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Climate Change, Crops, and Weeds

Climate change could benefit weeds more than crops?

As if the inter-relationships between plants, pest organisms, and the existing environment weren't staggeringly complex, the onus of potential global climate change bodes yet further complications of the fragile equation.

Viewing climate change as a looming challenge, two scientists have polished their trusty crystal ball and ventured into the future to predict the implications of multiple environmental changes on biotic interactions. S.G. Pritchard and J.S. Amthor, in their 2005 book, CROPS AND ENVIRONMENTAL CHANGE, address the effects of global warming, increasing atmospheric carbon dioxide and ozone oncentrations, and soil salinization on crop physiology and yield.

With a specific focus on major classes of crop pests, Drs. Pritchard and Amthor suggest that:

• Warming may favor most weeds in comparison to crops;


• Rising CO2 also is likely to enhance weed growth relative to crops;


• Being highly adaptable, many weed species can be expected to rapidly and more effectively adapt to increasing stresses such as rising atmospheric ozone and soil salinization;


• Warming trends most likely will also increase abundance, growth rate, and geographic range of many key crop-attacking insect pests;


• Warming may, depending on shifting precipitation patterns, stimulate microbial pathogens;


• Crop tissue chemistry, including nitrogen and water content as well as inducible defense mechanisms, is likely to evolve as environmental change occurs;


• On the plus side, rising CO2 may stimulate rhizobia and mycorrhizae and benefit both crop plants and soil dwelling symbionts;


• Warming (soil) may be beneficial in some regions, but harmful in those regions where optimal soil temperatures already exist.

There is much more intriguing information to support Pritchard and Amthor's contention "that crop plants are not the only organisms determining yield that are likely to be affected by environmental changes." The authors warn that generalizations about magnitudes of effects and whether they will be deleterious or beneficial for crops are still in the realm of conjecture due to a lack of experimental data.

Author: A.E. Deutsch (editor)
Source: IPMnet NEWS - Issue #135
Link: http://www.ipmnet.org

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