Search

Comprehensive marine management approaches, such as ecosystem based management and marine spatial planning, would benefit from quantitative, spatially explicit estimates of the cumulative impact of human activities on marine ecosystems. In this study, a method to map and quantify cumulative impact was applied to estimate the combined impact of multiple stressors on Tauranga Harbour, a large estuary in New Zealand. The impact of eight stressors on seven ecosystems was assessed at a 100 m resolution, using New Zealand-specific expert judgement on the vulnerability of different ecosystems to each stressor. Estimated cumulative impact tended to be highest in the southern basin and inner estuaries, corresponding with sensitive ecosystems and multiple stressors and reflecting what is known about the distribution of pressures in Tauranga Harbour. Using benthic community data as an independent estimate of ecological condition, we had the novel opportunity to validate cumulative impact predicted from the model. Only a weak relationship was found between the estimated cumulative impact and measured ecological condition and several reasons for this are considered. Substitution of a more realistic sediment layer improved model outputs, highlighting the importance of accurate input data, particularly for stressors or ecosystems with high impact weights. Different standardisation methods did not greatly affect the spatial distribution of cumulative impact patterns in the harbour. The study highlights some fundamental issues for consideration when using this cumulative impact mapping approach, such as the importance of involving the expert panel throughout the course of the study and the availability and quality of the data used to construct the model.

Ecosystem approaches to fisheries management (EAF) are increasingly relevant for intergovernmental fisheries policies, national management plans, and seafood certification guidelines. To aid in integration of EAF in tropical artisanal fisheries, this study evaluates the potential ecosystem impacts of four distinct fisheries (kelp forest, sandy shore, pelagic, and reef ecosystems) in Mexico, using quantitative trophic models and a comparable network developed using fishers’ traditional knowledge. Notably, the fishers’ model was actually more complex than science-based models and could be a highly useful baseline for subsequent collaborative efforts for ecosystembased management. At current fishing levels, these fisheries are not expected to have significant ecosystem impacts, though we identify species that could be potentially impacted if fishing effort were to considerably increase and that should be monitored. Explicitly considering ecological interactions—whether or not this can be fully integrated into reference points—in co-managed fisheries can help prioritize monitoring and management measures, supporting ecologically sustainable fisheries and the social and economic objectives of artisanal fishers.