## Valuation of Mangrove Restoration

Since the 2004 Indian Ocean tsunami, there has been strong interest globally in restoring mangrove ecosystems and their potential benefits from protecting coastlines and people from damaging storms. However, the net economic gains from mangrove restoration have been variable; there have been some notable project successes but also some prominent failures. There is also an ongoing debate over whether or not the cost of mangrove restoration is justified by the benefits these ecosystems provide. Although the high costs of mangrove restoration and the risk of failure have led to criticism of such schemes, perhaps the more pertinent concern should be whether the ex post option of restoration is economically beneficial compared to preventing irreversible mangrove conversion to alternative land uses. Case studies on mangrove valuation from Brazil and Thailand illustrate the key issues underlying this concern. Since much recent mangrove restoration has been motivated by the trees’ potential storm-protection benefit, a number of studies have valued mangroves for this purpose. However, mangroves are also valued for other important benefits, such as providing collected products for local coastal communities and serving as nursery and breeding grounds for off-shore fisheries. The implications of these benefits for mangrove restoration can be significant. It is also important to understand the appropriate use of benefit transfer when it is difficult to value restored mangroves, methods to incorporate the potential risk of mangrove restoration failure, and assessment of cost-effective mangrove restoration.

## Valuation of Marine Ecosystems

Water accounts for more than 70% of Earth’s surface, making marine ecosystems the largest and most important ecosystems of the planet. However, the fact that a large part of these ecosystems and their potential contribution to humans remains unexplored has rendered them unattractive for valuation exercises. On the contrary, coastal zones, , being the interface between the land, the sea, and human activities competing for space and resources, have been extensively studied with the objective of marine ecosystem services valuation. Examples of marine and coastal ecosystems are open oceans, coral reefs, deep seas, hydrothermal vents, abyssal plains, wetlands, rocky and sandy shores, mangroves, kelp forests, estuaries, salt marshes, and mudflats. Although there are arguments that no classification can capture the ways in which ecosystems contribute to human well-being and support human life, very often policymakers have to decide upon alternative uses of such natural environments. Should a given wetland be preserved or converted to agricultural land? Should a mangrove be designated within the protected areas system or be used for shrimp farming? To answer these questions, one needs first to establish the philosophical basis of value within the ecosystems framework. To this end, two vastly different approaches have been proposed. On the one hand, the nonutilitarian (biocentric) approach relies on the notion of intrinsic value attached to the mere existence of a natural resource, independent of whether humans derive utility from its use (if any) or preservation. Albeit useful in philosophical terms, this approach is still far from providing unambiguous and generally accepted inputs to the tangible problem of ecosystem valuation. The utilitarian (anthropocentric) perspective, on the other hand, assumes that natural environments have value to the extent that humans derive utility from placing such value. According to the total economic value (TEV) approach, this value can be divided into “use” and “nonuse.” Use values involve some interaction with the resource, either directly or indirectly, while nonuse values are derived simply from the knowledge that natural resources and aspects of the natural environment are maintained. Existence and altruistic values fall within this latter category. Not surprisingly, economists have long revealed a strong preference for the utilitarian approach. As a result, the valuation of marine ecosystems requires that we understand the ecosystem services they deliver and then attach a value to the services. But what tools are available to economists when valuing marine ecosystems? For the most part, ecosystem services are not traded in formal markets and thus actual prices are usually not available. Valuation techniques essentially seek different ways to estimate measures like Willingness To Pay (WTP), Willingness To Accept (WTA), or expenditures and costs. The techniques used for the valuation of ecosystem services can be divided into three main families: market-based, revealed preference, and stated preference. Finally, value-transfer methods are also used when estimates of value are available in similar contexts. All these methods have advantages and disadvantages, with different methods being suitable for different situations. Hence, extra caution is required during the design and implementation of valuation attempts.

## Valuation of Rainforest Preservation in the Amazon

Different ecosystem values of the Amazon rainforest are surveyed in economic terms. Spatial rainforest valuation is crucial for good forest management, such as where to put the most effort to stop illegal logging and forest fires, and which areas to designate as new nationally protected areas. Three classes of economic value are identified, according to who does the valuation: values accruing to the local and regional populations (of South America); carbon values (which are global); and other global (noncarbon) values. Only the first two classes are discussed. Three types of value are separated according to ecosystem service delivered from the rainforest: provisioning services; supporting and regulating services; and cultural and other human services. Net values of provisioning services, including reduced impact logging and various non-timber forest products, are well documented for the entire Brazilian Amazon at a spatially detailed scale and amount to at least $20–50/ha/year. Less-detailed information exists about values of fish, game, and bioprospecting from the Amazon, although their total values can be shown to be sizable. Many supporting and regulating services are harder to value economically, in particular climate regulation and watershed and erosion protection. Impacts of changed rainfall when Amazon rainforest is lost have been valued at detailed scale, but with relative model values of$10–20/ha/year. Carbon values are much larger, at a carbon price of $30/ton CO2, around$14,000/ha as capitalized value. The average per-hectare value of tourism and the health benefits from having the Amazon forest are low, and such values cannot easily be pinned down to individual areas of the Amazon. Finally, the biodiversity values of the Amazon, as accruing to the local and regional population, seem to be small based on recent stated-preference work in Brazil. Most of the values related to biodiversity are likely to be global and may. in principle, be very large, but the global components are not valued here. The concept of value is discussed, and a marginal valuation concept (practically useful for policy) is favored as opposed to an average or total valuation. Marginal value can be below average value (as is likely for biodiversity and tourism), but can also in some contexts be higher. This can occur where losing forest at a local scale increases the prevalence of forest fires and where it increases forest dryness, leading to a multiplier process whereby more forest is lost. While strides have recently been made to improve rainforest valuation at both micro- and macroscales, much work still remains.

## Valuation of Species Preservation

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.

## Valuation of Wetlands Preservation

All types of wetlands around the world are heavily threatened. According to the Ramsar Convention on Wetlands, they comprise “areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish, or salt.” While they are estimated still to cover 1,280 million hectares worldwide, large shares of wetlands were destroyed during the 20th century, mainly as a result of land use changes. According to the Millennium Ecosystem Assessment (MEA), this applies above all to North America, Europe, Australia, and New Zealand, but wetlands were also heavily degraded in other parts of the world. Moreover, degradation is expected to accelerate in the future due to global environmental change. These developments are alarming because wetlands deliver a broad range of ecosystem services to societies, contributing significantly to human well-being. Among those services are water supply and purification, flood regulation, climate regulation, and opportunities for recreation, to name only a few. The benefits humans derive from those services, however, often are not reflected in markets as they are public goods in nature. Thus, arguing in favor of the preservation of wetlands requires, inter alia, to make the non-marketed economic benefits more visible and comparable to those from alternative—generally private—uses of converted wetlands, which are often much smaller. The significance of the non-market value of wetland services has been demonstrated in the literature: the benefits derived from wetlands have been one of the most frequently investigated topics in environmental economics and are integrated in meta-analyses devoted to synthesizing the present knowledge about the value of wetlands. The meta-analyses that cover both different types of wetlands in different landscapes as well as different geographical regions are supplemented by recent primary studies on topics of increasing importance such as floodplains and peatlands, as they bear, for example, a large flood regulation and climate change mitigation potential, respectively. The results underpin that the conversion of wetlands is accompanied by significant losses in benefits. Moreover, wetland preservation is economically beneficial given the large number of ecosystem services provided by wetland ecosystems. Thus, decision-making that might affect the status and amount of wetlands directly or indirectly should consider the full range of benefits of wetland ecosystems.

## The Value of the Environment in Recreation

Natural environments represent background settings for most outdoor recreation activities, which are important non-consumptive benefits that people obtain from nature. Recreation has been traditionally considered a non-market service because it is practiced free of charge in public spaces and therefore of secondary relevance for the economy. Although outdoor recreation in natural parks became relevant during the 19th century, the increased popularity of recreation after the Second World War required tools for the assessment of recreational benefits, which were not considered in the evaluation of investments in recreational facilities, and increasing spending for recreational equipment captured the attention of outdoor recreation as an economic sector. In the 1990s, it was observed that many recreational activities were commercialized and started being considered equally important to tourism as a means to boost the economy of local communities. The expansion of outdoor recreation is reflected in a growing interest in the economic aspects, including cost–benefit calculations of the investments in recreational facilities and research on appropriate methods to evaluate the non-market benefits of recreation. The first economic technique used for valuing recreation was the travel cost method that consisted in the assessment of a demand curve, where the demanded quantity is the number of trips to a specific site and the cost is the unit cost of travel to the destination. After this first intuition, the number of contributions on recreation valuation exponentially grew, and new methods were proposed, including methods based on stated preferences for recreation that can be used when travel cost data that reveal consumers’ behavior are not available. A regular assessment of recreational benefits has several advantages for public policy, including the evaluation of investments and information on visitor profile and preferences, income, and price elasticity, which are essential to understand the market of outdoor recreation and propose effective strategies and recreation-oriented management. The increasing environmental pressure associated with participation in outdoor recreation required effective conservation activities, which in turn posed limitations to economic activities of local communities who live in contact with natural resources. Therefore, a balance between environmental, social, and economic interests is essential for recreational destination to avail of benefits without conflicts among stakeholders.

## Valuing the Benefits of Green Stormwater Infrastructure

Green stormwater infrastructure (GSI), a decentralized approach for managing stormwater that uses natural systems or engineered systems mimicking the natural environment, is being adopted by cities around the world to manage stormwater runoff. The primary benefits of such systems include reduced flooding and improved water quality. GSI projects, such as green roofs, urban tree planting, rain gardens and bioswales, rain barrels, and green streets may also generate cobenefits such as aesthetic improvement, reduced net CO2 emissions, reduced air pollution, and habitat improvement. GSI adoption has been fueled by the promise of environmental benefits along with evidence that GSI is a cost-effective stormwater management strategy, and methods have been developed by economists to quantify those benefits to support GSI planning and policy efforts. A body of multidisciplinary research has quantified significant net benefits from GSI, with particularly robust evidence regarding green roofs, urban trees, and green streets. While many GSI projects generate positive benefits through ecosystem service provision, those benefits can vary with details of the location and the type and scale of GSI installation. Previous work reveals several pitfalls in estimating the benefits of GSI that scientists should avoid, such as double counting values, counting transfer payments as benefits, and using values for benefits like avoided carbon emissions that are biased. Important gaps remain in current knowledge regarding the benefits of GSI, including benefit estimates for some types of GSI elements and outcomes, understanding how GSI benefits last over time, and the distribution of GSI benefits among different groups in urban areas.

## Vermiculture in Greenhouse Plants, Field Crop Production, and Hydroponics

Vermiculture is the art, science, and industry of raising earthworms for baits, feeds, and composting of organic wastes. Composting through the action of earthworms and microogranisms is commonly referred to as vermicomposting. Vermiculture is an art because the technology of raising earthworms requires a comprehensive understanding of the basic requirements for growing earthworms in order to design the space and the system by which organic wastes can be processed efficiently and successfully. It is a science because the technology requires a critical understanding and consideration of the climatic requirements, nutritional needs, growth cycles, taxonomy, and species of earthworms suitable for vermicomposting in order to develop a working system that supports earthworm populations to process successfully the intended organic wastes. The nature of the organic wastes also needs to be taken into careful consideration, especially its composition, size, moisture content, and nutritional value, which will eventually determine the overall quality of the vermicomposts produced. The quality of organic wastes also determines the ability of the earthworms to consume and process them, and the rate by which they turn these wastes into valuable organic amendments. The science of vermiculture extends beyond raising earthworms. There are several lines of evidence that vermicomposts affect plant growth significantly. Vermiculture is an industry because it has evolved from a basic household bin technology to commercially scaled systems in which economic activities emanate from the cost and value of obtaining raw materials, the building of systems, and the utilization and marketing of the products, be they in solid or aqueous extract forms. Economic returns are carefully valued from the production phase to its final utilization as an organic amendment for crops. The discussion revolves around the development of vermiculture as an art, a science, and an industry. It traces the early development of vermicomposting, which was used to manage organic wastes that were considered environmentally hazardous when disposed of improperly. It also presents the vermicomposting process, including its basic requirements, technology involved, and product characteristics, both in solid form and as a liquid extract. Research reports from different sources on the performance of the products are also provided. The discussion attempts to elucidate the mechanisms involved in plant growth and yield promotion and the suppression of pests and diseases. Certain limitations and challenges that the technology faces are presented as well.

## Water and Economy-Wide Modeling: An Overview

General equilibrium theory thinks of the economy as a collection of interconnected markets, each of which, in isolation and in combination, is driven toward some sort of equilibrium. Computable general equilibrium (CGE) models add to this abstract point of view by calibrating models of the economy using actual economic data. The aim is to empirically solve for equilibrium demand, supply, and price levels across the markets in the economy. Many areas of economic analysis, reform, and policymaking have benefitted from scrutiny in a CGE context. This is particularly true of issues to do with tax and tariff reform, where CGE models first gained prominence. More recently, the areas of environmental economics and regulation has attracted the attention of CGE modelers. Considerations of environment and environmental regulation, inevitably involve a consideration of issues to do with water. Such issues range from aquaculture through pricing of water to virtual water—and many points in between. In the analysis of each of these issues—and the role water plays in the overall economy, CGE models have made an important contribution to understanding and informed policymaking.

## Water Resources Planning Under (Deep) Uncertainty

Public investments in water infrastructure continue to grow where developed countries prioritize investments in operation and maintenance while developing countries focus on infrastructure expansion. The returns from these investments are contingent on carefully assessed designs and operating strategies that consider the complexities inherent in water management problems. These complexities arise due to several factors, including, but not limited to, the presence of multiple stakeholders with potentially conflicting preferences, lack of knowledge about appropriate systems models or parameterizations, and large uncertainties regarding the evolution of future conditions that will confront these projects. The water resources planning literature has therefore developed a variety of approaches for a quantitative treatment of planning problems. Beginning in the mid-20th century, quantitative design evaluations were based on a stochastic treatment of uncertainty using probability distributions to determine expected costs or risk of failure. Several simulation–optimization frameworks were developed to identify optimal designs with techniques such as linear programming, dynamic programming, stochastic dynamic programming, and evolutionary algorithms. Uncertainty was incorporated within existing frameworks using probability theory, using fuzzy theory to represent ambiguity, or via scenario analysis to represent discrete possibilities for the future. As the effects of climate change became palpable and rapid socioeconomic transformations emerged as the norm, it became evident that existing techniques were not likely to yield reliable designs. The conditions under which an optimal design is developed and tested may differ significantly from those that it will face during its lifetime. These uncertainties, wherein the analyst cannot identify the distributional forms of parameters or the models and forcing variables, are termed “deep uncertainties.” The concept of “robustness” was introduced around the 1980s to identify designs that trade off optimality with reduced sensitivity to such assumptions. However, it was not until the 21st century that robustness analysis became mainstream in water resource planning literature and robustness definitions were expanded to include preferences of multiple actors and sectors as well as their risk attitudes. Decision analytical frameworks that focused on robustness evaluations included robust decision-making, decision scaling, multi-objective robust decision-making, info-gap theory, and so forth. A complementary set of approaches focused on dynamic planning that allowed designs to respond to new information over time. Examples included adaptive policymaking, dynamic adaptive policy pathways, and engineering options analysis, among others. These novel frameworks provide a posteriori decision support to planners aiding in the design of water resources projects under deep uncertainties.

## Water Federalism in the United States of America

Water governance in the United States has followed a water federalism system, in which government functions are shared between federal and state authorities. Water federalism is the sharing of governance across different levels of government over freshwater quantity (water quantity federalism) and quality (water quality federalism). These terms have evolved throughout different eras of U.S. history. Initially, water federalism involved water quantity federalism only, and both state and federal governments had management prerogatives. The 1922 Colorado River Compact and the 1944 U.S. and Mexico Treaty are examples of a combination of horizontal and vertical federalisms. Then, the 1970s marked significant changes in water federalism. First, states regained control over water resources management. Second, water quality federalism arose as a subset of, and at the same time as, environmental federalism. The 1972 Clean Water Act is an example of cooperative federalism, which was commonly used to refer to environmental federalism. In the 21st century, a variety of environmental federalism frameworks have been offered to address the negative effects of climate change on water resources as well as other environmental issues. The contemporary literature on environmental federalism encompasses water quantity and water quality federalism. Throughout history, the role of American Indian tribal primacy has been overlooked in the water federalism literature. Another layer of government, the American Indian tribal government, should be included in discussing states versus federal water management prerogatives. Overall, new water quality and water quantity federalisms must be developed using institutional, sociocultural, and economic principles of good governance that foster a more inclusive, participatory, democratic, and engaged form of federalism.

## Water Security

Water security has emerged in the 21st century as a powerful construct to frame the water objectives and goals of human society and to support and guide local to global water policy and management. Water security can be described as the fundamental societal goal of water policy and management. This article reviews the concept of water security, explaining the differences between water security and other approaches used to conceptualize the water-related challenges facing society and ecosystems and describing some of the actions needed to achieve water security. Achieving water security requires addressing two fundamental challenges at all scales: enhancing water’s productive contributions to human and ecosystems’ well-being, livelihoods and development, and minimizing water’s destructive impacts on societies, economies, and ecosystems resulting, for example, from too much (flood), too little (drought) or poor quality (polluted) water.

## Water Supply, Sanitation, and the Environment

Sustainable Development Goal No. 6 (SDG 6) has committed all nations of the world to achieving ambitious water supply and sanitation targets by 2030 to meet the universal basic needs of humans and the environment. Many lower-middle-income countries and all low-income countries face an uphill challenge in achieving these ambitious targets. The cause of poor performance is explored, some possible ways to accelerate progress toward achieving SDG 6 are suggested. The analysis will be of interest to a three-part audience: (a) readers with a general interest on how SDG 6 can be achieved; (b) actors with policy interest on improving water supply and safe sanitation (WSS) service issues; and (c) activists skeptical of conventional WSS policy prescriptions who advocate out-of-the-box solutions to improve WSS delivery.

## Well Construction, Cones of Depression, and Groundwater Sharing Approaches

The importance of groundwater has become particularly evident in the late 20th and early 21st centuries due to its increased use in many human activities. In this time frame, vertical wells have emerged as the most common, effective, and controlled system for obtaining water from aquifers, replacing other techniques such as drains and spring catchments. One negative effect of well abstraction is the generation of an inverted, conically shaped depression around the well, which grows as water is pumped and can negatively affect water quantity and quality in the aquifer. An increase in the abstraction rate of a specific well or, as is more common, an uncontrolled increase of the number of active wells in an area, could lead to overexploitation of the aquifer’s long-term groundwater reserves and, in some specific contexts, impact water quality. Major examples can be observed in arid or semi-arid coastal areas around the world that experience a high volume of tourism, where aquifers hydraulically connected with the sea are overexploited. In most of these areas, an excessive abstraction rate causes seawater to penetrate the inland part of the aquifer. This is known as marine intrusion. Another typical example of undesirable groundwater management can be found in many areas of intensive agricultural production. Excessive use of fertilizer is associated with an increase in the concentration of nitrogen solutions in groundwater and soils. In these farming areas, well design and controlled abstraction rates are critical in preventing penetrative depression cones, which ultimately affect water quality. To prevent any negative effects, several methods for aquifer management can be used. One common method is to set specific abstraction rules according to the hydrogeological characteristics of the aquifer, such as flow and chemical parameters, and its relationship with other water masses. These management plans are usually governed by national water agencies with support from, or in coordination with, private citizens. Transboundary or international aquifers require more complex management strategies, demanding a multidisciplinary approach, including legal, political, economic, and environmental action and, of course, a precise hydrogeological understanding of the effects of current and future usage.

## What Is Public and What Is Private in Water Provision: Insights from 19th-Century Philadelphia, Boston, and New York

Water became the first public utility in the United States. Before public transportation and public regulation of utilities like electricity and gas, North American cities adopted public water, but this transition is a relatively recent phenomenon. Until the 1830s, both water supply and sewerage were seen as private entities to be managed by private companies and private individuals with nominal assistance from local governments. Water provision was often a blend of public and private efforts, and if residents wanted a well or a sewer built in their neighborhood, they had to help pay for it. Until the mid-19th century, residents of Northeast U.S. cities drew water for domestic uses from local ponds, rivers, and groundwater sources. At this time, procuring water was a daily activity for residents that was linked to economic class. The 19th century was a key period in the redefinition of water as a public-sector responsibility in the United States. The cities of Philadelphia, Boston, and New York illustrate this change. City officials made the gradual transition from relying on private water companies to implementing public management of the water supply. As increasing urbanization and growing immigrant populations rendered local and privately managed water sources undersupplied, elected officials began to search for new sources of water located beyond city limits. Philadelphia was the first to transition to public water management in 1801, followed by New York in 1842, and Boston in 1848. While each city’s history is unique, city officials took similar approaches to defining public and private with regard to water provision by gradually eliminating private water companies and by increasing funding for public works. Common themes included water pollution, the need to tap new water supplies further from the city centers, disease prevention, fire protection, and financial corruption, within both private water companies and municipal efforts to supply water. While most cities of the Northeast United States transitioned to municipal operation of water supply during the 19th century, the shift was not without its challenges and complexities. Funding shortages often prevented change, but crises, such as fire, drought, and infectious disease outbreaks, forced the hands of municipal officials. Timelines to public water varied. While Boston and Philadelphia achieved permanent public water in the early 19th century, New York experienced a longer trajectory. In each case, public management of water definitively triumphed over private. By the early 20th century, urban Americans conceptualized public and private differently than they had during the 19th century. Water management was at the center of this profound shift.

## Where Is Equity in Integrated Approaches for Water Resources Management?

The challenges of integrated approaches and equity in water resources management have been well researched. However, a clear division exists between scholars working on equity and those working on integration, and there is remarkably little systematic analysis available that addresses their interlinkages. The divide between these two fields of inquiry has increased over time, and equity is assumed rather than explicitly considered in integrated approaches for water resources management. Historically, global debates on water resources management have focused on questions of distributional equity in canal irrigation systems and access to water. This limited focus on distributional equity was side-lined by neoliberal approaches and subsequent integrated approaches around water resources management tend to emphasize the synergistic aspects and ignore the political trade-offs between equity and efficiency. The interlinkages among equity, sustainability, and integration need deeper and broader interdisciplinary analysis and understanding, as well as new concepts, approaches, and agendas that are better suited to the intertwined complexity of resource degradation.