Coastal Restoration Trust of New Zealand

Coastal Dune Ecosystem Reference Database

Assessment of anthropogenic threats to New Zealand marine habitats Technical Report

MacDiarmid, A., McKenzie, A., Sturman, J., Beaumont, J., Mikaloff-Fletcher, S., Dunne, J.
Journal / Source
Impact assessment, Human pressures, Marine threats, New Zealand, Habitats
This report describes an assessment of the relative impact of sixty-five potentially hazardous human activities that may affect sixty-two identifiable marine habitats in New Zealand’s territorial seas and 200 nautical mile Exclusive Economic Zone. THREATS IDENTIFIED AND/OR DESCRIBED: Global human activities, catchment based activities, human activity directly in the sea or stemming from a mixture of two or more of these. SCOPE OF SPECIES, HABITATS AND ECOSYSTEMS IMPACTED: New Zealand wide SPATIAL EXTENT OF THREAT STUDIED: New Zealand wide TEMPORAL EXTENT OF THREAT STUDIED: DATASETS USED IN THE ANALYSES: Expert knowledge in a quantifiable way to assess the relative impacts of threats METHODOLOGY USED TO IDENTIFY AND DETERMINE SEVERITY OF THREAT: The vulnerability of each habitat type to each particular threat was assessed based on expert assessment of five factors: spatial scale, frequency, functional impact of the threat, susceptibility of the habitat to the threat, and the recovery time of the habitat. The level of confidence the experts had was used as a measure of certainty to weight the response of each participant to a particular threat/habitat interaction. These results were averaged across various levels of the assessment to give the mean vulnerability for a habitat and mean impact of a threat. Interactions among threats were assumed to be additive. KEY FINDINGS OF THE ANALYSIS: The highest scoring threat over all marine habitats was ocean acidification. The second highest overall scoring threat was rising sea temperatures and the other seven threats deriving from global climate change all ranked 19= or higher in our study and indicated the importance of international threats to New Zealand’s marine ecosystems. Other main threats were from human activities in catchments, fishing (bottom trawling and dredging), invasive species, coastal engineering, and aquaculture. Generally, the number of threats to New Zealand’s marine habitats declines with depth, particularly below mean depths of about 50 m. The estimated magnitude or severity of those effects declines steeply with mean depth of the habitat. Reef, sand, and mud habitats in harbours and estuaries and along sheltered and exposed coasts were considered to be the most highly threatened habitats. The least threatened estuarine and harbour habitats were saltmarsh and mangrove forests. Slope and deep water habitats were among the least threatened and lowest ranked. The most threatened habitats were considered to be generally impacted by many threats and the least threatened habitats confronted by the fewest threats.