Carbon dioxide levels in the biosphere: Effects on plant productivity

Abstract

Human society is now inadvertently conducting a great biological and environmental experiment, the outcome of which is not known. Atmospheric carbon dioxide (CO₂) is increasing at the rate of 1.5 parts per million (ppm) per year. It has risen from 315 ppm to 340 ppm in the past 25 years — a 9% increase. Because CO₂ is among the factors which can limit the growth of plants, the increase may be beneficial. An increase in plant growth due to “fertilization”; of extra CO₂ has not been measured, but a 5 to 10% increase may already have occurred. Current data indicate that plants growing at higher than normal CO₂ levels are more tolerant of water, temperature, light, and atmospheric pollutant stresses. There are effects on carbon metabolism, plant growth and development, microbial activity, and terrestrial and aquatic plant communities. The current rising level of atmospheric CO₂ represents ,a dramatic change in a resource base and can affect the total biological productivity of the earth. A global change in a fundamental element of all plant life mandates the establishment of a research agenda for the assessment of unexplored frontiers. Increasing levels of atmospheric CO₂ will likely have major effects on food and the production of other renewable resources in the decades ahead.