Publication abstract
Recovery rates of UK seabed habitats after cessation of aggregate extraction
J. Foden*, S.I. Rogers* and A.P. Jones
Marine aggregate extraction and fishing using benthic gear are the two largest causes of physical disturbance to the UK seabed. Aggregate dredging is a damaging but highly spatially heterogenous pressure which, since 2001, has had a small footprint of < 1 % of that of demersal fishing. To understand the impacts of dredging, a meta-analysis of international literature was carried out of the physical (TPhys) and biological (TBio) recovery rates of the seabed, following cessation of dredge activity, in a range of habitats, hydrodynamic conditions and dredge intensities. Results of the meta-analysis were then used to estimate recovery times for the types of marine landscape targeted by the aggregate industry in UK waters.
Of the area dredged for aggregates in UK waters, 96 % occurred in sand or coarse sediment. Fifty percent of all extraction activity targeted coarse sediment plains of moderate tidal stress, which were found in the meta-analysis to have the longest period of TPhys (20 yrs) and the second longest TBio (8.7 yrs). In shallow coarse sediments with weak tidal stress, approximately 30 % of the habitat supported dredging at high intensity, and the habitat had the longest mean TBio of 10.75 yrs. In contrast, only 1.4 % of aggregate dredging activity occurred in estuaries, even though this landscape has the shortest TPhys and TBio recovery periods. Given that demersal fishing pressures are similarly concentrated on soft seabed, there is a risk of cumulative effects of different sectors operating in the same habitats
Reference:
J. Foden*, S.I. Rogers* and A.P. Jones (2009) Recovery rates of UK seabed habitats after cessation of aggregate extraction. European Marine Biology Symposium, Liverpool. 7 - 11th September 2007.
