Cameron S. Fletcher

Housing shadow prices in an inundation-prone suburb

For flood-prone urban areas, the prospect of increasing population densities and more frequent extreme weather associated with climate change is alarming. Proactive adaptation can reduce potential flood risks in theory. However, there is limited empirical economics exploring this issue, without which convincing residents within exposed areas to participate in adaptation is challenging. In this paper, a hedonic model is presented of property prices for a flood-prone inner-city suburb of Brisbane, Australia. The study defines a continuous flood-risk variable based on the vertical distances of properties relative to a flood level that occurs on average once every 100 years. The results show significant property-price discounting of 5.5 per cent per metre below the defined flood level. Detailed hedonic characteristics also provided shadow price estimates of housing characteristics and distances to amenities (such as bus-stops, train-stations, parks and bikeways) and these hedonics need to be considered when holistically assessing the dynamics of suburbs for adaptation planning.

Global Lessons for Adapting Coastal Communities to Protect against Storm Surge Inundation

ABSTRACT Harman, B.P.; Heyenga, S.; Taylor, B.M., and Fletcher, C.S. 2015. Global lessons for adapting coastal communities to protect against storm surge inundation. Coastal inundation as a result of global sea-level rise and storm surge events is expected to affect many coastal regions and settlements. Adaptation is widely accepted as necessary for managing inundation risk. However, managing inundation risk is inherently contentious because of many uncertainties and because a large number of stakeholder interests and values are mobilised. For these reasons, among others, adaptation progress in many countries has been slow. Despite progress in adaptation research, a critical knowledge gap remains regarding the appropriateness and applicability of various adaptation options, including their transferability between different coastal settings. We review the international literature on coastal adaptation options (including options to defend, accommodate, or retreat) to manage inundation risk, focusing on developed, liberal economies of Western Europe, North America, the U.K., Australia, and New Zealand. In doing so, we identify the favoured strategies adopted by these nations, probe the influence of physical and institutional context on the selection of these options, and identify what lessons might be exchanged or future directions inferred. The review places particular emphasis on the Australian experience as a comparative device to highlight some important distinctions. These distinctions focus on how government responsibility is exercised, including the degree of centralisation; the “fit” of options to local coastal environments and social values (i.e. their suitability and acceptability); and the transferability of different adaptation options in international contexts.

Dispersal and the design of effective management strategies for plant invasions: matching scales for success.

Dispersal of propagules makes invasions a fundamentally spatial phenomenon, and to be effective, management actions to control or eradicate invasive species must take this spatial structure into account. While there is a vibrant literature linking detailed dispersal measurements to the rate of invasive spread, and a separate literature focused on incorporating management into invasive models in order to improve the control of weeds, there are relatively fewer manuscripts incorporating state-of-the-art dispersal modeling and management modeling together to provide on-ground recommendations for structuring effective management. In this paper, we perform a generalized analysis of a spatially explicit, individual-based simulation model of invasion management with empirically determined dispersal processes, illustrated with the example of Miconia calvescens in the Australian Wet Tropics rain forest, to explore how matching the spatial scale of management to the spatial scale of the dispersal processes underpinning invasion influences the success of management. We find that management strategies designed to maximize the number of weeds removed from the management region, either in the first year of management or over longer periods, provide a poor estimate of the spatial scale of management that maximizes the probability of eradication. We show that achieving a goal of certainty of eradication requires exceeding a minimal spatial scale of management and total management resourcing. We generalize these results to examine how the spatial scale of dispersal drives the spatial scale of effective management strategies. These results show that to be effective, management of dispersal-driven invasions must occur at spatial scales determined by the scale of dispersal processes, and resourced accordingly. It illustrates how those scales might be calculated for a specific case for which detailed dispersal data are available and generalizes the result to highlight how dispersal scale drives the scale of effective management. The results highlight the importance of understanding the ecological drivers of invasion to structure effective management.

Hedonic Imputed Property Price Indexes: The Effects of Econometric Modeling Choices

In this paper we consider how choices in the econometric approach to impute prices affect the Tornqvist and Jevons hedonic imputed indexes. We compare the rolling window approach to estimation by smoothing methods. The main difference between the rolling window and the smoothing methods is in the way information is weighted. We propose that the Kalman filter smoother is the most appropriate estimator for the task as it optimally weights current and past information. We show the rolling window approach does not produce estimates that are attenuated over time leading to chain drift in the index. We also compare two alternative specifications to model property location. The empirical section uses data from a small and homogeneous market in the state of Queensland, Australia. The Tornqvist and Jevons indexes differ in value during periods of market volatility. This seems expected given their different weighting of transactions and the likelihood that price movements of properties at the upper and lower end of the price distribution might differ during periods of market volatility.

Assessment of monitoring power for highly mobile vertebrates

Monitoring of population trends is a critical component of conservation management, and development of practical methods remains a priority, particularly for species that challenge more standard approaches. We used field-parameterized simulation models to examine the effects of different errors on monitoring power and compared alternative methods used with two species of threatened pteropodids (flying-foxes), Pteropus conspicillatus and P. poliocephalus, whose mobility violates assumptions of closure on short and long timescales. The influence of three errors on time to 80% statistical power was assessed using a Monte Carlo approach. The errors were: (1) failure to count all animals at a roost, (2) errors associated with enumeration, and (3) variability in the proportion of the population counted due to the movement of individuals between roosts. Even with perfect accuracy and precision for these errors only marginal improvements in power accrued (-1%), with one exception. Improving certainty in the proportion of the population being counted reduced time to detection of a decline by over 6 yr (43%) for fly-out counts and almost 10 yr (71%) for walk-through counts. This error derives from the movement of animals between known and unknown roost sites, violating assumptions of population closure, and because it applies to the entire population, it dominates all other sources of error. Similar errors will accrue in monitoring of a wide variety of highly mobile species and will also result from population redistribution under climate change. The greatest improvements in monitoring performance of highly mobile species accrue through an improved understanding of the proportion of the population being counted, and consequently monitoring of such species must be done at the scale of the species or population range, not at the local level.

Managing breaches of containment and eradication of invasive plant populations.

Containment can be a viable strategy for managing invasive plants, but it is not always cheaper than eradication. In many cases, converting a failed eradication programme to a containment programme is not economically justified. Despite this, many contemporary invasive plant management strategies invoke containment as a fallback for failed eradication, often without detailing how containment would be implemented. We demonstrate a generalized analysis of the costs of eradication and containment, applicable to any plant invasion for which infestation size, dispersal distance, seed bank lifetime and the economic discount rate are specified. We estimate the costs of adapting eradication and containment in response to six types of breach and calculate under what conditions containment may provide a valid fallback to a breached eradication programme. We provide simple, general formulae and plots that can be applied to any invasion and show that containment will be cheaper than eradication only when the size of the occupied zone exceeds a multiple of the dispersal distance determined by seed bank longevity and the discount rate. Containment becomes proportionally cheaper than eradication for invaders with smaller dispersal distances, longer lived seed banks, or for larger discount rates. Both containment and eradication programmes are at risk of breach. Containment is less exposed to risk from reproduction in the ‘occupied zone’ and three types of breach that lead to a larger ‘occupied zone’, but more exposed to one type of breach that leads to a larger ‘buffer zone’. For a well-specified eradication programme, only the three types of breach leading to reproduction in or just outside the buffer zone can justify falling back to containment, and only if the expected costs of eradication and containment were comparable before the breach. Synthesis and applications. Weed management plans must apply a consistent definition of containment and provide sufficient implementation detail to assess its feasibility. If the infestation extent, dispersal capacity, seed bank longevity and economic discount rate are specified, the general results presented here can be used to assess whether containment can outperform eradication, and under what conditions it would provide a valid fallback to a breached eradication programme.

Body size and substrate type modulate movement by the western Pacific crown-of-thorns starfish, Acanthaster solaris

The movement capacity of the crown-of-thorns starfishes (Acanthaster spp.) is a primary determinant of both their distribution and impact on coral assemblages. We quantified individual movement rates for the Pacific crown-of-thorns starfish (Acanthaster solaris) ranging in size from 75–480 mm total diameter, across three different substrates (sand, flat consolidated pavement, and coral rubble) on the northern Great Barrier Reef. The mean (±SE) rate of movement for smaller (<150 mm total diameter) A. solaris was 23.99 ± 1.02 cm/ min and 33.41 ± 1.49 cm/ min for individuals >350 mm total diameter. Mean (±SE) rates of movement varied with substrate type, being much higher on sand (36.53 ± 1.31 cm/ min) compared to consolidated pavement (28.04 ± 1.15 cm/ min) and slowest across coral rubble (17.25 ± 0.63 cm/ min). If average rates of movement measured here can be sustained, in combination with strong directionality, displacement distances of adult A. solaris could range from 250–520 m/ day, depending on the prevailing substrate. Sustained movement of A. solaris is, however, likely to be highly constrained by habitat heterogeneity, energetic constraints, resource availability, and diurnal patterns of activity, thereby limiting their capacity to move between reefs or habitats.