Perhaps the best known consequence of enriching the air with CO2 is that plant growth and development is enhanced. This is because, at a fundamental level, carbon dioxide is the basis of almost all life on Earth; it is the primary raw material utilized by plants to produce the organic matter out of which they construct their tissues. Consequently, the more CO2 there is in the air, the better plants grow, be they terrestrial or aquatic. Such has been the conclusion of literally hundreds of laboratory and field experiments conducted over the years.
For an approximate doubling of the air's CO2 content, the wealth of data that has been accumulated over decades of meticulous research has convincingly demonstrated that the growth or productivity of most herbaceous plants rises by about a third, while that of most woody species increases by 50% or more. It should come as no surprise, therefore, that the father of modern research in this area -- Dr. Sylvan H. Wittwer -- has stated that "it should be considered good fortune that we are living in a world of gradually increasing levels of atmospheric CO2."
Wittwer, S.H. 1997. The global environment: It's good for food production. In: Michaels PJ (ed) State of the climate report: Essays on global climate change. New Hope Environmental Services, New Hope, p 8-13.
** Individual plant growth responses to increasing atmospheric CO2 may be viewed online at the Center for the Study of Carbon Dioxide and Global Change in its Plant Growth Database (http://www.co2science.org/data/plant_growth/plantgrowth.php), which is the largest repository of such information in the world on this subject.