Publications

This paper presents a survey of the empirical literature studying the relationship between health outcomes, temperature, and adaptation to temperature extremes. The objectives of the paper are to highlight the many remaining gaps in the empirical literature and to provide guidelines for improving the current Integrated Assessment Model (IAM) literature that seeks to incorporate human health and adaptation in its framework. I begin by presenting the conceptual and methodological issues associated with the measurement of the effect of temperature extremes on health, and the role of adaptation in possibly muting these effects. The main conclusion that emerges from the literature is that despite the wide variety of data sets and settings most studies find that temperature extremes lead to significant reductions in health, generally measured with excess mortality. Regarding the role of adaptation in mitigating the effects of extreme temperature on health, the available knowledge is limited, in part due to the few real-world data sets on adaptation behaviors. Finally, the paper discusses the implications of the currently available evidence for assessments of potential human health impacts of global climate change.

Biological diversity is known to play an important role in generating and maintaining ecosystem productivity and other functions and has consequently become a central focus of many efforts to preserve ecosystem services. Theoretical parallels suggest the diversity of fishing fleets may have a similarly important role in determining the productivity and ecological impacts of fisheries, but this possibility has rarely been explored. Here I present theoretical analyses showing that the diversity of métiers — combinations of technology, target species, and fishing grounds — and technical efficiencies in a fishing fleet have important impacts on the productivity, profitability, and ecological impacts of fisheries, particularly mixed-stock or multispecies fisheries. Diversification of métiers can increase yields and reduce threats to weak stocks in both managed and unmanaged multispecies fisheries. Diversification of technical efficiencies creates opportunities for larger profits in managed fisheries, but often decreases yields and worsens impacts on weak stocks in unmanaged fisheries. These results suggest that the potential impact of management may be highest in fisheries with diverse fleets.

Overfishing and degradation of the marine environment continue to plague coastal communities worldwide, with multiple diverse solutions being proposed. Territorial Use Rights for Fisheries (TURFs) is a fishery management approach that aligns fishers’ incentives with sustainability, while marine reserves have proven effective for ecosystem protection, and in some cases for fishery enhancement. These two management approaches are often used in isolation, leaving the potential utility of integrating them poorly understood. We examine cases where TURFs and marine reserves have been implemented together to create “TURF-reserves”. We compiled a database of 27 TURF-reserves and collected information on the governance, management, enforcement, fishing practices, fishing rights, regulations, and design attributes for each site. We address several research questions including: what species are managed with TURF-reserves, how are TURF-reserves created and who is involved in the process? Our findings show that the majority of surveyed TURF-reserves arose from previously established TURF systems that target a range of fisheries, and multiple entities play a role in TURF-reserve development and management. We also examine the differences between two TURF-reserve archetypes and find that those developed with a strong history of customary tenure share distinct qualities from those created in a more recently established, government-mandated system.

Anthropogenic impacts are increasingly affecting the world's oceans. Networks of marine protected areas (MPAs) provide an option for increasing the ecological and economic benefits often provided by single MPAs. It is vital to empirically assess the effects of MPA networks and to prioritize the monitoring data necessary to explain those effects. We summarize the types of MPA networks based on their intended management outcomes and illustrate a framework for evaluating whether a connectivity network is providing an outcome greater than the sum of individual MPA effects. We use an analysis of an MPA network in Hawai'i to compare networked MPAs to non-networked MPAs to demonstrate results consistent with a network effect. We assert that planning processes for MPA networks should identify their intended outcomes while also employing coupled field monitoring-simulation modeling approaches, a powerful way to prioritize the most relevant monitoring data for empirically assessing MPA network performance.

Environmental certification and consumer awareness programs are designed to create market incentives for implementing fisheries and aquaculture practices that are more sustainable. Typically focused on particular species and activities, such programs have so far triggered few changes to improve seafood sustainability. Here, we present a conceptual, system-wide fisheries and aquaculture certification program designed to recognize and promote change toward more sustainable and resilient seafood production systems. In contrast to previous efforts, this program concentrates on both ecosystems and various human stakeholders, relies on an adaptive management approach (termed “continual improvement”) to enhance outcomes, and considers socioeconomic factors. The goal of this program is to support the restoration and maintenance of healthy ecosystem states and thriving human communities as well as the improvement of whole social–ecological systems.

Marine spatial planning (MSP), whereby areas of the ocean are zoned for different uses, has great potential to reduce or eliminate conflicts between competing management goals, but only if strategically applied. The recent literature overwhelmingly agrees that including stakeholders in these planning processes is critical to success; but, given the countless alternative ways even simple spatial regulations can be configured, how likely is it that a stakeholder-driven process will generate plans that deliver on the promise of MSP? Here, we use a spatially explicit, dynamic bioeconomic model to show that stakeholder-generated plans are doomed to fail in the absence of strong scientific guidance. While strategically placed spatial regulations can improve outcomes remarkably, the vast majority of possible plans fail to achieve this potential. Surprisingly, existing scientific rules of thumb do little to improve outcomes. Here, we develop an alternative approach in which models are used to identify efficient plans, which are then modified by stakeholders. Even if stakeholders alter these initial proposals considerably, results hugely outperform plans guided by scientific rules of thumb. Our results underscore the importance of spatially explicit dynamic models for the management of marine resources and illustrate how such models can be harmoniously integrated into a stakeholder-driven MSP process.

The world's oceans are governed as a system of over 150 sovereign exclusive economic zones (EEZs, ∼42% of the ocean) and one large high seas (HS) commons (∼58% of ocean) with essentially open access. Many high-valued fish species such as tuna, billfish, and shark migrate around these large oceanic regions, which as a consequence of competition across EEZs and a global race-to-fish on the HS, have been over-exploited and now return far less than their economic potential. We address this global challenge by analyzing with a spatial bioeconomic model the effects of completely closing the HS to fishing. This policy both induces cooperation among countries in the exploitation of migratory stocks and provides a refuge sufficiently large to recover and maintain these stocks at levels close to those that would maximize fisheries returns. We find that completely closing the HS to fishing would simultaneously give rise to large gains in fisheries profit (>100%), fisheries yields (>30%), and fish stock conservation (>150%). We also find that changing EEZ size may benefit some fisheries; nonetheless, a complete closure of the HS still returns larger fishery and conservation outcomes than does a HS open to fishing.

The argument persists that the continued overexploitation by many fisheries around the world is evidence that current approaches to fisheries management are failing, and that more precautionary management approaches are needed. We review the available estimates of the status of fish stocks from three sources: the FAO's “State of Marine Resources”, a database on scientific stock assessments, and recent estimates from statistical models designed to determine the status of unassessed fish stocks. The two key results are (i) that stocks that are scientifically assessed are in better shape and indeed are not typically declining but rebuilding, and (ii) that large stocks appear to be in better shape than small stocks. These results support the view that stocks that are managed are improving, while stocks that are not managed are not. Large stocks receive far more management attention than small stocks in jurisdictions that have active fisheries management systems, and most unassessed stocks are simply not managed. We assert that fisheries management as currently practised can (and often does) lead to sustainable fisheries, and what is needed is to actively manage the unassessed fisheries of the world. More precautionary management is not necessarily needed to ensure the sustainability of managed fisheries.

A recent study by Burke et al. [Burke M, Miguel E, Satyanath S, Dykema J, Lobell D (2009) Proc Natl Acad Sci USA 106(49):20670–20674] reports statistical evidence that the likelihood of civil wars in African countries was elevated in hotter years. A following study by Buhaug [Buhaug H (2010) Proc Natl Acad Sci USA 107(38):16477–16482] reports that a reexamination of the evidence overturns Burke et al.’s findings when alternative statistical models and alternative measures of conflict are used. We show that the conclusion by Buhaug is based on absent or incorrect statistical tests, both in model selection and in the comparison of results with Burke et al. When we implement the correct tests, we find there is no evidence presented in Buhaug that rejects the original results of Burke et al.

Chondrichthyans—the class of fish that includes sharks and rays—are in a bad, bad way. Their numbers have plummeted, mostly due to overfishing, which is largely driven by the demand for shark fin soup (Jackson et al., 2001; Myers and Worm, 2003). All attempts at saving species have fallen short, not because of a lack of concern, but instead because of a lack of data. It is difficult to know just how depleted sharks and rays are in number, just as it is difficult to determine how and where conservation efforts are most desperately needed. This is concerning not just for chondrichthyans, but also for entire ecosystems, because the removal of large-bodied predators, such as sharks, can cause entire food webs to collapse (Stevens et al., 2000; Mumby et al., 2006; Heithaus et al., 2008).

To address this knowledge gap, Nicholas Dulvy of Simon Fraser University and co-workers in Canada, UK, USA, Australia, New Zealand and South Africa have performed a systematic evaluation of the relative extinction risk for more than 1000 species of sharks, rays and the less well known chimaeras (Dulvy et al., 2014). Their findings—which have been published in eLife—are alarming, but more importantly, the story they reveal helps to frame the chondrichthyan problem in ways that can help guide effective solutions.

Although market-based incentives have helped resolve many environmental challenges, conservation markets still play a relatively minor role in wildlife management. Establishing property rights for environmental goods and allowing trade between resource extractors and resource conservationists may offer a path forward in conserving charismatic species like whales, wolves, turtles, and sharks. In this paper, we provide a conceptual model for implementing a conservation market for wildlife and evaluate how such a market could be applied to three case studies for whales (minke [Balaenoptera acutorostrata], bowhead [Balaena mysticetus], and gray [Eschrictius robustus]). We show that, if designed and operated properly, such a market could ensure persistence of imperiled populations, while simultaneously improving the welfare of resource harvesters.

We are glad our recent paper in Ecological Applications has stimulated new discussion on the role of conservation markets in wildlife management. In their response, Smith et al. identify four important challenges to implementing a whale conservation market. We agree that the details of market-based policies are important and highlighted several challenges in our paper in the market design for whales. But we believe the challenges highlighted by Smith et al. (and indeed by our own analysis) will be present under any institutional regime and are surmountable in a market with appropriate design. The purpose of our paper was to propose a general framework for how a market for wildlife species such as whales might perform in order to stimulate new thinking on the many complexities associated with a market-based approach. We are delighted that our paper has accomplished this so quickly, and remain enthusiastic about the exciting research ahead.

The overall concern raised by Smith et al. is that, because whales are an impure public good, any policy that fails to capture all nonmarket benefits and potential free riding will lead to a suboptimal outcome. We agree that any approach that ignores nonmarket and external benefits could lead to a suboptimal outcome. Importantly, we never claimed that a conservation market would lead to a socially optimal outcome. Rather, we proposed that it could be Pareto improving (make both sides better off) relative to the status quo. Furthermore, if conservationists purchase all of the shares (which may well occur), then indeed this solution may be socially optimal; an important (and perhaps likely) scenario that Smith et al. failed to recognize. A simple version of the market, which has been mirrored for in-stream flow water rights, is to cap the whale harvest at the current level of take (provided it is biologically safe), and to provide a platform where conservationists can compensate whalers to reduce harvest from that point. If such trade occurs, and we have strong evidence that it could, it would improve the welfare of both sides. More complicated market designs are also possible, and our simulations illustrate several cases. That said, we think the impure public good nature of whales could lead to interesting new research and insights about market design and outcomes (compared to some reasonable counterfactual) in these contexts.

Property rights are commonly touted as a solution to common pool resource problems. In practice, however, the security of property rights over natural resources varies substantially; this may affect returns to ownership and asset values. We use an analytical model to examine the effects of insecure property rights to natural resources on the market value of assets. We then use a unique dataset of fisheries from three countries to examine empirically how differences in property rights affect market outcomes. We find significant asset market capitalization of insecurity arising from (1) ownership disputes, (2) illegal extraction from resource stocks, and (3) the possibility of government revocation of rights.

Increases in the demand and price for industrial metals, combined with advances in technological capabilities have now made deep-sea mining more feasible and economically viable. In order to balance economic interests with the conservation of abyssal plain ecosystems, it is becoming increasingly important to develop a systematic approach to spatial management and zoning of the deep sea. Here, we describe an expert-driven systematic conservation planning process applied to inform science-based recommendations to the International Seabed Authority for a system of deep-sea marine protected areas (MPAs) to safeguard biodiversity and ecosystem function in an abyssal Pacific region targeted for nodule mining (e.g. the Clarion–Clipperton fracture zone, CCZ). Our use of geospatial analysis and expert opinion in forming the recommendations allowed us to stratify the proposed network by biophysical gradients, maximize the number of biologically unique seamounts within each subregion, and minimize socioeconomic impacts. The resulting proposal for an MPA network (nine replicate 400 × 400 km MPAs) covers 24% (1 440 000 km²) of the total CCZ planning region and serves as example of swift and pre-emptive conservation planning across an unprecedented area in the deep sea. As pressure from resource extraction increases in the future, the scientific guiding principles outlined in this research can serve as a basis for collaborative international approaches to ocean management.

Widespread concern over global fish stocks has prompted an increase in research and initiatives aimed at rebuilding ailing fisheries and incentivizing sustainable fishing practices. This promising focus on solutions coincides with a burgeoning consumer and retailer demand for environmentally friendly products (Figure 1). Sustainability certification, labeling, and consumer guides (e.g., Marine Stewardship Council, Fair Trade, Seafood Watch, etc.) are signals that help eco-minded consumers identify products that meet their standards. Accurate signals offer an immense opportunity to incentivize sustainability, increasing demand and profits for sustainable producers. Yet, while the growing number of seafood certification programs and consumer seafood guides fuel and inform demand, the pace of change is slow. One key barrier to progress is the significant lag between the implementation of reforms and the recovery of fish stocks. Without preemptive credits within certification protocols for conservation actions that can be expected to benefit the stock over time, the incentives for reforms may be limited.

Many potential conservation reforms could qualify for preemptive credit, but the most conspicuous absence is the lack of credit for marine protected areas (MPAs). Marine protected areas are one of the most important tools for conserving the ocean's ecosystems. MPAs, similar to protected areas on land, are locations where regulations prohibit specific human activities. There has been considerable research about the effects of MPAs, particularly focused on a common class of MPAs in which all fishing is prohibited (no-take marine reserves). Studies from more than 120 no-take marine reserves around the world consistently reveal the conservation benefits of this type of protection, including higher total biomass, abundance, and average size of fish within reserves [1] (Figure 2). The data from these many existing MPAs, combined with improving spatial fisheries models, allow us to predict an MPA's future conservation benefits long before they are realized. Such empirically based model forecasts could be used to assign preemptive credit for MPAs within certification frameworks when the MPA is implemented. Doing so would reward existing MPAs for their contributions to sustainable fisheries and would provide more powerful short-term incentives to create well-designed new MPAs.

In the past decade, the study of dispersal of marine organisms has shifted from focusing predominantly on the larval stage to a recent interest in adult movement. Antitropical distributions provide a unique system to assess vagility and dispersal. In this study, we have focused on an antitropical wrasse genus, Semicossyphus, which includes the California sheephead, S. pulcher, and Darwin's sheephead, S. darwini. Using a phylogenetic approach based on mitochondrial and nuclear markers, and a population genetic approach based on mitochondrial control region sequences and 10 microsatellite loci, we compared the phylogenetic relationships of these two species, as well as the population genetic characteristics within S. pulcher. While S. pulcher and S. darwini are found in the temperate eastern Pacific regions of the northern and southern hemispheres, respectively, their genetic divergence was very small (estimated to have occurred between 200 and 600 kya). Within S. pulcher, genetic structuring was generally weak, especially along mainland California, but showed weak differentiation between Sea of Cortez and California, and between mainland California and Channel Islands. We highlight the congruence of weak genetic differentiation both within and between species and discuss possible causes for maintenance of high gene flow. In particular, we argue that deep and cooler water refugia are used as stepping stones to connect distant populations, resulting in low levels of genetic differentiation.

When sustainably managed, wild harvestsfrom the sea provide livelihoods and a vitalsource of protein for hundreds of millions ofpeople (1, 2). If managed well, these benefitsare perpetually renewable. However, numer-ous challenges can compromise the sustain-ability of this natural bounty. Ironically,a significant challenge arises because of thediversity of species caught in nearly all fish-eries. Although healthy diverse ecosystemscan provide resilience against some perturba-tions, fishing pressure in these ecosystems isalmost always geared to the strongest, mosteconomically valuable stocks. In the processof fishing, many other species are incidentallycaught including both (i) species that nobodywants to catch but are costly to avoid, com-monly called bycatch, and (ii) species withsubstantially lower economic value than tar-geted, highline stocks. Even when the targetstock is perfectly managed, these incidentallycaught stocks can collapse if their life historytraits make them more susceptible to a givenlevel of fishing effort than target species.Without regular monitoring and strong man-agement of all species, these weak stocks mayforce the closure of otherwise highly profit-able fisheries. One solution is to expand sci-entific assessments to all species affected byeach fishery, but this is prohibitively expen-sive. Fish are expensive to monitor, and asa result, even the majority of target speciesare currently not adequately assessed world-wide (3). Solving the weak stock problemrequires new innovation. In PNAS, Burgesset al. (4) offer a unique forecasting tool toinnovatively address this global challenge.If the looming collapse of overfished weakstocks could be foreseen well in advance, theenvironmental and economic costs of elimi-nating the problem before it occurs may be farless than the costs of restoring overharvestedspecies after the fact. Overharvesting weakstocks or bycatch species often triggers a reg-ulatory shutdown of the entire fishery to allowrebuilding (5). This rebuilding can last formany decades, because the life history traitsthat put the species at risk also mean that theirrecovery will be exceedingly slow. For exam-ple, weak stocks such as yelloweye rockfish inthe highly diverse rockfish assemblage alongthe west coast of the United States only standsa 50% chance of recovery by 2047, despitesignificant reductions in fishing pressure (6).

A recent highly cited paper from this journal develops a model predicting maximum sustainable yield (MSY) of a fishery using the historical maximum catch (MaxCatch). The model is parameterized with a small sample of fisheries from the United States, and is subsequently applied globally to estimate the benefits of fishery recovery. That empirical relationship has been adopted for many subsequent high-profile analyses. Unfortunately, the analysis suffers from two important oversights: (1) because the model is non-linear, it suffers from “retransformation bias” and therefore the results significantly understate MSY and (2) the analysis is parameterized from of a very limited data set and so generalizability of the fitted empirical relationship between MSY and MaxCatch to global fisheries is questionable. Here, we rectify both oversights and provide an updated estimate of the relationship between MSY and MaxCatch.

While detrital material is recognized as an important food source on coral reefs, its role in reef food webs remains unclear. We quantified standing stock and input rates to the detrital resource pool in exposed forereef and protected backreef habitats of Palmyra Atoll National Wildlife Refuge and measured the trophic structure of the overlying fish assemblage. While detrital standing stock was 1.6 times higher on the backreef than on the forereef, detrital input rates were 1.7 to 2.9 times higher on the forereef. Planktivores were the most abundant guild in the forereef habitat, and stable isotope signatures of detritus reflected a greater input from pelagic sources (i.e. depleted in ¹³C). In contrast, herbivores and detritivores numerically dominated the backreef habitat and detrital stable isotope signatures appeared to be predominately of benthic origin (i.e. enriched in ¹³C). Through total organic carbon (TOC) and nitrogen analyses we found that benthic detritus may represent a significant nutritional source. Converting total nitrogen into maximum protein estimates, we found high benthic deposition of protein (104 to 124 mg m^-2 d^-1) and organic carbon (184 to 190 mg m^-2 d^-1), but very low standing stocks of these materials (protein: 5 to 6 mg m^-2, organic carbon: 46 to 63 mg m^-2). While high water flow rates may explain low standing stocks of detritus in forereef habitats, the lower flow rates in backreef habitats suggest that removal of this material is via consumption by abundant roving detritivorous fishes. Our results provide support for the hypothesis that reef fish detritivory represents a significant consumer-mediated energy pathway, promoting nutrient recycling by linking many elements of a complex food web.

Managers are moving from a model of managing individual sectors, human activities, or ecosystem services to an ecosystem-based management (EBM) approach which attempts to balance the range of services provided by ecosystems. Applying EBM is often difficult due to inherent tradeoffs in managing for different services. This challenge particularly holds for estuarine systems, which have been heavily altered in most regions and are often subject to intense management interventions. Estuarine managers can often choose among a range of management tactics to enhance a particular service; although some management actions will result in strong tradeoffs, others may enhance multiple services simultaneously. Management of estuarine ecosystems could be improved by distinguishing between optimal management actions for enhancing multiple services and those that have severe tradeoffs. This requires a framework that evaluates tradeoff scenarios and identifies management actions likely to benefit multiple services. We created a management action-services matrix as a first step towards assessing tradeoffs and providing managers with a decision support tool. We found that management actions that restored or enhanced natural vegetation (e.g., salt marsh and mangroves) and some shellfish (particularly oysters and oyster reef habitat) benefited multiple services. In contrast, management actions such as desalination, salt pond creation, sand mining, and large container shipping had large net negative effects on several of the other services considered in the matrix. Our framework provides resource managers a simple way to inform EBM decisions and can also be used as a first step in more sophisticated approaches that model service delivery.