Increased CO2 Beneficial to Plants – A Climate Change Mythical Fact

12 October 2016 Geoffrey Craggs, JP, Research Analyst, Northern Australia and Land Care Research Programme

Background

Research conducted in the late 1990s and early 2000s, concluded that increasing the amount of carbon dioxide (CO2) available to plants serves to enhance development and optimise their growth. It was determined that raising levels of atmospheric CO2 would increase the openness of the stomata, the pores through which plants exchange gasses during photosynthesis. Open stomata, for instance, allow CO2 to be drawn down through a plant’s leaves, thus providing a pathway for oxygen and water to diffuse into the atmosphere.

Comment

This research suggested that increasing levels of CO2, as a result of global warming, would be of significant benefit to the world’s growing population by enhancing food growth and production, thereby ensuring food security. The scientists demonstrated results of plant growth responses of 30 per cent increases in herbaceous plants and up to 50 per cent in woody plants, obtained from experiments under controlled conditions using concentrations of atmospheric CO2 at 300 parts per million (ppm).  More recent research into plant development, in conditions of Free-Air Carbon dioxide Enrichment (FACE), resulted in plant growth averaging 40 per cent at CO2 concentrations of 475–600 ppm.

While plant physiological responses, water use and changes in chemical composition are subject to experimentation of elevated CO2, the consequential environmental and ecological effects must also be subject to investigation and analysis. Research needs to include the biological processes that transpose the carbon created though photosynthesis to the soil, and the effects on soil composition, structure and microbiology.

Increasing levels of CO2 to change or modify the chemical composition of plant tissues are likely to affect species which consume them. For instance insects could be adversely affected due to increased levels of sugars and starches and nitrogen concentrations in leaves. As well, ecosystem change could occur from altered chemistry, lessening the plant’s natural insect defence mechanisms. It is possible that there may be diverse consequences to the higher order mammal, reptile and bird species which naturally prey on those insects. Effects on human nutrition can be expected from poorer food quality: in FACE experiments, protein concentrations in grains of wheat, rice and barley, and in potato tubers, decreased by 5–14 per cent under elevated CO2.

Measurements undertaken by the Earth System Research Laboratory in Hawaii in September 2016 produced figures that indicate atmospheric CO2 has risen to exceed 400 ppm. Current projections are for concentrations to continue to rise to as much as 500–1000 ppm by the year 2100.

Research and investigation into ameliorating the effects of climate change on crop production is inadequate and not commensurate with increasing CO2. Investigation priorities must include considerations for the short to medium term and might include genetic modification, grafting and alternative methods of vegetative propagation. The extent to which countermeasures can ameliorate the effects of global warming, however, are currently limited and, in the long-term, agricultural problems related to extreme weather events, caused by climate change, will have the capacity to seriously harm cropping and global food production.

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