'Hyperalarming' Study Shows Massive Insect Loss

An anonymous reader quotes a report from The Washington Post: Insects around the world are in a crisis, according to a small but growing number of long-term studies showing dramatic declines in invertebrate populations. A new report suggests that the problem is more widespread than scientists realized. Huge numbers of bugs have been lost in a pristine national forest in Puerto Rico (Warning: source may be paywalled; alternative source), the study found, and the forest's insect-eating animals have gone missing, too. The latest report, published Monday in the Proceedings of the National Academy of Sciences, shows that this startling loss of insect abundance extends to the Americas. The study's authors implicate climate change in the loss of tropical invertebrates.

Bradford Lister, a biologist at Rensselaer Polytechnic Institute in New York, has been studying rain forest insects in Puerto Rico since the 1970s. 'We went down in '76, '77 expressly to measure the resources: the insects and the insectivores in the rain forest, the birds, the frogs, the lizards,' Lister said. He came back nearly 40 years later, with his colleague Andrés García, an ecologist at the National Autonomous University of Mexico. What the scientists did not see on their return troubled them. 'Boy, it was immediately obvious when we went into that forest,' Lister said. Fewer birds flitted overhead. The butterflies, once abundant, had all but vanished. García and Lister once again measured the forest's insects and other invertebrates, a group called arthropods that includes spiders and centipedes. The researchers trapped arthropods on the ground in plates covered in a sticky glue, and raised several more plates about three feet into the canopy. The researchers also swept nets over the brush hundreds of times, collecting the critters that crawled through the vegetation. Each technique revealed the biomass (the dry weight of all the captured invertebrates) had significantly decreased from 1976 to the present day. The sweep sample biomass decreased to a fourth or an eighth of what it had been. Between January 1977 and January 2013, the catch rate in the sticky ground traps fell 60-fold. The study also found a 30-percent drop in anole lizards, which eat arthropods. Some anole species have disappeared entirely from the interior forest. Another research team captured insect-eating frogs and birds in 1990 and 2005, and found a 50 percent decrease in the number of captures. The authors attribute this decline to the changing climate.

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