Summary1. Drylands support over 2 billion people and are major providers of critical ecosystem goods and services across the globe. Drylands, however, are one of the most susceptible biomes to degradation. International programmes widely recognize dryland restoration as key to combating global dryland degradation and ensuring future global sustainability. While the need to restore drylands is widely recognized and large amounts of resources are allocated to these activities, rates of restoration success remain overwhelmingly low. 2. Advances in understanding the ecology of dryland systems have not yielded proportional advances in our ability to restore these systems. To accelerate progress in dryland restoration, we argue for moving the field of restoration ecology beyond conceptual frameworks of ecosystem dynamics and towards quantitative, predictive systems models that capture the probabilistic nature of ecosystem response to management. 3. To do this, we first provide an overview of conceptual dryland restoration frameworks. We then describe how quantitative systems framework can advance and improve conceptual restoration frameworks, resulting in a greater ability to forecast restoration outcomes and evaluate economic efficiency and decision-making. Lastly, using a case study from the western United States, we show how a systems approach can be integrated with and used to advance current conceptual frameworks of dryland restoration. 4. Synthesis and applications. Systems models for restoration do not replace conceptual models but complement and extend these modelling approaches by enhancing our ability to solve restoration problems and forecast outcomes under changing conditions. Such forecasting of future outcomes is necessary to monetize restoration benefits and cost and to maximize economic benefit of limited restoration dollars.

This article develops a two-factor real options model of the harvesting decision over infinite rotations assuming a known stochastic price process and using a rigorous Hamilton-Jacobi-Bellman methodology. The harvesting problem is formulated as a linear complementarity problem that is solved numerically using a fully implicit finite difference method. This approach is contrasted with the Markov decision process models commonly used in the literature. The model is used to estimate the value of a representative stand in Ontario's boreal forest, both when there is complete flexibility regarding harvesting time and when regulations dictate the harvesting date. Copyright 2005, Oxford University Press.

This study addresses the debate over sensitivity of existence values as measured by contingent valuation to the scope of the good. We reconcile much of the debate within one theoretical model. If marginal WTP for existence goods is diminishing, then a given study that tested for sensitivity to scope over a range for which marginal WTP is high would be more likely to detect sensitivity to scope than another similar study that focused on a range for which marginal WTP is much lower. An empirical model is developed to demonstrate this point. The study finds that the existence value of remote wilderness parks are sensitive to scope, but that differences in WTP for given pro ortionate changes in scope vary over the WTP curve in a way consistent with diminishing marginal WTP...These results have significant implications for future contingent valuation work.-The Case .for Diminishing Marginal Existence Values This paper contributes to the debate over the use of contingent valuation to measure existence values. In the debates over environmental damage assessment, there has been much disagreement over the extent to which non-users of a compromised resource suffer economic damages [11, 16, 2, 5]. The sensitivity of measured existence values to changes in the size of scope of the good has been called into 'question [1, 3, 6, 14]. A number of studies have investigated the issue of insensitivity to scope [13, 4, 17, 18, 15], conducting empirical tests and proposing theoretical explanations. Much of the empirical literature focuses on whether or not existence values as estimated by CV are sensitive to scope of the existence good in question [3, 4, 5, 18]. For example in a study of migratory waterfowl deaths, Boyle et al [3] found insensitivity to scope of migratory waterfowl deaths for 2% or less of waterfowl populations, and recommended further research to investigate the measurement of the value of small changes in the provision of environmental goods. Much of the literature that interprets the implications of the debate do so in terms of the reliability of CV to measure existence values. Diamond and Hausman [7] review a number of CV studies that are not sensitive to scope and conclude that because individuals may not be able to distinguish between goods of different scope, reliability of CV estimates of existence values are suspect. In their study of the value of the 49th and 50th parks out of a system of 57 wilderness parks, McFadden and Leonard [14] conclude that CV estimates are not sensitive to scope in the case of unfamiliar and remote wilderness areas. Carson 141 reviews over 30 tests in which CV estimates are sensitive to scope and concludes that CV can produce reliable estimates in well constructed studies. Smith and Osborne [18] used a metaLanalysis of past CV studies to conclude that estimates of the values of changes in visibility are sensitive to scope, and that similar analysis could be used to determine the reliability of existence values for other goods. A number of papers have been concerned with how to devi...

In this article we develop a simulation model to evaluate the economic efficiency of fuel treatments and apply it to two sagebrush ecosystems in the Great Basin of the western United States: the Wyoming Sagebrush Steppe and Mountain Big Sagebrush ecosystems. These ecosystems face the two most prominent concerns in sagebrush ecosystems relative to wildfire: annual grass invasion and native conifer expansion. Our model simulates long-run wildfire suppression costs with and without fuel treatments explicitly incorporating ecological dynamics, stochastic wildfire, uncertain fuel treatment success, and ecological thresholds. Our results indicate that, on the basis of wildfire suppression costs savings, fuel treatment is economically efficient only when the two ecosystems are in relatively good ecological health. We also investigate how shorter wildfire-return intervals, improved treatment success rates, and uncertainty about the location of thresholds between ecological states influence the economic efficiency of fuel treatments.

Predation has an important influence on life history traits in many organisms, especially when they are young. When cues of trout were present, juvenile sticklebacks grew faster. The increase in body size as a result of exposure to cues of predators was adaptive because larger individuals were more likely to survive predation. However, sticklebacks that had been exposed to cues of predators were smaller at adulthood. This result is consistent with some life history theory. However, these results prompt an alternative hypothesis, which is that the decreased size at adulthood reflects a deferred cost of early rapid growth. Compared to males, females were more likely to survive predation, but female size at adulthood was more affected by cues of predators than male size at adulthood, suggesting that size at adulthood might be more important to male fitness than to female fitness.