In these environments, the water is often mineralized, especially rich in calcium salts. This results in a fascinating process: when the highly mineralized water flows through small waterfalls, drips, or springs, it can precipitate calcium carbonate onto the plants growing there, such as mosses, algae, and some herbs. Over time, these plants become covered by a mineral crust that slowly grows into a porous rock known as travertine.

It’s a natural process of “vegetal petrification” that creates unique landscapes.

Rare but Valuable Habitats

Carbonated springs that form travertine and calcareous wetlands are rare habitats with great value on a European scale. In the Catalan Pyrenees, we find some interesting examples, although they occupy small areas. Their importance lies both in the richness of plant species that thrive there and the rarity of such environments.

In general, their conservation status is acceptable or good, but there are pressures affecting them, particularly from livestock. Grazing is a traditional activity in these areas, but the concentration of herds — especially during dry periods — can lead to:

• Desiccation, from the capture or diversion of water.
• Ruderization, meaning the replacement of specialized vegetation by more common species due to excessive nutrients.
• Destruction of the plant cover, caused by trampling and excessive grazing.

Depending on the temperature and mineralization level of the water, different plant communities can be found. Springs and wetlands with carbonated waters have a vegetation distinct from those in softer waters, and often, in high mountain areas, you can observe differentiated patches of one type of vegetation and another in the same location.

The waters descending from Pic des Miques, which are very rich in calcium carbonate (hard water), seep down a steep, several-metres-wide slope as they reach the Escala Alta meadow, forming a dense carpet of mosses nourished by this flow.

Over time, the water running over the mosses reacts with the air and precipitates calcium carbonate, which builds up into a hard crust. As the years go by, this process ultimately forms travertine.

The Font de la Tosca in the Bonabé valley is cut halfway up the slope by an old path and a wall that used to drain the water downhill. The passage of people and livestock along the path weakened the wall, caused a separation of plant and moss communities, altered the natural flow of water (leaving part of the slope dry where the habitat could develop), and endangered the future viability of the ecosystem. The Alt Pirineu Natural Park has protected the Font de la Tosca thanks to the LIFE RESQUE ALPYR project, in coordination with the University of Barcelona. The route of the current path has been modified, and wooden walkways have been installed to allow visitors to appreciate the uniqueness of the site without causing any disturbance to the habitat. In addition, access by large animals and people is now prevented through wooden enclosures. All these actions are environmentally friendly and in line with the Park’s policies. An information panel will soon be installed for visitors, explaining the actions carried out, the uniqueness of the site, and its most characteristic species. A team of botanists from the University of Barcelona is responsible for conducting biological monitoring on the old path to detect whether the moss cover and travertine accumulation recover thanks to the physical protection of the site.