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Successful ocean management needs to consider not only fishing impacts but drivers of harvest. Consolidating post-1950 global catch and economic data, we assess which attributes of fisheries are good indicators for fishery development. Surprisingly, year of development and economic value are not correlated with fishery trophic levels. Instead, patterns emerge of profit-driven fishing for attributes related to costs and revenues. Post-1950 fisheries initially developed on shallow ranging species with large catch, high price, and big body size, and then expanded to less desirable species. Revenues expected from developed fisheries declined 95% from 1951 to 1999, and few high catch or valuable fishing opportunities remain. These results highlight the importance of economic attributes of species as leading indicators for harvestrelated impacts in ocean ecosystems.widely discussed interpretation of global fisheries development is that humans have preferentially fished high trophic level species, as evidenced by declining mean trophic level of catch since 1950. Under the "fishing down" explanation for this pattern (1), stocks high in food webs have been serially depleted through industrialized fishing. Essington et al. (2) propose instead that "fishing through" occurs by serially expanding into lower trophic level groups, while maintaining harvest high in food webs. Although the consequences of declining mean trophic level of catch are not fully understood, nonrandom harvest on food webs can lead to large ecosystem changes including trophic cascades (3, 4) or productivity shifts (5). Thus, mean trophic level of catch has been adopted as an indicator for the ecological impacts of fishing (6).For successful fisheries management, it will be necessary to move beyond the symptoms of fishing and to take into account drivers of harvest pressure that result in potentially significant ecosystem change. One step in this direction is to incorporate leading indicators for current and future impacts of fishing into management. What motivates fishermen? Modern industrialized fishing is a business activity, and harvest decisions are made to attain profits: revenues net of fishing costs. We expect that good indicators for fishing pressure are related to economic costs and benefits. One explanation suggested for the evolution of global fisheries development and declining mean trophic level of catch is that organisms high in food webs are more valuable, making them preferentially targeted by commercial harvesters (2). If this hypothesis was correct, trophic level could be a leading indicator for fishing pressure under profit-driven harvest.Using global data on catch (ref. 7; www.seaaroundus.org), exvessel price (8), and life history characteristics (9), we examine whether higher trophic level organisms are more valuable. We find that trophic level has little relation to economic opportunity or the pattern of commercial fishery development since 1950; however, the progression of fishing development demonstrates a clear pattern of profi...

Hundreds of dams have been proposed throughout the Amazon basin, one of the world’s largest untapped hydropower frontiers. While hydropower is a potentially clean source of renewable energy, some projects produce high greenhouse gas (GHG) emissions per unit electricity generated (carbon intensity). Here we show how carbon intensities of proposed Amazon upland dams (median = 39 kg CO2eq MWh−1, 100-year horizon) are often comparable with solar and wind energy, whereas some lowland dams (median = 133 kg CO2eq MWh−1) may exceed carbon intensities of fossil-fuel power plants. Based on 158 existing and 351 proposed dams, we present a multi-objective optimization framework showing that low-carbon expansion of Amazon hydropower relies on strategic planning, which is generally linked to placing dams in higher elevations and smaller streams. Ultimately, basin-scale dam planning that considers GHG emissions along with social and ecological externalities will be decisive for sustainable energy development where new hydropower is contemplated.

C ontemporary ecosystem change driven by a suite of global anthropogenic stressors has had reverberating consequences across genetic, population, community, and ecoregional scales (Díaz et al. 2019). Fine-scale changes in phenology, morphology, abundance, gene frequencies, and distribution of populations and species (eg Staudinger et al. 2013) can scale up to system-level conversions and biome shifts (Scheffer et al. 2009). Often driven by changing climate, many of these changes are manifest in ecological and physical stresses, including invasive-plant incursions, drought, desertification, severe fire, pest outbreaks, and geographic displacement of species. Extreme ecosystem changes are occurring with increasing frequency across a range of biomes, including coral bleaching in the tropics and grassification of shrublands (Figure 1). Ecosystem changes are expected to continue across many biomes even under scenarios with aggressive reductions in greenhouse-gas emissions, with globally distributed and radical ecosystem alterations predicted under high-emission scenarios (Nolan et al. 2018;Reid et al. 2018).We define these intensive and comprehensive system changes as ecosystem transformation (ie the emergence of a selforganizing, self-sustaining ecological or socioecological system that diverges considerably and irreversibly from prior historical ecosystem structure, composition, and function; Noss 1990). Transformations include ecosystem disruptions (eg Embrey et al. 2012) and occur across a range of temporal scales -for instance, from single-event high-intensity fires (Guiterman et al. 2018) to glacial-interglacial transitions spanning many millennia (Nolan et al. 2018) -and range widely in spatial extent, from a local community to entire biomes (Thompson et al. 2021). These changes pose critical threats to ecosystem services and consequently to human health and well-being, clean air and water, food security, sanitation, and disease mitigation (Whitmee et al. 2015).

Ecosystem transformation can be defined as the emergence of a self‐organizing, self‐sustaining, ecological or social–ecological system that deviates from prior ecosystem structure and function. These transformations are occurring across the globe; consequently, a static view of ecosystem processes is likely no longer sufficient for managing fish, wildlife, and other species. We present a framework that encompasses three strategies for fish and wildlife managers dealing with ecosystems vulnerable to transformation. Specifically, managers can resist change and strive to maintain existing ecosystem composition, structure, and function; accept transformation when it is not feasible to resist change or when changes are deemed socially acceptable; or direct change to a future ecosystem configuration that would yield desirable outcomes. Choice of a particular option likely hinges on anticipating future change, while also acknowledging that temporal and spatial scales, recent history and current state of the system, and magnitude of change can factor into the decision. This suite of management strategies can be implemented using a structured approach of learning and adapting as ecosystems change.

Risk management methods provide means to address increasing complexity for successful fisheries management by systematically identifying and coping with risk. The objective of this study is to summarize risk management practices in use in fisheries and to present strategies that are not currently used but may be applicable. Available tools originate from a variety of disciplines and are as diverse as the risks they address, including algorithms to aid in making decisions with multiple stakeholders, reserves to buffer against economic or biological surprises, and insurance instruments to help fishermen cope with economic variability. Techniques are organized in a two‐stage framework. In the first stage, risks are identified and analysed. Strategies presented in this category focus on decision analysis, including multicriteria decision‐making tools, and the related concept of risk assessment. Then in the treatment stage, identified risks can be transferred, avoided, or retained using tools such as the Precautionary Approach, portfolio management, financial contracts to manage price risk and horizontal integration. Published fishery applications are reviewed, and some empirical examples of risks and risk management using US fisheries data are presented.

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Intensifying global change is propelling many ecosystems toward irreversible transformations. Natural resource managers face the complex task of conserving these important resources under unprecedented conditions and expanding uncertainty. As once familiar ecological conditions disappear, traditional management approaches that assume the future will reflect the past are becoming increasingly untenable. In the present article, we place adaptive management within the resist–accept–direct (RAD) framework to assist informed risk taking for transforming ecosystems. This approach empowers managers to use familiar techniques associated with adaptive management in the unfamiliar territory of ecosystem transformation. By providing a common lexicon, it gives decision makers agency to revisit objectives, consider new system trajectories, and discuss RAD strategies in relation to current system state and direction of change. Operationalizing RAD adaptive management requires periodic review and update of management actions and objectives; monitoring, experimentation, and pilot studies; and bet hedging to better identify and tolerate associated risks.