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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. 1 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.” 2 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 3 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. 4 (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. 5 (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 6 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. 7 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.” 8 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. _______________________________________ Prepared by Peter Callow Waikaraka Estuary Managers Inc February 2011 ___ 9