Every spring since 1989, entomologists have set up tents in the meadows and woodlands of the Orbroicher Bruch nature reserve and 87 other areas in the western German state of North Rhine-Westphalia. The tents act as insect traps and enable the scientists to calculate how many bugs live in an area over a full summer period. Recently, researchers presented the results of their work to parliamentarians from the German Bundestag, and the findings were alarming: The average biomass of insects caught between May and October has steadily decreased from 1.6 kilograms (3.5 pounds) per trap in 1989 to just 300 grams (10.6 ounces) in 2014. One of the researchers said the decline is dramatic and depressing and it affects all kinds of insects, including butterflies, wild bees, and hoverflies. Another recent study has added to this concern. Scientists from the Technical University of Munich and the Senckenberg Natural History Museum in Frankfurt have determined that in a nature reserve near the Bavarian city of Regensburg, the number of recorded butterfly and Burnet moth species has declined from 117 in 1840 to 71 in 2013. But, declines in insect populations are hardly limited to Germany. A 2014 study in Science documented a steep drop in insect and invertebrate populations worldwide. By combining data from the few comprehensive studies that exist, lead author Rodolfo Dirzo, an ecologist at Stanford University, developed a global index for invertebrate abundance that showed a 45 percent decline over the last four decades. Dirzo points out that out of 3,623 terrestrial invertebrate species on the International Union for Conservation of Nature [IUCN] Red List, 42 percent are classified as threatened with extinction. http://e360.yale.edu/content/feature.msp?id=3012
For some time now - my entire adult life - the populations of moths at the lights I visit have been declining. They are now almost barren - tonight, for example, not a single moth with a wingspan of more than 4 cm at any of the local gas stations or streetlights. This despite relatively mild temperatures, a crescent moon only, light to moderate breeze and cloud cover, and brush-covered riverbank terrain nearby. When I was young, the hatches of large moths were represented at the lights - as many as six Polyphemus moths at an all night supermarket window in late May or early June was common, for example. A casual observer such as myself could expect to encounter them every year, routinely, without special effort. I haven't seen even one anywhere but one I had raised, briefly at my own house window, in more than ten years - despite working night shift jobs with plenty of outdoor travel etc.
two other factors: 1) Many larger insects feature "hopscotch stability" - wanderers from successful patches far away colonize a new patch, multiply, are discovered by their parasites and predators, are wiped out of that patch but not before producing a couple of wanderers, the wanderers colonize a distant patch while the parasites and predators die out in the first for lack of prey, repeat for thousands of years. In recent times good patches have become scarce - so by chance wanderers have no luck, and recently cleared patches have no source of recolonization. In addition, local disasters are more likely to take out an entire region's current fertile patch or patches - there being few. 2) Generalist predators and competitors have moved in from far away, can wreak havoc among the naive local fauna (example: a parasitic fly was deliberately introduced to the US to control Gypsy Moths, its favorite prey in Europe. It's favorite prey in the US is not Gypsy Moths but a hundred other moth species that have no inherited defense).
I've seen one - count it! - single praying mantis this whole summer. A dozen butterflies. Half a dozen bumblebees. Zero lacewings, and only the ladybugs that overwintered in our greenhouse. Even the wasps aren't trying to colonize my woodshed anymore! So what are the frogs and songbirds supposed to feed on? What's going to pollinate our food crops? It's partly insecticide use - which has been heavy, indiscriminate and devastating, with toxins lingering in soil and water long after a spraying - but also the eradication of habitat; wild vegetation cut down to stubble everywhere a power mower can reach. What is wrong with people? Can't we connect even two dots?
If you watch baseball, especially, and other sports on TV in the US, you will see advertisements for lawn care products that implicitly (via pictures and allusive claims) promise to kill all the arthropods in your grass. Seriously. All bugs in your lawn, dead, is the benefit being sold. Sterilization of the suburban landscape, deliberate. And they sell tons of the stuff.
