When we talk about the challenge of ending hunger and feeding a growing global population, most of the focus is put on increasing production. That’s not surprising — “more” is our solution to most social problems. But some of the hunger gap could be closed by making better use of the crops we do produce now. Take plant pests and diseases, which have historically laid waste to whole harvests. The Irish potato famine of the 1840s — caused by the oomycete Phytophthora infestans — led to the deaths of a million people and the emigration of another 2 million Irish. The 1943 Great Bengal Famine in India led to the deaths of some 3 million and was caused by a simple fungus. Even today, when farmers are better equipped to control pests and pathogens, between 10% and 16% of crop production each year is lost to biological threats. That’s enough food to feed hundreds of millions of people.
Pests and pathogens are weather-dependent, and many thrive in hotter, wetter climates — which is exactly the sort of change that global warming is predicted to create over the coming decades. In a new meta-analysis published in the journal Nature Climate Change, researchers from the University of Exeter and the University of Oxford looked at how plant pests and diseases will respond to a warming world, and found that their range has been steadily shifting toward both poles, as climate change warms higher latitudes. They found that crop pests have been spreading north and south a little less than 2 miles (3.2 km) a year since 1960, though there’s a lot of variety within individual species.
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We can already see the results of some of that pest expansion. Warmer winters have allowed the mountain pine beetle to take hold over a greater swath of the Pacific Northwest, allowing it to spread further and higher, at altitudes that in the past would have been too cold for the insect. As a result, the mountain pine beetle is now at epidemic levels throughout the American West. The rice blast fungus, present in scores of countries, has migrated to wheat, and has become a scourge of farmers in Brazil.
Dan Bebber, an author of the paper at the University of Exeter, said in a statement:
If crop pests continue to march polewards as the earth warms, the combined effects of a growing world population and the increased loss of crops to pests will pose a serious threat to global food security.
The truly scary possibility is that a new or re-emerging plant disease could decimate one of the few crops — rice, wheat, corn — that the global diet is based on. We’ve already had a few close calls. Wheat rust, which is caused by a fungus, devastated wheat crops in Africa, and is poised to spread to other major wheat-producing countries. It doesn’t help that over the years farmers have narrowed the genetic diversity of commodity crops, which limits our ability to respond if a new pest or disease takes hold. That’s why we need to support seed banks, which store a variety of strains within a crop, to ensure that farmers have weapons to respond to a new plant plague. They’ll need those bullets in a warmer world.