Studies from around the world agree: the world's insect population has decreased dramatically in the past few decades, and agriculture and other industries, as well as wildlife populations, will suffer if it continues.
In 2014, an international team of biologists estimated that arthropods (animals with an exoskeleton) had decreased by 45 percent worldwide over the past 45 years. In some places it's more: a study showed a 76 percent decrease in flying insects in German nature preserves over the past few decades, Ben Guarino reports for The Washington Post. That has triggered a decrease in populations of animals that eat insects, like lizards and birds.
Fewer insects means trouble for humans too. "Thirty-five percent of the world’s plant crops require pollination by bees, wasps and other animals. And arthropods are more than just pollinators. They’re the planet’s wee custodians, toiling away in unnoticed or avoided corners. They chew up rotting wood and eat carrion," Guarino reports. "Wild insects provide $57 billion worth of six-legged labor in the United States each year, according to a 2006 estimate."
Human behavior is believed to be the overarching cause, either because of pesticide use, habitat loss, or global warming. In tropical areas the decrease is more likely caused by rising temperatures, since those insects can only thrive in a very narrow temperature range, and the average temperature of rain forests has increased four degrees in the past 40 years.
In temperate areas, including the Americas, the decrease is more likely because of the effects of climate change, such as droughts. And what bugs are left are likely to eat more of farmers' crops as their metabolism increases, Guarino reports. But global warming isn't the only cause, since insect population declines in northern Europe and New England have been happening since before climate change was a problem there.
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