This documentary is about German research into the 75% drop in global insect numbers over 25 years. After demonstrating the research methods used to measure this decline, the filmmakers focus on the plight of specific insect species. Some entomologists predict total ecosystem collapse if insect populations decline any further.
The film also explores specific threats insects face: overuse of insecticides (particularly neonicotinoids), the spread of agricultural “deserts” (large cultivated areas devoid of flowers) and the herbicide Roundup.*
Scientists are most concerned about the plight of butterflies, moths and other pollinators – without them humanity can’t mass produce fruits and vegetables. Other insects play an important role in feeding fish, birds, frogs and small mammals. Their populations are also collapsing.
The segment I found most interesting features the mayor of Miami protesting the nightly spraying of his city with pesticides (theoretically to destroy mosquitoes carrying the Zika virus). Owing to the short mosquito life cycle (egg to egg in 11 days), pesticide overuse paradoxically increases mosquito numbers. Following pesticide spraying, mosquito recovery takes two days. Meanwhile it takes weeks for the insect predators that feed on them to recover.
*Although Roundup (which is meant to target weed) doesn’t kill bees, it reduces their heartbeat and brain oxygenation. This, in turn, impairs orientation and can prevent them from returning to the hive. In wild bees, this can result in brood death.