A map of human impacts to a “pristine” coral reef

Authors: K A Selkoe B S Halpern C M Ebert E C Franklin E R Selig K S Casey J Bruno R J Toonen

Publish Date: 2009/03/25

Volume: 28, Issue: 3, Pages: 635-650

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Abstract

Effective and comprehensive regionalscale marine conservation requires finegrained data on the spatial patterns of threats and their overlap To address this need for the Papahānaumokuākea Marine National Monument Monument in Hawaii USA spatial data on 14 recent anthropogenic threats specific to this region were gathered or created including alien species bottom fishing lobster trap fishing shipbased pollution ship strike risks marine debris research diving research equipment installation research wildlife sacrifice and several anthropogenic climate change threats ie increase in ultraviolet UV radiation seawater acidification the number of warm ocean temperature anomalies relevant to disease outbreaks and coral bleaching and sea level rise These data were combined with habitat maps and expert judgment on the vulnerability of different habitat types in the Monument to estimate spatial patterns of current cumulative impact at 1 ha 001 km2 resolution Cumulative impact was greatest for shallow reef areas and peaked at Maro Reef where 13 of the 14 threats overlapped in places Ocean temperature variation associated with disease outbreaks was found to have the highest predicted impact overall followed closely by other climaterelated threats none of which have easily tractable management solutions at the regional scale High impact threats most tractable to regional management relate to ship traffic Sensitivity analyses show that the results are robust to both data availability and quality Managers can use these maps to 1 inform management and surveillance priorities based on the ranking of threats and their distributions 2 guide permitting decisions based on cumulative impacts and 3 choose areas to monitor for climate change effects Furthermore this regional analysis can serve as a case study for managers elsewhere interested in assessing and mapping regionspecific cumulative human impactsWorldwide coral reef ecosystems have been transformed under the influence of direct and indirect effects of human activities Bruno et al 2007 Understanding the relationships between human activities and their ecological impacts and assessing the spatial distribution of these impacts are crucial steps in managing the use of coral reefs in a way that maximizes commercial and societal benefits while minimizing reef degradation Recent policy emphasis on spatial management of the oceans Crowder et al 2006 suggests an urgent need for highresolution maps of human activities and their ecological impacts The Papahānaumokuākea Marine National Monument Monument surrounds the string of atolls and banks known as the Northwestern Hawaiian Islands NWHI a vast area stretching over 2000 km A synthesis of the patterns of all types of human impacts across the archipelago can serve as a useful tool for managers implementing local scale spatial management of the Monument with an ecosystembased perspectiveThe isolated reefs of the Monument are considered to be relatively pristine compared with other coral reefs in closer proximity to human populations such as the main Hawaiian Islands Friedlander et al 2005 Pandolfi et al 2005 Field surveys have found that the reefs of the Monument have an unusual abundance of top predators high fish biomass low incidence of coral disease and large populations of sensitive seabirds marine mammals and turtles that have been extirpated elsewhere Harrison 1990 Friedlander and DeMartini 2002 Balazs and Chaloupka 2004 Parrish and Boland 2004 Kenyon et al 2006 Nevertheless the NWHI ecosystem has been affected by numerous past and ongoing human activities Friedlander et al 2005 Heinemann et al 2005 Information on the nature extent and locations of the ecological impacts of these activities is central to formulating management strategies and prioritiesPast approaches to evaluating the distribution and ecological impacts of human activities have almost all been tailormade to a specific ecosystem type or management question and most used expert opinion to evaluate or rank the ecological impact of activities reviewed in Selkoe et al 2008 A wellknown example is ‘Reefs at Risk’ Bryant et al 1998 which used an expert workshop to classify the world’s coral reefs into low medium and high threat categories based on their distance to sites of four types of potential threats While perhaps useful in some areas of the world these results were less appropriate for the unpopulated and vast setting of the Monument and some considered the approach lacking in scientific rigor Sale 2008Map of the cumulative impact to the Hawaiian archipelago as assessed by the globalscale analysis Halpern et al 2008 Data are raw cumulative impact scores from a model that averages scores across overlapping ecosystem types instead of summing as in the reported global results for comparability to the methodology hereThe cumulative impact mapping framework was applied here on a finer scale 1 ha resolution with locationspecific data to provide a more accurate and detailed view of the spatial distribution of cumulative impacts in the Monument This analysis was intended to provide needed guidance to the Monument on where to apply different management regulations and which threats are most in need of attention while also illustrating how the cumulative impact mapping framework Halpern et al 2007 2008 can be applied to understand threats to any region at any scale Comparing the new analysis to the global version also allowed us to directly assess the sensitivity of analyses conducted at different scales and therefore better assess what is gained by conducting higher resolution analyses

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