Human pressures on UK seabed habitats: a cumulative impact assessment

Abstract

European Member States are required to assess the status of marine waters, including analysis of cumulative effects. We developed a methodology for evaluating the impact of several human activities that constitute 4 direct pressures on the UK (England and Wales) seabed community: smothering, abrasion, obstruction (sealing), and extraction. The method was tested by mapping the spatial extent of individual and cumulative activities for 2007 by habitat type, quantifying the intensity of activities, and estimating impact using published recovery times. More than half (134 400 km 2 ) of the seabed was directly affected by human activities, of which only 165 km 2 (< 0.1%) was occupied by multiple activities. Benthic fishing accounted for 99.6% of the spatial footprint. Sensitivity to the pressures of human activities varied by habitat type, with estimated recovery times ranging from <1 mo for otter trawling in sand, to ~15 yr for co-occurring aggregate extraction and dredge material disposal in low-energy gravel habitat. Fully integrated, dynamically-linked environmental assessments are generally considered desirable for greater scientific understanding of an ecosystem. The methodology we present for quantifying cumulative effects is a step towards this. However, our findings indicate that a limited number of activities were the predominant cause of widespread, long recovery times of benthic fauna. This suggests that when time and resources are limited, single sector assessment rather than detailed evaluation of cumulative effects, can still usefully guide management. As the observed cumulative effects were primarily related to a few activities, it might reasonably be argued that management effort should be focused on spatially extensive activities, such as benthic fishing to mitigate most of the human impact on the UK seabed.

Similar effects of bottom trawling and natural disturbance on composition and function of benthic communities across habitats

“…Bottom trawl fisheries account for around 23% of global fisheries yield (FAO 2009) and are one of the most widespread sources of human disturbance affecting benthic communities in shallow shelf seas (Eastwood et al 2007, Foden et al 2011. The fishery physically disturbs the seabed by dragging the fishing gear over the seabed to catch bottom dwelling fish and benthic invertebrates.…”

Global analysis of depletion and recovery of seabed biota after bottom trawling disturbance

“…logistic recovery model | systematic review | metaanalysis | impacts | trawling F isheries using bottom trawls are the most widespread source of anthropogenic physical disturbance to global seabed habitats (1,2). Almost one-quarter of global seafood landings from 2011 to 2013 were caught by bottom trawls (3).…”

An approach for the identification of exemplar sites for scaling up targeted field observations of benthic biogeochemistry in heterogeneous environments

“…Many of these uses directly affect the benthic environment e.g. fishing using trawls, which accounts for 99.6% of the spatial footprint of human activities on the seabed (Foden et al 2010), impacts upon the structure and functioning of benthic communities (Kaiser et al 1998;van Denderen et al 2015), and the structure and stability of the bed (Schwinghamer et al 1998). It is not possible to remove the effects of these pressures when investigating shelf-scale processes in situ, so careful consideration must be given to these when findings are interpreted, including the differences between causative and correlated relationships.…”