evaluation-pest-wasps-nz

4. Overall impacts and sensitivityanalyses4.1 Annual impactsA breakdown of the costs of the impacts of Vespula wasps on New Zealand that were identified insection 3 is provided in Fig. 11. The direct use impacts of wasps were quantified at $75 million perannum. This is the sum of all of the costs shown in Fig. 11 except the ‘forgone honeydew honeyproduction’ column on the far right-hand side. This latter column represents the significantoption value for apiculture development around the upper South Island beech forests if waspscould be removed and totalled $58 million per annum. Therefore, the total quantifiable annualimpact of wasps on New Zealand was estimated at $133 million.$60 mAnnual Gains and Costs without Wasps$58 m$50 mCost of Vespula wasp impact$40 m$30 m$20 m$10 m$0 m$0 m $0 m $0 m $0 m $1 m $1 m $1 mVet visits for Training, fullwasp attacks cost of ER &poisioningAnimalHealthLowerpollinationcostsPollinationproductiongainsLowerpollinationcostsGP visits,hospitalstays, deathsForestry Arable Arable Horticulture HumanHealth$2 m $3 mSocial costs Wasp controlmanagementcostsTrafficcrashesProductionincreasewithoutwasps$4 m$28 mAvoided hives Clover costlost to wasps avoided$34 mN costsavoidedForegonehoneydewhoneyproductionApiculture Apiculture Apiculture Pastoral Pastoral ApicultureQuantifiable impacts of Vespula waspsFigure 11. Annual quantifiable impacts of Vespula wasps on New Zealand. Source: Sapere analysis.4.2 Net present value of impactsA breakdown of the NPV of impacts of Vespula wasps on New Zealand that were identified insection 3 is provided in Fig. 12. The NPV of direct use impacts was estimated at $772 million from2015 to 2050, while the option value for apiculture development around the upper South Islandbeech forests was estimated at an NPV of $578 million over the same period (Fig. 12). This gives atotal NPV impact of $1,350 million.4.3 Sensitivity analysisThere are some real uncertainties around the above estimates of the quantifiable costs of waspsto New Zealand as discussed in section 3, and it is quite common for the net effects arising froma given study to be overly optimistic. However, these potential biases can be investigated bytesting which key factors have the largest effect on the values estimated.The effect of such uncertainty on the study objectives is termed the ‘risk’, and this can becalculated by multiplying the probability of the estimate being true by the dollar value of thepredicted harm or gain. Sometimes it is very difficult to assess risks, as many factors may notAn evaluation of the costs of pest wasps in New Zealand35