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You may not like them in your house, but bugs are vital to ecosystems. And now it seems insects around the world are in a crisis, and it’s more serious — and widespread — than scientists realized. The insect population of a national forest in Puerto Rico is declining at an alarming rate, a new study has found. And the crash is restructuring the rainforest food web — the abundance of insect-eating animals has decreased, too.
The authors of the study cite climate change as the driving force behind the dramatic loss of tropical invertebrates.
While temperatures in the tropical forests of northeastern Puerto Rico have climbed two degrees Celsius since the mid-1970s, the biomass of arthropods – invertebrate animals such as insects, millipedes, and sowbugs – has declined by as much as 60-fold, according to new findings published in the Proceedings of the National Academy of Sciences.
The finding supports the recent United Nations Intergovernmental Panel on Climate Change warnings of severe environmental threats given a 2.0 degree Celsius elevation in global temperature. Like some other tropical locations, the study area in the Luquillo rainforest has already reached or exceeded a 2.0 degree Celsius rise in average temperature, and the study finds that the consequences are potentially catastrophic.
“Our results suggest that the effects of climate warming in tropical forests may be even greater than anticipated,” said Brad Lister, lead author of the study and a faculty member in the Department of Biological Sciences at Rensselaer Polytechnic Institute. “The insect populations in the Luquillo forest are crashing, and once that begins, the animals that eat the insects have insufficient food, which results in decreased reproduction and survivorship and consequent declines in abundance.”
The study “Climate Driven Declines in Arthropod Abundance Restructure a Rainforest Food Web” is based on data collected between 1976 and 2013 by the authors and the Luquillo Long Term Ecological Research program at three mid-elevation habitats in Puerto Rico’s protected Luquillo rainforest. During this time, mean maximum temperatures have risen by 2.0 degrees Celsius.
As arthropods declined, the study also found that simultaneous decreases occurred in Luquillo’s insect-eating animal population, which includes lizards, frogs, and birds.
“This study in PNAS is a real wake-up call – a clarion call – that the phenomenon could be much, much bigger, and across many more ecosystems,’ David Wagner, an expert in invertebrate conservation at the University of Connecticut who was not involved with this research, told the Washington Post. Wagner called the study “one of the most disturbing articles I have ever read.”
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