MI2 Ditch clearing

  This is a pressure (P) indicator. DPSIR = drivers, pressures, state, impact, responses.
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The draining of pristine mires was largely given up by 2001. Instead of draining new areas, emphasis has been lately put on ditch clearing and associated supplementary draining. Since 2001 these operations have been carried out on 60 000 to 80 000 hectares annually. In recent years the annual ditch clearing area has decreased to less than 60 000 hectares.

In total, 2,5 million hectares of mire, equalling 53% of the drained area, has been drained for the second time. As a part of ditch clearing operations new ditches may be dug in previously drained areas and larger collecting channels even in pristine parts of the mire.


Effects on biodiversity

On the whole, the effects of ditch clearing and supplementary draining are largely the same as those of first-time draining. Second-time draining speeds up the changes in vegetation caused by the changing hydrology. These changes decrease the amount of open mire habitats and therefore affect the species related to these. The effects of second-time drainage are, however, on a much smaller scale than the effects of first-time drainage of pristine mires.

In the absence of ditch clearing and supplementary draining operations a considerable number of drained mires would recover to a nearly pristine state. Especially uneffectively executed ditches and ditches dug in areas where the potential for tree growth is minimal normally beging to disappear in a few decades due to peat accumulation. The recovery of such mires may also be assisted by means of active restoration.


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