The extreme conditions of humidity, acidity and cold holding sway on the lake plateaux mean that organic matter is not fully broken down, so it builds up in hollows to form peat. Peat bogs are extremely useful. They are remarkable, rare, fragile and extremely precious habitats that are characterised by exceptional biodiversity. Here you can find rare species that are adapted to these difficult living conditions (high humidity, low temperatures, poor soils). The most common plant is peat moss (sphagnum) - real sponges that can stock up to 30 times their own weight in water! Peat bogs also play the role of a filter by purifying the air and water. They reduce erosion, help renew the phreatic zones, naturally store carbon and protect from flooding and drought. Under threat from human activity and climate change, this natural heritage is monitored closely.