For the first time in North American history, the numbers of bees, bats, butterflies, hummingbirds and other pollinators have fallen so low that there is scientific concern and public fear of a “pollinator collapse.” Such a “food chain collapse” might not only affect the health of wild species in our parks and refuges, but also our food security derived from agricultural landscapes. In particular, several bumblebee species, hummingbirds and monarch butterflies have suffered precipitous declines in forests, rangelands, fields and orchards.
For instance, the “eastern” (including Great Plains) migratory populations of monarch butterflies that overwinter in the mountains of Mexico have declined by more than 80% within the last two decades. One probable driving factor of this decline has been the loss of more than 1.3 billion stems of milkweed plants required by monarchs as larval host plants and as nectar sources to ensure their reproduction. Misuse and overuse of toxic herbicides—as well as land conversion and habitat fragmentation – are high among the many factors that have contributed to this decline.
The decline of several North American bumblebee species has been linked to the use of certain highly toxic neo-nicotinoid pesticides, to emergent diseases, to introduced parasites and to habitat loss triggered by climate change. A recently published analysis of historical specimen data for 21 North American bumble bee species found that 11 of the examined species have experienced populations declines of 50% or greater. A different set of factors may be involved with each other set of pollinators now considered at risk.