Dr. Sherwood B. Idso, a research physicist with U.S. Water Conservation Laboratory, Phoenix, Arizona, has found that the "greenhouse effect" could in fact turn out to be beneficial rather than harmful to the planet.[11] In his experiments, Dr. Idso has found that plants, when enriched with more carbon dioxide, "grow bigger and better, much like the plants of past geological epochs of biological prominence." Furthermore, "the efficiency with which plants use water to produce organic matter, essentially doubles with a doubling of the atmospheric carbon dioxide concentration. Moreover, for a tripling of the amount of carbon dioxide in the air, it nearly triples!"[12] According to Dr. Idso, because plants use water more efficiently with higher carbon dioxide concentrations, they will grow in places where they have not been able to grow in the past. Below ground, the soil will become more enriched, which will increase microbiological activity, such as increasing the supply of earthworms. Dr. Idso also has found that some plants increased net photosynthesis rates of exposed leaves by approximately 50 percent. In an experiment with orange trees exposed to increased carbon dioxide levels, he found after a 30-month period that the enhanced carbon dioxide-exposed trees were more than twice as large as the trees exposed to ambient air. Dr. Idso concludes, "It well could be that the rising carbon dioxide content of Earth's atmosphere is actually a blessing in disguise and one of the better things that could happen to mankind and nature.