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Article

Economics of Invasive Species  

Mark Eiswerth, Chad Lawley, and Michael H. Taylor

Introductions of nonnative invasive species can harm ecosystems, heighten the risk of native species extinctions and population reductions, and lead to substantial economic damages on a worldwide scale. Increasingly, economists have made contributions that help other researchers, policymakers, and society better understand the economic implications of invasive species as well as the most economically efficient approaches for managing them. The complexity of invasive species management problems has pushed economists to ask novel economic questions and to develop new analytical approaches in order to address specific policy questions. There are three areas, in particular, where the economic analysis of invasive species management has led to significant innovations. First, there are substantial challenges to quantifying economic damages from invasive species for application in benefit−cost analysis. The challenges relate to defining the counterfactual state of an invaded ecosystem with and without management/policy and to the fact that, in a given ecosystem, estimates of economic damages are available for only a subset of the species and for only a subset of damages for any one species. Recent economic research has proposed innovative approaches to systematically dealing with these two issues in the context of invasive species that have implications for applied benefit−cost analysis more broadly. Second, unique among natural resource management problems, invasive species have the feature that their current and future extents are directly tied to a country’s participation in international trade. This feature has led to innovative research into the design of efficient measures to prevent or delay invasive species introductions along national borders, and into the trade-offs between these measures and the use of border controls as protectionist tools. The issues of optimal inspection policy and the use of nontariff barriers as a form of covert protectionism both have implications beyond invasive species management. Third, researchers have developed bioeconomic models that integrate economic and biological factors in order to analyze strategies to more cost-effectively reduce the damages caused by invasive species. These modeling efforts have dealt with issues related to temporal and spatial dynamics of the biological invasions, imperfect information regarding the extent of the invasion and the effectiveness of management, linkages between management applied at different stages of an invasion, and complications arising from ecosystems’ crossing over ecological thresholds due to invasions. In the face of increasingly rapid ecosystem change due to global climate change, increases in extreme weather, urban encroachment into wild lands, and other factors, many of these features of invasive species management problems are likely to become features of ecosystem management more broadly in the near future if they are not so already.

Article

Economics and the Endangered Species Act  

Joe Kerkvliet

Economics plays strong roles in the design, implementation, and evaluation of the Endangered Species Act (ESA). First, the ESA’s language allows for economic analysis of critical habitat designations, recovery plan implementations, listing postponements, and the design of habitat-conservation plans. Extensive administrative changes to the ESA in the 1990s were designed to reduce economic costs and to elicit landowners’ cooperation. These reforms were partly motivated and guided by economic analysis. Second, economic analysis plays a role in providing credible estimates of the economic costs of ESA implementation. Cost estimates are highly variable and likely to depend on species’ characteristics and the effectiveness of recovery programs. Emerging evidence suggests that the 1990 reforms are reducing costs and increasing effectiveness. Third, economic science contributes to estimation of benefits. Because of the “public goods” nature of nearly all ecosystem and species conservation efforts, estimates must be based on stated preference methods. This use leads to difficulties in establishing the authenticity of benefits estimates. Also, research suggests that benefits estimates are highly sensitive to the spatial nature of the market (beneficiaries’ geographic locations). Future research needs to tackle both authenticity and spatial issues. Fourth, benefit–cost analysis (BCA) is required by law to inform many resource decisions affecting ecosystem and species conservation. Four illustrative BCAs show that whether benefits exceed costs is highly dependent on the authenticity of benefits based on stated preference methods and assumptions about the spatial nature of the market. Substantial uncertainty accompanies both benefit and cost estimates.

Article

Hominin Taxic Diversity  

Bernard Wood, Dandy Doherty, and Eve Boyle

The clade (a.k.a. twig of the Tree of Life) that includes modern humans includes all of the extinct species that are judged, on the basis of their morphology or their genotype, to be more closely related to modern humans than to chimpanzees and bonobos. Taxic diversity with respect to the hominin clade refers to evidence that it included more than one species at any one time period in its evolutionary history. The minimum requirement is that a single ancestor-descendant sequence connects modern humans with the hypothetical common ancestor they share with chimpanzees and bonobos. Does the hominin clade include just modern human ancestors or does it also include non-ancestral species that are closely related to modern humans? It has been suggested there is evidence of taxic diversity within the hominin clade back to 4.5 million years ago, but how sound is that evidence? The main factor that would work to overestimate taxic diversity is the tendency for paleoanthropologists to recognize too many taxa among the site collections of hominin fossils. Factors that would work to systematically underestimate taxic diversity include the relative rarity of hominins within fossil faunas, the realities that many parts of the world where hominins could have been living are un- or under-sampled, and that during many periods of human evolutionary history, erosion rather than deposition predominated, thus reducing or eliminating the chance that animals alive during those times would be recorded in the fossil record. Finally, some of the most distinctive parts of an animal (e.g., pelage, vocal tract, scent glands) are not likely to be preserved in the hominin fossil record, which is dominated by fragments of teeth and jaws.

Article

Speciesism and the Non-human  

Ragnhild Sollund

Speciesism is a concept that encompasses the ideology and practice humans perform in their discrimination against animals, based on the sole fact that they are not part of the human species. Speciesism legitimates animal abuse, animal exploitation, and theriocides (animal murder), as human practices with such consequences are justified and become part of daily routine. Speciesism is contingent on humans’ reliance on anthropocentric philosophy, language, culture more generally, and religion. The ideological and sociopsychological foundations for speciesism are located in discourse, difference, distance, and denial, which cause humans to create a moral circle, in which they are in the center while other animal species are situated in concentric circles around them. The animals’ position in relation to the human determines their treatment, rather than their interests, abilities, and cognitive skills, which call for stronger protection.

Article

Gender, Nonhuman Animals, and Education  

Annie Schultz

Educational theorists are increasingly concerned with the areas of environmental education, ecological education, and animal studies. As social and political efforts to “go green” and make our industrial and personal habits more sustainable and ethical increase, schools as socializing agents take up these initiatives. Students already engage with nonhumans in significant ways in schools: they might interact with live nonhuman animals in extracurricular activities; they might dissect nonhuman animals in their science classes; they might eat the bodies of nonhuman animals at lunch; and they might read about literary or poetic representations of nonhuman animals in English classes. A continuously developing area of educational theory is how the ways in which students engage with nonhuman animals is gendered. Posthumanism and ecofeminism are philosophical paradigms that educational theorists engage with to think through the ways hierarchies of sentiency, humanity, and rationality are propagated by literary, cultural, and metaphorical representations of nonhuman others. There is a long history of women-animal comparisons that is evident in the literature and other cultural artifacts that we teach about in schools. Many students are also served animals as food in school cafeterias. Ecofeminist scholars and scholars of educational philosophy are likewise concerned with the gendered aspects of animal bodies as food and how the ontological representations of the bodies of women and their labor manifest in schools. Educational researchers are investigating these literary, metaphorical, and cultural comparisons.

Article

Valuation of Species Preservation  

Robert P. Berrens and Therese Grijalva

Against a backdrop of increasing species imperilment, there is considerable empirical evidence that preserving threatened, endangered, and rare (TER) species provides significant economic benefits to society. But efforts to measure these benefits has generated both strong methodological and philosophical criticisms. Since the 1960s, economists have developed a battery of nonmarket valuation approaches for estimating economic values associated with changes in the quantity or quality of environmental goods and services. This battery includes both revealed preference and stated preference (SP) approaches (including the contingent valuation [CV] method), with only the latter capable of providing willingness to pay (WTP) estimates for nonuse values. The total economic value of TER species preservation can include nonconsumptive use values (e.g., wildlife watching), and may be especially composed of nonuse values (e.g., based on existence value motivations). By the early 1980s, applied CV studies focusing on TER species preservation had begun to accumulate. Early research centered in the United States. By the mid-1990s the first statistical meta-analysis of TER species NMV studies was completed, and was then updated a dozen years later. These metaregression functions facilitated potential benefit transfers, where the systematic structure of prior original studies could be used to estimate WTP values for a TER species in another setting (absent an original study). Since roughly 2010, the use of choice experiments as an alternative SP approach expanded rapidly. Likewise, the accumulation of additional SP studies generated new summary reviews and meta-analyses, including applications from both developed and developing countries, and expanded benefit transfer opportunities. Going forward, new studies will lead to updated meta-analyses, with additional statistical and theoretical sophistication. Critiques targeted to SP approaches (e.g., with respect to hypothetical bias and nonuse value motivations) will likely remain, and further validity testing and methods development are called for. However, from a pragmatic perspective, persistent efforts at quantification continue to help make the benefits of TER species preservation visible in the face of rapidly increasing species imperilment.

Article

The Harms and Crimes Against Plant Species  

Esteban Morelle-Hungría and Pablo Serra-Palao

In the 21st century, the socio-environmental crisis is not limited to the quantitative analysis of the biophysical conditions on a global or sub-global scale. Individual species are directly affected by the “dynamics of the Anthropocene”: climate change, extreme weather events, deforestation, the acidification of the oceans, pollution, the use of pesticides, and many other anthropogenic pressures. All of these pressures have serious implications for individual species. Among all these affected species, this entry focuses on plant species. The Anthropocene dynamics and their associated impacts on individual plant species can be perceived at a number of different levels and with varying degrees of intensity and severity. In green criminology, the conceptual complexity of the distinction between environmental damage and crime has been widely debated, mainly due to their different politico-legal responses. For this reason, it is essential to provide an overview of environmental harms and crimes that affect plant species. To achieve this, the analysis begins with a theoretical foundation of green criminology, outlining its origins, multiple definitions and perspectives, ethical foundations, and justice frameworks. From this green criminological perspective, the scientific literature on a selected list of harms and crimes against plant species is reviewed using a holistic and interdisciplinary approach.

Article

Barley in Archaeology and Early History  

Simone Riehl

In 2018 barley accounts for only 5% of the cereal production worldwide, and regionally for up to 40% of cereal production. The cereal represents the oldest crop species and is one of the best adapted crop plants to a broad diversity of climates and environments. Originating from the wild progenitor species Hordeum vulgare ssp. spontaneum, biogeographically located in the Fertile Crescent of the Near East, the domesticated form developed as a founder crop in aceramic Neolithic societies 11,000 years ago, was cultivated in monocultures in Bronze Age Mesopotamia, entered the New World after 1492 ce, reached a state of global distribution in the 1950s and had reached approximately 200 accepted botanical varieties by the year 2000. Its stress tolerance in response to increased aridity and salinity on one hand and adaptability to cool climates on the other, partially explains its broad range of applications for subsistence and economy across different cultures, such as for baking, cooking, beer brewing and as an animal feed. Although the use of fermented starch for producing alcoholic beverages and foods is globally documented in archaeological contexts dating from at least the beginning of the Holocene era, it becomes concrete only in societies with a written culture, such as Bronze Age Mesopotamia and Egypt, where beer played a considerable role in everyday diet and its production represented an important sector of productivity. In 2004 approximately 85% of barley production was destined for feeding animals. However, as a component of the human diet, studies on the health benefits of the micronutrients in barley have found that it has a positive effect on blood cholesterol and glucose levels, and in turn impacts cardiovascular health and diabetes control. The increasing number of barley-breeding programs worldwide focus on improving the processing characteristics, nutritional value, and stress tolerance of barley within the context of global climate change.

Article

Hybridity  

David Huddart

Hybridity captures various ways in which identities are characterized by complexity or mixed-ness rather than simplicity or purity. It is a term that functions as a description of how things simply are, but it frequently appears to take on the characteristics of a prescription. It is not only that identities on various scales are hybrid, but also that they ought to be hybrid, or should become more hybrid. This prescriptive sense prompts reflection on the processes that drive mixed identities, shifting attention away from a static hybridity toward a dynamic and unending hybridization. The idea’s use in many different disciplinary formations typically implies that, while all identities are minimally hybrid, specific historical shifts have exaggerated and accelerated hybridity. Those shifts are associated with European colonialism, the Atlantic slave trade, neocolonial echoes, globalization, and the rise of the cyborg. Such associations raise the question of resistance to the prescriptive recommendation of hybridity to the extent that hybrid cultures are so frequently an outcome of violent domination. Formerly colonized cultures strive to re-establish more fundamental identities, casting the hybridizing colonial period as a brief if damaging and disruptive interlude. Resistance is also found in former imperial centers, with multiculturalism perceived as a hybridizing threat to the core integrity of a melancholic post-imperialism. And commentators continue to warn that automation and related AI will make unexpectedly diverse jobs obsolete in the very near future, a hybrid cyborg future that occasionally begins to feel more machine than human. Ultimately, it may seem that hybridity is opposed to various forms of indigeneity, purity, or in the most general case, humanity in general. However, such oppositions would be misleading, principally because hybridity as a cultural fact and as a concept implies nothing of necessity. Each context demands specific attention to the ways it is hybrid, the processes of hybridization, and the stabilities that follow.

Article

Environmental Justice  

Christina L. Erickson

Environmental justice in social work is the study and practice of assuring all people are protected from environmental burdens and are able to live, work, learn, and play in safe and healthy communities. Reducing the burdens and increasing the benefits of nature and human-made infrastructures are important social work efforts toward environmental justice. Awareness of environmental injustices followed the social movements of Civil Rights, recognition of environmental degradations, and efforts to save large swaths of land and endangered species in the Wilderness Act. Environmental justice is intertwined with social and economic justice, and the pursuit engages social workers in local to international struggles for access to nature’s benefits, and freedom from hazards that are shielded from people who are economically wealthy. Moreover, environmental justice calls wealthy individuals and communities to realign resource consumption to reduce environmental degradation and increase environmental sustainability.

Article

Wildlife in Brazil: History, Threats, and Opportunities  

José Luiz de Andrade Franco and José Augusto Drummond

The rich variety of the tropical ecosystems and wildlife native to the current territory of Brazil has captured the attention of several groups of observers since the early 1800s. Wildlife and landscapes in particular generated a continuous stream of appreciation of their uniqueness and concern about their integrity. This perception affected government officials and foreign traveling naturalists of the 19th century, when dozens of French, German, Austrian, English, Belgians and North American naturalists traversed the immense territory of the former Portuguese colony that had been virtually closed to trained scientists. Throughout the 20th century, newly trained Brazilian scientists and again foreign scientists, besides government officials and activist citizens, continued to explore species, ecosystems, and landscapes of what now recognized as the largest tropical country of the world. More recently, the growing amount of information about the global distribution of biodiversity placed Brazil at the top of the ranking, as a truly “megadiverse” country. As a consequence, Brazil has engaged, through environmental non-governmental organizations (NGOs), government agencies, and foreign and locally trained scientists, in a remarkable series of successful projects aimed at the identification and protection of endangered species. The country has only recently built a cadre of wildlife and ecological scientists trained to initiate and manage these types of projects. Despite the fact that these efforts are still far from being a priority in terms of its national environmental policies, Brazil has been quite active and successful in the protection of some of its most endangered animal species and their habitats.

Article

Care Beyond Repair  

Heike Drotbohm

To care about and for others—that is other people, collectivities, plants, animals, or the climate—is a mundane and ubiquitous act. At some point in life, almost every human being needs to be cared for, encounters care, and eventually provides care. In anthropology, the critical notion of care provides an analytic tool for seriously considering life’s contingencies and for understanding the ways that people ascribe meaning to different kind of acts, attitudes, and values. This chapter argues that the concept’s normative dimension forms part of a cultural binarism that hierarchizes the world according to differently valued spheres of existence. Concentrating on this normativity as inherent to the notion, the chapter distinguishes three complementary empirical fields: care as (globalized) social reproduction, care as institutionalized asymmetry, and care beyond human exceptionalism. It becomes clear that care oscillates between two different perspectives, producing a particular tension. On the one hand, the care concept features a protective and conservative dimension that is congruent with the past. On the other hand, the concept incorporates a transformational dimension through its notions of development, progress, and improvement. To move beyond our own (potentially or inevitably) academic, Eurocentric, or human-centric understanding of the notion, this essay suggests moving “care beyond repair.” We can do so, first, by asking what role research plays in this differentiating ethics and, second, by identifying perspectives and positionalities that, at first glance, appear indistinct or inarticulate and hence do not confirm already-familiar categories of evaluation and distinction. Seen this way, care beyond repair draws attention to the making and unmaking of human existence.

Article

Ecofeminism and Education  

Jennifer Hatten-Flisher and Rebecca A. Martusewicz

Ecofeminism is a theoretical, political, and educational movement that draws specific parallels between the domination of women and other marginalized groups, and the degradation of nature. While much of ecofeminist thought is focused on examining the interconnectivity between social and environmental injustices, ecofeminism is as vast and varied as its feminist and ecological roots. Yet, ecofeminism is not without its critics. After being widely accused of essentializing women’s relationship with nature, the term fell out of favor with a lot of scholars in the 1990s. Those who have remained loyal to the term have argued that this was an unfair mischaracterization of the larger foundational ideas within ecofeminist work. Given the global environmental and social crises currently sweeping the planet, ecofeminism offers important, albeit diverse, theoretical, practical, and pedagogical perspectives for developing effective responses to such interrelated crises. As such, scholars across a variety of disciplines are revisiting (and reclaiming) ecofeminist thought. In the field of education, ecofeminism is influencing the ways that we approach questions of justice by offering an intersectional framework that insists on recognizing the interconnected roots of racism, sexism, poverty, ablism, and other social problems with ecological degradation. An ethics of care is woven throughout to form the basis of a pedagogy of responsibility whereby students learn to both critique these cultural foundations of violence and identify practices and relationships that help to create healthy sustainable communities.

Article

The Harms and Crimes Against Marine Wildlife  

Alison Hutchinson

The concept of crime within traditional criminological scholarship has tended to center on human or state victims. This anthropocentric focus facilitates speciesism within criminal law, where the recognition of, and responses to, environmental and wildlife victims are diminished. In contrast, and building on the foundations of critical criminology, green criminology is less confined by the strict definitions of crime found in orthodox criminology. The emergence of nonspeciesist perspectives within green criminology offers a means to expand the concept of crime and justice to recognize the numerous harms committed toward wildlife and environmental victims. It is well documented that marine species are under numerous and increasing pressures—from climate change, acidification of oceans, and the intensification of extractive ocean industries. Species who are also regarded as food resources face additional pressures from human exploitation as markets expand and demand grows. Very few of these pressures are actively criminalized. While fishing, mining, and polluting activities, and the disturbance and trade of protected species may be prohibited in certain situations, many detrimental practices toward marine species remain normative, condoned, and encouraged (e.g., fishing, shipping, and mining activities that involve the killing, displacement, or disruption of marine species). Transformative expansion of definitions of crime is urgently needed, to recognize the legal yet harmful behaviors that continue to victimize, exploit, kill, and potentially drive marine species to extinction.

Article

The Harms and Crimes of Farming/Food  

Ekaterina Gladkova

The processes of food production and consumption illuminate the relationship between society and the natural environment as well as the inner workings of the global political economy. As a result, food has been increasingly used by scholars to explore the world, and food-focused research is a rapidly growing research area within criminology. Studies of food crime and harm challenge the legal-procedural approach in criminology by examining harmful but legal activities and challenging the limitations of the victimhood construction. Industrial farming presents a useful case study for expanding the criminological research frontiers. Although a socially normalized and even encouraged practice, it is characterized by systemic harms rooted in the normal functioning of the capitalist food system. This includes harms against more-than-human animals, the natural environment, and communities living in that environment.

Article

Pollen, Allergens, and Human Health  

Rachel N. McInnes

Allergenic pollen is produced by the flowers of a number of trees, grasses, and weeds found throughout the world. Human exposure to such pollen grains can exacerbate pollen-related asthma and allergenic conditions such as allergic rhinitis (hay fever). While allergenic pollen comes from three main groups of plants—certain trees, grasses, and weeds—many people are sensitive to pollen from one or a few taxa only. Weather, climate, and environmental conditions have a significant impact on the levels and varieties of pollen grains present in the air. These allergenic conditions significantly reduce the quality of life of affected individuals and have been shown to have a major economic impact. Pollen production depends on both the current meteorological conditions (including day length, temperature, irradiation, precipitation, and wind speed/direction), and the water availability and other environmental and meteorological conditions experienced in the previous year. The climate affects the types of vegetation and taxa that can grow in a particular location through availability of different habitats. Land-use or land management is also crucial, and so this field of study has implications for vegetation management practices and policy. Given the influential effects of weather and climate on pollen, and the significant health impacts globally, the total effect of any future environmental and climatic changes on aeroallergen production and spread will be significant. The overall impact of climate change on pollen production and spread remains highly uncertain, and there is a need for further understanding of pollen-related health impact information. There are a number of ways air quality interacts with the impact of pollen. Further understanding of the risks of co-exposure to both pollen and air pollutants is needed to better inform public health policy. Furthermore, thunderstorms have been linked to asthma epidemics, especially during the grass pollen seasons. It is thought that allergenic pollen plays a role in this “thunderstorm asthma.” To reduce the exposure to, or impact from, pollen grains in the air, a number of adaptation and mitigation options may be adopted. Many of these would need to be done either through policy changes, or at a local or regional level, although some can be done by individuals to minimize their exposure to pollen they are sensitive to. Improved aeroallergen forecast models could be developed to provide detailed taxon-specific, localized information to the public. One challenge will be combining the many different sources of aeroallergen data that are likely to become available in future into numerical forecast systems. Examples of these potential inputs are automated observations of aeroallergens, real-time phenological observations and remote sensing of vegetation, social sensing, DNA analysis of specific aeroallergens, and data from symptom trackers or personal monitors. All of these have the potential to improve the forecasts and information available to the public.

Article

Human and Nonhuman Rights to Water  

Veronica Strang

All living kinds, human and nonhuman, require rights to water. A UN Declaration upholds rights to clean drinking water and basic sanitation for humans, and some environmental legislation seeks to assure minimal flows of water in ecosystems. However, such rights are situated within complex social and political relations that are often far from equal. The distribution and management of water is entangled in issues such as ethnicity, class, gender, and levels of enfranchisement, and is heavily dependent upon how beliefs and values about water are represented in dominant narratives. Although water has been regarded a “common good” for millennia, many forms of collective ownership of freshwater have been overridden by colonial appropriations and by attempts to enclose and privatize water resources and to reframe them as commercial assets. An accelerating global water crisis caused by climate change, intensifying farming, and the over-allocation of water resources reveals unsustainable pressures on freshwater ecosystems. There have been concomitant losses of access to water for less powerful human communities, and most particularly for nonhuman beings. As a result, approximately two hundred species become extinct every day. Widespread environmental degradation has caused indigenous communities to critique the exploitative practices of colonial societies and to promote alternate and more egalitarian visions of human-nonhuman relationships. Inspired by these alternate cultural beliefs and values, and sometimes in alliance with indigenous people, conservation organizations and environmental activists have sought ecological justice to protect nonhuman beings and their habitats. Many are demanding that the UN should declare “rights for nature” and that the International Court of Criminal Justice should define “ecocide” as an international crime. Anthropologists have challenged dominant dualisms about culture and nature, providing accounts of diverse cultural worldviews in which all living kinds inhabit a nonbifurcated world. They have underlined the fluid interelationalities between human and nonhuman beings and the material environment. Building on a strong disciplinary history of advocating for human rights, they are exploring ways to articulate nonhuman needs and interests, for example, in new forms of river catchment management. There is growing consensus about the need to encourage forms of “pan-species democracy” that will ensure that all living kinds have sufficient rights to water and to the conditions that enable them to flourish.

Article

Biodiversity Generation and Loss  

T.H. Oliver

Human activities in the Anthropocene are influencing the twin processes of biodiversity generation and loss in complex ways that threaten the maintenance of biodiversity levels that underpin human well-being. Yet many scientists and practitioners still present a simplistic view of biodiversity as a static stock rather than one determined by a dynamic interplay of feedback processes that are affected by anthropogenic drivers. Biodiversity describes the variety of life on Earth, from the genes within an organism to the ecosystem level. However, this article focuses on variation among living organisms, both within and between species. Within species, biodiversity is reflected in genetic, and consequent phenotypic, variations among individuals. Genetic diversity is generated by germ line mutations, genetic recombination during sexual reproduction, and immigration of new genotypes into populations. Across species, biodiversity is reflected in the number of different species present and also, by some metrics, in the evenness of their relative abundance. At this level, biodiversity is generated by processes of speciation and immigration of new species into an area. Anthropogenic drivers affect all these biodiversity generation processes, while the levels of genetic diversity can feed back and affect the level of species diversity, and vice versa. Therefore, biodiversity maintenance is a complex balance of processes and the biodiversity levels at any point in time may not be at equilibrium. A major concern for humans is that our activities are driving rapid losses of biodiversity, which outweigh by orders of magnitude the processes of biodiversity generation. A wide range of species and genetic diversity could be necessary for the provision of ecosystem functions and services (e.g., in maintaining the nutrient cycling, plant productivity, pollination, and pest control that underpin crop production). The importance of biodiversity becomes particularly marked over longer time periods, and especially under varying environmental conditions. In terms of biodiversity losses, there are natural processes that cause roughly continuous, low-level losses, but there is also strong evidence from fossil records for transient events in which exceptionally large loss of biodiversity has occurred. These major extinction episodes are thought to have been caused by various large-scale environmental perturbations, such as volcanic eruptions, sea-level falls, climatic changes, and asteroid impacts. From all these events, biodiversity has shown recovery over subsequent calmer periods, although the composition of higher-level evolutionary taxa can be significantly altered. In the modern era, biodiversity appears to be undergoing another mass extinction event, driven by large-scale human impacts. The primary mechanisms of biodiversity loss caused by humans vary over time and by geographic region, but they include overexploitation, habitat loss, climate change, pollution (e.g., nitrogen deposition), and the introduction of non-native species. It is worth noting that human activities may also lead to increases in biodiversity in some areas through species introductions and climatic changes, although these overall increases in species richness may come at the cost of loss of native species, and with uncertain effects on ecosystem service delivery. Genetic diversity is also affected by human activities, with many examples of erosion of diversity through crop and livestock breeding or through the decline in abundance of wild species populations. Significant future challenges are to develop better ways to monitor the drivers of biodiversity loss and biodiversity levels themselves, making use of new technologies, and improving coverage across geographic regions and taxonomic scope. Rather than treating biodiversity as a simple stock at equilibrium, developing a deeper understanding of the complex interactions—both between environmental drivers and between genetic and species diversity—is essential to manage and maintain the benefits that biodiversity delivers to humans, as well as to safeguard the intrinsic value of the Earth’s biodiversity for future generations.

Article

Sentinel Species of Marine Ecosystems  

Maria Cristina Fossi and Cristina Panti

A vigorous effort to identify and study sentinel species of marine ecosystem in the world’s oceans has developed over the past 50 years. The One Health concept recognizes that the health of humans is connected to the health of animals and the environment. Species ranging from invertebrate to large marine vertebrates have acted as “sentinels” of the exposure to environmental stressors and health impacts on the environment that may also affect human health. Sentinel species can signal warnings, at different levels, about the potential impacts on a specific ecosystem. These warnings can help manage the abiotic and anthropogenic stressors (e.g., climate change, chemical and microbial pollutants, marine litter) affecting ecosystems, biota, and human health. The effects of exposure to multiple stressors, including pollutants, in the marine environment may be seen at multiple trophic levels of the ecosystem. Attention has focused on the large marine vertebrates, for several reasons. In the past, the use of large marine vertebrates in monitoring and assessing the marine ecosystem has been criticized. The fact that these species are pelagic and highly mobile has led to the suggestion that they are not useful indicators or sentinel species. In recent years, however, an alternative view has emerged: when we have a sufficient understanding of differences in species distribution and behavior in space and time, these species can be extremely valuable sentinels of environmental quality. Knowledge of the status of large vertebrate populations is crucial for understanding the health of the ecosystem and instigating mitigation measures for the conservation of large vertebrates. For example, it is well known that the various cetacean species exhibit different home ranges and occupy different habitats. This knowledge can be used in “hot spot” areas, such as the Mediterranean Basin, where different species can serve as sentinels of marine environmental quality. Organisms that have relatively long life spans (such as cetaceans) allow for the study of chronic diseases, including reproductive alterations, abnormalities in growth and development, and cancer. As apex predators, marine mammals feed at or near the top of the food chain. As the result of biomagnification, the levels of anthropogenic contaminants found in the tissues of top predators and long-living species are typically high. Finally, the application of consistent examination procedures and biochemical, immunological, and microbiological techniques, combined with pathological examination and behavioral analysis, has led to the development of health assessment methods at the individual and population levels in wild marine mammals. With these tools in hand, investigators have begun to explore and understand the relationships between exposures to environmental stressors and a range of disease end points in sentinel species (ranging from invertebrates to marine mammals) as an indicator of ecosystem health and a harbinger of human health and well-being.

Article

Extinction  

Mark V. Barrow

The prospect of extinction, the complete loss of a species or other group of organisms, has long provoked strong responses. Until the turn of the 18th century, deeply held and widely shared beliefs about the order of nature led to a firm rejection of the possibility that species could entirely vanish. During the 19th century, however, resistance to the idea of extinction gave way to widespread acceptance following the discovery of the fossil remains of numerous previously unknown forms and direct experience with contemporary human-driven decline and the destruction of several species. In an effort to stem continued loss, at the turn of the 19th century, naturalists, conservationists, and sportsmen developed arguments for preventing extinction, created wildlife conservation organizations, lobbied for early protective laws and treaties, pushed for the first government-sponsored parks and refuges, and experimented with captive breeding. In the first half of the 20th century, scientists began systematically gathering more data about the problem through global inventories of endangered species and the first life-history and ecological studies of those species. The second half of the 20th and the beginning of the 21st centuries have been characterized both by accelerating threats to the world’s biota and greater attention to the problem of extinction. Powerful new laws, like the U.S. Endangered Species Act of 1973, have been enacted and numerous international agreements negotiated in an attempt to address the issue. Despite considerable effort, scientists remain fearful that the current rate of species loss is similar to that experienced during the five great mass extinction events identified in the fossil record, leading to declarations that the world is facing a biodiversity crisis. Responding to this crisis, often referred to as the sixth extinction, scientists have launched a new interdisciplinary, mission-oriented discipline, conservation biology, that seeks not just to understand but also to reverse biota loss. Scientists and conservationists have also developed controversial new approaches to the growing problem of extinction: rewilding, which involves establishing expansive core reserves that are connected with migratory corridors and that include populations of apex predators, and de-extinction, which uses genetic engineering techniques in a bid to resurrect lost species. Even with the development of new knowledge and new tools that seek to reverse large-scale species decline, a new and particularly imposing danger, climate change, looms on the horizon, threatening to undermine those efforts.