In 1946, the Argentine government made what has since been described as a "colossal mistake"—introducing twenty North American beavers (Castor canadensis) from Canada to the remote wilderness of Tierra del Fuego at the southern tip of South America. What was intended to stimulate a fur trade industry has instead become one of the most devastating biological invasions in the Southern Hemisphere, with the beaver population exploding to an estimated 100,000 to 200,000 individuals that have fundamentally transformed Patagonian ecosystems.[1][2][3]
Dead forest (caused by beavers) in Tierra del Fuego ...
Origins of the Invasion
The Argentine Navy imported ten pairs of beavers from Manitoba, Canada, releasing them near Lake Fagnano with the ambitious goal of establishing a commercial fur industry and attracting settlers to the sparsely populated region. Ironically, beavers weren't even officially authorized as game animals in Argentina until 1981, and by that time the fur trade concept had already failed—beaver products like top hats had gone out of fashion by mid-century.[1][4][5]
Tom Lamb, a Canadian settler known as "Mr. North" for expanding the national frontier and restocking beaver populations that had nearly gone extinct from fur trading in North America, transported the animals to Tierra del Fuego. The introduction occurred during a period when Argentina sought to assert sovereignty and encourage development in its southernmost territories, viewing the land as "empty and sterile."[6]
Explosive Population Growth
Without natural predators—no bears, wolves, or large carnivores that control beaver populations in North America—the introduced beavers thrived spectacularly. The population dynamics have been remarkable:[1][7]
- By 1962, beavers had crossed the Beagle Channel to reach new areas[4]
- By the late 1990s, beavers had reached the Chilean mainland, crossing the Strait of Magellan[2][4]
- By 2024-2025, researchers estimate the population at between 65,000 and 200,000 individuals, with different surveys providing varying estimates depending on methodology[8][9][3]
Research from the Journal of Mammalogy reveals that beaver survival rates in Patagonia exceed those recorded in North America, and the animals demonstrate remarkable plasticity in habitat use, thriving in both forests and steppes—a habitat previously assumed to be subprime. Colony sizes and kit production are actually higher in steppe environments than in forests.[10]
Ecological Devastation
The beavers' impact on Tierra del Fuego's ecosystems has been described by scientists as "the largest landscape alteration in sub-Antarctic forests since the last ice age."[2]
Forest Destruction
The damage to native lenga beech forests (Nothofagus pumilio) has been catastrophic. These ancient trees, which can take a century to reach maturity, can be felled by a single beaver in just a few days. Unlike North American trees that have co-evolved with beavers over millions of years, Patagonian species lack adaptations to withstand beaver activity:[11]
- North American trees like willows, cottonwood, and alder resprout when cut down, produce defensive chemicals, and tolerate wet soils[2]
- Patagonian beeches regenerate from seed banks in the soil—when areas flood, seeds become covered with mud and water and die, preventing forest recovery[3]
Studies show beavers have damaged more than half the land where lenga forests once flourished along waterways, causing a loss of almost 15 tons of biomass per hectare. A 2023 study found that native forest cover in Tierra del Fuego decreased by 15.5% between 1986 and 2019, with beavers responsible for 56% of this loss (forestry activity accounted for 44%).[12][13]
Invasive beavers are destroying Tierra del Fuego | National ...
Hydrological Transformation
Beavers have colonized approximately 93-94% of rivers in the Tierra del Fuego archipelago. According to Wildlife Conservation Society figures, 25% of the forest and 95% of the archipelago's basins have been affected by beaver dams. More than 90% of rivers and streams on the Chilean half of Tierra del Fuego have been redirected by beaver activity.[11][9][3]
A 2019 study using satellite imagery identified approximately 70,000 beaver dams on the Argentine side of Tierra del Fuego alone. These dams have devastated an estimated 120 square miles of peatlands, forests, and grasslands—an area nearly double the size of Washington, D.C.[2]
Carbon Release and Climate Impact
The ecological damage extends to climate change contributions. The destruction releases carbon that had been sequestered in trees and peatlands for centuries. Downed trees and disturbed soil release stored carbon as the beeches rot, making the beaver invasion emblematic of a global, under-appreciated problem of invasive species accelerating carbon emissions.[11]
Economic and Infrastructure Costs
The financial toll of the beaver invasion is substantial:
- A recent study estimates beaver-related damages cost Argentina approximately $66 million annually[2]
- The University of Chile estimated the socio-economic impact at $73 million, including biodiversity loss, impeded wood production, flooded grazing areas, and carbon release[11]
- If unchecked, Chile's losses could amount to another $260 million over 20 years[11]
Infrastructure damage includes flooding of roads and culverts, destruction of agricultural land, and in 2017, beavers chewed through fiber optic cables, disrupting internet and cellular service in Ushuaia, Tierra del Fuego's largest city.[2]
Eradication Efforts
Binational Agreement
In 2008, Argentina and Chile signed a historic binational agreement to restore environments affected by beavers through complete eradication—recognizing that mere population control would be insufficient. This collaboration represents one of the largest eradication projects ever attempted globally.[1][14][15]
Global Environment Facility Project
The effort has received significant international support. Chile co-sponsored a $7.8 million project with the Global Environment Facility (GEF) to control beaver populations in Chilean Patagonia, with $2.1 million coming from the international aid agency. The GEF Beaver Project has been working for nearly five years to coordinate strategies between both countries.[8][16][3]
Pilot Projects and Feasibility
Between October 2015 and June 2018, researchers conducted pilot eradication projects across seven test areas on the Argentine side of Isla Grande de Tierra del Fuego. Ten trappers ("restorers") used lethal traps, body-grip traps, snares, and occasionally firearms. In one pilot area, they captured 197 beavers in traps and shot an additional seven.[9][2]
The findings were both encouraging and sobering. Researchers confirmed eradication is technically feasible but estimated it would cost approximately $31 million over 17 years to eliminate beavers from Argentine Tierra del Fuego alone. The effort becomes significantly harder in mountain zones, where specialists must deploy an average of 23 traps per kilometer of waterway to catch one beaver—and these areas have the highest beaver densities.[17][9]
Ongoing Challenges
Several obstacles complicate eradication:
- Geographic inaccessibility: Tierra del Fuego consists of numerous rugged islands that are difficult to access, and costs are prohibitive in remote areas like western peat bogs[9]
- Climate conditions: Harsh weather and terrain make consistent trapping campaigns difficult[6]
- Institutional continuity: Researchers express concern about maintaining long-term political and financial commitment[6]
- Economic pressures: In Argentina, where inflation has pushed a third of the population into poverty, garnering support for beaver eradication competes with pressing social needs[2]
As one official noted, "achieving eradication will depend on sustained political will." If even one beaver survives on any island, they could repopulate the entire archipelago and potentially spread back to the mainland.[2]
Community Response and Adaptation
Some Patagonian residents have found creative ways to address the invasion. Miguel Gallardo, a former Chilean forest service officer, was so disturbed by discovering "ghost forests" of dead lenga trees that he quit his job in 2015 to launch Navarino Beaver, a tourism company allowing visitors to trek through devastated forests, hunt beavers, and taste beaver meat prepared "al disco."[2]
Local hunters display pelts that have been tanned and prepared for sale, though demand remains minimal at around $10 per pelt—too low to motivate sufficient hunting pressure. Attempts to promote beaver meat consumption and commercialize the fur trade have consistently fallen short of control goals.[4][2]
Lessons and Legacy
The beaver invasion of Tierra del Fuego stands as a cautionary tale about the unintended consequences of species introductions. One observer wryly noted that anyone considering importing beavers should also import bears, their natural predators. The case illustrates how even well-intentioned development schemes can produce cascading ecological disasters when natural checks and balances are absent.[1]
The invasion also reveals the complexity of invasive species management. While beavers are celebrated ecosystem engineers in North America—creating wetlands that benefit countless species—the same behaviors prove catastrophic when transplanted to ecosystems that evolved without them. As National Geographic contributor Gallardo reflects: "The beavers aren't at fault—tree cutting is in their nature. The responsibility lies with humans."[2]
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- https://en.wikipedia.org/wiki/Beavers_in_Southern_Patagonia
- https://www.nationalgeographic.com/animals/article/beaver-overpopulation-tierra-del-fuego
- https://www.latimes.com/world/mexico-americas/la-fg-beavers-tierra-del-fuego-2017-story.html
- https://jonsadventure.wordpress.com/2013/02/07/history-lesson-1-beaver-invasion-of-tierra-del-fuego/
- https://www.scientificamerican.com/article/north-american-beaver-invasion-occupies-forests-and-steppes-in-southern-chile-and-argentina/
- https://www.environmentandsociety.org/arcadia/beavercene-eradication-and-settler-colonialism-tierra-del-fuego
- https://martinezbeavers.org/patagonia-beaver-paranoia/
- https://www.patagonjournal.com/index.php?option=com_content&view=article&id=4396%3Acastores-en-patagonia-preocupante-hallazgo-de-un-ejemplar-en-isla-riesco&catid=78%3Amedioambiente&Itemid=268&lang=en
- https://wildlife.org/wild-cam-how-feasible-is-beaver-eradication-in-argentina/
- https://academic.oup.com/jmammal/article/98/1/283/2452629
- https://phys.org/news/2021-04-brought-humans-beavers-threaten-patagonia.html
- https://globalpressjournal.com/americas/argentina/as-burgeoning-beaver-population-disrupts-ecosystem-argentina-prepares-to-exterminate-nonindigenous-species/
- https://www.cr2.cl/eng/effects-of-native-forest-cover-loss-from-forestry-activity-and-beavers-on-carbon-reservoirs-in-the-chilean-patagonia/
- https://brb.sprep.org/sites/default/files/2021-12/pilot-programme-beavers-environmental-restoration.pdf
- https://www.islandinvasives.org/files/2025/02/10_Schiavini_2019.pdf
- https://www.nature.com/articles/s41598-023-45657-4
- https://www.aag.org/north-american-beavers-in-south-american-forests/
- https://wildlife.onlinelibrary.wiley.com/doi/abs/10.1002/jwmg.22706
- https://commons.princeton.edu/patagonia/invasive-species-management/
- https://www.reddit.com/r/Beavers/comments/181mkl1/beavers_in_chile/
- https://latam.beyondba.com/patagonia-tours/wildlife/beavers-in-tierra-del-fuego/
- https://www.islandconservation.org/patagonias-phantom-forests-beavers/
- https://www.patagonia.ca/stories/planet/activism/leave-it-to-beavers/story-149108.html
- https://whitememorialcc.org/event/biological-invasions/
- https://www.tandfonline.com/doi/full/10.1080/25729861.2021.1973290
- https://www.geostrategis.com/p_beaver-tierra-del-fuego.htm
- https://www.vice.com/en/article/beaver-slayers-of-patagonia/
- https://cnre.vt.edu/about/newsmagazine/articles/research-spotlight/201608/researchers-help-design-incentive-programs-to-rid-south-america-.html
- https://en.mercopress.com/2021/10/13/chilean-scientists-studying-the-impact-of-invasive-species-in-tierra-del-fuego
- https://www.un-redd.org/news/chile-restores-its-native-forests-affected-canadian-beaver
- https://mcmsc.asu.edu/sites/g/files/litvpz576/files/2024-09/MTBI 2017 Beaver Infestation Report.pdf
- https://www.facebook.com/groups/2489985901214334/posts/3640062886206624/
- https://www.thegef.org/projects-operations/database?f[0]=focal_areas%3A2205&f[1]=project_country_national%3A41&f[2]=project_country_national%3A45&f[3]=project_country_national%3A48&f[4]=project_country_national%3A51&f[5]=project_country_national%3A67&f[6]=project_country_national%3A81&f[7]=project_country_national%3A83&f[8]=project_country_national%3A93&f[9]=project_country_national%3A96&f[10]=project_country_national%3A100&f[11]=project_country_national%3A111&f[12]=project_country_national%3A116&f[13]=project_country_national%3A127&f[14]=project_country_national%3A129&f[15]=project_country_national%3A134&f[16]=project_country_national%3A135&f[17]=project_country_national%3A145&f[18]=project_country_national%3A147&f[19]=project_country_national%3A168&f[20]=project_country_national%3A173&f[21]=project_country_national%3A140971&page=4
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