The windscreen phenomenon: anecdata is not scientific evidence

The windscreen phenomenon refers to people’s perception that there are fewer insects being splattered on their windscreen than they used to see. It is one of the most common anecdotes presented as evidence of global insect decline in the Insectageddon stories. But anecdotes are not scientific evidence. Anecdotes describe local conditions, not globally-relevant facts.

People often claim the ‘windscreen phenomenon’ is established evidence and proven fact. But a search of academic journal databases returns only one published study that has used car windscreens to measure changes in local insect abundance. In that study, Anders Møller compared insect abundance (although it’s not clear from the Methods if he actually measured density) with breeding rates of insectivorous birds in an agricultural landscape in Denmark. Data was collected in the same way at the same location for 20 years, which is very impressive, and analysis showed an 80% decline in insects across the period. Continue reading