Publication Abstract

Assessing and predicting the relative ecological impacts of disturbance on habitats with different sensitivities

J.G. Hiddink, S. Jennings and M.J. Kaiser

Methods for assessing habitat sensitivity to human impacts are needed to assess the sustainability of existing impacts, to develop spatial management plans and to support meaningful environmental impact assessments. These methods should be quantitative, validated, repeatable and applicable at the scale of impacts and the scale of management.

Existing methods for assessing the sensitivity of marine habitats to human impacts have tended to rely on expert judgement and/or scoring systems. They are neither validated, quantitative nor repeatable.

We developed a quantitative, validated and repeatable method for assessing the sensitivity of seabed habitats to physical disturbance and delineating and mapping habitat sensitivity on large spatial scales (>10⁵ km²). The method assumed that sensitivity is related to the recovery time of production or biomass, as predicted using a validated size-based model that takes account of the effects of natural disturbance.

As trawling disturbance is the most widespread direct human impact on shelf seas, this was used as an example of anthropogenic physical disturbance. We mapped habitat sensitivity to trawling in 9 km² boxes across an area of 125000 km² in the North Sea.

Habitat sensitivities varied widely, and a trawling frequency of 5y^-1 in the least sensitive habitat had the same ecological effect as trawling 0.3y^-1 in the most sensitive habitat (based on production). If trawling effort was held constant but redirected to the least sensitive habitats, the existing impacts on production and biomass were reduced by 36% and 25% respectively.

Synthesis and applications. The reported method enables managers to predict the implications of changing patterns of human impact when establishing spatial management plans. In the context of fisheries management, this will support: the identification and selection of fishing grounds that minimise the adverse ecological effects of fishing, the selection of closed areas (both representative and highly sensitive), the comparison of management options that might reduce the overall environmental impacts of fishing, and any future steps towards the application of environmental impact assessment in advance of fishery development.

Reference

J.G. Hiddink, S. Jennings and M.J. Kaiser (2007) Assessing and predicting the relative ecological impacts of disturbance on habitats with different sensitivities. Journal of Applied Ecology, 44: 405-413