evaluation-pest-wasps-nz

3.6.3 Non-use impactsTo determine non-use impacts of wasps on the environment and biodiversity, the TEV approachincludes bequest and existence values. However, these are generally challenging to estimate.Kerr & Sharp (2008) conducted a choice experiment to estimate community preferences andvalues of the impact of wasps on indigenous species in the South Island. This focussed onchanges in welfare caused by wasps, and how this changed the flow of services from the naturalenvironment and indigenous biodiversity. They explored the attributes of the beech forestecosystem with and without wasps, and asked people living in the South Island to choosetheir single preferred state, to reveal preferences about the outcomes of wasp management inNelson Lakes National Park. The statuses of birds and insects were used as attributes to valuethe ecological effects of wasps, and value was revealed via a monetary attribute of ‘cost to yourhousehold each year for the next five years’. This was presented as being paid via household rateslevied to fund wasp management at rates of $0, $25, $50 or $100. Preferences were for attributessuch as fewer wasp stings, more birds, more insects and lower costs. Kerr & Sharp’s (2008) surveyinvolved educating participants about wasp distribution, impacts and control. They noted thattheir values would not therefore represent values held by the general population who may havemuch less understanding of wasp impacts or their management.Kerr & Sharp (2008) found that the surveyed community was willing to spend large amounts ofmoney to protect and enhance bird and insect populations at Lake Rotoiti (Table 11). For example,wasp control that halted the decline in insect numbers was worth c. $150 per year to the averagehousehold in their survey, which was estimated to be worth c. $625 to the average household over5 years. Summing this across approximately 300 000 households in the South Island yielded atotal present value benefit of $195 million.Table 11.Kerr & Sharp’s (2008) choice modelling results.OutcomeMean annualvalue perhouseholdPV @ 10% over5 yearsAggregate over300 000 householdsProbability of stings increases by 10% –$60 –$250 –$75mFew birds –$300 –$1,250 –$375mPlentiful birds $120 $500 $150mFew insects –$150 –$625 –$195mPlentiful insects $90 $375 $113mThese findings suggest that New Zealanders value both recreation and the existence value ofa biodiverse natural environment very highly, and it could be argued that Kerr & Sharp (2008)probably captured not only a use value of recreation, but also a portion of the bequest andexistence value.3.7 Benefits of waspsWasps not only have negative impacts on the environment and New Zealand’s economy, butalso bring some benefits. To examine some of these benefits, we interviewed Geoff Watts, aChristchurch-based exporter of wasp larvae and venom. Geoff exports wasp comb to Japan,where the larvae/pupae are eaten, and also exports freshly killed wasps to the USA, where theirvenom is used to treat anaphylaxis. This benefit was not quantified, but it was understood thatthis export trade has declined in recent years due to less favourable exchange rates.An evaluation of the costs of pest wasps in New Zealand33