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To understand the scope and scale of the loss of biodiversity, tools are required that can be applied in a standardized manner to all species globally, spanning realms from land to the open ocean. We used data from the International Union for the Conservation of Nature Red List to provide a synthesis of the conservation status and extinction risk of cetaceans. One in 4 cetacean species (26% of 92 species) was threatened with extinction (i.e., critically endangered, endangered, or vulnerable) and 11% were near threatened. Ten percent of cetacean species were data deficient, and we predicted that 2–3 of these species may also be threatened. The proportion of threatened cetaceans has increased: 15% in 1991, 19% in 2008, and 26% in 2021. The assessed conservation status of 20% of species has worsened from 2008 to 2021, and only 3 moved into categories of lesser threat. Cetacean species with small geographic ranges were more likely to be listed as threatened than those with large ranges, and those that occur in freshwater (100% of species) and coastal (60% of species) habitats were under the greatest threat. Analysis of odontocete species distributions revealed a global hotspot of threatened small cetaceans in Southeast Asia, in an area encompassing the Coral Triangle and extending through nearshore waters of the Bay of Bengal, northern Australia, and Papua New Guinea and into the coastal waters of China. Improved management of fisheries to limit overfishing and reduce bycatch is urgently needed to avoid extinctions or further declines, especially in coastal areas of Asia, Africa, and South America. [ABSTRACT FROM AUTHOR]

Lack of guidance for interpreting the definitions of endangered and threatened in the U.S. Endangered Species Act (ESA) has resulted in case-by-case decision making leaving the process vulnerable to being considered arbitrary or capricious. Adopting quantitative decision rules would remedy this but requires the agency to specify the relative urgency concerning extinction events over time, cutoff risk values corresponding to different levels of protection, and the importance given to different types of listing errors. We tested the performance of 3 sets of decision rules that use alternative functions for weighting the relative urgency of future extinction events: a threshold rule set, which uses a decision rule of x% probability of extinction over y years; a concave rule set, where the relative importance of future extinction events declines exponentially over time; and a shoulder rule set that uses a sigmoid shape function, where relative importance declines slowly at first and then more rapidly. We obtained decision cutoffs by interviewing several biologists and then emulated the listing process with simulations that covered a range of extinction risks typical of ESA listing decisions. We evaluated performance of the decision rules under different data quantities and qualities on the basis of the relative importance of misclassification errors. Although there was little difference between the performance of alternative decision rules for correct listings, the distribution of misclassifications differed depending on the function used. Misclassifications for the threshold and concave listing criteria resulted in more overprotection errors, particularly as uncertainty increased, whereas errors for the shoulder listing criteria were more symmetrical. We developed and tested the framework for quantitative decision rules for listing species under the U.S. ESA. If policy values can be agreed on, use of this framework would improve the implementation of the ESA by increasing transparency and consistency. Evaluando Reglas de Decisión para Categorizar el Riesgo de Extinción de Especies con el Fin de Desarrollar de Criterios Cuantitativos de Alistamiento en el Acta de Especies en Peligro de los EE. UU. [ABSTRACT FROM AUTHOR]

Good management models and good models for understanding biology differ in basic philosophy. Management models must facilitate management decisions despite large amounts of uncertainty about the managed populations. Such models must be based on parameters that can be estimated readily, must explicitly account for uncertainty, and should be simple to understand and implement. In contrast, biological models are designed to elucidate the workings of biology and should not be constrained by management concerns. We illustrate the need to incorporate uncertainty in management models by reviewing the inadequacy of using standard biological models to manage marine mammals in the United States. Past management was based on a simple model that, although it may have represented population dynamics adequately, failed as a management tool because the parameter that triggered management action was extremely difficult to estimate for the majority of populations. Uncertainty in parameter estimation resulted in few conservation actions. We describe a recently adopted management scheme that incorporates uncertainty and its resulting implementation. The approach used in this simple management scheme, which was tested by using simulation models, incorporates uncertainty and mandates monitoring abundance and human-caused mortality. Although the entire scheme may be suitable for application to some terrestrial and marine problems, two features are broadly applicable: the incorporation of uncertainty through simulations of management and the use of quantitative management criteria to translate verbal objectives into levels of acceptable risk. [ABSTRACT FROM AUTHOR]

Using genetic data to estimate dispersal is attractive because direct estimation is often infeasible. Unfortunately, analytical tools remain rudimentary. Various standard population genetic formulae estimate dispersal rates between populations but require unrealistic assumptions, such as equal population size. Recent increases in computer speed enable simulations of genetic processes in populations. We designed simulation models to evaluate the adequacy of using analytical formulae to estimate dispersal rates needed for conservation decisions. Our models incorporated genetic stochasticity. They adhered closely to the assumptions of the standard formulae except that we relaxed the assumption that all populations were equal in size. We found that measures of population differentiation, such as the statistic ΦS T , varied greatly over time, reflecting the stochastic nature of genetic systems. In some cases, however, even large amounts of variation over time made no difference in defining population structure for management purposes, whereas in other cases the opposite was true. Statistics of genetic differentiation were so variable that management decisions based on analytical formulae would often be incorrect. Adjoining populations with little dispersal between them that should be managed separately were by chance alone so genetically similar that they appear panmictic, incorrectly implying that they should be managed as a single unit. The form of distributions of these statistics was complex and did not conform to standard statistical distributions. Furthermore, differences between these distributions for equal and unequal abundance cases indicated that pursuits of simple adjustments to analytical formulae are unlikely to be fruitful. In contrast, our simulation technique can be used in a decision analysis framework because it incorporates uncertainties into a probability distribution. We conclude with a case in which a manager wants to know... [ABSTRACT FROM AUTHOR]

Focuses on articles that introduce methods for analyzing uncertainty to conservation biologists working with terrestrial systems. Motivation of marine conservation biologists in developing innovative techniques for incorporating uncertainty into both data analysis and decision making; Appropriateness of techniques developed for marine problems to address terrestrial problems.

Uncertainties about biological data and human effects often delay decisions on management of endangered species. Some decision makers argue that uncertainty about the risk posed to a species should lead to precautionary decisions, whereas others argue for delaying protective measures until there is strong evidence that a human activity is having a serious effect on the species. We have developed a method that incorporates uncertainty into the estimate of risk so that delays in action can be reduced or eliminated. We illustrate our method with an actual situation of a deadlock over how to manage Hector's dolphin (Cephalorhychus hectori). The management question is whether sufficient risk is posed to the dolphins by mortalities in gillnets to warrant regulating the fisheries. In our quantitative risk assessment, we use a population model that incorporates both demographic ( between-individual) and environmental ( between-year) stochasticity. We incorporate uncertainty in estimates of model parameters by repeatedly running the model for different combinations of survival and reproductive rates. Each value is selected at random from a probability distribution that represents the uncertainty in estimating that parameter. Before drawing conclusions, we perform sensitivity analyses to see whether model assumptions alter conclusions and to recommend priorities for future research. In this example, uncertainty did not alter the conclusion that there is a high risk of population decline if current levels of gillnet mortality continue. Sensitivity analyses revealed this to be a robust conclusion. Thus, our analysis removes uncertainty in the scientific data as an excuse for inaction. [ABSTRACT FROM AUTHOR]

Under the U.S. Endangered Species Act (ESA), a species can be listed if it is at risk “in all or a significant portion of its range,” but the ESA provides no guidance on how to interpret this key phrase. We propose a simple test to determine whether the areas of a species' range in which it is currently at risk amount to a significant portion: If the species were to become extirpated from these areas, at that point would the entire species be at risk? If so, then these areas represent a significant portion of the species' range. By establishing the species itself as the point of reference for determining significance, this test directs attention to biological risk factors and avoids difficulties inherent in subjective evaluations of importance to humans. For broadly distributed species this framework could provide ESA protection due to cumulative risks before the entire species met the criteria to be considered threatened or endangered. This framework also allows a somewhat broader concept of range to include major components of diversity necessary for long-term persistence. The concept of a historical template (i.e., conditions under which the species was known to be viable) is important in providing a fixed reference point for evaluating viability. Empirical examples illustrate how these concepts have been applied in recent ESA listing determinations. Most ESA-listed units of Pacific salmon (Oncorhynchus spp.) can be divided into multiple strata that differ in terms of ecology, geology, or life-history traits of the component populations. The goal of ESA recovery planning is to restore viable populations in enough strata that the listed unit as a whole is no longer threatened or endangered in all or a significant portion of its range. In a recent review of Pacific herring (Clupea pallasii ) in Puget Sound, current status (some populations increasing and others declining) was evaluated in the context of the historical template, and it was concluded that current patterns of distribution and abundance do not depart substantially from what would be expected at any point in time under natural conditions in a large metapopulation. The Canadian lynx (Lynx canadensis ) is ESA listed in the contiguous United States, where it occurs in four geographic areas. Populations in one region, the Northern Rockies/Cascades, have always been the most important for long-term persistence of the species in the United States. Because the other regions never contained more than limited amounts of good-quality lynx habitat, those areas are not considered to represent a significant portion of the species' range. [ABSTRACT FROM AUTHOR]

The article focuses on the significance of the genetic diversity on biological diversity. The Conservation on Biological Diversity (CBD) recognizes genetic diversity as an explicit goal. It adds that the CBD is a body responsible to develop and implement a National Biodiversity Strategy and Action Plan (NBSAP). It also suggests that less than half of the reviewed countries have included the goal of conserving genetic variation of wild animals and plants, while 20% recognize the need for monitoring such level of variation.

The authors reflect on the legal language contained in U.S. Endangered Species Act. In particular, they are concerned with the risks to a species in a significant portion of its range when the entire species is not at risk of extinction. They discuss the meaning of likely to be endangered in the foreseeable future and conclude that it means a greater than50% probability in the next 20 years. They argue that societal values are in the legal and policy domain and not the scientific realm.

The authors reports that the vaquita (Gulf of California porpoise, Phocoena sinus), is in imminent danger of extinction by the use of gillnet fishing in El Golfo de Santa Clara and San Felipe, Mexico as of December 2007. They call for the use of economic incentives to the fishing communities as a way of halting the use of such nets, and the incidental death of the porpoises caused by their use. Using computer models, they found that the vaquita has two years before they reach a population level of no return.

This article is a defense of a previous article called "A biological framework for evaluating whether an ESA species is threatened or endangered in a 'significant portion of its range'" that was critiqued by other scholars. In that paper, the authors argued for a changed definition of the way that the U.S. Endangered Species Act (ESA) defines the significant portion of its range (SPOIR). The authors also argue that their idea of SPOIR would give species that are not threatened or endangered greater protection. Finally, the authors explain the process by which they were asked to develop a SPOIR framework and they acknowledge that adopting the framework would be to redesign how ESA defines threatened and endangered species.