Increased CO2 and higher temperatures will be good for plants, so we’ll have more food – so global warming won’t be all bad, right?
Photo by Rene Schwietzke
This argument was first propagated by the Greening Earth Society, (see paper :
Forecasting World Food Supplies: The Impact of the Rising Atmospheric CO2 Concentration, Craig D. Idso and Keith E. Idso) and recently made a reappearance in the Competitive Enterprise Institute’s attempt to debunk Al Gore’s movie, An Inconvenient Truth.
I came across it again in the OISM’s 1998 paper about global warming that was linked to in a recent comment.
The truth is, we don’t know. A recent study suggests that rising CO2 could help plants grow in desert areas.
Many other studies suggest that CO2, in general, does have a positive effect on plant growth.
CO2 may give fast growing plants an edge (see here). Invasive plants might have an edge, but there appear to be limits:
(from Evidence of a feedback mechanism limiting plant response to elevated carbon dioxide, Nature 364, (1993), Diaz et al., emphasis mine)
In short-term experiments under productive laboratory conditions, native herbaceous plants differ widely in their potential to achieve higher yields at elevated concentrations of atmospheric carbon dioxide. The most responsive species appear to be large fast-growing perennials of recently disturbed fertile soils. These types of plants are currently increasing in abundance but it is not known whether this is an effect of rising carbon dioxide or is due to other factors. Doubts concerning the potential of natural vegetation for sustained response to rising carbon dioxide have arisen from experiments on infertile soils, where the stimulus to growth was curtailed by mineral nutrient limitations. Here we present evidence that mineral nutrient constraints on the fertilizer effect of elevated carbon dioxide can also occur on fertile soil and in the earliest stages of secondary succession. Our data indicate that there may be a feedback mechanism in which elevated carbon dioxide causes an increase in substrate release into the rhizosphere by non-mycorrhizal plants, leading to mineral nutrient sequestration by the expanded microflora and a consequent nutritional limitation on plant growth.
In plain English, different plants will respond differently to increased CO2. Many crops do not appear to grow better with more CO2 in the atmosphere.
One way to cope with global warming would be to use excess CO2 to boost the growth of certain plants, then burn those plants for fuel (Source).
Some further reading:
Climate change and world food supply
Rabett Run: Weeds grow well in high CO2. Crops?
Food-crop yields in future greenhouse-gas conditions lower than expected
EPA: Agriculture and Food Supply
Climate Change and Crop Yields: Beyond Cassandra, David Schimel: An analysis of recent data from a wide variety of field experiments suggests that previous studies overestimated the positive effects of higher carbon dioxide concentrations on crop yields.
Google Search for the paper by Idso and Idso, referred to above.
