Auckland Airport Mangrove Removal

Client: Auckland International Airport
Date: 2015

We were engaged in 2010 as environmental consultants for the Auckland International Airport Mangrove Removal Project.   The proposal was to remove mangroves from the Coastal Marine Area within an approximately 13 ha embayment adjacent to the runway.  The works were considered necessary due to the presence of 1500-2000 black swans which were utilising the area of mangroves and creating a potential airstrike hazard at sunset.  There had been several “near misses” involving the 5 – 6 kg birds (which were flying across the runway in groups of up to 49 birds), and one airstrike incident causing over $1M worth of damage to an aircraft.  Other methods utilised by AIAL to deter the birds from the area had been unsuccessful.

As well as assessing ecological effects of the proposed works, the preparation of the consent application included consultation with interested parties, a geotechnical assessment of in-situ sediment strength for use of the proposed mulcher machinery, a tidal dispersion assessment, the development of physical works methodologies to minimise adverse effects in the Coastal Marine Area and close collaboration and negotiation with the Auckland Council to devise consent conditions to allow an adaptive management approach for these works (as this was the first consent authorising mechanical mangrove removal in the Auckland Region).

Key Aspects:

  • Assessment of Environmental Effects
  • Coastal Marine Area disturbance and deposition
  • Consultation and consent procurement
  • Monitoring and management plan
  • Baseline ecological and substrate monitoring
  • Monitoring of mulch dispersal during physical works
  • Four years of benthic recovery compliance monitoring
  • Mangrove management plan for other Airport coastal areas

Client: Auckland International Airport
Date: 2015

The work has also involved designing and carrying out a comprehensive monitoring programme incorporating baseline monitoring, monitoring during the physical works to guide the adaptive management approach and post-works monitoring to gauge benthic recovery.

 

Monitoring has been transect-based and has included:

  • Field measurements of concentrations of Dissolved Oxygen (DO) in the water column over mulched areas.
  • Sampling of epifauna quadrats to assess the number and diversity of animals observed at the surface of the mudflat.
  • Collection of sediment core samples for taxonomic analysis of macroinvertebrates to assess infaunal communities.
  • Field measurements of the depth of the oxic sediment layer and of sediment accretion/loss within the embayment.
  • Collection of sediment samples for laboratory analysis of Total Organic Carbon (TOC).
  • Qualitative assessments of transects (e.g. presence of areas of seagrass, mangrove seedlings, algae, observations of remaining pneumatophores and/or mangrove mulch).

The analysis and interpretation of the results of the above assessments has been undertaken during the preparation of regular monitoring reports which have been prepared and submitted to the Auckland Council as required by the consent conditions.  Following four years of post-works monitoring, it was agreed with Auckland Council in 2015 that the benthic recovery monitoring programme could be ceased.

 

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