Download Submission on the Proposed Regional Policy Statement 2010

Waikaraka Estuary Managers Incorporated
Submission on the Proposed Regional Policy Statement 2010
Note: Quotations from the proposed RPS are reproduced in blue.
Rewording proposed by WEM is shown in green.
PART 1 Bay of Plenty Region
1.7 Precautionary approach (page 9)
WEM Response:
1. We agree that a precautionary approach is certainly desirable or even
essential when dealing with such matters as genetically modified organisms.
However, if applied to all activities it will stifle innovative approaches and
delay progress unnecessarily.
2. The use of a precautionary approach needs to be limited in some way, to
be specified in 1.7, that will ensure that it is only employed when a direct
approach would be generally considered to be foolhardy.
PART 2 Issues and Objectives
2.2.2 Natural character and the ecological functioning of the coastal environment
(page 21)
2.2.2 para. 2 (on p.22) includes the following:
“Increased sediment and nutrient input has the capacity to change ecosystem
dynamics, encouraging the growth of some naturally occurring but rapidly
colonising species, such as mangroves, and providing additional nutrient for
nuisance species, such as sea lettuce, which can have a detrimental impact.”
WEM Response:
1. We wholeheartedly applaud this statement except that it falls short of
addressing the whole problem. Mangroves are indeed colonising areas of
clear foreshore, but they are also invading the habitats of other species such
as seagrass, and marginal plants including various rushes. These are the
very species that are known to be ecologically essential in providing habitat
for valued animals, including the threatened banded rail and spotless crake
which nest in rushes. WEM discovered evidence of past invasion when,
during 2008, mature mangroves were cut from an area of about 0.5ha at the
extreme head of Waikaraka Estuary. A large part of the foreshore beneath
these mangroves was found to be composed mostly of a solid mass of fine
(dead) root matter. The appearance and texture of these root remains
appeared identical to that of the healthy rush roots on the adjacent foreshore.
Our conjecture is that this area was previously saltmarsh habitat.
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WEM Response to 2.2.2. para. 2 (continued)
2. WEM request a change of wording to para. 2 of 2.2.2 as follows:
“Increased sediment and nutrient input has the capacity to change ecosystem
dynamics, encouraging the growth of some naturally occurring but rapidly
colonising species such as mangroves, which are also known to be invasive
and are actively displacing other ecologically essential plant species. The
increased nutrient levels also aid the growth of nuisance species, such as sea
lettuce, having a detrimental impact.”
2.2.2 para. 5 on p.22
The work of BoP Coast Care Groups in replanting sand dunes is rightly
acknowledged. WEM would like to see the work of the Estuary Care Groups
similarly acknowledged. These Care Groups, aided by specialists from NIWA
and University of Waikato, have gained detailed knowledge of the estuarine
ecosystems pertaining to their degradation by siltation, nutrient loading and
mangrove proliferation and have made huge progress in restoring the
estuaries of Tauranga Harbour. It should be noted that this restoration is
being thwarted by Regional Councils’ insistence that mangroves should
remain in parts of our estuaries.
Table2 - Objective2 (page 24)
WEM Response:
We strongly object to the omission of any mention of “restoration” in this
objective. We propose that Objective 2 is re-written as:
"Restoration of degraded areas and the preservation and enhancement of
those areas presently in a generally good state, to ensure healthy ecological
functioning and a genuine improvement in natural character"
The title of Policy CE 2A (page 90) should therefore be re-written as:
“Preservation of high natural character and restoration of degraded areas
within the coastal environment.”
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PART 3 Policies and Methods
(page 92)
Policy CE 6B: Enabling the management of mangroves
“Manage mangroves to avoid the adverse effects of mangrove proliferation
while ensuring consideration of the ecological benefits associated with the
mangrove communities.”
WEM Response:
1. We endorse the existence of adverse effects resulting from mangrove
proliferation, but challenge Regional Council’s assertion that there are
worthwhile ecological benefits associated with mangrove communities within
the Tauranga Harbour. We believe, in fact, that there has been a significant
reduction in net ecological benefits resulting from mangrove colonisation for
the reasons explained below under (a). The framing of Policy CE 6B is
therefore flawed.
2. Regional Council’s belief that mangroves have a role in providing a
beneficial habitat for coastal flora and fauna within the inter-tidal zone is now
highly contentious. It is vitally important that there is further informed scientific
debate among the parties involved to resolve this issue.
3. The Regional Council goes on to state that the following points be taken
into account when considering mangrove management.
For ease of
reference I have reproduced them in full.
(a) Habitat value of the site
WEM response:
1. Consideration of the habitat value of a site is the right place to start
providing that the assessment of that value is not based on false assumptions
or misinterpreted observations.
2. We contend that mangrove growth effectively diminishes habitat value. As
explained in our response to Para. 2.2.2 on page 1, there is a net loss in
habitat value of a given area of mangrove cover compared with clear
foreshore and therefore a reduction in biodiversity of that area.
3. NIWA Information Series No. 31 by Malcolm Green et al, 2003 makes a
reference to mangroves as being a habitat for several species of marine
animal, and we accept that as fact. However, it also states that fewer species
inhabit the mangroves than an equivalent area of clear foreshore.
4. There has recently been much publicity surrounding the discovery of “dead
zones” of stinking black mud in areas of mechanically mulched mangroves.
RNZ Forest & Bird representatives have attributed this to the suffocating
action of the covering of mulch. However, it is well known among the Estuary
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WEM Response para. 4 (continued)
Care Groups that the mud beneath established colonies of mangroves is
exactly as the “dead zones” have been described. The sub-surface mud is
anaerobic, black and smells strongly of hydrogen sulphide when disturbed.
This is a natural outcome of continued accumulation of sediment plus the
continual drop of salt-laden leaf litter from the mangrove plants.
5. We contend that there are few, if any, ecological benefits associated with
mangrove communities, particularly when these are compared with the
advantages of clear foreshore. We cannot understand, therefore, how
Regional Council can consider that mangrove colonies have any beneficial
ecological habitat value in estuarine situations.
6. We would like Regional Council to present peer-reviewed documented
scientific evidence that “…the ecological benefits associated with the
mangrove communities” actually do exist.
(b) The value of the mangroves as a buffer against coastal erosion
WEM Response:
It may be the case that mangroves buffer coastal erosion at specific locations,
but we consider it to be a limited attribute. Moreover, WEM considers that
use of mangroves in the role of erosion control is unsustainable because of
the burden of controlling the spread of seedlings, for the reasons stated on
page 8. Other methods of controlling coastal erosion need to be found.
(c) The risk of mangroves spreading into non-vegetated coastal areas or
significant native estuarine vegetation communities (eg saltmarsh and
seagrass habitats)
WEM Response:
There seem to be few, if any, places where mangroves present in the harbour
are not actively spreading. They are spreading into unvegetated areas and
they are spreading into areas of saltmarsh and seagrass. Point (c) is
therefore totally misleading as it misrepresents a certainty as a risk.
(d) Relative age and maturity of the mangroves
WEM Response:
We are acutely aware of the highly degrading effects of mangroves on the
coastal environment as previously detailed. Relative age or maturity has no
mitigating effect whatever. Point (d) has no merit and should be deleted.
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(e) Restrictions on access to beaches, wetlands and recreation areas,
navigational access and safety
WEM Response:
Mangroves are restricting or completely preventing access to beaches,
wetlands and recreation areas and of course that provides every justification
for their removal. However, it should be recognised that in the case of
beaches, the area to which access is denied is now no longer beach. It is
covered in a significant depth of anaerobic mud that has accumulated under
the mangroves. So, rather than the loss of access being an issue, it is the loss
or degradation of the feature, together with it’s specific community of wildlife,
that is the real issue.
(f) Adverse effects on amenity, cultural, landscape, seascape values
WEM Response:
Mangrove habitat appears to tick all the boxes for adverse effects in the
above-mentioned aspects. There is a widespread loss of access to water for
amenity purposes and loss of clear water for paddling, swimming, boating and
other aquatic recreation. Seascape value is reduced where the sea is hidden
by mangrove canopy, and few would agree that mangrove coverage actually
enhances the landscape.
(g) Levels of sedimentation and ability for sediment remobilisation
WEM Response:
1. The levels of sedimentation and ability for remobilisation are irrelevant to
the “keep or cut” decision process. Sediment accumulates beneath mangrove
colonies, so sediment depth incrementally increases and is therefore not a
robust indicator for a decision-making criterion.
2. The relative ability for sediment remobilisation has even less relevance.
As an example, Waikaraka Estuary is acknowledged to have very low tidal
action and stream outflow flushing, yet since the bulk of mangroves have
been removed (authorised by grant of Resource Consent) there has been
significant remobilisation and flushing out of silt. Shell banks and firm sand
have reappeared from under the mud. The mobilisation and flushing is further
evidenced by the observation of the cut stumps of mangroves that in many
places exceed 100mm in height above the local silt level.
3. Stands of mangroves left in any area are a potential threat to the whole
harbour. The propagules drop and float away to find a place to take root
wherever the tide and wind take them. As explained later on page 8, we do
not consider that maintaining “protected” colonies of mangroves is a
sustainable practice.
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(h) The existence and implementation of a catchment management plan
for the area
WEM Response:
The existence and implementation of a catchment management plan is an
essential requirement for aiding restoration and preservation of the coastal
environment. However, whether or not a plan is in place for a particular area
is not regarded as relevant in deciding whether or not mangroves may be
removed.
Policy CE 6B: Explanation
(page 92) (Reproduced in full for ease of reference)
Para. 1
“Policy CE 6B enables decisions regarding mangrove management to be
made on a case-by-case basis taking into account both the threats of
mangrove expansion and the ecological value of established mangrove
communities to the ecosystem”
WEM Response:
Mangrove expansion is more than a threat, it has become a certainty, and we
now consider that established mangrove colonies in the Tauranga Harbour
have less ecological value than clear foreshore. Certainly we know that the
number of animal species found in mangrove stands and associated
sediments is lower than that found on adjacent intertidal sandflats. (Reference
NIWA Information Series No. 31 “For and against mangrove control” of 2003)
We therefore assert that relative to clear foreshore, mangroves colonies have
less ecological value and less biodiversity.
Para. 2
“Mangroves are indigenous plants and can play an important role in coastal
ecosystems by enhancing water quality, protecting coastal margins from
erosion, and providing habitat for coastal flora and fauna within the inter-tidal
zone”
WEM Response:
1. To our knowledge, there is no evidence that mangroves enhance water
quality. If evidence does exist then it should be presented.
2. Mangroves demonstrably do not provide a habitat for coastal flora. They
are a dominant species expanding as a monoculture. NO other flora have
been seen locally to co-exist with mangroves without being displaced by them
(except where mangroves are growing poorly and sparsely in areas of sand or
other hard ground). For example, seagrass beds were depleted at Waikaraka
until mangrove cutting took place, and the beds are now regenerating.
Margins of rush are currently being infiltrated and displaced by mangroves.
3. The infiltration of rushes is a particularly serious threat to bird species
including the banded rail and spotless crake which nest in rushes. Estuary
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Care Group workers have never seen evidence of any bird species nesting in
mangroves and a local representative of RNZ Forest & Bird confirms that they
have never observed birds nesting in mangroves. While we are forced by
Regional Council to leave marginal strips of mangroves as “buffer zones”, the
infiltration continues. For fauna in general, there appears to be no positive
benefit as a habitat, as many more species are denied access to the
mangrove-colonised area than presently utilise a similar area of clear
foreshore. Furthermore, wading birds cannot wade within mangroves.
Wading birds are now in abundance on Waikaraka Estuary following
mangrove removal over the last 9 years or so. Wherever mangroves spread
there is a consequent loss of habitat for wading birds.
4. It has become obvious to WEM and all of the other estuary care groups, as
well as many other people actively engaged in the mangrove debate, that
mangroves are not a net benefit to the ecology of the foreshore. We are
unaware of any evidence that mangroves enhance water quality and there is
no evidence that they provide a worthwhile and valued habitat for coastal flora
and fauna. In fact there is much evidence to the contrary. Mangrove growth
brings a consequent reduction in biodiversity.
Para. 3
“Accelerated sedimentation and nutrient supply has been identified as
contributing to the expansion of mangroves seaward of the intertidal zone in
Tauranga and Ohiwa harbours. Rapid expansion of mangrove communities
can have adverse effects on the balance of the ecosystem as well as amenity,
recreation, public access and the natural character of the coastal marine area”
WEM Response:
Rapid expansion of mangrove communities invariably does have adverse
effects through loss of habitat for other beneficial species of flora and fauna
(including humans!). The evidence is all around us and is now well
documented. We require that “….can have adverse effects….” be replaced
by “…...has recognised adverse effects……”
Para. 4
“When considering removal, Policy CE 6B enables a differentiation to be
made on the basis of location relative to historic coverage of mangroves. The
removal of mangroves is likely to be more acceptable where they are shown
to be occurring outside the area of historic coverage as identified in the
Regional Coastal Environmental Plan.”
WEM Response:
1. From the accumulated knowledge on the subject of mangrove occupation,
WEM no longer sees any relevance in the concept of using historic coverage
as a criterion for deciding upon removal or retention. We believe that
mangroves have no ecological net benefit to the harbour. They are actually a
threat. To make a case for retaining them in certain areas for historical
reasons makes no sense to us.
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2. Para. 4 states that the area of historic coverage is as identified in the
Regional Coastal Environment Plan. The writer made a careful on-line search
of that document but has failed to locate that information. Would Regional
Council please check the location of the document identifying the historic
coverage of mangroves and make it publicly available.
A definition of
“historic” in that context is also required. (Requested on page 8 under
Appendix A - Definitions.)
PART 4: Monitoring the RPS and the anticipated environmental results
4.2 Table on page 145
Coastal environment
Objective 2
Third statement under “Anticipated environmental results”:
“The role of mangroves in protecting coastal margins from erosion and
providing habitat for coastal flora and fauna within the inter-tidal zone is
maintained.”
WEM Response:
1. We consider that the maintaining of mangrove colonies for the purpose of
erosion control is an unsustainable practice. The number of new seedlings
appearing in a season is largely determined by the area of mature mangroves
that remain to drop their propagules, which then float away to root wherever
the wind and tide deposit them. Mangroves do not produce new shoots from
their roots, and propagules do not remain dormant in the mud waiting to be
exposed. New plants grow only from freshly deposited propagules.
2. The task of removing the seedling crop arising from areas of mature
mangroves is never-ending and is very likely to exhaust the enthusiasm and
motivation of the Care Groups. It is unrealistic to expect Care Groups to fulfil
this obligation in perpetuity.
3. As explained on page 3 under (a) Habitat value of the site, we have
established to our satisfaction that mangroves do not provide a habitat for
coastal flora, and the habitat value for fauna is far reduced from that of clear
foreshore. We challenge the Regional Council on this issue and request that
the third statement is deleted.”
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Appendix A - Definitions
1. Mean High Water Springs (page 165)
This term is generally not well understood. WEM therefore prefer to see the
“official” Land Information New Zealand (LINZ) definition adopted, as follows:
“The average of the levels of each pair of successive high waters during that
period of about 24 hours in each semi-lunation (approximately every 14 days),
when the range of the tide is greatest (Spring Range).”
(Source:http://www.linz.govt.nz/hydro/tidal-info/tidal-tro/definitions/index.aspx)
2. It would be very helpful to include definitions for the terms “historic”,
“native” and “indigenous” as used in the RPS.
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Prepared by Peter Callow
Waikaraka Estuary Managers Inc
February 2011
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