Balance of nature: human damage of an ecosystem (Introduction)

by David Turell , Saturday, April 10, 2021, 15:15 (1323 days ago) @ David Turell

Putting beavers into an Argentinian forest becomes a disaster in 70 years:

https://www.nationalgeographic.co.uk/environment-and-conservation/2019/07/argentina-bro...

"Beavers were supposed to “enrich” Patagonia, economically and ecologically. At least that was the ambition of Argentina’s military when it flew 10 pairs of Canadian beavers from Manitoba to Tierra Del Fuego, Argentina’s southernmost province, in 1946. The soldiers set the beavers loose on the shores of Lake Fagnano in hopes of spurring a fur trade and attracting more residents to the sparsely populated area.

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"...a television series that aired from 1938 to 1972, expressed concern about the fragility of the experiment. Beavers are monogamous; if one of the animals were to die, the program’s announcer fretted, its mate would be unlikely to reproduce.

"But such worry was misplaced. While the fur trade never materialised, what did explode were beaver numbers.

"In contrast to North America, which is home to bears and wolves, the island of Tierra del Fuego has very few natural predators that hanker after beaver meat. With access to extensive forests and steppes they could colonise without fear, the beavers rapidly dispersed and multiplied.

"In the 1960s, beavers crossed to the Chilean side of Tierra del Fuego. “They don’t recognise borders. In fact, they eat the border fence,” quips Felipe Guerra Díaz, the Chilean national coordinator for the beaver project of the Global Environment Facility (GEF), an international partnership that funds environmental efforts. By the early 1990s, residents began spotting beavers in the Brunswick Peninsula on the Chilean mainland, meaning the creatures had braved the unpredictable currents of the Strait of Magellan.

"In their wake they left phantom forests. North American trees have evolved over millions of years to survive beavers’ industrious chewing, explains Ben Goldfarb, an environmental journalist and author of Eager: The Surprising, Secret Life of Beavers and Why They Matter. “Trees like willow, cottonwood, American beech, and alder have all evolved responses to beaver chewing and flooding. They re-sprout when you cut them down, produce defensive chemicals, and tolerate wet soils.” But because beavers are not native to South America, the continent’s trees have not developed the same defences.

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"Left largely unchecked since then, GEF estimates the beaver population has grown to between 70,000 and 110,000 in Patagonia and Tierra del Fuego. The beavers have colonised at least 27,027 square miles of territory and decimated nearly 120 square miles (31,000 hectares) of peat bogs, forests and grasslands—an area almost twice the size of Washington, D.C. A 2009 scientific paper calls beavers’ impact in Patagonia “the largest landscape-level alteration in subantarctic forests since the last ice age.”

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"Beavers have damaged infrastructure, too, flooding highways and culverts, and damaging farmland. They often chew through fences meant to contain sheep; in 2017, beavers gnawed through fibre-optic cables in Tierra del Fuego, knocking out internet and cell service in its biggest city. Guerra Díaz says a recent study shared with GEF suggests damage caused by beavers costs Argentina alone £53 million a year.

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"Earlier this year, researchers released the preliminary results from their pilot project in Argentina’s Esmeralda-Lasifashaj region, which ran from October 2016 to January 2017. During that period, 10 trappers, which the report calls “restorers,” lay body-gripping traps and snares around the designated area, which is popular among cross-country skiers. Overall, they caught 197 beavers in traps and shot an additional seven beavers. The trappers believed they had completely rid the area of the animals, only to later spot several on motion-triggered cameras. It was unclear whether the errant beavers were “re-invaders” that had trudged in from outside the pilot area or if they had survived the trappers’ initial attempts at capture.

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"Tierra del Fuego is made up of hundreds of small, rugged islands that are difficult to reach. If beavers survive on even one, Curto warns, they could repopulate the entire archipelago and even spread back to the mainland. After the pilot studies are completed in the next few years, the governments of Chile and Argentina will need to agree on how to proceed; pursuing different strategies in each country would result in certain failure. Curto explains: “Achieving eradication will depend exclusively on sustained political will.'”

Comment: The obvious response is never disturb functional ecosystems. Yellowstone is better because the wolves are back. And introducing beaver predators will only make the mess worse. It is all part of the necessary bush of life.