261-280 of 333 Results

Article

The Role of Tourism in Sustainable Development  

Robert B. Richardson

Sustainable development is the foundational principle for enhancing human and economic development while maintaining the functional integrity of ecological and social systems that support regional economies. Tourism has played a critical role in sustainable development in many countries and regions around the world. In developing countries, tourism development has been used as an important strategy for increasing economic growth, alleviating poverty, creating jobs, and improving food security. Many developing countries are in regions that are characterized by high levels of biological diversity, natural resources, and cultural heritage sites that attract international tourists whose local purchases generate income and support employment and economic development. Tourism has been associated with the principles of sustainable development because of its potential to support environmental protection and livelihoods. However, the relationship between tourism and the environment is multifaceted, as some types of tourism have been associated with negative environmental impacts, many of which are borne by host communities. The concept of sustainable tourism development emerged in contrast to mass tourism, which involves the participation of large numbers of people, often in structured or packaged tours. Mass tourism has been associated with economic leakage and dependence, along with negative environmental and social impacts. Sustainable tourism development has been promoted in various ways as a framing concept in contrast to these economic, environmental, and social impacts. Some literature has acknowledged a vagueness of the concept of sustainable tourism, which has been used to advocate for fundamentally different strategies for tourism development that may exacerbate existing conflicts between conservation and development paradigms. Tourism has played an important role in sustainable development in some countries through the development of alternative tourism models, including ecotourism, community-based tourism, pro-poor tourism, slow tourism, green tourism, and heritage tourism, among others that aim to enhance livelihoods, increase local economic growth, and provide for environmental protection. Although these models have been given significant attention among researchers, the extent of their implementation in tourism planning initiatives has been limited, superficial, or incomplete in many contexts. The sustainability of tourism as a global system is disputed among scholars. Tourism is dependent on travel, and nearly all forms of transportation require the use of non-renewable resources such as fossil fuels for energy. The burning of fossil fuels for transportation generates emissions of greenhouse gases that contribute to global climate change, which is fundamentally unsustainable. Tourism is also vulnerable to both localized and global shocks. Studies of the vulnerability of tourism to localized shocks include the impacts of natural disasters, disease outbreaks, and civil unrest. Studies of the vulnerability of tourism to global shocks include the impacts of climate change, economic crisis, global public health pandemics, oil price shocks, and acts of terrorism. It is clear that tourism has contributed significantly to economic development globally, but its role in sustainable development is uncertain, debatable, and potentially contradictory.

Article

Sea Level Rise and Coastal Management  

James B. London

Coastal zone management (CZM) has evolved since the enactment of the U.S. Coastal Zone Management Act of 1972, which was the first comprehensive program of its type. The newer iteration of Integrated Coastal Zone Management (ICZM), as applied to the European Union (2000, 2002), establishes priorities and a comprehensive strategy framework. While coastal management was established in large part to address issues of both development and resource protection in the coastal zone, conditions have changed. Accelerated rates of sea level rise (SLR) as well as continued rapid development along the coasts have increased vulnerability. The article examines changing conditions over time and the role of CZM and ICZM in addressing increased climate related vulnerabilities along the coast. The article argues that effective adaptation strategies will require a sound information base and an institutional framework that appropriately addresses the risk of development in the coastal zone. The information base has improved through recent advances in technology and geospatial data quality. Critical for decision-makers will be sound information to identify vulnerabilities, formulate options, and assess the viability of a set of adaptation alternatives. The institutional framework must include the political will to act decisively and send the right signals to encourage responsible development patterns. At the same time, as communities are likely to bear higher costs for adaptation, it is important that they are given appropriate tools to effectively weigh alternatives, including the cost avoidance associated with corrective action. Adaptation strategies must be pro-active and anticipatory. Failure to act strategically will be fiscally irresponsible.

Article

Seed Banking as Future Insurance Against Crop Collapses  

Fiona Hay

Food security is dependent on the work of plant scientists and breeders who develop new varieties of crops that are high yielding, nutritious, and tolerate a range of biotic and abiotic stresses. These scientists and breeders need access to novel genetic material to evaluate and to use in their breeding programs; seed- (gene-)banks are the main source of novel genetic material. There are more than 1,750 genebanks around the world that are storing the orthodox (desiccation tolerant) seeds of crops and their wild relatives. These seeds are stored at low moisture content and low temperature to extend their longevity and ensure that seeds with high viability can be distributed to end-users. Thus, seed genebanks serve two purposes: the long-term conservation of plant genetic resources, and the distribution of seed samples. Globally, there are more than 7,400,000 accessions held in genebanks; an accession is a supposedly distinct, uniquely identifiable germplasm sample which represents a particular landrace, variety, breeding line, or population. Genebank staff manage their collections to ensure that suitable material is available and that the viability of the seeds remains high. Accessions are regenerated if viability declines or if stocks run low due to distribution. Many crops come under the auspices of the International Treaty on Plant Genetic Resources for Food and Agriculture and germplasm is shared using the Standard Material Transfer Agreement. The Treaty collates information on the sharing of germplasm with a view to ensuring that farmers ultimately benefit from making their agrobiodiversity available. Ongoing research related to genebanks covers a range of disciplines, including botany, seed and plant physiology, genetics, geographic information science, and law.

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

Smart Cities and Water Infrastructure  

Katherine Lieberknecht

Water infrastructure is the system of physical (both built and environmental), social (e.g., governance), and technological elements that move water into, throughout, and out of human communities. It includes, but is not limited to, water supply infrastructure (e.g., pipe systems, water treatment facilities), drainage and flood infrastructure (e.g., storm sewers, green infrastructure systems, levees), and wastewater treatment infrastructure (e.g., pipe systems, wastewater treatment plants, reclaimed water facilities). Smart city approaches to water infrastructure emphasize integration of information and communication technologies with urban water infrastructure and services, usually with the goal of increasing efficiency and human well-being. Smart water meters, smart water grids, and other water-related information and communication technologies have the potential to improve overall infrastructure efficiency, to reduce water use, to match new water supplies with appropriate water uses, to innovate wastewater treatment, and to protect residents from floods and other water-related climate events. However, without stronger attention to issues of equity, social systems, governance, ecology, and place, a smart city approach to water infrastructure may achieve efficiencies but fail to generate broader socioecological values or to contribute toward climate adaptation.

Article

Smart One Water: An Integrated Approach for the Next Generation of Sustainable and Resilient Water Systems  

Sunil K. Sinha, Meghna Babbar-Sebens, David Dzombak, Paolo Gardoni, Bevlee Watford, Glenda Scales, Neil Grigg, Edgar Westerhof, Kenneth Thompson, and Melissa Meeker

Quality of life for all people and communities is directly linked to the availability of clean and abundant water. Natural and built water systems are threatened by crumbling infrastructure, floods, drought, storms, wildfires, sea-level rise, population growth, cybersecurity breaches, and pollution, often in combination. Marginalized communities feel the worst impacts, and responses are hampered by fragmented and antiquated governance and management practices. A standing grand challenge for the water sector is transitioning society to a future where current silos are transformed into a significantly more efficient, effective, and equitable One Water system-of-systems paradigm—in other words, a future where communities are able to integrate the governance and management of natural and engineered water systems at all scales of decision-making in a river basin. Innovation in digital technologies that connect data, people, and organizations can be game changers in addressing this societal grand challenge. It is envisioned that advancing digital capabilities in the water sector will require a Smart One Water approach, one that builds upon new technologies and research advancements in multiple disciplines, including those in engineering, computer science, and social science. However, several fundamental knowledge gaps at the nexus of physical, social, and cyber sciences currently exist on how a nationwide Smart One Water approach can be created, operationalized, and maintained. Convergent research is needed to investigate these gaps and improve our current understanding of Smart One Water approaches, including the costs, risks, and benefits to diverse communities in the rural-to-urban continuum. At its core, implementing the Smart One Water approach requires a science-based, stakeholder-driven, and artificial intelligence (AI)–enabled cyberinfrastructure platform, one that can provide a robust framework to support networks of river-basin collaborations. We refer to this envisioned cyberinfrastructure foundation as the digital research and operational platform (DROP). DROP is envisioned to exploit advances in data analytics, machine learning, information, communication, and decision support technologies for the management of One Water systems via AI-enabled digital twins of river-basin systems. Deploying DROP at a large-basin scale requires an understanding of (a) physical water systems (natural and engineered) at the basin scale, which interact with each other in a dynamic environment affected by climate change and other societal trends and whose data, functions, and processes must be integrated to create digital twins of river basins; (b) the social aspects of One Water systems by understanding the values and perspectives of stakeholders, costs and benefits of water management practices and decisions, and the specific needs of disadvantaged populations in river basin communities; (c) approaches for developing and deploying the digital technologies, analytics, and AI required to efficiently operate and manage Smart One Water systems in small to large communities; (d) strategies for training and advancing the next-generation workforce who have expertise on cyber, physical, and social aspects of One Water systems; and (e) lessons learned from testing and evaluating DROP in diverse testbeds. The article describes a strategic plan for operationalizing Smart One Water management and governance in the United States. The plan is based on five foundational pillars: (a) river-basin scale governance, (b) workforce development, (c) innovation ecosystem, (d) diversity and inclusion, and (e) stakeholder engagement. Workshops were conducted for each foundational pillar among diverse stakeholders representing federal, state, and local governments; utilities; industry; nongovernmental organizations; academics; and the general public. The workshops confirmed the strong desire of water communities to embrace, integrate, and grow the Smart One Water approach. Recommendations were generated for using the foundational pillars to guide strategic plans to implement a national-scale Smart One Water program and facilitate its adoption by communities in the United States, with global applications to follow.

Article

Social and Environmental Implications of Plantation Agriculture in Malaysia and Indonesia  

Jean-François Bissonnette and Rodolphe De Koninck

Plantation farming emerged as a large-scale system of specialized agriculture in the tropics under European colonialism, in opposition to smallholding subsistence agriculture. Despite large-scale plantations in the tropics, smallholdings have consistently formed the backbone of rural economies, to the extent that they have become the main producers of some of the former plantation crops. In the early 21st century, oil palm has become the third most important cash crop in the world in terms of area cultivated, largely due to the expansion of this crop in Malaysia and Indonesia. Although in these countries, oil palm is primarily cultivated in large plantations, smallholders cultivate a large share of the territory devoted to this crop. This is related to the programs set up by governments of Malaysia and Indonesia during the second half of the 20th century, to provide smallholders with land plots in capital intensive large-scale oil palm schemes. Despite the relative success encountered by these programs in both countries, policymakers have continued to insist on the development of private centrally managed large-scale plantations. Yet, smallholding family farming has remained the most resilient economic activity in rural areas of the tropics. This system has proven adaptive to environmental change and, given proper access to markets and capital, particularly responsive to market signals. Today, many small-holdings are still characterized by the diversity of crops cultivated, low use of chemical inputs, reliance on family labor, and high levels of ecological knowledge. These are some of the main factors explaining why small family farms have proven more efficient than large plantations and, in the long term, more economically and ecologically resilient. Yet, large-scale land acquisitions for monocrop production remain a current issue, highlighting the paradox of the latest stage of agrarian capitalism and of its persistent built-in disregard for environmental deterioration.

Article

Social Equity, Land Use Planning, and Flood Mitigation  

Malini Roy and Philip Berke

Every flood event reveals hidden disparities within cities—disparities in capacities to anticipate, respond to, and recover from disasters. Studies examining drivers of disparity have found that highly socially vulnerable (e.g., poor, minority) neighborhoods sustain more damage, have access to fewer recovery resources, and experience slower recovery. Climate change and unregulated growth are likely to exacerbate these disparities. Scholars argue that disparities along the lines of race and income are partly due to inadequate planning. Planning for flood mitigation has lacked a deep understanding of values and has therefore overlooked needs and exacerbated physical vulnerability in socially vulnerable neighborhoods. Increasing local and international attention to the socioeconomic drivers of disaster impacts elicits the question: How can land use planning foster more equitable hazard mitigation practices that meet the needs identified by marginalized communities? Equitable hazard mitigation is advanced through three dimensions. First, contextual equity involves preparing an information base that asks who is vulnerable to flooding, who has (not) been engaged in planning decisions that affect vulnerability to flooding, and why. Recognizing contextual inequities in plans is the first step to making visible historic discrimination and addressing drivers of persisting political disenfranchisement. Second, procedural equity involves organizing a participation process that critically considers whom participation processes should target, how stakeholders should be inclusively engaged, and how multiple values should inform policy priorities. Dedicated planning-participation processes can repair past legacies of power information imbalances and co-produce planning goals. A process where vulnerable, marginalized citizens have as much information and as much say in policy decisions as others adds nuance to planners’ understanding of needs, and enables the incorporation of overlooked values into distribution of land use policies. Third, distributional equity involves designing planning policies so that flood mitigation services and infrastructure are directed to neighborhoods and households most in need. Moreover, distributional equity considerations need to be integrated across the local government plans (e.g., transportation plan, housing plan, and hazard mitigation plan) that affect growth in hazardous areas. Social equity outcomes further rely on the degree of knowledge transfer between the three dimensions. The effectiveness of distributional equity is critically dependent on contextual and procedural equity and affects how plan outcomes align with the needs and values of disadvantaged and vulnerable communities. Likewise, the scope of contextual equity is shaped by historical distributional and procedural equity or lack thereof. To advance equitable outcomes, more research is required on the implementation and effectiveness of different land use planning approaches. Future inquiries should examine social equity through a multihazard lens; empirically analyze the causal relationships among the contextual, procedural, and distributional equity; and explore the effectiveness of different planning tools and governance structures in fostering socially equitable hazard mitigation.

Article

Socio-Technical Transitions to Sustainability  

Frank W. Geels

Addressing persistent environmental problems such as climate change or biodiversity loss requires shifts to new kinds of energy, mobility, housing, and agro-food systems. These shifts are called socio-technical transitions because they involve not just changes in technology but also changes in consumer practices, policies, cultural meanings, infrastructures, and business models. Socio-technical transitions to sustainability are challenging for mainstream social sciences because they are multiactor, long-term, goal-oriented, disruptive, contested, and nonlinear processes. Sustainability transitions are being investigated by a new research community, which uses a socio-technical Multi-Level Perspective (MLP) as one of its orienting frameworks. Focusing on multidimensional struggles between “green” innovations and entrenched systems, the MLP suggests that transitions involve alignments of processes within and between three analytical levels: niche innovations, socio-technical regimes, and an exogenous socio-technical landscape. To understand more specific change mechanisms, the MLP mobilizes ideas from evolutionary economics, sociology of innovation, and institutional theory. Different phases, actors, and struggles are distinguished to understand the complexities of sustainability transitions, while still providing analytical traction and policy advice. The MLP draws attention to socio-technical systems as a new unit of analysis, which is more comprehensive than a micro-focus on individuals and more concrete than a macro-focus on a green economy. It also forms a new analytical framework that spans several stale dichotomies in environmental social science debates related to agency or structure and behavioral or technical change. The MLP accommodates stability and change and offers an integrative view on transitions, ranging from local projects to niche innovations to sector-level regimes and broader societal contexts. This new interdisciplinary research is attracting increasing attention from the European Environment Agency, International Panel on Climate Change (IPCC), and Organization for Economic Cooperation and Development (OECD).

Article

Soil Quality as Affected by Intensive Versus Conservative Agricultural Managements  

Luigi Badalucco

Soils, the earth’s skin, are at the intersection of the lithosphere, hydrosphere, atmosphere, and biosphere. The persistence of life on our planet depends on the maintenance of soils as they constitute the biological engines of earth. Human population has increased exponentially in recent decades, along with the demand for food, materials, and energy, which have caused a shift from low-yield and subsistence agriculture to a more productive, high-cost, and intensive agriculture. However, soils are very fragile ecosystems and require centuries for their development, thus within the human timescale they are not renewable resources. Modern and intensive agriculture implies serious concern about the conservation of soil as living organism, i.e., of its capacity to perform the vast number of biochemical processes needed to complete the biogeochemical cycles of plant nutrients, such as nitrogen and phosphorus, crucial for crop primary production. Most practices related to intensive agriculture determine a deterioration even in the short-middle term of their physical, chemical, and biological properties, which all together contribute to soil quality, along with an overexploitation of soils as living organisms. Recent trends are turning toward styles of agriculture management that are more sustainable or conservative for soil quality. Usually, use of soils for agricultural purposes deflect them at various degrees from the “natural” soil development processes (pedogenesis), and this shift may be assumed as a divergence from soil sustainability principles. For decades, the misuse of land due to intensive crop management has deteriorated soil health and quality. A huge plethora of microorganisms inhabits soils, thus acting as “the biological engine of the earth”; indeed, this microbiota serves the soil ecosystem, performing several fundamental functions. Therefore, management practices might be planned looking at the safeguard of soil microbial diversity and resilience. In addition, each unexpected alteration in numberless soil biochemical processes, being regulated by microbial communities, may represent an early and sensible signal of soil homeostasis weakening and, consequently, warn about soil conservation. Within the vast number of soil biochemical processes and connected features (bioindicators) virtually effective to measure the sustainable soil exploitation, those related to the mineralization or immobilization of the main nutrients (C and N), including enzyme activity (functioning) and composition (diversity) of microbial communities, exert a fundamental role because of their involvement in soil metabolism. Comparing the influence of many cropping factors (tillage, mulching and cover crops, rotations, mineral and organic fertilization) under both intensive and sustainable managements on soil microbial diversity and functioning, through both chemical and biological soil quality indicators, makes it possible to identify the most hazardous diversions from soil sustainability principles.

Article

Soil Resources, the Delivery of Ecosystem Services and Value  

David A. Robinson, Fiona Seaton, Katrina Sharps, Amy Thomas, Francis Parry Roberts, Martine van der Ploeg, Laurence Jones, Jannes Stolte, Maria Puig de la Bellacasa, Paula Harrison, and Bridget Emmett

Soils provide important functions, which according to the European Commission include: biomass production (e.g., agriculture and forestry); storing, filtering, and transforming nutrients, substances, and water; harboring biodiversity (habitats, species, and genes); forming the physical and cultural environment for humans and their activities; providing raw materials; acting as a carbon pool; and forming an archive of geological and archaeological heritage, all of which support human society and planetary life. The basis of these functions is the soil natural capital, the stocks of soil material. Soil functions feed into a range of ecosystem services which in turn contribute to the United Nations sustainable development goals (SDGs). This overarching framework hides a range of complex, often nonlinear, biophysical interactions with feedbacks and perhaps yet to be discovered tipping points. Moreover, interwoven with this biophysical complexity are the interactions with human society and the socioeconomic system which often drives our attitudes toward, and the management and exploitation of, our environment. Challenges abound, both social and environmental, in terms of how to feed an increasingly populous and material world, while maintaining some semblance of thriving ecosystems to pass on to future generations. How do we best steward the resources we have, keep them from degradation, and restore them where necessary as soils underpin life? How do we measure and quantify the soil resources we have, how are they changing in time and space, what can we predict about their future use and function? What is the value of soil resources, and how should we express it? This article explores how soil properties and processes underpin ecosystem services, how to measure and model them, and how to identify the wider benefits they provide to society. Furthermore, it considers value frameworks, including caring for our resources.

Article

Soil Salinization  

Pichu Rengasamy

Salt accumulation in soils, affecting agricultural productivity, environmental health, and the economy of the community, is a global phenomenon since the decline of ancient Mesopotamian civilization by salinity. The global distribution of salt-affected soils is estimated to be around 830 million hectares extending over all the continents, including Africa, Asia, Australasia, and the Americas. The concentration and composition of salts depend on several resources and processes of salt accumulation in soil layers. Major types of soil salinization include groundwater associated salinity, non–groundwater-associated salinity, and irrigation-induced salinity. There are several soil processes which lead to salt build-up in the root zone interfering with the growth and physiological functions of plants. Salts, depending on the ionic composition and concentration, can also affect many soil processes, such as soil water dynamics, soil structural stability, solubility of essential nutrients, and pH and pE of soil water—all indirectly hindering plant growth. The direct effect of salinity includes the osmotic effect affecting water and nutrient uptake and the toxicity or deficiency due to high concentration of certain ions. The plan of action to resolve the problems associated with soil salinization should focus on prevention of salt accumulation, removal of accumulated salts, and adaptation to a saline environment. Successful utilization of salinized soils needs appropriate soil and irrigation management and improvement of plants by breeding and genetic engineering techniques to tolerate different levels of salinity and associated abiotic stress.

Article

Soil Sediment Loading and Related Environmental Impacts from Farms  

Vito Ferro

Beyond damage to rainfed agricultural and forestry ecosystems, soil erosion due to water affects surrounding environments. Large amounts of eroded soil are deposited in streams, lakes, and other ecosystems. The most costly off-site damages occur when eroded particles, transported along the hillslopes of a basin, arrive at the river network or are deposited in lakes. The negative effects of soil erosion include water pollution and siltation, organic matter loss, nutrient loss, and reduction in water storage capacity. Sediment deposition raises the bottom of waterways, making them more prone to overflowing and flooding. Sediments contaminate water ecosystems with soil particles and the fertilizer and pesticide chemicals they contain. Siltation of reservoirs and dams reduces water storage, increases the maintenance cost of dams, and shortens the lifetime of reservoirs. Sediment yield is the quantity of transported sediments, in a given time interval, from eroding sources through the hillslopes and river network to a basin outlet. Chemicals can also be transported together with the eroded sediments. Sediment deposition inside a reservoir reduces the water storage of a dam. The prediction of sediment yield can be carried out by coupling an erosion model with a mathematical operator which expresses the sediment transport efficiency of the hillslopes and the channel network. The sediment lag between sediment yield and erosion can be simply represented by the sediment delivery ratio, which can be calculated at the outlet of the considered basin, or by using a distributed approach. The former procedure couples the evaluation of basin soil loss with an estimate of the sediment delivery ratio SDRW for the whole watershed. The latter procedure requires that the watershed be discretized into morphological units, areas having a constant steepness and a clearly defined length, for which the corresponding sediment delivery ratio is calculated. When rainfall reaches the surface horizon of the soil, some pollutants are desorbed and go into solution while others remain adsorbed and move with soil particles. The spatial distribution of the loading of nitrogen, phosphorous, and total organic carbon can be deduced using the spatial distribution of sediment yield and the pollutant content measured on soil samples. The enrichment concept is applied to clay, organic matter, and all pollutants adsorbed by soil particles, such as nitrogen and phosphorous. Knowledge of both the rate and pattern of sediment deposition in a reservoir is required to establish the remedial strategies which may be practicable. Repeated reservoir capacity surveys are used to determine the total volume occupied by sediment, the sedimentation pattern, and the shift in the stage-area and stage-storage curves. By converting the sedimentation volume to sediment mass, on the basis of estimated or measured bulk density, and correcting for trap efficiency, the sediment yield from the basin can be computed.

Article

Soils, Science, Society, and the Environment  

Colin R. Robins

Soils are the complex, dynamic, spatially diverse, living, and environmentally sensitive foundations of terrestrial ecosystems as well as human civilizations. The modern, environmental study of soil is a truly young scientific discipline that emerged only in the late 19th century from foundations in agricultural chemistry, land resource mapping, and geology. Today, little more than a century later, soil science is a rigorously interdisciplinary field with a wide range of exciting applications in agronomy, ecology, environmental policy, geology, public health, and many other environmentally relevant disciplines. Soils form slowly, in response to five inter-related factors: climate, organisms, topography, parent material, and time. Consequently, many soils are chemically, biologically, and/or geologically unique. The profound importance of soil, combined with the threats of erosion, urban development, pollution, climate change, and other factors, are now prompting soil scientists to consider the application of endangered species concepts to rare or threatened soil around the world.

Article

Soil Tilth and Management  

Lars J. Munkholm, Mansonia Pulido-Moncada, and Peter Bilson Obour

Soil tilth is a dynamic and multifaceted concept that refers to the suitability of a soil for planting and growing crops. A soil with good tilth is “usually loose, friable and well granulated”; a condition that can also be described as the soil’s having a good “self-mulching” ability. On the other hand soils with poor tilth are usually dense (compacted), with hard, blocky, or massive structural characteristics. Poor soil tilth is generally associated with compaction, induced by wheel traffic, animal trampling, and/or to natural soil consolidation (i.e., so-called hard-setting behavior). The soil-tilth concept dates back to the early days of arable farming and has been addressed in soil-science literature since the 1920s. Soil tilth is generally associated with soil’s physical properties and processes rather than the more holistic concepts of soil quality and soil health. Improved soil tilth has been associated with deep and intensive tillage, as those practices were traditionally considered the primary method for creating a suitable soil condition for plant growth. Therefore, for millennia there has been a strong focus both in practice and in research on developing tillage tools that create suitable growing conditions for different crops, soil types, and climatic conditions. Deep and intensive tillage may be appropriate for producing a good, short-term tilth, but may also lead to severe long-term degradation of the soil structure. The failure of methods relying on physical manipulation as means of sustaining good tilth has increased the recognition given to the important role that soil biota have in soil-structure formation and stabilization. Soil biology has only received substantial attention in soil science during the last few decades. One result of this is that this knowledge is now being used to optimize soil management through strategies such as more diverse rotations, cover crops, and crop-residue management, with these being applied either as single management components or more preferably as part of an integrated system (i.e., either conservation agriculture or organic farming).Traditionally, farmers have evaluated soil tilth qualitatively in the field. However, a number of quantitative or semi-quantitative procedures for assessing soil tilth has been developed over the last 80 years. These procedures vary from simply determining soil cloddiness to more detailed evaluations whereby soil’s physical properties (e.g., porosity, strength, and aggregate characteristics) are combined with its consistency and organic-matter measurements in soil-tilth indices. Semi-quantitative visual soil-evaluation methods have also been developed for field evaluation of soil tilth, and are now used in many countries worldwide.

Article

State of the Art of Contingent Valuation  

Tim Haab, Lynne Y. Lewis, and John Whitehead

The contingent valuation method (CVM) is a stated preference approach to the valuation of nonmarket goods. It has a 50+-year history beginning with a clever suggestion to simply ask people for their consumer surplus. The first study was conducted in the 1960s and over 10,000 studies have been conducted to date. The CVM is used to estimate the use and non-use values of changes in the environment. It is one of the more flexible valuation methods, having been applied in a large number of contexts and policies. The CVM requires construction of a hypothetical scenario that makes clear what will be received in exchange for payment. The scenario must be realistic and consequential. Economists prefer revealed preference methods for environmental valuation due to their reliance on actual behavior data. In unguarded moments, economists are quick to condemn stated preference methods due to their reliance on hypothetical behavior data. Stated preference methods should be seen as approaches to providing estimates of the value of certain changes in the allocation of environmental and natural resources for which no other method can be used. The CVM has a tortured history, having suffered slings and arrows from industry-funded critics following the Exxon Valdez and British Petroleum (BP)–Deepwater Horizon oil spills. The critics have harped on studies that fail certain tests of hypothetical bias and scope, among others. Nonetheless, CVM proponents have found that it produces similar value estimates to those estimated from revealed preference methods such as the travel cost and hedonic methods. The CVM has produced willingness to pay (WTP) estimates that exhibit internal validity. CVM research teams must have a range of capabilities. A CVM study involves survey design so that the elicited WTP estimates have face validity. Questionnaire development and data collection are skills that must be mastered. Welfare economic theory is used to guide empirical tests of theory such as the scope test. Limited dependent variable econometric methods are often used with panel data to test value models and develop estimates of WTP. The popularity of the CVM is on the wane; indeed, another name for this article could be “the rise and fall of CVM,” not because the CVM is any less useful than other valuation methods. It is because the best practice in the CVM is merging with discrete choice experiments, and researchers seem to prefer to call their approach discrete choice experiments. Nevertheless, the problems that plague discrete choice experiments are the same as those that plague contingent valuation. Discrete choice experiment–contingent valuation–stated preference researchers should continue down the same familiar path of methods development.

Article

State of the Art of Hedonic Pricing  

Dennis Guignet and Jonathan Lee

Hedonic pricing methods have become a staple in the environmental economist’s toolkit for conducting nonmarket valuation. The hedonic pricing method (HPM) is a revealed preference approach used to indirectly infer the value buyers and sellers place on characteristics of a differentiated product. Environmental applications of the HPM are typically focused on housing and labor markets, where the characteristics of interest are local environmental commodities and health risks. Despite the fact that there have been thousands of hedonic pricing studies published, applications of the methodology still often grapple with issues of omitted variable bias, measurement error, sample selection, choice of functional form, effect heterogeneity, and the recovery of policy-relevant welfare estimates. Advances in empirical methodologies, increased quality and quantity of data, and efforts to link empirical results to economic theory will surely further the use of the HPM as an important nonmarket valuation tool.

Article

Stormwater Management and Roadways  

Nigel Pickering and Somayeh Nassiri

Nonpoint source pollution is common in highly developed areas worldwide, degrading downstream water quality conditions and causing algal growth, aquatic toxicity, and sometimes fish kills. Stormwater runoff that results from rainfall or snowmelt events creates high-flow runoff from impervious surfaces and adjacent areas transporting multiple pollutants to the receiving waters. Although water quality regulations in the developed world have been effective in cleaning up wastewater discharges, their success with remediating stormwater discharges has not been consistent. An exploration of the sources, characteristics, and treatment of roadway runoff, a type of runoff that can be toxic and more difficult to manage because of the linear nature of the road network, is necessary. Since 1975, there have been more than 50 major roadway studies quantifying the sources and types of runoff contaminants like sediment, metals, inorganic salts, and organic compounds. Vehicle sources of pollutants are considered the most pernicious of all roadway contaminants, with brakes and tires being major sources. In the last decade, the leachate from tire wear particles has been linked to toxicity in coho salmon. Nonstructural stormwater management minimizes contamination by using source controls; for example, the elimination of almost all lead in automotive fuel has reduced roadway lead contamination significantly and the introduction of low-copper brake pads in the United States is expected to reduce roadway copper contamination over time. Structural stormwater management practices treat contaminated roadway runoff using small natural treatment systems; this is due in large part to the linear nature of roadways that makes larger regional systems more difficult. Since 2000, treatment performance has improved; however, there is still a great need for further improvement. Suggestions for treatment improvements include designing with low maintenance in mind; applying machine learning to the existing data; improving the understanding of road-land pollutant dynamics; using a transdisciplinary applied research approach to identify the means to improve treatment and reduce toxicity; improving the media used in treatment systems to enhance performance; improving structural strength of permeable pavement; and increasing implementation by facilitating ways to allow/encourage small, effective, and less costly alternatives.

Article

Stormwater Management at the Lot Level: Engaging Homeowners and Business Owners to Adopt Green Stormwater Infrastructure  

Anand D. Jayakaran, Emily Rhodes, and Jason Vogel

The Clean Water Act of 1972 was the impetus for stormwater management in the United States, followed by the need for many cities to comply with consent decrees associated with combined sewer overflows. With rapidly growing urban centers and the attendant increasing costs of managing stormwater with larger stormwater facilities, green stormwater infrastructure (GSI) was deemed a useful measure to distribute the management of stormwater across the landscape. The management of stormwater has evolved from simply removing it as quickly as it is generated in order to prevent flooding, to intentionally detaining stormwater on the landscape. Typically, low-frequency large events are detained in central stormwater holding facilities, while GSI is employed to manage smaller high-frequency events, slowing and treating stormwater on the landscape itself. Installing GSI close to the source of runoff production ensures that stormwater directed towards these facilities are small enough in volume, so as not to overwhelm these systems. Within these GSI systems, the natural assimilative capacity of soils and plants slows and breaks down many of the pollutants that are found in stormwater runoff. The requirement for a broad spatial distribution of GSI across the landscape necessitates an acceptance of these technologies, and the willingness of the managers of these urban landscapes to maintain these systems on a continual basis. The policies put in place to transfer the responsibility of stormwater management onto individual lot owners range from regulations imposed on those that develop the landscape for commercial and industrial purposes, to incentives offered to individual lot owners to install GSI practices for the first time on their properties. GSI is, however, not a silver bullet for all stormwater ills, and care has to be taken in how it is deployed in order not to exacerbate systemic environmental and racial inequities. A careful and considered adoption of GSI that includes the desires, values, and the needs of the community in conjunction with the environmental goals they are designed to address is critical.

Article

Subsurface Flow of Water in Soils and Geological Formations  

Gerrit de Rooij

Henry Darcy was an engineer who built the drinking water supply system of the French city of Dijon in the mid-19th century. In doing so, he developed an interest in the flow of water through sands, and, together with Charles Ritter, he experimented (in a hospital, for unclear reasons) with water flow in a vertical cylinder filled with different sands to determine the laws of flow of water through sand. The results were published in an appendix to Darcy’s report on his work on Dijon’s water supply. Darcy and Ritter installed mercury manometers at the bottom and near the top of the cylinder, and they observed that the water flux density through the sand was proportional to the difference between the mercury levels. After mercury levels are converted to equivalent water levels and recast in differential form, this relationship is known as Darcy’s Law, and until this day it is the cornerstone of the theory of water flow in porous media. The development of groundwater hydrology and soil water hydrology that originated with Darcy’s Law is tracked through seminal contributions over the past 160 years. Darcy’s Law was quickly adopted for calculating groundwater flow, which blossomed after the introduction of a few very useful simplifying assumptions that permitted a host of analytical solutions to groundwater problems, including flows toward pumped drinking water wells and toward drain tubes. Computers have made possible ever more advanced numerical solutions based on Darcy’s Law, which have allowed tailor-made computations for specific areas. In soil hydrology, Darcy’s Law itself required modification to facilitate its application for different soil water contents. The understanding of the relationship between the potential energy of soil water and the soil water content emerged early in the 20th century. The mathematical formalization of the consequences for the flow rate and storage change of soil water was established in the 1930s, but only after the 1970s did computers become powerful enough to tackle unsaturated flows head-on. In combination with crop growth models, this allowed Darcy-based models to aid in the setup of irrigation practices and to optimize drainage designs. In the past decades, spatial variation of the hydraulic properties of aquifers and soils has been shown to affect the transfer of solutes from soils to groundwater and from groundwater to surface water. More recently, regional and continental-scale hydrology have been required to quantify the role of the terrestrial hydrological cycle in relation to climate change. Both developments may pose new areas of application, or show the limits of applicability, of a law derived from a few experiments on a cylinder filled with sand in the 1850s.