Kate J. Helmstedt

Cost-efficient fenced reserves for conservation: single large or two small?

Fences that exclude alien invasive species are used to reduce predation pressure on reintroduced threatened wildlife. Planning these continuously managed systems of reserves raises an important extension of the Single Large or Several Small (SLOSS) reserve planning framework: the added complexity of ongoing management. We investigate the long-term cost-efficiency of a single large or two small predator exclusion fences in the arid Australian context of reintroducing bilbies Macrotis lagotis, and we highlight the broader significance of our results with sensitivity analysis. A single fence more frequently results in a much larger net cost than two smaller fences. We find that the cost-efficiency of two fences is robust to strong demographic and environmental uncertainty, which can help managers to mitigate the risk of incurring high costs over the entire life of the project.

Interior fences can reduce cost and uncertainty when eradicating invasive species from large islands

Summary The conservation of many threatened species can be advanced by the eradication of alien invasive animals from islands. However, island eradications are an expensive, difficult and uncertain undertaking. An increasingly common eradication strategy is the construction of ‘interior fences’ to partition islands into smaller, independent eradication regions that can be treated sequentially or concurrently. Proponents argue that, while interior fences incur substantial up front construction costs, they reduce overall eradication costs. However, this hypothesis lacks an explicit theoretical or empirical justification. We formulate a general theory that relates the number of interior fences to the magnitude and variation of the economic cost of island eradication. We use this theory to explore the conditions under which interior fences represent a defensible management strategy, under cost and risk minimisation objectives. We then specifically consider the forthcoming eradication of cats Felis catus from Dirk Hartog Island, Western Australia, by parameterising our general theory using published data on the cost and success of previous projects. Our results predict that under a wide range of reasonable conditions, interior fences can reduce the expected cost of a successful invasive alien animal eradication from large islands. On Dirk Hartog Island, interior fences will marginally reduce eradication costs, with two fences reducing expected costs by 3%. Interior fences have a much more substantial effect on the variability of eradication costs: two fences reduce the width of the 95% confidence bounds by more than one-third and halve the size of the average project cost overrun/underrun. Our results reveal that the construction of interior fences is a defensible management strategy for eradicating alien invasive species from islands. However, the primary benefit of interior fences will be risk management, rather than a reduction in expected project costs.

Abiotic and biotic interactions determine whether increased colonization is beneficial or detrimental to metapopulation management.

Increasing the colonization rate of metapopulations can improve persistence, but can also increase exposure to threats. To make good decisions, managers must understand whether increased colonization is beneficial or detrimental to metapopulation persistence. While a number of studies have examined interactions between metapopulations, colonization, and threats, they have assumed that threat dynamics respond linearly to changes in colonization. Here, we determined when to increase colonization while explicitly accounting for non-linear dependencies between a metapopulation and its threats. We developed patch occupancy metapopulation models for species susceptible to abiotic, generalist, and specialist threats and modeled the total derivative of the equilibrium proportion of patches occupied by each metapopulation with respect to the colonization rate. By using the total derivative, we developed a rule for determining when to increase metapopulation colonization. This rule was applied to a simulated metapopulation where the dynamics of each threat responded to increased colonization following a power function. Before modifying colonization, we show that managers must understand: (1) whether a metapopulation is susceptible to a threat; (2) the type of threat acting on a metapopulation; (3) which component of threat dynamics might depend on colonization, and; (4) the likely response of a threat-dependent variable to changes in colonization. The sensitivity of management decisions to these interactions increases uncertainty in conservation planning decisions.

Innovating at the food, water, and energy interface

Food, energy, and water (FEW) systems are inexorably linked. Earths changing climate and increasing competition for finite land resources are creating and amplifying challenges at the FEW nexus. Managing FEW systems to mitigate these negative impacts and stresses is a pressing policy issue. The FEW interface is often managed as three independent systems, missing disruptive opportunities for streamlined integrated management. We contend that existing technologies can be reframed and emerging technologies can be harnessed for integrated FEW management, changing the way that each resource system operates within the broader system. We discuss solutions to three main challenges to integrating FEW system management: resolving spatiotemporal disconnections over multiple scales; closing resource loops; and creating actionable information. Sustainable resource management is critical for humanity, as well as for functioning trade systems and ecological health. Embracing integrated management in FEW systems would enable policy makers and managers to more efficiently and effectively secure critical resource systems in the face of global change.

Improving private land conservation with outcome‐based biodiversity payments

1. Payments to private landholders for providing biodiversity land can improve conservation outside protected areas. Input-based payments are widely used despite evidence they are often ineffective at improving biodiversity outcomes. Meanwhile little has been done to assess how to use outcome-based payments to maximize biodiversity, despite growing academic interest. We compare different outcome-based allocation methods to assess which returns the greatest benefits for biodiversity. 2. We predicted the likely landholder actions in response to outcome-based payments. We incorporated strategic interactions between landholders under four different funding allocation methods: the commonly applied “set-price” allocation method; capacity-based payments; proportional payment; and payment for change. We compared biodiversity outcomes (percentage change in abundance of a species of conservation interest), return on investment and cost-effectiveness of each method. 3. The set-price allocation method, despite its common usage, is the least cost-effective method that we test. Regardless of cost, it only results in better biodiversity outcomes than other methods under a very narrow range of conditions (high initial target species abundance and low profitability). 4. The profitability of the property, and to a lesser degree initial population size, will influence which allocation method will perform best. Most perform well when the initial population of the species of conservation interest is very small and profitability negligible. Only one method – based on change in population – performs well across all scenarios. This method outperforms the others particularly when the property has a higher profitability and low initial numbers of animals. 5. Policy implications. Pursuing conservation on private land using outcome-based payments for biodiversity can result in varied levels of success depending on the allocation methods used to support payment decisions. Allocation method choice should be based on a transparent analysis that incorporates both the dynamics of the ecological system and interactions between individual landholders. This analysis can guide adoption of funding allocation methods that greatly increase biodiversity outcomes.

Two Approximate Dynamic Programming Algorithms for Managing Complete SIS Networks

Inspired by the problem of best managing the invasive mosquito Aedes albopictus across the 17 Torres Straits islands of Australia, we aim at solving a Markov decision process on large Susceptible-Infected-Susceptible (SIS) networks that are highly connected. While dynamic programming approaches can solve sequential decision-making problems on sparsely connected networks, these approaches are intractable for highly connected networks. Inspired by our case study, we focus on problems where the probability of nodes changing state is low and propose two approximate dynamic programming approaches. The first approach is a modified version of value iteration where only those future states that are similar to the current state are accounted for. The second approach models the state space as continuous instead of binary, with an on-line algorithm that takes advantage of Bellmans adapted equation. We evaluate the resulting policies through simulations and provide a priority order to manage the 17 infested Torres Strait islands. Both algorithms show promise, with the continuous state approach being able to scale up to high dimensionality (50 nodes). This work provides a successful example of how AI algorithms can be designed to tackle challenging computational sustainability problems.

Valuable habitat and low deforestation can reduce biodiversity gains from development rights markets

1.Illegal private land deforestation threatens global biodiversity, even in areas with native habitat requirements stipulated by law. Compliance can be improved by allowing landholders to meet legal reserve requirements by buying and selling the rights to have deforested land through a Tradeable Development Rights system (TDR). While this policy mechanism may prevent native habitat area loss, the spatial pattern of reserved areas will shift, creating novel landscape patterns. The resulting altered fragmentation and connectivity of habitat will impact biodiversity. TDR may also allow landholders to earn rent on land they never intended on converting, resulting in additional deforestation elsewhere and net habitat loss. 2.We construct a simulation model to explore the potential implications for biodiversity when development rights can be traded, compared with the landscape resulting from enforced individual compliance with deforestation laws. 3.We find that where future deforestation is very likely, a TDR market can provide better outcomes for both biodiversity and agriculture, resulting in more connected habitat networks with larger fragments and fewer edge effects. However, the TDR market can be harmful if future deforestation is unlikely, or if one habitat type is tightly spatially correlated with high economic returns from agriculture. 4.Policy implications. Allowing landholders to buy and sell the rights to keep more cleared land than legally stipulated will result in transformed multi-use landscapes. Losses of native habitat in some areas will be offset in others. We conclude that trading forest development rights has the potential to improve habitat configurations, but that careful consideration should be given to current species distributions and likely future deforestation scenarios.