Wetland restoration in protected areas of the Pyrenees and the Alps

Within the framework of the LIFE RESQUE ALPYR project, coordinated by the Center for Advanced Studies of Blanes (CEAB-CSIC), different types of actions are carried out to restore peat bog ecosystems in protected areas of the Pyrenees and the Alps.

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 wetlands 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 wetlands

The majority of peat bogs in the Pyrenees do not host adult pines, but the colonization and growth of trees in these wetlands 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.

Colonization of a peat bog by black pine. Author: Eulàlia Pladevall.

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.

Selective felling of trees carried out in Pla Muntaner. Author: Marc Garriga.

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.