility, Idso and Idso (1994) reviewed the scientific literature of the ten-year period 1983-1992, finding that the percentage growth enhancement resulting from atmospheric CO2 enrichment is typically greater when plants are exposed to growth-retarding stresses --such as those imposed by low levels of sunlight, inadequate soil moisture, high soil salinity, elevated air temperatures and the presence of aerial pollutants-- than it is under ideal growth

growth of the plants (adapted from Paez et al., 1983). Although these environmental stresses clearly have a negative impact on the plants of both CO2 treatments, the plants exposed to the higher CO2 concentration exhibit a greater percentage growth