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.