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Wetland vegetation, Thornton mire Credit: Ken Readshaw


The ‘leaky’ limestone landscape that predominates over much of the Yorkshire Dales means that water can disappear underground into sinkholes and appear again perhaps kilometres away from springs. The water often emerges rich in dissolved carbonate minerals that can re-precipitate as limestone material (called ‘tufa’).

Fens are types of wetlands where peat-formation occurs, but unlike blanket bogs (which are rain-fed and acidic) the water that sustains them is mineral-rich and from surface run-off or from underground sources. One of the finest fens in the Dales is to be found on the edge of Malham Tarn.

Lowland raised bogs occur where there is a build up of vegetation until the surface is raised above the surroundings and becomes colonised by bog mosses that thrive in and help create acidic conditions. The National Park contains some great examples of such bogs sitting alongside and next to fens, so there is often a rich variety of plants ranging from ones that like wet, alkaline soils to those which prefer acidic conditions.

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