New reports indicate that the affects of global warming on the world's food supply could be worse than previously thought.
According to three new scientific reports, global agriculture, already predicted to be stressed by climate change in coming decades, could go into steep, unanticipated declines in some regions due to complications that scientists have so far inadequately considered.
"Many people assume that we will never have a problem with food production on a global scale. But there is a strong potential for negative surprises," said Francesco Tubiello, a physicist and agricultural expert at the NASA/Goddard Institute of Space Studies, who coauthored all three papers.
Studies in the past 10 years suggest that mounting levels of carbon dioxide in the air—believed to be the basis of human-caused climate change—may initially bolster the photosynthetic rate of many plants, and, along with new farming techniques, possibly add to some crop yields. Between now and mid-century, higher temperatures in northerly latitudes will probably also expand lands available for farming, and bring longer growing seasons.
However, these gains will be likely canceled by agricultural declines in the tropics, where even modest 1- to 2-degree rises are expected to evaporate rainfall and push staple crops over their survival thresholds.
Existing research estimates that developing countries may lose 135 million hectares (334 million acres) of prime farm land in the next 50 years. After mid-century, continuing temperature rises—5 degrees Celsius or more by then, are expected to start adversely affecting northern crops as well, tipping the whole world into a danger zone.
The report has also said that higher temperatures may also prompt outbreaks of weeds and pests, and affect plant or animal physiology.
For example, more recent modeling suggests that cattle ticks and bluetongue (a viral disease of sheep and cattle) will move outward from the tropics to areas such as southern Australia.
Other new models suggest that higher temperatures will limit the ability of modern dairy-cow breeds to convert feed into milk, and lead to declines in livestock fertility and longevity. As temperatures rise in northerly latitudes, the ability of crop pests to survive winters is expected to improve, enabling them to attack spring crops in regions where they were previously kept at bay during this vulnerable time.
The reports also cites that farmers may temporarily mitigate some effects of the changing climate by moving toward adaptations.
Adaptations already being considered or set up include regional climate-forecasting systems that enable farmers to switch to different crops or change the timing of plantings; introduction of new varieties or species that can withstand anticipated conditions; and improved flood-mitigation and water-storage facilities.