Lake Geneva Quagga Mussels: Invasive Species, Biodiversity Loss, and The Search for Solutions

Late last year, Guardian biodiversity reporter Phoebe Weston joined ecologists on a floating research station above Lake Geneva to witness a transformation under the surface. Quagga mussels, an invasive species, have exploded in numbers, coating pipes and outcompeting native life. The episode surveys how these mussels fuel a cascade through the lake’s food web, threaten cooling systems at EPFL, and complicate long-running experiments that rely on stable temperatures.

Beyond Lake Geneva, the discussion broadens to other invasive species such as red squirrels, Himalayan balsam, and Japanese knotweed, and the human factors that move species around—ships, planes, and gardeners exchanging seeds. The conversation also weighs the ethics and practicality of control methods, from contraception to biological controls, while acknowledging that eradicating entrenched invasives is rarely feasible. Climate change adds another layer of complexity, prompting radical ideas like assisted colonisation and shifting expectations about what “balance” in ecosystems might look like.

Ultimately the episode asks whether we should intervene more aggressively or accept a new ecological normal, while recognizing that nature, even in crisis, has a tendency to reinvent itself over time.

Introduction: The setting and the transformation beneath Lake Geneva

The Guardian’s Madeleine Finlay speaks with Phoebe Weston, the Guardian biodiversity correspondent, as the episode opens with a sunset over Lake Geneva and a floating research station. Weston describes a surface that looks normal, but below it has already changed dramatically. Mussels are so densely packed that ropes holding the station in place become coated in quagga mussels, glittering as if they are costume jewelry. The visual is a shocking reminder that invasive species can restructure an ecosystem virtually overnight.

“It’s like a meadow of quagga mussels. They’re absolutely everywhere.”  This image anchors the episode’s driving question: how did a relatively recent invader come to dominate an entire lake’s invertebrate biomass, and what does that portend for the broader environment?

Biology and spread: why quagga mussels matter

Quagga mussels are described as one of the planet’s most potent invasive species. Weston notes their biology: a single female can release up to a million eggs and they can spawn year-round in temperatures as low as 5 °C. They can reach depths of 250 metres in Lake Geneva, where dark conditions and low oxygen prevail, yet the mussels thrive—feeding on phytoplankton and filtering large volumes of water daily. In some lakes, these mussels can account for more than 99% of invertebrate biomass, effectively rewriting local food webs and cascading through fisheries that communities rely on.

Impacts on ecology and infrastructure: a cascade through the system

The mussels’ siphoning of phytoplankton reshapes the lake’s energy base, triggering effects up the food chain. Weston explains the broader implications for biodiversity and ecosystem function, while also highlighting a striking, immediate risk: EPFL’s cooling system. The institute’s cooling pipes have become clogged with mussels, threatening not only summer comfort but also ongoing experiments such as Tokamak, a nuclear fusion facility that requires precise temperature control to prevent equipment damage. The mussels’ impact thus links a lakeside invasion to a major scientific installation, underscoring how invasions can intersect with human infrastructure in surprising ways.

Global context and costs: why this matters beyond Lake Geneva

Weston connects the Lake Geneva situation to a global trend: invasive species are a leading driver of biodiversity decline and can impose staggering costs. A 2023 estimate cited in the episode puts the annual human cost of invasive species at over $400 billion. The conversation expands to familiar European and North American examples—parakeets in London, Himalayan balsam along canal banks, and Japanese knotweed—illustrating how human activity facilitates species’ movements across continents and creates novel ecological niches that native species struggle to fill.

Strategies and debates: can we stop invasions or manage them?

The discussion turns to possible responses. One approach is biosecurity at borders to prevent introductions; another is post-arrival management. A notable idea is using contraceptives in the environment to reduce populations of longer-lived mammals like grey squirrels, a method highlighted for its humane potential but accompanied by unknown risks and ethical considerations. Biological control, wherein a native or introduced predator reduces the invasive species’ numbers, is discussed as a promising, albeit slow and carefully tested, option. The episode emphasizes that even when such controls are effective on isolated islands, complex continental ecosystems carry significant risk and are often resistant to “quick fixes.”

Ethics and pitfalls: playing God with ecosystems

Listeners hear cautionary notes about unintended consequences. The host and guests acknowledge that releasing new species to control invasives could create a new problem, and the literature stresses the necessity of decades of testing before any release. The metaphor of “closing the stable door after the horse has bolted” frames the debate: once a species has a foothold, how much can we realistically influence its trajectory without triggering collateral damage?

Climate change and radical ideas: assisted colonisation as a policy option

Climate change is shown to be a major driver of new invaders and changing niches. Charlie Gardiner, an ecologist, proposes assisted colonisation—transplanting non-native species to places where climate conditions are expected to resemble those of origin habitats in the coming decades. The rationale is pragmatic: as climates shift, species that are currently absent may become better suited to new ranges. The idea is controversial and radical because it intentionally relocates organisms across regions, which could carry invasive risks or ecological disruptions. Gardiner notes that the origin region matters; species from nearer latitudes or longitudes may be less likely to cause trouble than those from more distant places.

Reflections: a world in transition and the search for a new equilibrium

As the episode nears its end, Weston and Bass of the University of Geneva offer a nuanced caution. The Anthropocene is underscored as a period in which human activity rapidly reshapes ecosystems. Bass speaks to a sense of inevitability and resilience: there may be no perfect fix, but nature can adapt and reinvent itself. A potential long-term horizon envisions future organisms evolving to feed on quagga mussels, or Lake Geneva finding a new ecological equilibrium. In a world where some lakes remain quagga-free, the dialogue remains hopeful about research opportunities even amid alarming changes.

Conclusion: toward trusted science and ongoing inquiry

The episode closes by situating the Lake Geneva drama within The Guardian's Age of Extinction project, which tracks global biodiversity loss and explores strategies to tackle the biodiversity crisis. The conversation between Weston's field reporting and the perspectives of ecologists, researchers, and the host offers a candid portrait of the complexity, urgency, and possibility inherent in managing invasive species while acknowledging the limits of human control over nature.