Jan Zalasiewicz and Colin Waters
The Anthropocene hypothesis—that humans have impacted “the environment” but also changed the Earth’s geology—has spread widely through the sciences and humanities. This hypothesis is being currently tested to see whether the Anthropocene may become part of the Geological Time Scale. An Anthropocene Working Group has been established to assemble the evidence. The decision regarding formalization is likely to be taken in the next few years, by the International Commission on Stratigraphy, the body that oversees the Geological Time Scale. Whichever way the decision goes, there will remain the reality of the phenomenon and the utility of the concept.
The evidence, as outlined here, rests upon a broad range of signatures reflecting humanity’s significant and increasing modification of Earth systems. These may be visible as markers in physical deposits in the form of the greatest expansion of novel minerals in the last 2.4 billion years of Earth history and development of ubiquitous materials, such as plastics, unique to the Anthropocene. The artefacts we produce to live as modern humans will form the technofossils of the future. Human-generated deposits now extend from our natural habitat on land into our oceans, transported at rates exceeding the sediment carried by rivers by an order of magnitude. That influence now extends increasingly underground in our quest for minerals, fuel, living space, and to develop transport and communication networks. These human trace fossils may be preserved over geological durations and the evolution of technology has created a new technosphere, yet to evolve into balance with other Earth systems.
The expression of the Anthropocene can be seen in sediments and glaciers in chemical markers. Carbon dioxide in the atmosphere has risen by ~45 percent above pre–Industrial Revolution levels, mainly through combustion, over a few decades, of a geological carbon-store that took many millions of years to accumulate. Although this may ultimately drive climate change, average global temperature increases and resultant sea-level rises remain comparatively small, as yet. But the shift to isotopically lighter carbon locked into limestones and calcareous fossils will form a permanent record. Nitrogen and phosphorus contents in surface soils have approximately doubled through increased use of fertilizers to increase agricultural yields as the human population has also doubled in the last 50 years. Industrial metals, radioactive fallout from atomic weapons testing, and complex organic compounds have been widely dispersed through the environment and become preserved in sediment and ice layers.
Despite radical changes to flora and fauna across the planet, the Earth still has most of its complement of biological species. However, current trends of habitat loss and predation may push the Earth into the sixth mass extinction event in the next few centuries. At present the dramatic changes relate to trans-global species invasions and population modification through agricultural development on land and contamination of coastal zones.
Considering the entire range of environmental signatures, it is clear that the global, large and rapid scale of change related to the mid-20th century is the most obvious level to consider as the start of the Anthropocene Epoch.
Peter Kareiva and Isaac Kareiva
The concept of biodiversity hotspots arose as a science-based framework with which to identify high-priority areas for habitat protection and conservation—often in the form of nature reserves. The basic idea is that with limited funds and competition from humans for land, we should use range maps and distributional data to protect areas that harbor the greatest biodiversity and that have experienced the greatest habitat loss. In its early application, much analysis and scientific debate went into asking the following questions: Should all species be treated equally? Do endemic species matter more? Should the magnitude of threat matter? Does evolutionary uniqueness matter? And if one has good data on one broad group of organisms (e.g., plants or birds), does it suffice to focus on hotspots for a few taxonomic groups and then expect to capture all biodiversity broadly? Early applications also recognized that hotspots could be identified at a variety of spatial scales—from global to continental, to national to regional, to even local. Hence, within each scale, it is possible to identify biodiversity hotspots as targets for conservation.
In the last 10 years, the concept of hotspots has been enriched to address some key critiques, including the problem of ignoring important areas that might have low biodiversity but that certainly were highly valued because of charismatic wild species or critical ecosystem services. Analyses revealed that although the spatial correlation between high-diversity areas and high-ecosystem-service areas is low, it is possible to use quantitative algorithms that achieve both high protection for biodiversity and high protection for ecosystem services without increasing the required area as much as might be expected.
Currently, a great deal of research is aimed at asking about what the impact of climate change on biodiversity hotspots is, as well as to what extent conservation can maintain high biodiversity in the face of climate change. Two important approaches to this are detailed models and statistical assessments that relate species distribution to climate, or alternatively “conserving the stage” for high biodiversity, whereby the stage entails regions with topographies or habitat heterogeneity of the sort that is expected to generate high species richness.
Finally, conservation planning has most recently embraced what is in some sense the inverse of biodiversity hotspots—what we might call conservation wastelands. This approach recognizes that in the Anthropocene epoch, human development and infrastructure are so vast that in addition to using data to identify biodiversity hotspots, we should use data to identify highly degraded habitats and ecosystems. These degraded lands can then become priority development areas—for wind farms, solar energy facilities, oil palm plantations, and so forth. By specifying degraded lands, conservation plans commonly pair maps of biodiversity hotspots with maps of degraded lands that highlight areas for development. By putting the two maps together, it should be possible to achieve much more effective conservation because there will be provision of habitat for species and for economic development—something that can obtain broader political support than simply highlighting biodiversity hotspots.
Although the concept of biodiversity emerged 30 years ago, patterns and processes influencing ecological diversity have been studied for more than a century. Historically, ecological processes tended to be considered as occurring in local habitats that were spatially homogeneous and temporally at equilibrium. Initially considered as a constraint to be avoided in ecological studies, spatial heterogeneity was progressively recognized as critical for biodiversity. This resulted, in the 1970s, in the emergence of a new discipline, landscape ecology, whose major goal is to understand how spatial and temporal heterogeneity influence biodiversity. To achieve this goal, researchers came to realize that a fundamental issue revolves around how they choose to conceptualize and measure heterogeneity. Indeed, observed landscape patterns and their apparent relationship with biodiversity often depend on the scale of observation and the model used to describe the landscape. Due to the strong influence of island biogeography, landscape ecology has focused primarily on spatial heterogeneity. Several landscape models were conceptualized, allowing for the prediction and testing of distinct but complementary effects of landscape heterogeneity on species diversity. We now have ample empirical evidence that patch structure, patch context, and mosaic heterogeneity all influence biodiversity. More recently, the increasing recognition of the role of temporal scale has led to the development of new conceptual frameworks acknowledging that landscapes are not only heterogeneous but also dynamic. The current challenge remains to truly integrate both spatial and temporal heterogeneity in studies on biodiversity. This integration is even more challenging when considering that biodiversity often responds to environmental changes with considerable time lags, and multiple drivers of global changes are interacting, resulting in non-additive and sometimes antagonistic effects. Recent technological advances in remote sensing, the availability of massive amounts of data, and long-term studies represent, however, very promising avenues to improve our understanding of how spatial and temporal heterogeneity influence biodiversity.
Regimes of environmental stress are exceedingly complex. Particular stressors exist within continua of intensity of environmental factors. Those factors interact with each other, and their detrimental effects on organisms are manifest only at relatively high or low strengths of exposure—in fact, many of them are beneficial at intermediate levels of intensity. Although a diversity of environmental factors is manifest at any time and place, only one or a few of them tend to be dominant as stressors. It is useful to distinguish between stressors that occur as severe events (disturbances) and those that are chronic in their exposure, and to aggregate the kinds of stressors into categories (while noting some degree of overlap among them).
Climatic stressors are associated with extremes of temperature, solar radiation, wind, moisture, and combinations of these factors. They act as stressors if their condition is either insufficient or excessive, in comparison with the needs and comfort zones of organisms or ecosystem processes. Chemical stressors involve environments in which the availability of certain substances is too low to satisfy biological needs, or high enough to cause toxicity or another physiological detriment to organisms or to higher-level attributes of ecosystems. Wildfire is a disturbance that involves the combustion of much of the biomass of an ecosystem, affecting organisms by heat, physical damage, and toxic substances. Physical stress is a disturbance in which an exposure to kinetic energy is intense enough to damage organisms and ecosystems (such as a volcanic blast, seismic sea wave, ice scouring, or anthropogenic explosion or trampling).
Biological stressors are associated with interactions occurring among organisms. They may be directly caused by such trophic interactions as herbivory, predation, and parasitism. They may also indirectly affect the intensity of physical or chemical stressors, as when competition affects the availability of nutrients, moisture, or space.
Extreme environments are characterized by severe regimes of stressors, which result in relatively impoverished ecosystem development. This may be a consequence of either natural or anthropogenic stressors. If a regime of environmental stress intensifies, the resulting responses include a degradation of the structure and function of affected ecosystems and of ecological integrity more generally. In contrast, a relaxation of environmental stress allows some degree of ecosystem recovery.
Leon C. Braat
The concept of ecosystem services considers the usefulness of nature for human society. The economic importance of nature was described and analyzed in the 18th century, but the term ecosystem services was introduced only in 1981. Since then it has spurred an increasing number of academic publications, international research projects, and policy studies. Now a subject of intense debate in the global scientific community, from the natural to social science domains, it is also used, developed, and customized in policy arenas and considered, if in a still somewhat skeptical and apprehensive way, in the “practice” domain—by nature management agencies, farmers, foresters, and corporate business. This process of bridging evident gaps between ecology and economics, and between nature conservation and economic development, has also been felt in the political arena, including in the United Nations and the European Union (which have placed it at the center of their nature conservation and sustainable use strategies).
The concept involves the utilitarian framing of those functions of nature that are used by humans and considered beneficial to society as economic and social services. In this light, for example, the disappearance of biodiversity directly affects ecosystem functions that underpin critical services for human well-being. More generally, the concept can be defined in this manner: Ecosystem services are the direct and indirect contributions of ecosystems, in interaction with contributions from human society, to human well-being.
The concept underpins four major discussions: (1) Academic: the ecological versus the economic dimensions of the goods and services that flow from ecosystems to the human economy; the challenge of integrating concepts and models across this paradigmatic divide; (2) Social: the risks versus benefits of bringing the utilitarian argument into political debates about nature conservation (Are ecosystem services good or bad for biodiversity and vice versa?); (3) Policy and planning: how to value the benefits from natural capital and ecosystem services (Will this improve decision-making on topics ranging from poverty alleviation via subsidies to farmers to planning of grey with green infrastructure to combining economic growth with nature conservation?); and (4) Practice: Can revenue come from smart management and sustainable use of ecosystems? Are there markets to be discovered and can businesses be created? How do taxes figure in an ecosystem-based economy? The outcomes of these discussions will both help to shape policy and planning of economies at global, national, and regional scales and contribute to the long-term survival and well-being of humanity.
Elisabet Lindgren and Thomas Elmqvist
Ecosystem services refer to benefits for human societies and well-being obtained from ecosystems. Research on health effects of ecosystem services have until recently mostly focused on beneficial effects on physical and mental health from spending time in nature or having access to urban green space. However, nearly all of the different ecosystem services may have impacts on health, either directly or indirectly. Ecosystem services can be divided into provisioning services that provide food and water; regulating services that provide, for example, clean air, moderate extreme events, and regulate the local climate; supporting services that help maintain biodiversity and infectious disease control; and cultural services.
With a rapidly growing global population, the demand for food and water will increase. Knowledge about ecosystems will provide opportunities for sustainable agriculture production in both terrestrial and marine environments. Diarrheal diseases and associated childhood deaths are strongly linked to poor water quality, sanitation, and hygiene. Even though improvements are being made, nearly 750 million people still lack access to reliable water sources. Ecosystems such as forests, wetlands, and lakes capture, filter, and store water used for drinking, irrigation, and other human purposes. Wetlands also store and treat solid waste and wastewater, and such ecosystem services could become of increasing use for sustainable development.
Ecosystems contribute to local climate regulation and are of importance for climate change mitigation and adaptation. Coastal ecosystems, such as mangrove and coral reefs, act as natural barriers against storm surges and flooding. Flooding is associated with increased risk of deaths, epidemic outbreaks, and negative health impacts from destroyed infrastructure. Vegetation reduces the risk of flooding, also in cities, by increasing permeability and reducing surface runoff following precipitation events.
The urban heat island effect will increase city-center temperatures during heatwaves. The elderly, people with chronic cardiovascular and respiratory diseases, and outdoor workers in cities where temperatures soar during heatwaves are in particular vulnerable to heat. Vegetation and especially trees help in different ways to reduce temperatures by shading and evapotranspiration. Air pollution increases the mortality and morbidity risks during heatwaves. Vegetation has been shown also to contribute to improved air quality by, depending on plant species, filtering out gases and airborne particulates. Greenery also has a noise-reducing effect, thereby decreasing noise-related illnesses and annoyances. Biological control uses the knowledge of ecosystems and biodiversity to help control human and animal diseases.
Natural surroundings and urban parks and gardens have direct beneficial effects on people’s physical and mental health and well-being. Increased physical activities have well-known health benefits. Spending time in natural environments has also been linked to aesthetic benefits, life enrichments, social cohesion, and spiritual experience. Even living close to or with a view of nature has been shown to reduce stress and increase a sense of well-being.
Giles Jackson and Megan Epler Wood
This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Environmental Science. Please check back later for the full article.
Ecotourism is an evolving field that originated in the 1980s, when leading conservationists explored and wrote seminal papers on how tourism could contribute to the conservation of natural areas. Hector Ceballos Lascurain coined the first definition, and the International Union for Conservation of Nature, the World Wildlife Fund, Conservation International, and The Nature Conservancy all undertook research and documentation of the benefits and potential risks of ecotourism in the 1990s. The International Ecotourism Society, founded in 1990, brought together conservation organizations and businesses to create the first definition that was globally accepted in short form: Responsible travel to natural areas that conserves the environment and sustains the well-being of local people.
Small group tour operators flourished during the 1990s, bringing travelers to a growing number of natural areas worldwide, together with top guiding, high-caliber interpretation, and strong ethical contributions to local wellbeing. Many important micro, small, and medium sized enterprises were founded in high biodiversity regions of Latin America, Asia, Africa, Antarctica, Australia, and throughout the Pacific Islands and the Caribbean, offering life-changing experiences while helping build conservation economies and inspiring positive action.
In 2015, nature-based tourism was estimated to have an economic value worldwide of hundreds of billions of dollars annually in protected areas alone, driven by the growing need of a rapidly urbanizing world to experience and reconnect with wild nature. However, this growth has not resulted in growing budgets to safeguard and manage natural areas, which are increasingly under threat. Scientific concerns that poor business practices under the guise of ecotourism might irreversibly damage fragile natural areas have led the conservation community to de-emphasize ecotourism as a conservation tool in favor of business certification. But these efforts have reached only a small percentage of the corporate sector of the eight trillion dollar global tourism industry.
Although the net economic, social, and environmental contributions of ecotourism have not been fully accounted for, the research to date has confirmed the conservation value of ecotourism—among the first examples of social enterprise. One well-documented case is Wilderness Safaris, an $89 million company operating in 58 destinations in Southern Africa in 2015, which reinvests at least 5% of its gross profit (before taxation and depreciation) to help protect the natural assets and support local communities on which the business depends. This example suggests that ecotourism can yield benefits for the conservation of biodiversity and can benefit local communities on a large scale. To increase ecotourism’s role in sustainable development, more businesses will need to scale up, and government management of tourism will require improved impact measurements, updated regulatory strategies, and effective policy mechanisms to garner a greater portion of tourism revenue.
Jean Louis Weber
This is an advance summary of a forthcoming article in the Oxford Research Encyclopedia of Environmental Science. Please check back later for the full article.
Environmental accounting is an attempt to broaden the scope of the accounting frameworks used to assess economic performance in order to take stock of elements that are not adequately recorded in books. Although national accounting has been the driving force, environmental accounting encompasses all accounting frameworks, including national accounts, financial accounting standards, and accounts established to assess the costs and benefits of plans and projects.
There are several approaches to economic environmental accounting at the national level. One purpose is the calculation of the genuine economic welfare, by taking into account the losses from environmental damages caused by economic activity and the gains from unrecorded services provided by nature. Particular attention is given here to the calculation of a “Green GDP” or “Adjusted National Income” and/or “Genuine Savings,” as well as natural assets value and depletion. A different view considers the damages caused to renewable natural capital and the resulting maintenance and restoration costs. Beside approaches of benefits and costs, more descriptive accounts in physical units are produced with the purpose of assessing resource use efficiency. With regard to natural assets, the focus can be on the ones directly used by the economy, or more broadly on the ecosystem capacity to deliver services, ecosystem resilience, and its possible degradation.
These different approaches are not necessarily contradictory, although controversies are noted in the literature. The discussion focuses on issues such as the legitimacy of combining values obtained with shadow prices (needed to value the elements that are not priced by the market) with the transaction values recorded in the national accounts, the relative importance of accounts in monetary vs. physical units, and ultimately, the goals for environmental accounting. These goals include assessing the sustainability of the economy in terms of conservation (or increase) of the net income flow and total economic wealth (the weak sustainability paradigm) in relation to the sustainability of the ecosystem, which supports livelihoods and well-being in the broader sense (strong sustainability).
In 2012, the UN Statistical Commission adopted an international statistical standard called SEEA-CF (System of Environmental-Economic Accounting Central Framework). The SEEA-CF covers only items that are mature enough to be proposed for implementation by national statistical offices. A second volume on SEEA-Experimental Ecosystem Accounting (EEA) was added in 2013, to supplement the SEEA-CF with a research agenda and the development of tests. Experiments of the SEEA-EEA are developing at the initiative of the World Bank (WAVES), UNEP (VANTAGE, ProEcoServ), or the CBD (SEEA-ENCA-QSP).
Beside the SEEA, and in relation to it, we can mention other environmental accounting frameworks, developed for specific purposes: “material flow accounting” (MFA), which is now a regular framework at the OECD; the IPCC guidelines for UNFCCC reporting; the Ecological Footprint; and the Millennium Ecosystem Assessment of 2005. Environmental accounting is also a subject of interest for business, both as a way to assess impacts, costs, and benefits of projects and to define new accounting standards to assess long-term performance and risks.
David E. Clay, Sharon A. Clay, Thomas DeSutter, and Cheryl Reese
Since the discovery that food security could be improved by pushing seeds into the soil and later harvesting a desirable crop, agriculture and agronomy have gone through cycles of discovery, implementation, and innovation. Discoveries have produced predicted and unpredicted impacts on the production and consumption of locally produced foods. Changes in technology, such as the development of the self-cleaning steel plow in the 18th century, provided a critical tool needed to cultivate and seed annual crops in the Great Plains of North America. However, plowing the Great Plains would not have been possible without the domestication of plants and animals and the discovery of the yoke and harness. Associated with plowing the prairies were extensive soil nutrient mining, a rapid loss of soil carbon, and increased wind and water erosion. More recently, the development of genetically modified organisms (GMOs) and no-tillage planters has contributed to increased adoption of conservation tillage, which is less damaging to the soil. In the future, the ultimate impact of climate change on agronomic practices in the North American Great Plains is unknown. However, projected increasing temperatures and decreased rainfall in the southern Great Plains (SGP) will likely reduce agricultural productivity. Different results are likely in the northern Great Plains (NGP) where higher temperatures can lead to increased agricultural intensification, the conversion of grassland to cropland, increased wildlife fragmentation, and increased soil erosion. Precision farming, conservation, cover crops, and the creation of plants better designed to their local environment can help mitigate these effects. However, changing practices require that farmers and their advisers understand the limitations of the soils, plants, and environment, and their production systems. Failure to implement appropriate management practices can result in a rapid decline in soil productivity, diminished water quality, and reduced wildlife habitat.
Fred Mackenzie and Abraham Lerman
The tendency to represent natural processes as cycles—from Latin cyclus and Greek κυκλος—is undoubtedly rooted in the human observations of repeating or periodic phenomena. The oldest notions of the water cycle, as water cycling between the Earth, air, and back to earth, are mentioned in the Old Testament and by Greek philosophers, from the 900s to 300s
The main “bioessential” chemical elements are carbon (C), nitrogen (N), phosphorus (P), oxygen (O), and hydrogen (H). These are represented in the mean composition of aquatic photosynthesizing organisms as the atomic abundance ratio C:N:P = 106:16:1 or as (CH2O)106(NH3)16(H3PO4). In land plants, estimates of mean composition vary from C:N:P = 510:4:1 to 2057:17:1. On land, the photosynthesizing organisms are much more efficient than in water by being able to incorporate more carbon atoms for each atom of phosphorus. The bioessential elements are coupled by the living organisms in the exogenic cycle, the processes at and near the Earth’s surface, and in the endogenic cycle of the processes that include subduction into the Earth’s interior and return to the surface. The main reservoirs of the bioessential elements are very different: although oxygen is the most abundant element in the Earth’s crust, most of it is locked in silicate minerals as SiO2, and the forms available to biogeochemical cycling are oxygen in water and, as a product of photosynthesis, as gas O2 in the atmosphere. Carbon is in the atmospheric reservoir of CO2 gas and dissolved in ocean and fresh waters. The main nitrogen reservoir is the molecular N2 in the atmosphere and oxidized and reduced nitrogen compounds in waters. Phosphorus occurs in the oxidized form of the phosphate-ion in crustal minerals, from where it is leached into the water.
The natural cycle of the bioessential elements has been greatly perturbed since the late 1700s by human industrial and agricultural activities, the period known as the Anthropocene epoch. The increase in CO2, CH4 and NOx emissions to the atmosphere from fossil-fuel burning and land-use changes has rapidly and strongly modified the chemical composition of the atmosphere. This change has affected the balance of solar radiation absorbed by the atmosphere—generally known as “climate change”—and the acidity of surface-ocean waters, referred to as “ocean acidification.” CO2 in water is a weak acid that dissolves carbonate minerals, biogenically and inorganically formed in the ocean, and it thus modifies the chemical composition of ocean water. Overall, a major anthropogenic perturbation of the biogeochemical cycles has been the faster increase in atmospheric concentration of CO2 than its removal from the atmosphere by plants, dissolution in the ocean, and uptake in mineral weathering.