Peatlands, those mysterious ecosystems...

When we think of mountain ecosystems, we probably think of large forests of fir, beech or black pine trees. If we climb a peak in the Pyrenees, we can contemplate the views, perhaps pass through rocky crags and possibly have lunch near a lake or a stream. Well, here, in these waterlogged areas that accumulate water or next to the Pyrenean lakes, we can find our main ecosystem, the peat bog o tremedalThe area is a habitat of great environmental importance and unique biodiversity.

But what do we mean by peat bog?

A peat bog is an aquatic ecosystem, which, like a good dish, has been cooked over a very low heat. The cooking vessel is a depression in the ground, where rain or water from streams has created the base for the main ingredient of the dish. What we are referring to is a type of moss, called sphagnos. Normally, the mosses that cover rocks or trees have rootlets to attach themselves to the substrate, but these do not. Although they are not fixed to the ground, they have a stratospheric water absorption capacity. Both stems and leaves have "water storage" cells distributed among the photosynthetic cells that act as sponges absorbing water and mineral salts. The mosses at the top grow, while those at the bottom decay. This is where other ingredients of our stew come in, the fungi and soil bacteria. They decompose the dead organic matter, but under conditions of lack of oxygen (anoxia), "special" compounds are generated into the environment. Just as a cook can "over-salt" a dish, these chemicals cause an "acidification" of the soil. That is, they change a chemical property of water, the pH. Sphagnum is the main ingredient, but we also have other additions to our stew. In peat bogs with a more fluvial water supply, not so much because of rainfall or humidity, we find some plants. Examples include cotton grass with its white hairy spikelets, rushes and their cutting leaves, peat bog heather, water clover and ferns. But if there is one thing that strikes us, it is two ecological strategies "invented" by plants to survive in an acidic, anoxic, water-saturated and nutrient-poor environment. The first, represented by the sundew or flytrap, and the greasepaint or strip of violet flowers, carnivorous plants that "supplement their diet" with insects that they hunt, and secondly the orchids with fungi in their roots that would "capture" nutrients. And now, in order to have a "dish with substance", we need to add the last condiments to our recipe, the fauna. There are insects that live in this habitat, such as the marsh pearly butterfly, amphibians such as the red-legged frog, the webbed newt or the Pyrenean newt and the peat bog lizard, which is linked to this ecosystem.

This slow-burning process requires rainy weather and low temperatures in order to produce an adequate bacterial and fungal fermentation. However, we also need a long chronological time for the ecosystem to mature and for the formation of the peat...

Peat, lignite, hard coal and anthracite...

All the remains of sphagnum, lichen, plant and animal remains are fermented by the decomposing organisms, giving rise to a light brown or black organic material, the peat. This substrate is porous, of low density and with a high volume of water. This material grows, producing a "bulging" of the ground, detectable to the naked eye. In mature ecosystems it would be found under living plants and would constitute the basic structure of the ecosystem. Since ancient times, dried peat has been used as a fuel and over the centuries, it has been chemically transformed into the different types of coalCoal, lignite or anthracite. 

A bit of history...

The Roman historians Pliny the Elder and Tacitus already described peatlands in Scandinavia. These ecosystems are believed to have been present in Europe since the last ice age, but have suffered a major decline since the 18th century, mainly to exploit the land for agricultural or livestock purposes. Apart from their usefulness as fuel in the form of peat or charcoal, dried sphagnum has been used as a compress or poultice for wounds, especially in times of war, due to its absorbent and antiseptic properties. Peat bogs are a source of information for the scientific community, as they bear witness to environmental changes. Among the layers of sediment that form the peat, we can find indicators of other eras, such as pollen, fungal spores, remains of animal tissue, seeds or even mummified human corpses. A very curious one is the "Tollund man"In 1950, this mummified body from the Iron Age, specifically from the 4th century BC, was found in peat bogs in Denmark, providing information about his clothing, his physical constitution, the cause of his death and even his last meal. Apart from these interesting discoveries, we found chemical traces, which allow us to know what the atmospheric chemical composition was like in the past, whether there were volcanic eruptions or biological extinctions.

Currently, the viability of these ecosystems depends on desiccation and the balance of atmospheric gases, such as CO₂. Let us not forget that we are at a time of high levels of greenhouse gases, which increase the global temperature of the planet, and also in periods of recurrent drought, which do not favour these fragile ecosystems. 

Where can we find peat bogs?

These ecosystems can be found in many European countries and, of course, in Spain, mainly on the Cantabrian slopes and in the Pyrenees. In a more relict form in the Montes de Toledo, the Sierra de Albarracín and the Sierra Nevada. 

Where to visit peat bogs in the Pyrenees...

• Alt Pirineu Natural Park (Lleida): On the classic ascent of the Pica d'Estats, from the Vall Ferrera refuge. Here we find the Plans de Sotllo peatlandA wooden footbridge was built in 2017 to protect it near the lake of the same name. The 170-metre structure prevents erosion caused by the high volume of hikers climbing the iconic peak. 

• Ordesa National Park (Huesca): Between 2150 m and 2500 m we find the Ordesa alpine peat bogs. Located in pasture areas, on the high plains of the tributary ravines of the Ordesa valley. Formed in the meanders of the rivers, they do not have sphagnum trees, but they do have endemic plants that are worthy of protection. 

• Valley of Aguas Tuertas (Huesca): In the past, there was a glacier that later collapsed, and above it there is a meandering riverbed with peat bogs. The vegetation is made up of sphagnum, rushes, horsetail ferns, carnivorous plants such as the grass and spring daffodils.

• Ibones de Anayet (Huesca): Located in the Tena valley, we can see two types of peat bogs, some located in clogged lakes and others on the banks of rivers. They are always watched over by the peak of the same name, which is, by the way, a volcanic piton. That is to say, the petrified chimney of the volcano, the external part or caldera, has collapsed. 

• Rust Channel (Huesca): Belonging to the municipality of Canfranc, in this valley you can find the lake of las Negras de Anayetand just below it the the raft of Las Negras. In the latter habitat there is a very interesting peat bog, with reeds and water clover, among other protected plants. 

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