Thousands of years

The picture shows an auger with a soil profile (Rheic Histosol) extracted in the Ribetehilos lagoon (Doñana National Park, SW Spain). Peats are wet areas where organic residues accumulate and do not decompose due to limited microbial activity because of anoxic and acidic conditions. Peatlands act as very effective carbon sinks.
Peatlands in this area were formed when the advance of the dunes closed the mouths of streams, hampering drainage and forming lakes. Currently, these water bodies are suffering clogging processes. A meter of peat, as shown in the photograph may take several thousands of years to form.