For example, one-third of all monarchs aggregating in the Michoacan in Mexico were killed in a recent blizzard. If the monarchs had been dispersed over many sites, the blizzard would not have been such a major blow to the world's monarch population. Some farming methods also threaten pollinators by destroying their habitats. Large-scale modern agricultural operations produce extensive fields of a single crop, and when the crop's short season is over, nothing remains for bees to eat. Extensive irrigation also destroys solitary bees' underground nests and increases the damage that fungi do to their broods.
Habitat fragmentation can be equally harmful to pollinators.
Tallgrass prairie in Iowa that once sprawled across five million acres is now reduced to only 200 acres, some of it in isolated fragments too small and too far apart to support pollinator populations. Realizing the importance of the crop, Peru passed laws to protect Brazil nut trees, but failed to protect the surrounding forest as well. This led to a highly dysfunctional ecosystem consisting of isolated Brazil nut trees surrounded by pasture. Without the forest, orchid bees could not survive to pollinate the trees. The decline of the Brazil nut has implications for more than Peru's economy, as the Brazil nut tree is a key player in its ecosystem.