World Insect Population Declines

World Insect Population Declines

Climate change continues to destroy more of our planet


Image: CDN

A species extremely important to our ecosystem and global health is in danger. Insects around the world are in a crisis, according to a growing number of long-term studies showing dramatic declines in invertebrate populations. Huge numbers of bugs have been lost in a pristine national forest in Puerto Rico and the forest's insect-eating animals have gone missing too.

In 2014, an international team of biologists estimated that, in the past 35 years, the abundance of invertebrates such as beetles and bees had decreased by 45%. In places where long-term insect population data is available, mainly in Europe, insect numbers are plummeting. A study last year showed a 76% decrease in flying insects in the past few decades in German nature preserves. A report recently published in the Proceedings of the National Academy of Sciences shows that this loss of insect abundance extends to the Americas. The study's authors say climate change is to blame for the loss of tropical insects.

Species who rely on insects as their food source — and, up the food chain, the predators which eat these animals — are likely to suffer from these declines. Pollination of both crops and wild plants are also affected, as is nutrient cycling in the soil.

Some 80% of wild plants rely on insects for pollination; 60% of birds rely on insects as a food source, according to the study.

"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," said David Wagner, an expert in invertebrate conservation at the University of Connecticut who was not involved with this research. He added, "This is one of the most disturbing articles I have ever read."

If Puerto Rico is the island of enchantment — "la isla del encanto" — then its rainforest is "the enchanted forest on the enchanted isle," he said. The forest, named El Yunque, is well-protected. Spanish King Alfonso XII claimed the jungle as a 19th-century royal preserve. Decades later, Theodore Roosevelt made it a national reserve, and El Yunque remains the only tropical rainforest in the National Forest system. "We went down in '76, '77 expressly to measure the resources: the insects and the insectivores in the rainforest, the birds, the frogs, the lizards," Bradford Lister, a biologist at Rensselaer Polytechnic Institute, 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 disturbed 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. "Everything is dropping," Lister said. “The most common invertebrates in the rainforest - the moths, the butterflies, the grasshoppers, the spiders and others - are all far less abundant.”

Lister and Garcia attribute this crash to climate. In the same 40-year period as the arthropod crash, the average high temperature in the rainforest increased by 4 degrees Fahrenheit.  The invertebrates that live there, likewise, have adapted to these temperatures and fare poorly outside them; bugs cannot regulate their internal heat.

A recent analysis of climate change and insects, published in August in the Journal Science, predicts a decrease in tropical insect populations, according to an author of that study, Scott Merrill, who studies crop pests at the University of Vermont.

Surely, we can see we are in a global climate crisis, if one has not realized by now.

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