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Subject: search.filters.subject.Horowhenua District

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    Cost benefit analysis of riparian planting options for freshwater coastal streams in Horowhenua : ngā utu kia piki te Mauri o ngā wai a Parawhenuamea : a thesis presented in partial fulfilment of the requirements for the degree of Master of Environmental Management, Massey University, Manawatū, New Zealand
    (Massey University, 2014) Tangatatai, Tene
    Freshwater ecosystem health is an important policy priority in New Zealand, recently highlighted by the government’s launch of the ‘Freshwater Reform 2013’. One practical way of improving freshwater ecosystem health is riparian planting. In this context, the aim was to develop and apply a cost benefit analysis (CBA) methodology to evaluate riparian planting options for restoring five freshwater coastal streams of importance to iwi/hapu in the Horowhenua, drawing on two distinct disciplines – freshwater ecology and economics. Essential to this CBA methodology was an explicit evaluation of a desired policy outcome. Accordingly, attention was given to assessing what constitutes the desired policy outcome that is ‘freshwater ecosystem health of coastal streams’. This assessment was based on developing a detailed understanding of the attributes that must managed to achieve ‘freshwater ecosystem health’ including: in-stream temperature, periphyton, sediment, water flows, ecological connectivity, nitrate and ammonia, key fish species and stream invertebrates. The CBA methodology then focused on developing a new systems framework (interrelated ecosystem ‘biophysical structures’, ‘processes’ and ‘functions’) for assessing the ecological role of riparian vegetation in improving freshwater ecosystem health. Non-market economic values required for CBA calculations were then derived using a benefit transfer method. Data from three study sites (Karapiro South Waikato, Hurunui Canterbury, and Canterbury) based on ‘choice experiment’ values were evaluated for their suitability for use in the policy site (Horowhenua). The suitability of data from study sites for use in the policy site applied the Welch T test and Wilcoxon rank sum, using ‘personal income’ as the assessment criterion. Over 100 hundred planting scenarios were then tested by CBA, with almost all having positive net present values for both 5m and 10m width planting options. The study concludes with a discussion of the practical and policy implications of these findings, and highlights the limitations of this study and how these can be overcome in future research. Keywords: Indigenous, ecosystem health, freshwater coastal streams, riparian, environmental cost benefit analysis, benefit transfer.
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    The effects of introduced predators and the invasive weed Tradescantia fluminensis ( Vell.) (Commelinaceae) on the land snail Powelliphanta traversi traversi (Powell) (Gastropoda: Pulmonata: Rhytididae : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Ecology at Massey University
    (Massey University, 2001) Bennett, Shaun James
    Powelliphanta traversi traversi (Powell) was studied at two forest remnants in the Horowhenua District. The effects of introduced predators, predator control, the invasive weed Tradescantia fluminensis (Vell.), and Grazon® herbicide on these snails were investigated. Brodifacoum poison was used in two areas of Lake Papaitonga Scenic Reserve to determine the effect of rodent control on P. t. traversi. Mouse abundance (inferred from tracking tunnel indices) was reduced in both poisoned areas below levels observed in two other areas that were not poisoned. Rat abundance was reduced below pre-poisoning levels but only to levels below one of the non-poison areas. In each poison and non-poison area, four 100m2 quadrats were searched for P. t. traversi snails immediately before poisoning, and 12 and 19 months after poisoning commenced. After 19 months, only one poisoned area showed an overall increase in the number of snails, with significantly more live snails found (45) than at either of the two previous searches (22 before poisoning and 28 after 12 months of poisoning) (P<0.05). Numbers of empty P. t. traversi shells found in each area decreased at each search suggesting that shell accumulation is constant rather than seasonal. Rats were the greatest identified predator of P. t. traversi at Lake Papaitonga (17.87% of all empty shells), but the proportion of shells damaged by blackbirds and song thrushes was also high (11.91% of all empty shells) and increased from pre-poisoning numbers in three of the areas. Overall, there was no conclusive evidence to suggest that the numbers of live P. t. traversi increased as a result of rodent poisoning during the time period of this study. The effect of T. fluminensis on the movements of P. t. traversi at Prouse Bush was determined using harmonic radar. There was large variation in the movements and a highly significant difference between individual snails (P<0.01), with some snails regularly moving between areas of T. fluminensis and leaf litter. There was no significant difference in the mean daily displacement of movements by snails in leaf litter and T. fluminensis, but T. fluminensis did appear to affect home range size. Snails always found under T. fluminensis had significantly smaller mean 90% home range estimates (43.91 m2) than snails that were only ever found in leaf litter or those that moved between litter and T. fluminensis (171.35 m2 and 610.14 m2 respectively) (P<0.05). Snails in T. fluminensis had a significantly wider size-frequency distribution than those in leaf litter (P<0.05) and no live snails <35mm were found in leaf litter. There was no significant difference between the size-frequency distributions of empty shells found in both habitats, but their density was significantly greater in leaf litter (P<0.05). Powelliphanta traversi traversi regularly use T. fluminensis as a habitat and any control measures affecting this weed in native bush remnants need to be considered with regard to their possible effects on these snails. The toxicity of a 1.4% Grazon® solution (active ingredient triclopyr) to P. t. traversi was investigated by first using three life history stages of the brown garden snail (Cantareus aspersus Müller). After 149 days, there was significantly greater mean mortality of C. aspersus exposed to a direct spray and to a sprayed environment (82.34% and 78.40% respectively) than in a control treatment (36.95%) (P<0.05). Cantareus aspersus egg mortality (86.00%) was significantly greater than adult and juvenile snail mortality (66.86 and 62.20% respectively) (P<0.05). Five P. t. traversi snails were also exposed to a single environmental spray of a 1.4% Grazon solution but no mortality or detrimental effects were observed after 149 days. A 1.4% Grazon solution does not appear to be toxic to P. t. traversi snails when sprayed on leaf litter where the snails live so Grazon appears to be a suitable herbicide for controlling T. fluminensis in forest remnants containing P. t. traversi.