Climate change will affect plant pests and diseases in the same way it affects infectious disease agents.

By
Dennis Owusu Boateng
Cocoa Swollen Shoot Disease Control Unit (Ghana Cocoa Board)

Climate change will affect plant pests and diseases in the same way it affects infectious disease agents. In other words, the range of many insects will expand or change, and new combinations of pests and diseases may emerge as natural ecosystems respond to altered temperature and precipitation profiles. Any increase in the frequency or severity of extreme weather events, including droughts, heat waves, windstorms, or floods, could also disrupt the predator-prey relationships that normally keep pest populations in check. An explosion of the rodent population that damaged the grain crop in Zimbabwe in 1994, after 6 years of drought had eliminated many rodent predators, shows how altered climate conditions can intensify pest problems. The effect of climate on pests may add to the effect of other factors such as the overuse of pesticides and the loss of biodiversity that already contribute to plant pest and disease outbreaks [300].

The ingenuity of farmers, breeders, and agricultural engineers, and the natural resilience of biological systems, will help buffer many of the negative effects of climate change on agriculture. However, experts believe that over the longer term, the accumulated stresses of sustained climate change stand a good chance of disrupting agro-ecosystems and reducing global food productivity.

The regions thought to be most vulnerable to productivity declines are semiarid and arid areas where rain-fed, nonirrigated agriculture predominates. Unfortunately, many of these areas as in sub-Saharan Africa, South and East Asia, and on some Pacific islands are already hard-pressed agriculturally and suffer from high rates of malnutrition. In Senegal, for example, one study predicts a 30-percent yield decline with a 4�C rise in temperatures and no change in rainfall from current levels. The effect of this kind of agricultural decline on local food security would be severe. The negative effects of climate change on agriculture in poor countries could put an additional 40 to 300 million people at risk of hunger by 2060 [301].

Perhaps the greatest long-term danger to human health from climate change will be the disruption of natural ecosystems, which provide an array of services that ultimately support human health. Biotic systems whether in forests, rangelands, aquatic environments, or elsewhere provide food, materials, and medicines; store and release fresh water; absorb and detoxify wastes; and satisfy human needs for recreation and wilderness. They are also intimately involved in sustaining the genetic basis of agriculture.

These systems will likely undergo major reorganization as global temperatures rise and rainfall patterns change more rapidly than they have in the past 10,000 years. Rough estimates of the effects of a doubling of atmospheric CO2 levels show a major redistribution of Earth’s vegetation. As much as one third to one half of all plant communities and the animals that depend on them might shift in response to changing ecological conditions.

References and notes
292. A. McMichael et al., eds., Climate Change and Human Health (World Health Organization, Geneva, 1996), p. 218.

293. J. Patz, et al., “Global Climate Change and Emerging Infectious Diseases,” Journal of the American Medical Association, Vol. 275, No. 3 (1996), p. 580.

294. A. McMichael et al., eds., Climate Change and Human Health (World Health Organization, Geneva, 1996), p. 82.

295. A. McMichael et al., eds., Climate Change and Human Health (World Health Organization, Geneva, 1996), p. 220.

296. A. McMichael et al., eds., Climate Change and Human Health (World Health Organization, Geneva, 1996), p. 220.

297. A. McMichael et al., eds., Climate Change and Human Health (World Health Organization, Geneva, 1996), pp. 96-100.

298. A. McMichael et al., eds., Climate Change and Human Health (World Health Organization, Geneva, 1996), pp. 110-111.

299. A. McMichael et al., eds., Climate Change and Human Health (World Health Organization, Geneva, 1996), pp. 110, 111, 114.

300. A. McMichael et al., eds., Climate Change and Human Health (World Health Organization, Geneva, 1996), pp. 111-113.

301. A. McMichael et al., eds., Climate Change and Human Health (World Health Organization, Geneva, 1996), pp. 115-121.
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