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To:
Rivers and Catchment Services Group
Waikato Regional Council
Submission on:
Proposed Whangamata Mangrove Removal Consent Applications
Name:
Royal Forest and Bird Protection Society of New Zealand Inc
Address:
Alan Fleming
Royal Forest and Bird Protection Society of New Zealand Inc
PO Box 70 171
TAURANGA 3155
Dear Sir or Madam:
Forest & Bird opposes all of the applications on the following grounds:
1. The activities proposed are contrary to the policies of the NZ Coastal policy
Statement 2010.
2. The rate of mangrove spread has slowed to a negligible increase.
3. There are no plans by the Council to lessen sediment coming from the catchment
and the 2007Whangamata Harbour Plan failed to address sediment from exotic
forestry plantations in the catchment and their contribution to harbour
sedimentation. There is no evidence that the controls on soil erosion in the Waikato
Regional Plan are lessening the source of sediment into the streams flowing into
Whangamata Estuary
4. The application exacerbates the impacts of catchment erosion and climate
warming which are prime drivers of mangrove expansion in the Whangamata
harbour. It does not adequately acknowledge the role mangroves plays in
moderating these impacts on the coastal ecosystem by growing on sediment in
estuaries, utilising additional nitrogen from run-off (albeit less in this particular
catchment than many others) and regulating rising carbon dioxide
concentrations by converting carbon dioxide into biomass and substrate sinks.
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5. Forest and Bird is concerned that Waikato Regional Council is using ratepayers
resources for unjustified mangrove removal but effectively taking no steps to address
catchment erosion and associated sedimentation of freshwater and coastal
environments.
6. This consent fails to address any changes in the rate of sediment transport into the
estuary, whether the Regional Plan is having any effects on lessening sediment
moving into the estuary and quantifying whether the rate of accretion of tidal flats is
lessening or static.
7. The application relies on data on mangrove removal from Tauranga Harbour, where
the hydrodynamics are quite different from Whangamata. In those parts of Tauranga
Harbour that have some similarities, monitoring has not shown the flushing effect of
fine sediments inferred in the application and A.E.E.
8. The clearance areas proposed in the Moanaanuanu Estuary will have little or no
effect on flood abatement or sediment transport. The causeway itself is the major
impediment to flood flows, reducing flow velocity creating conditions where
sediment starts dropping out of river flows. This sediment is then deposited on the
mud flats above the causeway (with or without mangroves) and then redistributed
around that part of the harbour.
9. The illegal removal of mangroves from an area adjacent to the Moanaanuanu
causeway has done nothing to change the muddy nature of the sediment there.
Primarily as the causeway is the main barrier to flood flows, reducing river flows
leading to sediment deposition and increased mangrove habitat.
10. Mangrove clearance on a number of the areas up the Moanaanuanu Estuary are
likely to mobilise silt moving down the river and into the marina. Areas E1, E2 and D
appear to trap sediment that would otherwise go downstream and some depositing
in the marina. This would create on-going increased maintenance.
11. There has been no credible monitoring evidence to verify either way whether any of
the objectives of the previous mangrove clearance consents have been achieved
(greater biological diversity, improved harbour flushing and reversion to a cleaner
harbour). The only credible changes have been aesthetic and social, where some
people feel better with mangroves removed. There is a lack of information relating
to “numerous examples of estuary life has recovered post mangrove removal ...”
(see 4 - The Issue in the A.E.E.).
12. Most of the sites proposed for clearance fail to meet the ‘benefits’ list apart from providing
access for locals to mud flats.
13. The application relies on the Harbourcare A.E.E., yet much of the information in the
AEE was not accepted as credible by the Environment Court
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14. The significantly different hydrodynamics of clearance areas in Tauranga Harbour
cannot be confidently applied to Whangamata Harbour.
15. The application seeks 30 and then 35 ha of clearance, yet the need may be current,
but appears to be unlikely beyond 5 years, when most of the work proposed will be
completed.
16. In Forest and Bird’s previous submission re mangrove removal within the
Whangamata harbour (mulching machine application 2010), we requested
information from the Waikato Regional Council of documented research which
shows that mangroves display sea grass. There is no information on this matter in
the current application or A.E.E.
17. It is unclear as to who will accept the ongoing task and costs of mangrove
removal, i.e. seedling removal. This role could potentially continue indefinitely.
18. There is inadequate information with regard to mitigation of adverse effects.
19. There is no detail with regard to:

the scientific design of monitoring

size of trial areas associated with other mangrove removal methods outside
of the 1 ha (racking or plucking) trial area.

Who will undertake the monitoring?
20. It appears that the 1 ha pilot trial (racking or plucking) will occur concurrently with
other clearance methods being implemented. This is counter intuitive as adverse
effects associated with the larger clearance methodologies could not be avoided by
implementing a potentially better method as undertaken in the trial area?
21. The A.E.E. talks favourably of the recent cutting head trials in Tauranga but fails
to mention that the Bay of Plenty Regional Council did not adopt this
methodology as the cost was significantly greater than using the mangrove
mulcher.
Yours Sincerely
Alan Fleming
Central North Island Field Officer
Royal Forest and Bird Protection Society of New Zealand