A recently published article in Eco.Mont – Journal on Protected Mountain Areas Research and Management helps answer these questions. The paper summarizes the ecological context of the project, the main conservation challenges facing high-mountain aquatic ecosystems, and the restoration actions being implemented through LIFE RESQUE ALPYR.

Unique Yet Vulnerable Ecosystems

Mountain lakes, peatlands and wet meadows are among Europe’s most unique ecosystems. Despite covering relatively small areas, they host highly specialized biodiversity adapted to demanding and often extreme environmental conditions.

Over recent decades, these habitats have been exposed to numerous pressures. One of the most significant has been the introduction of fish into lakes that were historically fishless. The presence of trout and minnows has altered natural food webs and caused significant impacts on amphibians and aquatic invertebrates.

At the same time, overgrazing, the abandonment of traditional mowing, and forest encroachment into wetland areas have contributed to the progressive degradation of peatlands and wet meadows of high ecological value.

More Than Habitat Restoration

The article highlights a key idea: restoring an ecosystem does not simply mean protecting the species that live there. It means restoring the ecological relationships that keep it alive and functioning.

Several previous studies have shown that the recovery of aquatic communities can generate positive effects beyond the lakes themselves, benefiting species that depend on insects associated with these ecosystems, such as insectivorous bats and the Pyrenean desman.

Although the project’s final results will be presented in the coming months, this publication helps explain the questions that gave rise to LIFE RESQUE ALPYR and the scientific foundations behind each of its actions.

Reference: Buchaca, T., Tiberti, R., Pladevall-Izard, E., Bello, L., Mattioli, G., Pérez-Haase, A., Pou-Rovira, Q., Riera, C. i Ventura, M. (2026). The Restoration of Aquatic Ecosystems in the Alps and Pyrenees: A Case Study from the LIFE RESQUE ALPYR Project. eco.mont – Journal on Protected Mountain Areas Research and Management, 18(2S). https://doi.org/10.1553/eco.mont-18-2s44

On the occasion of the International Day for Biological Diversity, the LIFE RESQUE ALPYR project highlights one of the major conservation challenges facing mountain aquatic ecosystems: the loss of biodiversity caused by the introduction of fish into lakes where they were not originally present.

High-altitude aquatic ecosystems are highly valuable reservoirs of biodiversity. Despite harsh environmental conditions, they host highly specialized biological communities adapted to cold, nutrient-poor waters and strong seasonal fluctuations. It is precisely this specialization that also makes them particularly vulnerable to any disturbance.

One of the most significant transformations has been the introduction of fish, mainly for recreational purposes. This process began centuries ago with the translocation of native trout from nearby rivers, but it intensified during the second half of the 20th century with the introduction of other non-native species such as minnows, used as live bait in sport fishing.

The ecological impact of these introductions goes far beyond simply adding a new species

Fish prey heavily on insect larvae, aquatic invertebrates, and amphibians, disrupting the food web and altering the functioning of the entire ecosystem. The consequences include algal proliferation, reduced oxygenation and water transparency, and the disappearance of species characteristic of these habitats.

However, the effects are not limited to the aquatic environment. Many terrestrial species depend on insects emerging from these lakes as a food resource, meaning that these imbalances can also affect birds, bats, and small mammals.

In response to this situation, ecological restoration has become a key tool

The LIFE RESQUE ALPYR project, coordinated by CEAB-CSIC, is working to restore these ecosystems in the Pyrenees and the Alps by removing introduced fish and monitoring the recolonization by native fauna.

This is a slow and technically complex process. Depending on the type of introduced species and the characteristics of each lake, restoration may require several years of continuous fieldwork.

To assess biodiversity recovery, scientific teams combine classical monitoring techniques with advanced molecular tools such as environmental DNA (eDNA). This technology makes it possible to detect the presence of species from fragments of genetic material they leave in the water, without the need for direct observation.

In addition, the analysis of sediments accumulated at the bottom of lakes offers an exceptional historical perspective. This natural archive allows researchers to reconstruct what biodiversity was like before human disturbances and to better understand how far present-day ecosystems have diverged from their original state.

Marking the International Day for Biological Diversity, the project’s principal investigator, Teresa Buchaca, explains in this video why preserving high-mountain aquatic biodiversity is essential for maintaining the ecological balance of these unique ecosystems.

In this fourth —and penultimate— year, all planned conservation actions have been successfully carried out. In addition to the annual actions that have been repeated since 2022, this year stands out for the successful second application of rotenone, conducted in a broader and more complex setting. We have also completed the remaining interventions in the peatlands, in the area surrounding Lake Djouan in the Alps, and at Font de la Tosca in the Pyrenees.

The first results from the scientific and technical monitoring of the restored sites are encouraging: improvements are already becoming visible and are expected to be fully confirmed in the coming years.It has been an especially productive year for environmental education and outreach, with more than 1,000 participants. There has also been extensive dissemination of results within the scientific and technical communities, and significant progress has been made in knowledge transfer and replicability.

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The pilot test, which will start this week, aims to eliminate introduced species and restore the ecological balance of these high-mountain ecosystems. The trial will involve the use of rotenone, a biodegradable ichthyocide. The results of the action will provide essential data to evaluate the effectiveness and safety of this product, contributing to the development of safe protocols for the application of piscicides to mitigate the impact of introduced species, such as minnows, in high mountain lakes.

The initiative is part of a broader strategy to restore high-mountain aquatic habitats within the framework of the LIFE RESQUE ALPYR project, with the aim of converting the restored lakes into biodiversity reserves and ecological corridors.

The environmental impact of minnows in high mountain lakes

One of the main threats to high mountain lakes is the presence of introduced fish, which reduce the biodiversity of native species and disrupt the balance of the ecosystem.

Among the introduced fish species, minnows (Phoxinus spp.) have the greatest ecological impact and also pose the greatest challenge for demographic control. It is a small cyprinid with rapid growth and a high reproductive rate, highly adaptable and capable of forming dense populations.

Conventional capture techniques used to remove fish from high-mountain lakes do not always yield satisfactory results when minnows are present. For this reason, it is necessary to explore alternative methods.

A Pioneering Initiative

Rotenone is a natural, biodegradable ichthyocide extracted from various tropical and subtropical plant species of the legume family. These plants, along with others with toxic properties such as those of the genus Verbascum, have traditionally been used for fishing in rivers and lakes around the world, depending on the plant species available, including in the Pyrenees.

In the environment, rotenone degrades rapidly, persisting for only a few days or weeks. To date, its use as an ichthyocide has been primarily applied in North America, Australia, New Zealand, the United Kingdom, and northern Europe—especially Norway—with some isolated experiences in the rest of Europe, including Spain.

The LIFE RESQUE ALPYR features two pilot trials using rotenone, pioneering actions in the context of high-mountain lakes in Europe.

The first of these trials took place in 2024 at Lake Manhèra (Val d’Aran). This is the only precedent so far for the application of rotenone in a high-mountain lake in Europe. The intervention was successful, as the minnows were eradicated and the lake is currently recovering its biodiversity, with the recolonisation of amphibians and various invertebrates, such as certain dragonflies, which had disappeared due to the introduction of the minnow.

In the Tres Estanys area, two applications are planned: the first at Lake Tres Estanys del Mig, scheduled between September 2 and 4, and a few weeks later at Tres Estanys de Baix. The goal is to restore the ecological integrity of these sites and to increase knowledge about the use of rotenone in a more complex scenario, acting on two lakes whose combined volume is three times that of Lake Manhèra.

The intervention will be carried out by Sorelló, Estudis al Medi Aquàtic, S.L. and Associació La Sorellona, under the scientific coordination and supervision of the Centre for Advanced Studies of Blanes (CEAB-CSIC) and the Institute of Environmental Diagnosis and Water Studies (IDAEA-CSIC), with the direct support of the Alt Pirineu Natural Park and Forestal Catalana. The entire process will be monitored with visits from specialists from Norway, a leading country in this type of application, and through a rigorous monitoring program to ensure the safety and effectiveness of this innovative technique.

Nothing exceptional so far—except that these might be the first Rana temporaria tadpoles to complete metamorphosis in Lake Leità in many decades!

Since the 1960s, the lake had been colonized by an introduced population of brook trout, a salmonid native to North America, introduced into several park lakes at a time when the devastating effects of fish introduction into these ecosystems were still unknown. Among these effects, the presence of fish tends to prevent Rana temporaria from reproducing in the same environments due to predation on both tadpoles and adults.

However, since 2023, an ecological restoration action has been underway at Lake Leità as part of the LIFE RESQUE ALPYR project, aiming to return the lake to its natural, fish-free condition. This year, the project team is working to remove the last remaining brook trout individuals, but the first positive effects of the eradication are already becoming visible. As early as 2024, unusual movements of frogs had been observed around the lake… these few tadpoles might be the first of many new generations of Rana temporaria in this lake!

Image of Lac Leità, in Parco Nazionale del Gran Paradiso

Explore, observe, and collaborate — these are the three key steps to becoming a vital part of the project. Thanks to your observations of aquatic flora and fauna in high mountain lakes, we can gather essential data to better understand these fragile and protected ecosystems and apply improved conservation strategies.

How to participate

Taking part is easy — all you need is a mobile device and the desire to contribute to science:

• Download the iNaturalist app (available for iOS and Android).
• Create an account and search for the project: LIFE RESQUE ALPYR.
• Observe aquatic flora and fauna in high mountain lakes.
• Take a photo and upload your observation. For our research, fish and amphibians are especially valuable!
• Add the species name if you know it (if not, the iNaturalist community will help).
• Include the exact location — if you don’t have coverage, you can save the data and upload it later.

To make it even easier, we’ve prepared a visual guide infographic explaining all the steps clearly. You can download (horizontal or vertical) or view it here.

Why your participation matters

Observing and collecting data in high mountain environments is not easy. But with your help, we can overcome this challenge and gather valuable information on priority species and habitats — especially those located in Natura 2000 areas.

This shared knowledge helps us make better decisions for biodiversity conservation and strengthens the connection between science and society.

Join the LIFE RESQUE ALPYR project on iNaturalist!

With each observation, you actively contribute to protecting some of the most spectacular and vulnerable landscapes in Europe.

Turn your visit to mountain lakes into a scientific action!

One of the event highlights was the participation of the LIFE RESQUE ALPYR project. Jordi Delgado, educational coordinator from Sorellona, opened the event with an introductory talk explaining about the project’s objectives, the main conservation actions being carried out, and why removing invasive species is crucial to protecting the natural balance of these glacial lakes, formed thousands of years ago.

Later, during the workshop sessions, students took on the role of scientists with the activity “The Food Web in High Mountain Lakes.” This interactive game invited them to explore how species were connected in these ecosystems and how a single invasive species could disrupt the entire food chain and threaten ecological balance.

Through play and reflection, participants learned about the extreme conditions in these lakes — very low temperatures, scarce nutrients, and months of darkness due to snow and ice — and discovered the species adapted to live there. They also saw how human action could help restore these environments.

This workshop aimed to foster ecological awareness from an early age, equipping young learners with the knowledge and curiosity to understand, appreciate, and protect their natural surroundings.

The LIFE RESQUE ALPYR team is proud to take part in this educational initiative, which is organized by the Green Schools Network, with the support of the Pont de Suert Town Council, the Wildlife Centre, and Fundesplai.

A day to learn, share, and above all, reconnect with nature in a meaningful and conscious way.

Giorgia Mattioli, from the University of Pavia, presented a poster illustrating the eradication dynamics of alien fish from 15 lakes in the Italian Alps, four already eradicated by the LIFE BIOAQUAE project and the remaining eleven addressed by the current LIFE RESQUE ALPYR project. Thanks to the combination of various mechanical methods (fyke nets, gillnets, rod-angling, and electrofishing), which preserve the lakes’ native fauna, the population density of introduced fish can be reduced until they are completely eradicated. Taking into account the complexity and uniqueness of each individual lake, these data can serve as a guide for future ecological restoration actions in high‑altitude lakes under similar conditions.

Lucia Bello, from the University of Calabria, contributed with an oral presentation on the cross‑ecosystem effects induced by alien fish on various insectivore groups associated with high‑altitude lakes. These lakes can serve as important prey sources for a variety of semi‑aquatic and terrestrial insectivore predators present in these ecosystems, ranging from ground‑dwelling invertebrates (such as spiders and beetles), to birds (dipper and other passerines) and mammals (shrews and bats). Since insectivores and introduced fish compete for a shared food resource (aquatic macroinvertebrates in their larval and/or adult stages), our research seeks to determine whether the presence of fish in these lakes can negatively affect the insectivore community.

The Conservation Biology Conference for Early Career Researchers

The Conservation Biology Conference for Early Career Researchers (ECR) is organized by the Society for Conservation Biology Italy Chapter APS (SCB Italy) and represents a key opportunity for young researchers at the start of their careers. It offers a stimulating environment in which they can present their work and network with peers and established scholars in the field. The theme of the second ECR conference in 2025, held in L’Aquila, was “Biodiversity and Global Change: a Conservation Perspective.”

You can find more information and the full conference program on the official SCB Italy website.

Alpine lakes are undergoing deep and rapid ecological changes. The findings, based on 643 samples collected between 2006 and 2024 from 101 lakes and ponds, reveal a significant regression of cold-specialist species such as Arctodiaptomus alpinus and Daphnia pulicaria. These species, highly sensitive to environmental disturbances, offer crucial signals of the ecological balance in high-mountain aquatic ecosystems.

“Alpine lakes act as ecological sentinels. Despite being located within protected areas, they are undergoing a silent but profound transformation. The decline of cold-adapted species is a clear warning of the combined impact of global warming and local human pressures,” explains Rocco Tiberti, lead researcher and first author of the study.

A fragile and threatened ecosystem

Zooplankton play a fundamental role in aquatic food webs. In mountain lakes—often naturally fishless—these communities typically occupy the top of the pelagic food chain. The introduction of exotic species, mainly trout and cyprinids, disrupts this balance and promotes the loss of larger, more vulnerable zooplankton taxa.

Added to this pressure is climate change, which has led to a rise of over 1°C in the average annual temperature in the region in less than two decades. This warming trend affects ice cover dynamics, accelerates thawing, and reduces the availability of suitable habitats for cold-adapted species. The result is a marked “thermophilization” of aquatic communities: cold-loving species are being gradually replaced by others better adapted to warmer conditions.

“This is a phenomenon we observe in other ecosystems under climate stress, but here the impact is more direct and more visible due to the simplicity of these food webs,” adds Tiberti.

In addition to their ecological function, zooplankton also serve as sensitive bioindicators of lake health. Shifts in their composition and abundance reflect a range of environmental changes, from temperature increases to species introductions and diffuse pollution.

Towards active management of mountain lakes in the face of global change

Despite the worrying outlook, the study highlights that action is still possible. Effectively protecting pristine lakes—especially medium to large ones that remain fish-free—and restoring degraded systems by eradicating invasive species are both feasible and already underway in several protected areas.

As part of the LIFE RESQUE ALPY project, national parks such as Gran Paradiso National Park and Mont Avic Natural Park are implementing restoration actions in high-mountain lakes, with promising early results.

Furthermore, the retreat of Alpine glaciers is giving rise to new proglacial lakes, which could become important refuge habitats for sensitive species. Careful management of these newly forming ecosystems could help safeguard a portion of the region’s threatened aquatic biodiversity.

The study’s authors emphasize that high-mountain lakes are ecosystems of exceptional ecological and scientific value. Their structural simplicity makes them ideal natural laboratories for studying the effects of global change, but it also renders them particularly vulnerable, with limited capacity to buffer rapid disturbances.

“The loss of cold-adapted zooplankton is not just the disappearance of unique species—it represents a functional shift in the ecosystem. These dynamics are an early warning of what may happen in similar high-altitude regions around the world,” the researchers conclude.

The document The Loss of Biodiversity in the Current Global Change Scenario defines biodiversity as the variety of habitats, species, and genetic diversity, and highlights the ecosystem services it provides, such as pollination, air and water purification, and climate regulation.

Despite our dependence on these services, biodiversity continues to decline at an alarming rate. According to the IUCN, more than 46,300 species are severely at risk of extinction, which is 30% of those assessed by the organization.

One of the highlighted initiatives in the report to tackle this issue is the LIFE RESQUE ALPYR project, which is essential for the restoration of habitats and the preservation of species in particularly vulnerable ecosystems.

Main Causes

The latest Science for Policy report from CSIC identifies five key factors, all of anthropogenic origin, responsible for the accelerated loss of biodiversity:

• Habitat destruction and degradation: The construction of infrastructures, urbanization, intensive agriculture and livestock farming, bottom trawling… Many human activities damage or directly destroy habitats, and with them, the species that inhabit them.
• Overexploitation of resources: The abusive extraction of raw materials puts numerous species at risk.
• Pollution: The impact of pesticides and insecticides, pollution from other chemical waste, and plastics affect all ecosystems, especially aquatic ones.
• Invasive species: Globalization has accelerated the introduction of exotic species with invasive behavior, which displace or eliminate native species and disrupt the dynamic balance of ecosystems.
• Climate change: The increase in temperatures, droughts, and extreme weather events exacerbate this situation.

Most Relevant Consequences

The loss of biodiversity has devastating effects on ecosystems and society, which the document outlines. In summary, these include:

• Disruption of ecosystem services: Pollination, natural pest control, water purification, and the availability of food and medicines are at risk.
• Irreparable loss of genetic heritage: Species that have taken millions of years to evolve are going extinct, and they perform key and irreplaceable functions in ecosystems.
• Cascading effects: The disappearance of one species alters the entire biological network, affecting many others that eventually also disappear.
• Less resilient ecosystems: The simplification of ecosystems makes them less capable of recovering from environmental changes.
• Impacts on human health: Altered ecosystems increase the spread of zoonoses (diseases transmitted from animals to humans) and the spread of pandemics. Nature rich in species acts as a filter and buffer for zoonotic jumps, meaning that infectious agents pass between species, reducing the likelihood of them reaching humans. It has also been scientifically proven that living in healthy natural environments benefits both physical and mental well-being.

LIFE RESQUE ALPYR: A Project for Biodiversity Restoration

In the face of this crisis, projects like LIFE RESQUE ALPYR play a key role in the conservation and restoration of natural habitats. The project focuses on restoring high-altitude aquatic ecosystems, such as ponds, which have been particularly affected by the introduction of invasive species.

One of the key actions of the project is the eradication of introduced fish species in the Pyrenees and Alps ponds, which have led to the disappearance of native amphibians and invertebrates. Using techniques like electric fishing and nets, the project aims to restore the ecosystem’s ecological balance and allow for the natural recovery of species. These restored ponds show improvements in water quality, transparency, and the return of disappeared species.

Additionally, LIFE RESQUE ALPYR promotes environmental awareness and outreach actions to raise public consciousness about the importance of conserving high-mountain ecosystems.

Proposed Measures to Halt the Biodiversity Crisis

Experts emphasize the need for urgent actions by governments, companies, and citizens. It is essential to promote a rational management of natural resources, halt the overexploitation of raw materials, and change production and consumption systems to reduce the ecological footprint, limiting food waste and other resources. It is also crucial to regulate and reduce the use of chemicals such as pesticides, herbicides, and insecticides across all sectors, while encouraging sustainable, low-impact activities, including tourism.

Furthermore, regulations and actions must be implemented to conserve and, when necessary, restore natural habitats such as mature forests, wetlands, and seagrass meadows. The use of new technologies, such as artificial intelligence, environmental DNA, and satellite detection, can enhance biodiversity monitoring and enable earlier action. Finally, fostering shared responsibility among governments, businesses, and citizens is crucial to ensuring ambitious and sustainable environmental policies that balance biodiversity protection with the needs of rural areas.

La pérdida de la biodiversidad en el actual escenario de cambio global has been coordinated by María Begoña García (IPE-CSIC), Mario Díaz (MNC-CSIC), Daniel Oro (CEAB-CSIC), Esperança Gacia (CEAB-CSIC), Jaime Bosch (IMIB-CSIC), Paola Laiolo (IMIB-CSIC)

You can access the full report, at this link.