SUBMISSION on the PROPOSED MANGROVE REMOVAL – WHANGAMATA HARBOUR by the Royal Forest and Bird Protection Society of New Zealand Inc (Forest & Bird). Submitter: Forest & Bird Contact person: Alan Fleming (Central North Island Field Officer). Address for service: Forest and Bird PO Box 70 171 TAURANGA 3155 Date: Phone: 07 544 4987 Cell: 021 988 295 Email: a.fleming@forestandbird.org.nz 4 October 2010 2 Introduction Mangroves in the Whangamata harbour are an important natural ecosystem which contributes to the ecosystem productivity of both the Whangamata harbour and adjacent coastal waters. They contribute nutrients to local fisheries and shell fisheries and provide wetland bird habitat and feeding areas. They are part of Whangamata harbour’s natural landscape signature. Forest and Bird wish to oppose these applications on the basis of: Unknown effects associated with mechanised mangrove removal in Tauranga harbour. Catchment management may not be reducing the amount of sediment entering the Whangamata harbour1. Unwise use of ratepayer’s resources. The scale of the removal. Forest and Bird are also requesting further information on: Whether the increase in mangrove distribution is encroaching on other coastal and marine habitats, and The role of mangroves in mitigating global warming. However if Environment Waikato (EW) does consent to these applications, or parts of the applications, Forest and Bird is seeking a number of outcomes associated with mitigation and monitoring of consents given. 1 Forest and Bird would like to undertake an analysis of this plan and present that analysis to the hearings committee. M:\\Marine\Mangroves\Whangamata 3 Flooding in the Moanaanuanu Estuary/Wentworth River Forest and Bird acknowledge concerns / effects expressed in the application about flooding in this area associated with an increase in mangroves. This includes modelling of future flood risk in the Wentworth River in 2080 Mechanised removal of mangroves in Tauranga harbour and unknown effects. Forest and Bird opposed the use of mechanised removal of mangroves in Tauranga harbour on the basis it may result in: An increase in the number of resource consent applications for mangrove removal within Tauranga and throughout the country. An increase in both the rate and total area of mangroves removed. We understand that monitoring of mangrove removal in the Tauranga Harbour: Has been largely ‘observation based’. Includes some sampling of the seabed to identify changes in the benthos community. Includes some bird counts. We understand that the mulch created by this machine has not dispersed / decomposed and that the council believes it will over time. We understand that an algae has been observed growing on the mulch in Omokoroa estuary area (Tauranga harbour) and has created an anaerobic environment that gives of hydrogen sulphide gas. Given that tidal currents in Whangamata harbour are low compared with Tauranga harbour this could result in mulch not dispersing, associated algae growth, high levels of hydrogen sulphide and dispersal of nuisance algae onto Whangamata beach, i.e. similar to the situation of sea lettuce on Mount Maunganui beaches. We are unsure of nutrient levels in the Whangamata harbour. M:\\Marine\Mangroves\Whangamata 4 Use of ratepayers resources Forest and Bird is concerned that the 4 ‘northern’ regional councils are using ratepayers resources for ‘mangrove management’, i.e. staff time, funding, mechanized mangrove removal ... and effectively reducing the regional councils ability to address catchment erosion and associated sedimentation of freshwater and coastal environments. Forest and Bird understand that the recent consent application to mechanically remove mangroves in Tauranga harbor cost approx $90,000. Whangamata Harbour and Catchment Management Plan Forest and Bird understand that the proposed removal of mangrove is part of a wider catchment management program aimed at reducing sediment input to the harbour and restoring native biodiversity to the catchment and harbour. It has been promulgated that the Whangamata Harbour and Catchment Management Plan will reduce the amount of sediment entering the harbour over time. A large percentage of the harbour catchment is exotic forestry. Forest and Bird wish to undertake an assessment of the current district plan rules, proposed national standards associated with harvesting of exotic forest and present this analysis to the hearing committee. Scale and necessity of mangrove removal Forest and Bird does not oppose the removal of mangroves that are encroaching on bird roost areas or to clear drains and stream outlets (where appropriate). However we do have concerns with regard to the necessity and proposed scale of mangrove removal in these applications. We note that Environment Waikato’s website http://www.ew.govt.nz/Projects/Lookingforward-to-a-healthier-harbour-in-Whangamata/Whangamata-Mangrove-ManagementOptions-Report/#Heading2 states: M:\\Marine\Mangroves\Whangamata 5 “The rapid expansion of mangroves in the Whangamata catchment since 1944 slowed in the late 1990s. Since then mangroves in Whangamata have increased in height but not in area. In fact the area of mangroves has decreased by about four hectares.” If EW does consent to this application, or parts of this application Forest and Bird are seeking a significant reduction in the amount of mangroves removed in the Whangamata harbour. This will be based on further analysis of the application and presentation to the hearing committee. Duration of consent The applicant is seeking a consent of 35 years (for hand clearance). If during this period it was determined that the pulling of mangroves was detrimental to the harbour, how would EW stop residents pulling mangrove seedlings? If EW does consent to this application, or parts of this application, Forest and Bird seek a consent of 15 years so an assessment on whether continued hand pulling is warranted can be done at that time. Adverse effects of mangrove removal There are several adverse effect associated with the removal of mangroves in Whangamata harbour. These include: Effect on fish species Effect on birds A reduction in the uptake of mangrove-derived material within the mangrove forest and export to adjacent habitats. Potential mobilisation of sediments and smothering of adjacent seagrass and shellfish beds. Role of mangroves in mitigating global warming. M:\\Marine\Mangroves\Whangamata 6 Potential effect on the Whangamata surf break. Effect on Fish Species We note that the applicant has not conducted a fish survey within the mangel or harbour. Whangamata harbour may be an important juvenile nursery for a number of common estuarine species including yellow eyed mullet (Aldrichetta forsteri), parore (Girella tricuspidata) and short finned eel (Anguilla australis). Research on fishes in temperate mangroves has focused strongly on the role of mangroves as fish nurseries (Morrisey et al. 2010). Since 2002 eleven studies have been published (10 in temperate Australia and 1 in New Zealand). An earlier Australian study identified mangels as important juvenile nursery areas (Bell et al. 1984). Morrisey et al. 2007 found that parore was common only in eastern coast estuaries. Short finned eels (Anguilla australis) were a common component of the fish–mangrove assemblages on both coasts. There may also be connectivity between fish populations within the Whangamata mangel to surrounding habitat mosaics including seagrass habitat. Jelbart et al. (2007), working in the Pittwater Estuary just north of Sydney, found seagrass beds closer to mangroves had greater fish densities and diversities than more distant beds, especially for juveniles. This study included Parore. The removal of mangrove in the harbour would reduce this size of this potentially important fish nursery area. Effect on Birds Morrisey et al 2010 concludes that available evidence suggests that there are no New Zealand birds that are exclusively found in mangroves, but that many species make extensive use of them for roosting, feeding or breeding. This report also states that M:\\Marine\Mangroves\Whangamata 7 Beauchamp (n.d.) noted that mangroves are “the only northern habitat of the banded rail … and are a substantial breeding habitat for New Zealand kingfisher”. Shaw et al 2010 states: “The scale of the area being proposed will represent a significant loss of feeding habitat for banded rail”. This will result in a reduction of the current banded rail population in the Whangamata mangel. Uptake of mangrove-derived material within the mangrove forest and export to adjacent habitats. Morrisey et al 2010 found that information on nutrient and energy flows between mangroves and other habitats in temperate estuaries is relatively limited, but identifies that recent studies, such as that in Matapouri Estuary, northern New Zealand (Alfaro et al. 2006), suggested that estuarine consumers exploit a range of sources of primary production (seagrasses, mangroves, benthic microalgae and macroalgae) rather than being dependent on one particular source. Fresh mangrove and seagrass material appears to play a relatively minor, local role in the overall estuarine food web, but detritus derived from these plants and exported via tidal movement may play a more significant role via the detrital pathway. Macroalgae, such as Hormosira banksii, can be an important source of organic material to estuarine food webs and is abundant year round among mangrove pneumatophores and seagrass beds, indicating an additional, indirect role for these habitats. Shaw et al 2010 mentions the relationship of mangrove derived material to adjacent habitats and coastal environment. “Potential cumulative adverse effects of this clearance scenario are as follows: M:\\Marine\Mangroves\Whangamata 8 A reduction by approximately 36% of the contribution that mangroves and their associated biota (e.g. Neptunes necklace) make to the estuarine food chain. If seagrass or shellfish beds fail to establish within cleared areas, the contribution that these areas make to the estuarine food may be permanent”. Role of mangroves in mitigating global warming Catchment erosion and climate warming are prime drivers of mangrove expansion in the Whangamata harbour. The increase in mangroves plays a role in moderating these impacts on the coastal ecosystem; by growing on sediment in estuaries, utilising additional nitrogen from run-off and regulating rising carbon dioxide concentrations by converting carbon dioxide into biomass and substrate sinks. There is no assessment in this application on how much sequestered carbon would be lost as a result of mangrove removal. Forest and Bird recommend that the 4 northern regional councils undertake an assessment of the role of mangroves in mitigating global warming including the amount of carbon sequestered in mangels. The LUCAS (Land Use Carbon Analysis System) project may assist regional councils in this assessment. Encroachment of other coastal and marine habitats Forest and Bird is concerned if mangroves are encroaching and threatening other marine habitats. For example several studies show that seaward expansion of mangrove habitat onto accreting intertidal flats is a feature of New Zealand estuaries. These flats are often important bird roosts and feeding areas. In addition tidal creeks and drainage channels can provide conduits for mangrove propagules to penetrate into saltmarsh habitats. We note that mangrove encroachment into salt marsh is not well documented in New Zealand estuaries (Morrisey et al. 2007). M:\\Marine\Mangroves\Whangamata 9 Shaw et al 2010 identifies that sedimentation and the spread of mangroves has resulted in the loss of seagrass beds in Whangamata harbour. This is on the basis of 1944 aerial photographs showing areas of seagrass in the Moanaanuanu Estuary within an area that is now mangrove shrubland. I have also been shown earlier photos of an estuary in Tauranga harbour where mangel is now found in areas where seagrass was once found (B Rowson pers comm.) However the question I ask is has the mangrove displaced the seagrass or has the seagrass been smothered by sediments. I have been unable to find any documented research which shows that mangroves displays seagrass and request any information on this matter. Forest and Bird also note the following: A 2004 survey of Whangamata Harbour (Shaw et al 2010) has shown that of the 410 Ha of harbour, 101 is Mangrove with approximately 100 Ha in other plant species. Only 3 Ha is sand beaches with the remainder is classified as intertidal flats or subtidal channels. Comparison with a similar study in 1996 shows a slight increase in seagrass, static mangrove areas and a slight decrease in saltmarsh, i.e. during the period 1996 to 2004 both mangrove and seagrass habitat increased? Shaw et al 2010 identifies that the removal of mangroves may result in the potential mobilisation of sediments and smothering of seagrass and shellfish beds in as an intermediate effect Monitoring and monitoring conditions A report on the success of the Whangamata Harbour and Catchment Management Plan in terms of sediment reduction should be undertaken by EW prior to any consideration being given to removal of mangroves. M:\\Marine\Mangroves\Whangamata 10 However if EW does consent to these applications, or parts of the applications, monitoring conditions should address the adverse effects identified in this submission both prior to and post any clearance. This includes: Effect on fish species Effect on birds Transfer of mangrove-derived material within the mangrove forest and export to adjacent habitats. Potential mobilisation of sediments and smothering of adjacent seagrass and shellfish beds Recolonisation of seagrass beds in areas of mangrove removal Forest and Bird support Shaw et al 2010 recommendations that monitoring conditions should: Include monitoring of mitigation measures, e.g. control of weeds and pest animals within saltmarsh, and that restoration works need to be successful, and in some cases ongoing, if the effects of habitat loss due to mangrove removal are to be adequately mitigated and compensated for. Within mulched areas, monitoring should document the dispersal pathways and/or in-situ decomposition of mulchate and, if mulchate is dispersed to other communities (e.g. seagrass beds), the health of those communities. Monitoring needs to document any mobilisation and redistribution of sediment, and this should be undertaken at sites both immediately adjacent to and well removed from tidal channels. The monitoring programme needs to whether adverse effects have occurred and whether adverse effects have been adequately addressed, prior to any second clearance stage being approved. In addition we are seeking that a fish survey of the mangroves be undertaking prior to any mangrove removal. Low J 2010 (Beca report) proposes that: M:\\Marine\Mangroves\Whangamata 11 “The results of monitoring should be reported to the consent authority at least one month prior to Stage 2 commencing, with stage two contingent on the effects of stage 1 being confirmed to be minor with evidence of species recovery consistent with the adjacent Mangrove-free habitats.” This does not give the community, stakeholders and interested parties sufficient time to assess and make submissions to EW on whether stage 2 should proceed or not. A monitoring report should be sent to all stakeholders and available to the community 2 months prior to EW given consideration as to whether stage 2 should commence or not. There should also be the ability for persons to make submissions on this report for the council’s consideration. It is also proposed that mangrove clearance occur over two years, with clearance in the second year dependant on the initial clearance not resulting in significant adverse effects. EW should take an adaptive management approach as some of the anticipated results may not have occurred in the 1st year, e.g. decomposition / dispersal of mulch. Any stage 2 removals should not commence until mulchate is complete dispersed / decomposed. Inappropriate use of ratepayers resources Forest and Bird understand that improvement of the areas marked “A” on the map and “D” in the photo provided by EW was supposed to be the responsibility of the Whangamata Marina Society as mitigation for a destroyed wetland, and has yet to be enhanced to a satisfactory level in regard to the loss of the original wetland for the benefit of the marina development. Forest and Bird are concerned at the apparent externalising of costs onto ratepayers for something that is the responsibility of the marina developers. M:\\Marine\Mangroves\Whangamata 12 Mulcher head If EW does consent to these applications, or parts of the applications they should considered use of a finer mulcher head. Mitigation measures If EW does consent to these applications, or parts of the applications, mitigation measures should include: pest control, i.e. to mitigate direct predation on birds and competition for food (invertebrates). Restoration of terrestrial margins. Control of pest plants in all remaining areas of saltmarsh throughout the harbour. Outcomes sought Forest and Bird are seeking the following outcomes: That these resource consent applications are declined. That EW undertake an investigation of reports that an algae has been observed growing on the mulch in Omokoroa estuary area (Tauranga harbour) and has created an anaerobic environment that gives of hydrogen sulphide gas. That monitoring results from mechanised removal of mangroves in Tauranga harbour are considered by EW prior any further consideration of mangrove removal in Whangamata harbour. If EW do consent to this application, or parts of this application Forest and Bird are seeking: A significant reduction in the amount of mangroves removed in the Whangamata harbour. This will be based on further analysis of the application and presentation to the hearing committee. M:\\Marine\Mangroves\Whangamata 13 A consent duration of 15 years so an assessment on whether continued hand pulling is warranted can be done at that time. Forest and Bird wish to speak to this submission. References Alfaro, A.C. 2006. Benthic macro-invertebrate community composition within a mangrove/seagrass estuary in northern New Zealand. Estuarine Coastal and Shelf Science 66, 97–110. Beca Carter Hollings & Ferner Ltd (Beca) in association with Wildland Consultants and the Isthmus Group. Jelbart, J.E., Ross, P.M. & Connolly, R.M. 2007. Fish assemblages in seagrass beds are influenced by the proximity of mangrove forests. Marine Biology 150, 993–1002. Low, J. 2010. Whangamata Mangroves- Assessment of Effects of Removal. Beca Carter Hollings & Ferner Ltd. Morrisey, D., Beard, C., Morrison, M., Craggs, R. & Lowe, M. 2007. The New Zealand mangrove: review of the current state of knowledge. Auckland Regional Council Technical Publication No. 325. Auckland, New Zealand: Auckland Regional Council. Morrisey, D.J. & Swales, A. & Dittmann, S. & Morrison, M.A. & Lovelock, C.E. & Beard, C.M. 2010. The ecology and management of temperate mangroves. Oceanography and Marine Biology: An Annual Review, 2010, 48, 43-160. Shaw, W. & Martin, T. & Long J. 2010. Ecological assessment of proposed mangrove clearance at Whangamata. Wildlands Consultants Ltd Report No. 2310 M:\\Marine\Mangroves\Whangamata