Scourge of invasive plants and animals is an 'extinction event on par with the asteroid that killed the dinosaurs'

Brown tree snakes were accidentally introduced in Guam. It ate
many native birds into extinction. (Photo by David Clode, Unsplash)

Black rats, brown tree snakes and water hyacinth are only a few of the more than 3,500 invasive species "wreaking havoc across the planet, destroying crops, disseminating pathogens, depleting fish people rely on for food and driving native plants and animals toward extinction, according to a major report backed by the United Nations," reports Dino Grandoni of The Washington Post. "The landmark assessment found harmful invasive species cost society more than $423 billion a year. . . .A tally only expected to grow as the modern age of global trade and travel continues. . . . The result is a great scrambling of the planet's flora and fauna, with dire implications for humans and the ecosystems they depend on."

Continental globe-trotting "is one of the main causes of Earth's ongoing biodiversity crisis, an extinction event on par with the asteroid that killed the dinosaurs," Grandoni explains. Invasive species are playing a role in 60 percent of extinctions, according to the report, which was created by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, a body made up of more than 140 countries that provide policymakers with scientific assessments to help protect Earth's biodiversity and prevent extinctions. Aníbal Pauchard, a professor at the University of Concepción in Chile who co-chaired the group behind the report, told Grandoni: "It's normal that species move. It's not normal that a species crosses the Atlantic. . . . Not normal that it goes from Australia to Chile."

The report names the black rat as "most widespread invasive animal, which spread by stowing away on ships and scurried its way not only into dense cities but onto far-flung islands as well, where it has decimated ground-nesting seabirds and other animals," Gradoni reports. "The impact of land-dwelling rats on islands is so profound that even nearby reef fish can feel it after the rodents alter the flow of nutrients into the ocean. . . . . On the island of Guam, the voracious brown tree snake has already driven several native birds to extinction."

An innocent-looking water hyacinth floats in a pond at the
Memphis Zoo, Tenn. (Photo by Joshua J. Cotten, Unsplash)

Aquatic systems are facing epic invasions with dire outcomes. "In the Caribbean, venomous lionfish are driving down the numbers of native fish. In the Great Lakes, zebra mussels are clogging the intake pipes of drinking water systems and power plants," Grandino writes. "But one of the most devastating aquatic invaders is a delicate-looking flower," a free-floating plant that spreads so aggressively, "it can cover entire ponds and lakes, leaving a matted mess that impedes boat traffic and fishing. . . . The plants suck up so much water that they render lakes dry and leave communities without drinking water. The report lists the water hyacinth, "which is popping up everywhere from Africa to Australia, the most widespread invasive plant on Earth."

Researchers list prevention as the best solution "through border monitoring and import control," Grandino reports. "In December, nations agreed to try to reduce the spread of harmful invasive species by at least half by 2030 as part of an international agreement."