What data is available from a few direct studies of insect populations indicates that worldwide insect numbers are in decline. Scientists have only classified one million species of insects; there are perhaps 4 million more unrecorded. Immature people with invertebrate phobias may say, "good news", but NOT. Insects are responsible for keeping ecosystems in balance and they contribute immensely to man's ability to feed himself through pollination and predation on crop-munching insects. Bees are the 'poster child' of a general decline in insect populations with a 30-40% decline caused by colony collapse syndrome. Monarch butterflies are another high profile case of disappearing insects; their caterpillar's only food plant, milkweed, has been severely impacted by herbicide use and cultivation. Scientist worry that because the insect world is so large, gradual declines may not be immediately apparent until its too late. According to global monitoring data for 452 species there has been a 45% decline in invertebrate populations over the last forty years. Of course the causes of insect mortality are well known: abuse of pesticides, overuse of nitrogen fertilizer, the spread of monoculture, and destruction of natural habitat. Another possible threat is the increase in atmospheric CO₂ which has reduced the protein contained in pollen by thirty percent since 1842.
A group of British conservation organizations say three-quarters of the world's flowering plants, including human food plants, rely on pollination by invertebrates to produce seeds. One-third of human crop production by volume is so dependent. Insects are a vital food source for amphibians, birds, and small mammals such as bats. Predatory insects consume a massive amount of pest species that damage crops. Insects, therefore, are an indispensable part of Earth's web of life.
To fully understand the problem more monitoring of insect populations on a global basis is needed. Citizen science can play a role here. If 800,000 Indians can come together in Udar Pradesh to plant a record number of trees, then gardeners and outdoor enthusiasts can be trained to collect badly needed data for making meaningful population comparisons. In some places like Europe enough data has been collected already to begin addressing the root problem of insect declines. But changing entrenched methods of agriculture that is poisoning the landscape is difficult. Governments have yet to take the possibility of the collapse of agriculture as the existential threat that it is.