Publications

As the cruise ship industry moves towards ever larger vessels, many tourist destinations are faced with dilemmas about how to accommodate the latest generation of ships, which require deeper and wider shipping pathways. The location of nearshore shipping channels traveled by cruise ships has important environmental and economic implications, as dredging larger lanes damages habitat, ship traffic produces sediment plumes that can smother adjacent sensitive habitats (e.g., coral reefs, seagrass beds), and dredging costs vary spatially. These environmental and economic costs should ideally be evaluated in the context of projected benefits from increased tourism. To inform decision-making on cruise ship pathway design, we evaluated tradeoffs among tourism revenue to the local economy, dredging costs, direct coral damage and sedimentation impacts to coral reefs of alternative cruise ship approach channels for the island of Bermuda. We compiled economic data on cruise tourism and dredging costs and developed a sediment particle tracking model, overlaid on maps of coral cover, to track the spread of sediment particles and resulting coral sedimentation caused by cruise ships. Using our models we compared two viable routes, if dredged, for larger ships to reach Bermuda, along with a scenario of no dredging in which the next generation of larger ships is not accommodated. Our tradeoff analysis shows that the status quo (no dredging; no larger ships) scenario performs relatively well except for the risk of a significant loss in tourism revenue. When selecting between the two channel upgrade scenarios, the south channel upgrade is preferable if dredged material can be reused, thereby recouping dredging costs; otherwise, there is a strong tradeoff between upgrade costs and coral sedimentation. While developed with data layers and inputs specific to Bermuda, this analytical approach could easily be configured to other locations facing similar spatial planning decisions about whether and where to allow pathways for larger cruise ships.

Temperature variation within a year can impact biological processes driving population abundances. The implications for the ecosystem services these populations provide, including food production from marine fisheries, are poorly understood. Whether and how temperature variability impacts fishery yields may depend on the number of harvested species and differences in their responses to varying temperatures. Drawing from previous theoretical and empirical studies, we predict that greater temperature variability within years will reduce yields, but harvesting a larger number of species, especially a more functionally diverse set, will decrease this impact. Using a global marine fisheries dataset, we find that within-year temperature variability reduces yields, but current levels of functional diversity (FD) of targeted species, measured using traits related to species' responses to temperature, largely offset this effect. Globally, high FD of catch could avoid annual losses in yield of 6.8% relative to projections if FD were degraded to the lowest level observed in the data. By contrast, species richness in the catch and in the ecosystem did not provide a similar mitigating effect. This work provides novel empirical evidence that short-term temperature variability can negatively impact the provisioning of ecosystem services, but that FD can buffer these negative impacts.

Only 2.1% of the ocean is in actively managed marine protected areas (MPAs). Achieving the United Nations' target of 10% of the ocean protected by 2020 will require an aggressively implemented mix of large MPAs in remote areas, and small MPAs in inhabited coastal areas. Replication of small no-take MPAs (marine reserves) in coastal areas at the global scale is more likely to occur if reserves are designed as investment opportunities – ‘fish banks’ that produce new profits based on ecosystem services such as tourism and fish production. Here a pro forma business plan for a marine reserve using private investment and local management is presented. Total annual profit before the reserve was €254,000 (from fishing only); in year 8 after creation of the reserve, profit (fishing+tourism) was €3.3 million. Given the right conditions, the net present value of the reserve can be between 4 and 12 times greater than the no-reserve counterfactual. In our model, (1) the tourism sector covers the costs of creation and operation of the reserve as an investment in a profitable business; and (2) fishers become shareholders and receive income from tourist access fees; their profits increase as soon as one year after the creation of the reserve. A series of financing mechanisms to create and manage fish banks is also proposed. If designed properly, fish banks can help restore marine biodiversity and ecosystem services, and can create jobs, help fishers, and bring in significantly greater economic profits than the absence of protection.

Spatial property rights in the ocean, such as territorial user right fisheries (TURFs), are increasingly used to overcome the tragedy of the commons. TURFs engender vastly different fishing incentives than in a common pool race; while this likely enhances conservation beyond an open access setting, conservation organizations may desire even greater protection. We argue that because TURFs are property rights, their implementation opens the door for “private conservation,” for example, where a conservation organization would purchase a set of TURFs to create an un-fished marine reserve network. This possibility has interesting implications for biodiversity conservation, fishery management, and economic incentives, yet has received almost no attention in the literature. We examine this issue in a numerical spatial-dynamic bioeconomic fishery model. Among other novel findings, we show: (i) Private acquisition of TURFs is likely to be a relatively inexpensive marine conservation strategy, particularly if the conservationist can capture some of the “conservation rents” that accrue due to spillover; (ii) Accounting for the strategic response of remaining fishermen can significantly reduce the cost of conservation; and (iii) The degree of fishing cooperation across TURFs plays a pivotal role in the costs of conservation; more-cooperative TURF owners engage in more “free” conservation, dramatically reducing the overall costs of achieving a particular conservation target.

To improve fishery management, there is an increasing need to understand the long-term consequences of natural and anthropogenic climate variability for ecological systems. New England’s iconic cod populations have been in decline for several decades and have recently reached unprecedented lows. We find that 17% of the overall decline in Gulf of Maine cod biomass since 1980 can be attributed to positive phases of the North Atlantic Oscillation (NAO). This is a consequence of three results: i) a 1-unit increase in the NAO winter index is associated with a 17% decrease in the spring biomass of age-1 cod the following year; ii) this NAO-driven decrease persists as the affected cohort matures; iii) fishing practices appear to exacerbate NAO’s direct biological effect such that, since 1913, a 1-unit increase in the NAO index lowers subsequent cod catch for up to 19 years. The Georges Bank cod stock displays similar patterns. Because we statistically detect a delay between the NAO and subsequent declines in adult biomass, our findings imply that observed current NAO conditions can be used in stock forecasts, providing lead time for adaptive policy. More broadly, our approach can inform forecasting efforts for other fish populations strongly affected by natural and anthropogenic climatic variation.

Managing fisheries presents trade-offs between objectives, for example yields, profits, minimizing ecosystem impact, that have to be weighed against one another. These trade-offs are compounded by interacting species and fisheries at the ecosystem level. Weighing objectives becomes increasingly challenging when managers have to consider opposing objectives from different stakeholders. An alternative to weighing incomparable and conflicting objectives is to focus on win–wins until Pareto efficiency is achieved: a state from which it is impossible to improve with respect to any objective without regressing at least one other. We investigate the ecosystem-level efficiency of fisheries in five large marine ecosystems (LMEs) with respect to yield and an aggregate measure of ecosystem impact using a novel calibration of size-based ecosystem models. We estimate that fishing patterns in three LMEs (North Sea, Barents Sea and Benguela Current) are nearly efficient with respect to long-term yield and ecosystem impact and that efficiency has improved over the last 30 years. In two LMEs (Baltic Sea and North East US Continental Shelf), fishing is inefficient and win–wins remain available. We additionally examine the efficiency of North Sea and Baltic Sea fisheries with respect to economic rent and ecosystem impact, finding both to be inefficient but steadily improving. Our results suggest the following: (i) a broad and encouraging trend towards ecosystem-level efficiency of fisheries; (ii) that ecosystem-scale win–wins, especially with respect to conservation and profits, may still be common; and (iii) single-species assessment approaches may overestimate the availability of win–wins by failing to account for trade-offs across interacting species.

In recent decades, aquaculture has emerged as a viable method to help supply the growing global demand for seafood; however, expansion of the industry comes with potential negative impacts. Regulatory decisions governing aspects like aquaculture farming practices and farm siting inherently lead to trade-offs between profitability and the health of the surrounding environment through impacts including pollution, disease, and disturbance from escaped fish. Efficiently and sustainably scaling up aquaculture will require the development of methods for explicitly examining the trade-offs among these impacts and socioeconomic objectives. We developed a model to assess these trade-offs and illustrate the approach with a case study of salmon aquaculture in southern Chile. In the case study we found evidence that all 21 farms with approved permits may be underperforming on both profitability and the protection of ecosystem health. Our model suggests that explicit evaluation of trade-offs can illuminate the potential for improvements on multiple outcomes simultaneously.

In recent decades, the Internet, together with information and communication technologies such as personal computers and cellular phones, has provided an electronic alternative to newspapers and printed materials. We examine how Internet adoption has affected worldwide demand for newsprint and printing and writing papers. We find that the Internet has reduced demand for newsprint in all regions. These regions include the United States, the Organization for Economic Co-operation and Development (OECD) countries other than the United States, the countries of the former Soviet Union (Reform), the Asian countries not in the OECD (Asia), and developing countries in Africa and Latin America. The effect is strongest in the United States, where we predict that as of 2011 newsprint consumption would have been 4 times higher in the absence of the Internet. The effects on printing and writing papers are more varied. The Internet is found to have reduced consumption in the United States and OECD countries, had a negligible effect in Asia and the Reform region, and increased consumption in Africa and Latin America. By accounting for Internet adoption, our new demand estimates have the potential to improve forecasts of paper consumption contained in forest outlook studies.

The challenges of common-pool resource harvesting have confronted the world's fisheries for centuries. Efforts to mitigate these challenges have led to an extensive literature on fishery performance under alternative management practices, but relatively little evidence exists on the factors that drive the adoption of these management approaches. In this study, a database describing 67 fishery cooperatives around the world is analyzed to help fill this gap. The analysis is focused on two widely implemented catch share management strategies, Territorial Use Rights Fisheries and Individual Quotas. Our empirical approach and interpretation of results are organized according to Ostrom's social-ecological systems framework. Among the evaluated factors, governance aspects appear to be most important to management adoption, specifically the presence of legal conditions on cooperative existence, and the strength of law and stability of governing institutions. It is postulated that the same factors that favor adoption of specific catch share management strategies would also generally play a positive role in their performance. If this is true, our results highlight the importance of considering both sets of factors when trying to spread the implementation of management tools, and show that enabling conditions associated to existing governance structures deserve great emphasis by those who seek to adopt management strategies like catch shares.

There have been dramatic advances in understanding the physical science of climate change, facilitated by substantial and reliable research support. The social value of these advances depends on understanding their implications for society, an arena where research support has been more modest and research progress slower. Some advances have been made in understanding and formalizing climate-economy linkages, but knowledge gaps remain [e.g., as discussed in (1, 2)]. We outline three areas where we believe research progress on climate economics is both sorely needed, in light of policy relevance, and possible within the next few years given appropriate funding: (i) refining the social cost of carbon (SCC), (ii) improving understanding of the consequences of particular policies, and (iii) better understanding of the economic impacts and policy choices in developing economies.

Fisheries managers seek to maintain sustainable fisheries production, but successful management often requires the pursuit of multiple biological, ecological, and socioeconomic objectives simultaneously. Fisheries managers must choose among a broad range of harvest control methods (HCMs) to meet management objectives. This review identifies strengths and weaknesses of eight HCMs and evaluates their ability to meet a multitude of common biological, ecological, and socioeconomic management objectives such as protecting spawning biomass, reducing bycatch, and sustaining fishers’ profit. Evidence suggests that individual HCMs often fail to meet management objectives and may unintentionally create incentives to race to fish, discard catch and overcapitalize fishing operations. These limitations can be overcome by strategically combining multiple controls or incorporating rights-based and spatial management.

Data from 4,713 fisheries worldwide, representing 78% of global reported fish catch, are analyzed to estimate the status, trends, and benefits of alternative approaches to recovering depleted fisheries. For each fishery, we estimate current biological status and forecast the impacts of contrasting management regimes on catch, profit, and biomass of fish in the sea. We estimate unique recovery targets and trajectories for each fishery, calculate the year-by-year effects of alternative recovery approaches, and model how alternative institutional reforms affect recovery outcomes. Current status is highly heterogeneous—the median fishery is in poor health (overfished, with further overfishing occurring), although 32% of fisheries are in good biological, although not necessarily economic, condition. Our business-as-usual scenario projects further divergence and continued collapse for many of the world’s fisheries. Applying sound management reforms to global fisheries in our dataset could generate annual increases exceeding 16 million metric tons (MMT) in catch, $53 billion in profit, and 619 MMT in biomass relative to business as usual. We also find that, with appropriate reforms, recovery can happen quickly, with the median fishery taking under 10 y to reach recovery targets. Our results show that commonsense reforms to fishery management would dramatically improve overall fish abundance while increasing food security and profits.

Marine protected areas (MPAs) are a commonly applied solution to coral reef degradation, yet coral reefs continue to decline worldwide. We argue that expanding the range of MPAs to include degraded reefs (DR-MPA) could help reverse this trend. This approach requires new ecological criteria for MPA design, siting, and management. Rather than focusing solely on preserving healthy reefs, our approach focuses on the potential for biodiversity recovery and renewal of ecosystem services. The new criteria would help identify sites with the highest potential for recovery and the greatest resistance to future threats (e.g., increased temperature and acidification) and sites that contribute to MPA connectivity. The DR-MPA approach is a compliment rather than a substitute for traditional MPA design approaches. We believe that the DR-MPA approach can enhance the natural, or restoration-assisted, recovery of DRs and their ecosystem services; increase total reef area available for protection; promote more resilient and better-connected MPA networks; and improve conditions for human communities dependent on MPA ecosystem services.

Understanding changes in productivity for populationsof exploited marine fish is important for appropriatemanagement and conservation. Britten et al. (1) showthat, on average, the productivity of fish stocks havedeclined 3% per decade. This figure was an unweightedmean, and therefore gave equal weight to all stocks,regardless of size. An unweighted mean is a useful mea-sure of changing productivity, particularly when consid-ering conservation of individual stocks. However, foodsecurity is a central concern for many countries border-ing the ocean, so we should also ask, “How can changesin productivity influence the total biomass in the oceanand the total catch derived from that biomass?”To explore this question, I repeated Britten et al.’sanalysis (1) with the 224 stocks used by Szuwalski et al.(2) from the RAM Legacy Stock Assessment Database.I calculated the average decadal change in productivity(Rmax) over all stocks weighted by the average bio-mass of the stock and then by average catch. Weight-ing changes in productivity by biomass essentiallyremoved the negative trend in productivity (−0.06%average decadal change). Weighting changes in pro-ductivity by the average catch produced a positivetrend in productivity (+1%). This finding suggests thatthe net productive capacity of the ocean has changedvery little over time (at least for the stocks in the anal-ysis) and that productivity has increased for the stocksfrom which most catch in the RAM database is de-rived. Reproducing figure 1 of ref. 1 with changes inproductivity weighted by catch highlights that a fewLMEs account for a large proportion of the catch andmost LMEs have net positive changes in productivity(Fig. 1).

Well-managed fisheries support healthy ocean ecosystems, coastal livelihoods and food security for millions of people. However, many communities lack the resources to implement effective fisheries management. No-take marine reserves are a ubiquitous management intervention that provide conservation benefits and under certain circumstances can provide long-term fishery benefits as a result of larval and adult emigration from reserve boundaries. But, support for marine reserves by fishery participants is often limited due to short-term economic impacts resulting from foregone yields. In this study, we examine the timing and magnitude of economic impacts of marine reserves by utilizing a novel metric that discounts future economic benefits of enhanced productivity resulting from reserve protection. We ask under what circumstances long-term benefits outweigh short-term impacts of marine reserve implementation. We simulate fisheries for six species commonly caught in coastal environments and show that while conservation benefits accrue rapidly, more than a decade is often required to provide net fisheries benefits, even under circumstances favourable for reserves. We explore a suite of strategies for mitigating these short-term economic losses, including flexible reserve designs, loans and enhanced ex-vessel revenues. Results indicate that market-based incentives show promise to offset short-term economic losses. Our findings highlight the importance of understanding and communicating likely outcomes from marine reserve implementation and the need to engage supply chain actors to incentivize marine conservation that minimizes impacts to fishermen.