ECOLOGICAL EVALUATION OF A POTENTIAL COMPENSATION WETLAND ADJACENT TO THE PROPOSED NIKAU PALM ROAD CLEANFILL AT PARAPARAUMU R3113a ECOLOGICAL EVALUATION OF A POTENTIAL COMPENSATION WETLAND ADJACENT TO THE PROPOSED NIKAU PALM ROAD CLEANFILL AT PARAPARAUMU Contract Report No. 3113a May 2013 Project Team: Frances Forsyth - Field survey and report author Chris Bycroft - Field assessment and report author Prepared for: Higgins Projects Ltd C/- Cuttriss Consultants Ltd 33 Kapiti Road, Paraparaumu P.O. Box 386 Paraparaumu WELLINGTON OFFICE: 7A SUNLIGHT GROVE, ELSDON, P.O. BOX 50-539, PORIRUA Ph 04-237-7341; Fax 04-237-7496 HEAD OFFICE: 99 SALA STREET, P.O. BOX 7137, TE NGAE, ROTORUA Ph 07-343-9017; Fax 07-343-9018, email [email protected], www.wildlands.co.nz CONTENTS 1. INTRODUCTION 1 2. BACKGROUND 2 3. METHODS 2 4. MAZENGARB WETLAND 2 4.1 Overview 2 4.2 Wetland vegetation 3 4.3 Flora 3 4.4 Environmental pest plants 3 4.5 Fauna 3 5. MUAUPOKO WETLAND 4 5.1 Overview 4 5.2 Wetland vegetation description 4 5.3 Flora 4 5.4 Environmental pest plants 4 5.5 Fauna 5 6. COMPARISON OF THE TWO WETLANDS 5 7. RESTORATION OPPORTUNITIES FOR MUAUPOKO WETLAND 5 8. CONCLUSIONS 6 ACKNOWLEDGMENTS 6 REFERENCES 6 APPENDICES 1. Wetland maps 8 2. Vascular plants recorded at the wetlands 10 3. Site photographs - Mazengarb Wetland 14 4. Site photographs - Muaupoko Wetland 17 © 2013 Contract Report No. 3113a Reviewed and approved for release by: _______________________ W.B. Shaw Director/Principal Ecologist Wildland Consultants Ltd Wildland Consultants Ltd 2013 This report has been produced by Wildland Consultants Ltd for Higgins Projects Ltd. All copyright in this report is the property of Wildland Consultants Ltd and any unauthorised publication, reproduction, or adaptation of this report is a breach of that copyright. © 2013 Contract Report No. 3113a 1. INTRODUCTION Cuttriss Consultants Ltd, on behalf of Higgins Projects Ltd and Goodman Contractors Ltd, is applying to Kapiti Coast District Council and Greater Wellington Regional Council for resource consents to create a new cleanfill site in the Mazengarb catchment, at Paraparaumu. Wildland Consultants Ltd was commissioned by Cuttriss Consultants to undertake an ecological assessment of a wetland in the Muaupoko catchment, hereafter referred to as the Muaupoko Wetland. This wetland has been proposed as a potential compensation site to mitigate the potential loss of a wetland at the cleanfill site, hereafter referred to as the Mazengarb Wetland (Figure 1). This report provides ecological descriptions of both wetlands, including delineation of the wetland boundaries and a discussion of the relative ecological merits of each wetland. Figure 1: Location map showing the Mazengarb Wetland, site of the proposed cleanfill, and the Muaupoko Wetland, proposed as a compensation site, and the relevant stream catchments. © 2013 1 Contract Report No. 3113a 2. BACKGROUND The Mazengarb and Muaupoko wetlands have mainly mineral soils and are classified as both swamps and seepages1, with water supply from overland flow and groundwater. Very small areas of standing water are present in both wetlands, with some surface channels, and gentle, permanent, internal flows. The Mazengarb Wetland lies along the floor of a steep-sided, fault-defined valley and is the source for a stream known as the Mazengarb Drain in the Waikanae River catchment. The Muaupoko Wetland is also in the Waikanae River catchment and is the source of one of the many tributaries of the Muaupoko Stream. This wetland lies in more gently-rolling hill country and, being less constrained by the topography, is broader in extent than the Mazengarb Wetland (Appendix 1, Figures 2 and 3). Both wetlands are in a relatively poor ecological condition as they have been grazed by domestic stock for many years. 3. METHODS Walk-through surveys of both wetlands were undertaken on 22 March 2013. An earlier survey of the Mazengarb Wetland was carried out on 11 August 2011. A total of ten person hours were spent on plant species identification and boundary delineation. The wetlands were mapped and described (Appendix 1), and all vascular plant species present were recorded (Appendix 2). Avifauna heard or seen at the sites were also recorded. 4. MAZENGARB WETLAND 4.1 Overview The wetland is surrounded by pasture which is dominated by exotic grasses and thistles with isolated pockets of indigenous shrubland: commonly kanuka (Kunzea ericoides), tauhinu (Ozothamnus leptophyllus) and Coprosma rhamnoides, particularly in the valley folds. Blackberry (Rubus fruticosus agg.) is present at the bottom (north end) of the valley. There is one clump of toetoe (Austroderia fulvida) in the pasture. Slopes to the northwest have been planted in pines (Pinus radiata) but also have significant areas of self-regenerating, indigenous forest, the canopy of which comprises mainly kanuka and mahoe (Melicytus ramiflorus). 1 Wetland definitions from Johnson and Gerbeaux 2004. © 2013 2 Contract Report No. 3113a The wetland boundary was delineated during the field survey and the wetland has an area of 0.45 ha. This boundary includes all tributary wetlands. Few of the steep side gullies contained wetlands. 4.2 Wetland vegetation Vegetation in the wetland is mostly scattered rushes (Juncus sarophorus and Juncus effusus), giant umbrella sedge (Cyperus ustulatus) and ocassional pukio (Carex virgata) over a diverse understorey dominated by Isolepis prolifer, water pepper (Persicaria hydropiper), creeping buttercup (Ranunculus repens) and exotic grassland species: Yorkshire fog (Holcus lanatus), browntop ( Agrostis capillaris), narrow-leaved plantain (Plantago lanceolatum), white clover (Trifolium repens), and lotus (Lotus pedunculatus). Rushes are more prevalent at the drier edges of the wetland where the understory is dominated by exotic grasses such as Yorkshire fog. The vegetation is fairly uniform apart from the high exotic component and there is no raupo (Typha orientalis) or toetoe (Austroderia fulvida). 4.3 Flora Twenty-one indigenous vascular plant species and 23 adventive species were recorded during the site visit (Appendix 2). None of the indigenous species recorded are classified as ‘Threatened’ or ‘At Risk’, as per de Lange et al. (2008). 4.4 Environmental pest plants There were no regionally significant pest plants in the Mazengarb Wetland or surrounding pasture. Blackberry is present and is likely to spread unless controlled as there are extensive patches along riparian reaches on neighbouring land. Gorse is uncommon - less than 0.1% of total cover - but likely to increase if grazing pressure and pasture management is reduced. 4.5 Fauna Birds No birds were seen in the wetland on any of the visits. Birds observed in the area were typical of the pasture habitat. Indigenous species recorded included: red-billed gull (Larus novahollandiae scopulinus), North Island fantail (Rhipidura fulginosa placabilis), paradise shelduck (Tadorna variegata), New Zealand pipit (Anthus novaeseelandiae), grey warbler (Gerygone igata), and silvereye (Zosterops lateralis). Introduced species recorded included rook (Corvus frugilegus), blackbird (Turdus merula), and European goldfinch (Carduelis carduelis). Red-billed gull is classified as Threatened-Nationally Vulnerable (Miskelly et al. 2008), but is likely to be only an occasional visitor © 2013 3 Contract Report No. 3113a Large numbers of common blue butterfly (Zizina otis labradus) were observed in the pasture during the March 2013 survey. 5. MUAUPOKO WETLAND 5.1 Overview The wetland is mostly surrounded by pasture dominated by exotic grasses and thistles, with occasional very small patches of kanuka, mahoe, and blackberry. A plantation pine forest lies to the southeast and one finger of wetland reaches up into this forest. That section of the wetland is not currently grazed. A small stream flows from the lower (northern) end of the wetland, which then flows through a residential property with many exotic trees. The wetland covers an area of 1.64 ha. 5.2 Wetland vegetation description Vegetation in the wetland is mostly scattered rushes - Juncus sarophorus and occasional soft rush (Juncus effusus) - within a diverse cover dominated by Isolepis prolifer with water pepper (Persicaria hydropiper), creeping buttercup (Ranunculus repens), and exotic grassland species (Yorkshire fog, browntop, narrow-leaved plantain, white clover, and lotus). Several very small areas are dominated by toetoe, raupo, and Cyperus ustulatus sedgeland. The vegetation is quite varied and all areas which are not dominated by toetoe, raupo, and fernland have a relatively high exotic component. In drier areas the rushland contains abundant exotic grasses (e.g. Yorkshire fog). In the permanently-wet sites the cover is dominated by Isolepis prolifer and water pepper. Key areas of raupo reedland and toetoe tussockland are shown in Figure 2. In the finger of wetland surrounded by plantation forest, the main cover is Hypolepis ambigua fernland. 5.3 Flora Nineteen indigenous vascular plant species and 26 adventive species were recorded during the site visit (Appendix 2). None of the indigenous species recorded are classified as ‘Threatened’ or ‘At Risk’, as per de Lange et al. (2009). 5.4 Environmental pest plants There are no regionally significant pest plants in the wetland or in the general area. Three environmental pest plants were present on land surrounding the wetland: Darwin’s barberry (Berberis darwinii), gorse, and blackberry. The cover of these species are currently low (<1%),