Pássaros e insetos escasseando na Europa.

Pássaros e insetos escasseando na Europa.

Originally shared by John Baez

Where have all the insects gone?

In Germany, it seems the population of insects has dropped about 75% over the last decade. This is bound to affect birds and other animals higher up the food chain.. and indeed, bird populations have been dropping too.

The cause is unclear, though places for birds to live have been going away, and the use of neonicotinoid pesticides, known to kill insects, has been rising over this time.

Here's the news:

...a new set of long-term data is coming to light, this time from a dedicated group of mostly amateur entomologists who have tracked insect abundance at more than 100 nature reserves in western Europe since the 1980s.

Over that time the group, the Krefeld Entomological Society, has seen the yearly insect catches fluctuate, as expected. But in 2013 they spotted something alarming. When they returned to one of their earliest trapping sites from 1989, the total mass of their catch had fallen by nearly 80%. Perhaps it was a particularly bad year, they thought, so they set up the traps again in 2014. The numbers were just as low. Through more direct comparisons, the group—which had preserved thousands of samples over 3 decades—found dramatic declines across more than a dozen other sites.

One can hope it's some sort of mistake. But it seems these folks are being careful:

The members monitored each site only once every few years, but they set up identical insect traps in the same place each time to ensure clean comparisons. Because commercially available traps vary in ways that affect the catch, the group makes their own. Named for the Swedish entomologist René Malaise, who developed the basic design in the 1930s, each trap resembles a floating tent. Black mesh fabric forms the base, topped by a tent of white fabric and, at the summit, a collection container—a plastic jar with an opening into another jar of alcohol. Insects trapped in the fabric fly up to the jar, where the vapors gradually inebriate them and they fall into the alcohol. The traps collect mainly species that fly a meter or so above the ground. For people who worry that the traps themselves might deplete insect populations, Sorg notes that each trap catches just a few grams per day—equivalent to the daily diet of a shrew.

Sorg says society members saved all the samples because even in the 1980s they recognized that each represented a snapshot of potentially intriguing insect populations. "We found it fascinating—despite the fact that in 1982 the term ‘biodiversity' barely existed," he says. Many samples have not yet been sorted and cataloged—a painstaking labor of love done with tweezers and a microscope. Nor have the group's full findings been published. But some of the data are emerging piecemeal in talks by society members and at a hearing at the German Bundestag, the national parliament, and they are unsettling.

Beyond the striking drop in overall insect biomass, the data point to losses in overlooked groups for which almost no one has kept records. In the Krefeld data, hover flies—important pollinators often mistaken for bees—show a particularly steep decline. In 1989, the group's traps in one reserve collected 17,291 hover flies from 143 species. In 2014, at the same locations, they found only 2737 individuals from 104 species.

The picture here shows a hover fly.

Since their initial findings in 2013, the group has installed more traps each year. Working with researchers at several universities, society members are looking for correlations with weather, changes in vegetation, and other factors. No simple cause has yet emerged. Even in reserves where plant diversity and abundance have improved, Sorg says, "the insect numbers still plunged."

This consistent with other trends. For example, bird populations have been dropping in Europe. In 2014, a study published in Ecology Letters revealed that most common species (the top 1/4) had dropped in population by 92% since 1980.

We are in the midst of a mass extinction event. A mass extinction event is a bottleneck. The species that make it through will make up our future. So, it's a time when small changes can make a big difference.

Bird and insect populations can bounce back quickly if we let them... unless they go extinct. So: help these species in your back yard. Help stop the use of neonicotinoid pesticides. Help support nature reserves. Help stop development that destroys wild or semi-wild land.

The quote is from this article by Gretchen Vogel:

http://www.sciencemag.org/news/2017/05/where-have-all-insects-gone

The photo is by Jef Meul for National Geographic. Here's the paper on bird populations in Europe:

https://www.seo.org/wp-content/uploads/2014/11/ecology-letters.pdf

An overview of the 6th mass extinction:

http://www.biologicaldiversity.org/programs/biodiversity/elements_of_biodiversity/extinction_crisis/

#savetheplanet