MarHADS - Applied in the Auckland Council Region

This case study marks one of the first uses of the MarHADS tool after its development between 2008 and 2011. Development of the model was undertaken by NIWA but this project was initiated by Auckland Council (AC) in early 2013.

The tool was developed with the aim of bringing some form of standardisation to the assessment and comparison of marine habitat values within regions and at a national level. It was designed to critically assess the relative state and value of costal habitats throughout New Zealand and at a regional level and as such assist in the management and decision making process of coastal areas.

Method

Auckland Council (AC) contracted NIWA to undertake these initial trials of the MarHADS tool in the AC region. They initially tested the tool by applying it to specific areas of marine habitat that lay at either end of the range in habitat quality and human impacts e.g. mangroves forest in the Whangateau Esturary; perceived to be most pristine and Tamaki estuary; being most heavily impacted but human activities. Once the tool was demonstrated to yield useful information, AC then required NIWA to apply the tool to all habitats within a selected sub-region (e.g. Entire Whangateau estuary).

The tool incorporates five types of knowledge about marine habitats. These are:

  1. The quantity of habitat
  2. Habitat vulnerability
  3. The nationally threatened and at risk species that may occur within particular habitats.
  4. Habitat quality
  5. The ecosystem goods and services provided by marine habitats.

While the initial testing of the model focussed on specific habitats, mainly mangroves and sea grass, throughout multiple separate estuaries later applications of the tool focused on all habitats within selected locations. The AC chose to assess 17 different habitats within the Whangateau estuary assessing vulnerability to human activities. 

 Findings

This application of MarHADS by the Auckland Council indicated that the numbers of nationally endangered or threatened species occurring in a habitat type showed little to no variation between testing zones. The combined assessment of mangrove habitat within each estuary as a whole provided a clear indication of a probable impact gradient in the western Hauraki Gulf, with a regular decline in the total number of scores indicating a least impacted environment from Whangateau estuary in the north to Tamaki estuary in the south.

In using the MarHADS tool a major limiting factor is the quality and amount of input data available. For the tool to be effective a good understanding of the system(s) in question must be held, and adequate amounts of suitable input data are required for a reasonable comparison with other similar systems.

To utilise the tool an understanding is required of:

  • The spatial distribution of the environment being assessed, which in most cases is displayed in a habitat map.
  • The likely threats to a habitat, their scale and functional impact, as well as the resilience of the habitat to those particular threats and the recovery timescale once the threat is removed.
  • The presence of nationally threatened and at risk species, the number of invasive species, water quality, sediment quality, the degree to which the expected biotic assemblage remains intact.
  • An overall assessment of the degree to which expected ecosystem features and functions remain in operation.
  • The level of regulatory, provisioning, and non-consumptive ecosystem goods and services provided by the assessed habitats, although desirable, is not essential as national defaults for these values can be used, though these remain to be tested and compared against local information.

Given the timeframes for which the workshop for this study was run it was deemed that the MarHADS tool was successfully applied to mangrove habitats in several zones throughout five estuaries, seagrass beds in three of these estuaries, and to 17 benthic habitats occurring throughout one estuary in particular (Whangateau estuary). It was noted that the wider application of the tool would have been more desirable, increasing the range of habitats for which the tool could be tested, but even under this limiting time constraint there was sufficient room to prove the tools effectiveness.

The AC stated that; “Our experience in this project indicates that familiarisation with the available information is a key to rapid application of the tool.”

It appears that in order for this tool to be used efficiently and successfully there is a key need to understand and learn both MarHADS functionality as well as having a strong and practical understanding of the area that is being analysed.

Associated Models

Marine Habitat Assessment Decision Support Tool (MarHADS)

Regional councils have an important role in the undertaking the preservation of natural character and protection of indigenous vegetation and fauna.

References

MacDiarmid, A B; Stenton-Dozey, J and Roulston, H (2014). Testing and applying the MarHADS tool in the Auckland Council region. Prepared by NIWA for Auckland Council. Auckland Council technical report, TR2014/004 (PDF)