School of BioSciences - Research Publications
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ItemLimitations of outsourcing on-the-ground biodiversity conservation(WILEY, 2016-12)To counteract global species decline, modern biodiversity conservation engages in large projects, spends billions of dollars, and includes many organizations working simultaneously within regions. To add to this complexity, the conservation sector has hierarchical structure, where conservation actions are often outsourced by funders (foundations, government, etc.) to local organizations that work on-the-ground. In contrast, conservation science usually assumes that a single organization makes resource allocation decisions. This discrepancy calls for theory to understand how the expected biodiversity outcomes change when interactions between organizations are accounted for. Here, we used a game theoretic model to explore how biodiversity outcomes are affected by vertical and horizontal interactions between 3 conservation organizations: a funder that outsourced its actions and 2 local conservation organizations that work on-the-ground. Interactions between the organizations changed the spending decisions made by individual organizations, and thereby the magnitude and direction of the conservation benefits. We showed that funders would struggle to incentivize recipient organizations with set priorities to perform desired actions, even when they control substantial amounts of the funding and employ common contracting approaches to enhance outcomes. Instead, biodiversity outcomes depended on priority alignment across the organizations. Conservation outcomes for the funder were improved by strategic interactions when organizational priorities were well aligned, but decreased when priorities were misaligned. Meanwhile, local organizations had improved outcomes regardless of alignment due to additional funding in the system. Given that conservation often involves the aggregate actions of multiple organizations with different objectives, strategic interactions between organizations need to be considered if we are to predict possible outcomes of conservation programs or costs of achieving conservation targets.
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ItemPrioritizing eradication actions on islands: it's not all or nothing(WILEY, 2016-06)Summary Many highly diverse island ecosystems across the globe are threatened by invasive species. Eradications of invasive mammals from islands are being attempted with increasing frequency, with success aided by geographical isolation and increasing knowledge of eradication techniques. There have been many attempts to prioritize islands for invasive species eradication; however, these coarse methods all assume managers are unrealistically limited to a single action on each island: either eradicate all invasive mammals, or do nothing. We define a prioritization method that broadens the suite of actions considered, more accurately representing the complex decisions facing managers. We allow the opportunity to only eradicate a subset of invasive mammals from each island, intentionally leaving some invasive mammals on islands. We consider elements often omitted in previous prioritization methods, including feasibility, cost and complex ecological responses (i.e. trophic cascades). Using a case study of Australian islands, we show that for a fixed budget, this method can provide a higher conservation benefit across the whole group of islands. Our prioritization method outperforms simpler methods for almost 80% of the budgets considered. On average, by relaxing the restrictive assumption that an eradication attempt must be made for all invasives on an island, ecological benefit can be improved by 27%. Synthesis and applications. Substantially higher ecological benefits for threatened species can be achieved for no extra cost if conservation planners relax the assumption that eradication projects must target all invasives on an island. It is more efficient to prioritize portfolios of eradication actions rather than islands.
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ItemPlanning Marine Reserve Networks for Both Feature Representation and Demographic Persistence Using Connectivity Patterns(PUBLIC LIBRARY SCIENCE, 2016-05-11)Marine reserve networks must ensure the representation of important conservation features, and also guarantee the persistence of key populations. For many species, designing reserve networks is complicated by the absence or limited availability of spatial and life-history data. This is particularly true for data on larval dispersal, which has only recently become available. However, systematic conservation planning methods currently incorporate demographic processes through unsatisfactory surrogates. There are therefore two key challenges to designing marine reserve networks that achieve feature representation and demographic persistence constraints. First, constructing a method that efficiently incorporates persistence as well as complementary feature representation. Second, incorporating persistence using a mechanistic description of population viability, rather than a proxy such as size or distance. Here we construct a novel systematic conservation planning method that addresses both challenges, and parameterise it to design a hypothetical marine reserve network for fringing coral reefs in the Keppel Islands, Great Barrier Reef, Australia. For this application, we describe how demographic persistence goals can be constructed for an important reef fish species in the region, the bar-cheeked trout (Plectropomus maculatus). We compare reserve networks that are optimally designed for either feature representation or demographic persistence, with a reserve network that achieves both goals simultaneously. As well as being practically applicable, our analyses also provide general insights into marine reserve planning for both representation and demographic persistence. First, persistence constraints for dispersive organisms are likely to be much harder to achieve than representation targets, due to their greater complexity. Second, persistence and representation constraints pull the reserve network design process in divergent directions, making it difficult to efficiently achieve both constraints. Although our method can be readily applied to the data-rich Keppel Islands case study, we finally consider the factors that limit the method's utility in information-poor contexts common in marine conservation.
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ItemPlacing invasive species management in a spatiotemporal context(WILEY, 2016-04)
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ItemCost and feasibility of a barrier to halt the spread of invasive cane toads in arid Australia: incorporating expert knowledge into model-based decision-making(Wiley, 2017-02-01)Summary 1. Active engagement with practitioners is a crucial component of model‐based decision‐making in conservation management; it can assist with data acquisition, improve models and help narrow the ‘knowing–doing’ gap. 2. We worked with practitioners of one of the worst invasive species in Australia, the cane toad Rhinella marina, to revise a model that estimates the effectiveness of landscape barriers to contain spread. The original model predicted that the invasion could be contained by managing artificial watering points on pastoral properties, but was initially met with scepticism by practitioners, in part due to a lack of engagement during model development. 3. We held a workshop with practitioners and experts in cane toad biology. Using structured decision‐making, we elicited concerns about the original model, revised its structure, updated relevant input data, added an economic component and found the most cost‐effective location for a barrier across a range of fixed budgets and management scenarios. We then conducted scenario analyses to test the sensitivity of management decisions to model revisions. 4. We found that toad spread could be contained for all of the scenarios tested. Our modelling suggests a barrier could cost $4·5 M (2015 AUD) over 50 years for the most likely landscape scenario. The incorporation of practitioner knowledge into the model was crucial. As well as improving engagement, when we incorporated practitioner concerns (particularly regarding the effects of irrigation and dwellings on toad spread), we found a different location for the optimal barrier compared to a previously published study (Tingley et al. 2013). 5. Synthesis and applications. Through engagement with practitioners, we turned an academic modelling exercise into a decision‐support tool that integrated local information, and considered more realistic scenarios and constraints. Active engagement with practitioners led to productive revisions of a model that estimates the effectiveness of a landscape barrier to contain spread of the invasive cane toad R. marina. Benefits also include greater confidence in model predictions, improving our assessment of the cost and feasibility of containing the spread of toads.
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ItemDynamic Programming(Springer Berlin Heidelberg, 2015)
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ItemTranslocation strategies for multiple species depend on interspecific interaction type(WILEY, 2016-06)Conservation translocations, anthropogenic movements of species to prevent their extinction, have increased substantially over the last few decades. Although multiple species are frequently moved to the same location, current translocation guidelines consider species in isolation. This practice ignores important interspecific interactions and thereby risks translocation failure. We model three different two-species systems to illustrate the inherent complexity of multispecies translocations and to assess the influence of different interaction types (consumer-resource, mutualism, and competition) on translocation strategies. We focus on how these different interaction types influence the optimal founder population sizes for successful translocations and the order in which the species are moved (simultaneous or sequential). Further, we assess the effect of interaction strength in simultaneous translocations and the time delay between translocations when moving two species sequentially. Our results show that translocation decisions need to reflect the type of interaction. While all translocations of interacting species require a minimum founder population size, which is demarked by an extinction boundary, consumer-resource translocations also have a maximum founder population limit. Above the minimum founder size, increasing the number of translocated individuals leads to a substantial increase in the extinction boundary of competitors and consumers, but not of mutualists. Competitive and consumer-resource systems benefit from sequential translocations, but the order of translocations does not change the outcomes for mutualistic interaction partners noticeably. Interspecific interactions are important processes that shape population dynamics and should therefore be incorporated into the quantitative planning of multispecies translocations. Our findings apply whenever interacting species are moved, for example, in reintroductions, conservation introductions, biological control, or ecosystem restoration.
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ItemA conservation planning approach to mitigate the impacts of leakage from protected area networks(WILEY, 2015-06)Protected area networks are designed to restrict anthropogenic pressures in areas of high biodiversity. Resource users respond by seeking to replace some or all of the lost resources from locations elsewhere in the landscape. Protected area networks thereby perturb the pattern of human pressures by displacing extractive effort from within protected areas into the broader landscape, a process known as leakage. The negative effects of leakage on conservation outcomes have been empirically documented and modeled using homogeneous descriptions of conservation landscapes. Human resource use and biodiversity vary greatly in space, however, and a theory of leakage must describe how this heterogeneity affects the magnitude, pattern, and biodiversity impacts of leakage. We combined models of household utility, adaptive human foraging, and biodiversity conservation to provide a bioeconomic model of leakage that accounts for spatial heterogeneity. Leakage had strong and divergent impacts on the performance of protected area networks, undermining biodiversity benefits but mitigating the negative impacts on local resource users. When leakage was present, our model showed that poorly designed protected area networks resulted in a substantial net loss of biodiversity. However, the effects of leakage can be mitigated if they are incorporated ex-ante into the conservation planning process. If protected areas are coupled with nonreserve policy instruments such as market subsidies, our model shows that the trade-offs between biodiversity and human well-being can be further and more directly reduced.
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