Positive impact

climatologists have always regarded carbon dioxide (co₂) as dangerous since it is supposed to be one of the principle causes of global warming. But then co₂ also performs the valuable function of enhancing floral growth.

Rise in atmospheric co₂ concentration and possible concomitant climate change has been seen to affect ecosystems and agricultural production. Water vapour and greenhouse gases like co₂ affect the heat balance of the earth by absorbing long-wave radiations. Thus, surface temperature would have been much higher in the absence of greenhouse gases. This is referred to as the 'climate effect'.

co₂ has a 'biological effect' as well, as it serves as a medium for photosynthetic carbon assimilation and thus enhances plant growth and yield. Increase in air temperature brings crop temperature closer to the optimum -- crops ripen faster due to simulation by co₂ and its interaction with temperature.

Several types of plant exposure systems have been developed to investigate the impacts of rising atmospheric co₂ concentration, says D C Uprety of the division of plant physiology, Indian Agricultural Research Institute (iari ), New Delhi. These systems include leaf chambers, controlled environmental plant growth cabinets, greenhouses, open-top field chambers, sunlight environmental plant growth chambers and free air stream gas enrichment systems, which provide information on plant responses to gaseous treat-ment. The iari's observations have shown that with an increase in co₂ concentration in the coming years, the earth's plant life will also become more efficient at conserving and utilising moisture, thus enabling plants to grow in dry conditions and empowering them to reclaim great tracts of land previously lost due to desertification. A greater vegetative cover would reduce the adverse effects of soil erosion. One of the secondary consequences of an increase in co₂ is an enhancement of the activity of soil rhizosphere organisms, which provide growth-promoting effects beneath the soil surface, lengthen the life of absorptive root hair and increase the area of root surface available for water and nutrient uptake. co₂ also increases light, water and nitrogen absorption efficiency of plants.

co₂ concentration has risen in the past and may continue to rise. Thus, the earth may continue to experience a positive net transfer of organic carbon from dead vegetative tissue to living vegetative tissue. This transfer could increase the planet's abundance of living plants bringing about an increase in species richness or biodiversity of earth's natural plant communities. The legacy of the industrial revolution -- rise in atmospheric co₂ could thus bring about a rebirth of the "biosphere and the beginning of a biological rejuvenation".