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

The insects that inhabit lakes are often larval stages that will metamorphosize and eventually emerge as flying adults. On land they are a vital food source for many terrestrial animals living around the lakes. Fish heavily predate on insect larvae, consequently reducing the number of insects that make it out of the water. This could result in less food for insectivores, such as spiders, predatory beetles and centipedes that live around these lakes.

As a part of the Life RESQUE ALPYR project, we studied 12 high mountain lakes in the Western Italian Alps. Four lakes were fishless, four lakes were undergoing fish removal, and four still had established fish populations. We placed traps near the lakes shore and farther away to capture ground-dwelling invertebrates, and we also sampled insect larvae to assess the prey availability, i.e. emerging insects.

What did we find?

Compared to lakes with fish, fishless lakes had much more emerging aquatic insects, confirming that fish reduce an important food source for animals on land. We also found more ground-dwelling predators near the lake shoreline, suggesting their habitat preference and importance of lake insects as a food source.

Interestingly, we didn’t observe any big differences in ground-dwelling predator numbers between lakes with and without fish. This suggests that while aquatic insects play a role in shaping nearby terrestrial communities, other factors may also influence predator abundance, and that more lakes are needed in future studies to get a clear picture of this relationship.

Although more research is needed to fully understand the impact of introduced fish on ground dwelling predators, our study highlights the important connection between lake and surrounding land ecosystems. Changes in one environment often trigger to responses in the other and understanding these relationships is essential in designing effective conservation strategies for these unique high mountain areas.

This news results from the Master’s Degree Project in Biology (2025) by Gea Lukšić (Department of Biology, Lund University), carried out under the guidance and supervision of Rocco Tiberti and Lucia Bello (Department of Biology, Ecology and Earth Sciences (DiBEST), University of Calabria) and Anders Persson, Department of Biology (Lund University).

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

In Alpine-type mountains, because the physiography is very complex and abrupt, these semi-aquatic ecosystems occupy very small areas, linked to the relief units where the phreatic water remains next to the soil surface, such as margins of ponds or edges of streams or fountains.

These wetlands are ecosystems with particular conditions, since the soil waterlogged. This soil conditions of hypoxia or anoxia imply important limitations for plants and other soil organisms. The poor oxygenation of the soil causes the plant litter (roots and fallen aerial parts) and other organic remains decompose very slowly, and, therefore, the organic matter accumulates in the form of peat.

Another common fact in these mires is the low concentration of mineral nutrients that their waters hold, which makes them a moderately to extremely oligotrophic and acidic environment, a situation that translates into moderate to low plant growth rates.

Fragile and vulnerable environments

They also offer refuge to highly specialized species, a lot of which being unique and rare species. Among them are some species of Carex or Sphagnum only found in a few Pyrenean localities.

Due to these particularities, both the vegetation and the organisms that live in peatlands are very sensitive to environmental changes. Among these changes, stand out the decrease in precipitation, the increase in temperatures and human activity.

The loss and degradation of peatlands that has occurred in recent decades has led to a decrease of 70% of their total area in Europe.

The abandonment of traditional uses of the mountains, one of the causes of the colonization of trees in these mires

The majority of peat bogs in the Pyrenees do not host adult pines, but the colonization and growth of trees in these mires has more than doubled in the last 70 years, details researcher Eulàlia Pladevall from the University of Barcelona. This sharp increase is due to the abandonment of traditional land uses, the global increase in temperature, and the prolongation of summer drought periods.

“The presence of pine trees in the peat bogs also dates back to ancient times. But in many cases, especially in those at moderate elevations, the tree cover has increased significantly, going from very sparse stands of poorly grown pine trees to moderately dense covers,” adds professor Josep M. Ninot.

The expansion and growth of trees in areas with peat bogs causes a decrease in available water, compromising the long-term conservation of these habitats. The shade generated by the tree crowns also harms the biodiversity of the peat bogs, since the intensity of light that reaches the herbaceous plants and mosses is lower.

Recovery tasks for high mountain peatlands

This summer season, the selective felling of trees carried out in Pla Muntaner, within the heritage mountain of “Tossal, St. Magi, Castell and Abad” of the Generalitat of Catalonia in the municipality of Montferrer and Castellbò, which is located in the Alt Pirineu Natural Park.

“The action has been able to be carried out completely this beginning of summer, preventing that it did not affect any habitat or sensitive species. The combination of volunteers and professional forestry workers in this task has at the same time allowed for effective work and an improvement in the environmental awareness of citizens through volunteering in nature restoration actions such as this one,” declares Marc Garriga, director of the Alt Pirineu Natural Park.

The task of felling, clearing branches and stacking remains has been carried out through volunteers (with hand tools) and workers (with chainsaws) from the Mountain Forests Project Foundation, with the participation of eight volunteers, and it has allowed 2,050 trees to be cut in 2.4 hectares that encompass the 1.5 hectare peat bog. Five tree groups (about five trees each) have been left for the purpose of wildlife refuge. As far as possible, work has been done with manual means to avoid damaging the peaty system.

The extraction of the logs generated and the crushing of the remains of branches generated outside the wetland have been managed by the company Sefocat, which has carried out it with a forestry tractor with a winch and a hammer crusher without entering the peaty system at any time, to avoid degrading it.

The technical supervision has been carried out by the managing body of the Alt Pirineu Natural Park, and the scientific monitoring has been carried out by the research group GEOVEG of the University of Barcelona.

During the visit, the scientific and technical personnel of the project LIFE RESQUE ALPYR showed to the visiting staff of the Parc national du Mercantour and Parco Naturale Alpi Marittime some of the project action sites.

In particular, the first day was devoted to show the eradication techniques used within to remove the minnows from some lakes (Lakes Balena, Balena 3, and Leita) and the second day to those used to remove salmonids (Lake Nero-Miserin).

The final day was dedicated to an exchange of ideas and experiences among the participants, to understand the ecological pressure exerted by fishing activities in national parks and to discuss the conservation strategies adopted by the protected areas to stem the impacts of introduced fish.