Thursday, November 30, 2017

The Windshield Phenomenon

Image result for bug windshield

Environmental and Science Education

I found a couple of newspaper reports this fall on windshield surveys, an informal measure of the abundance and diversity of bugs, splattered of course.  The numbers are remembered by those who look as more when observers were kids and fewer now.

Some of you may remember summer trips when stopping for gasoline included washing and scraping car windshields, of bug guts and topping up windshield washer fluid was a standard part of the stop.  This has become a much more uncommon practice.

But how do we know that numbers and kinds have declined. Maybe it has something to do with the aerodynamic changes in car design, from boxes to round, aerodynamic surfaces.

As a test of this idea, the Royal Society for the Protection of Birds (RSPB) conducted its Big Bug Count in 2004. Participants, some 40,000 drivers, cleaned their number plates and then drove for a specified number of miles (20 and 80). At the end, they were asked to count the insects using a grid referred to as the "splatometer" to make the counting easier and more accurate. They found an average of 1 bug every 5 miles. It was the first mass study into possible causes of insect decline. Unfortunately, the study was not repeated. You may see the splatometer used in this study here. There is also an earlier version here. It was used in a trial study.

In October 2017 PLOS One published a research paper by Caspar A. Hallmann and 11 other scientists that provides a much more accurate measure of the decline noted informally by windshield observers. It uses a standardized procedures--trap construction, size and design, trap orientation, slope of the location, netting type and ground sealing. The research is also relatively long-term (27 years, 1989 - 2016). The paper is ominously titled "More than 75 percent decline over 27 years in total flying biomass in protected areas." The research was conducted in protected nature areas in Germany. Here is the abstract.

Global declines in insects have sparked wide interest among scientists, politicians, and the general public. Loss of insect diversity and abundance is expected to provoke cascading effects on food webs and to jeopardize ecosystem services. Our understanding of the extent and underlying causes of this decline is based on the abundance of single species or taxonomic groups only, rather than changes in insect biomass which is more relevant for ecological functioning. Here, we used a standardized protocol to measure total insect biomass using Malaise traps, deployed over 27 years in 63 nature protection areas in Germany (96 unique location-year combinations) to infer on the status and trend of local entomofauna. Our analysis estimates a seasonal decline of 76%, and mid-summer decline of 82% in flying insect biomass over the 27 years of study. We show that this decline is apparent regardless of habitat type, while changes in weather, land use, and habitat characteristics cannot explain this overall decline. This yet unrecognized loss of insect biomass must be taken into account in evaluating declines in abundance of species depending on insects as a food source, and ecosystem functioning in the European landscape.

There is much more research to do, e.g., causation, geographical extent and the possible cascade of effects throughout ecosystem. Hallman et. al., paid attention to weather/climate and noted that the temperatures observed during the study should have favored flying insects. They didn't.

The news article in the Washington Post by Ben Guarino may be found here. The report in the Ottawa Citizen by Tom Speer is found here.

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