Quoting from the paper:
Since crop domestication 10,000 years ago, farmers have beenProblems are not just limited to old strains spreading further north, new strains are being detected:
plagued by multitudes of pests and pathogens (hereafter termed
pests) causing starvation and social upheaval. Classic examples
include the 1840s Irish potato famine caused by the oomycete
Phytophthora infestans and the 1943 Great Bengal Famine due to the
fungus Helminthosporium oryzae. The threat persists. Between 10
and 16% of crop production is lost to pests, with similar losses postharvest. Indeed, losses of major crops to fungi and oomycetes alone amount to enough to feed 8.5% of today's population.
Recently emerged strains of the rusts Puccinia graminis and
P. striiformis are among the most virulent and rapidly spreading
pathogens ever seen, and a new and invasive lineage of P. infestans
has rapidly displaced other late blight genotypes.
This movement is bad news for our crops and therefore our food supply. The authors of the research conclude that this seem to be at least partly caused by global warming reducing the cold to the north of the range of these pathogens, and partly caused by factors such as increasing transport of food (and thus their pathogens) across the world by man for their own uses, overcoming natural barriers to spread such as large sandy deserts and cold, and potentially greater use of monoculture as crops as we progress north from Africa.