You are looking at 41-60 of 191 articles
Charles A. Francis
Adaptation of cropping systems to weather uncertainty and climate change is essential for resilient food production and long-term food security. Changes in climate result in substantial temporal modifications of cropping conditions, and rainfall and temperature patterns vary greatly with location. These challenges come at a time when global human population and demand for food are both increasing, and it appears to be difficult to find ways to satisfy growing needs with conventional systems of production. Agriculture in the future will need to feature greater biodiversity of crop species and appropriate design and management of cropping and integrated crop/animal systems. More diverse and longer-cycle crop rotations will need to combine sequences of annual row crops such as maize and soybean with close-drilled cereals, shallow-rooted with deep-rooted crops, summer crops with winter crops, and annuals with perennials in the same fields. Resilience to unpredictable weather will also depend on intercropping, with the creative arrangement of multiple interacting crop species to diversify the field and the landscape. Other multiple-cropping systems and strategies to integrate animals and crops will make more efficient use of natural resources and applied inputs; these include systems such as permaculture, agroforestry, and alley cropping. Future systems will be spatially diverse and adapted to specific fields, soil conditions, and unique agroecozones. Production resilience will be achieved by planting diverse combinations of species together in the same field, and economic resilience through producing a range of products that can be marketed through different channels. The creation of local food webs will be more appropriate in the future, as contrasted with the dominance of global food chains today. Materials considered “waste” from the food system, including human urine and feces, will become valuable resources to be cycled back into the natural environment and into food production. Due to the increasing scarcity of fertile land, the negative contributions of chemicals to environmental pollution, the costs of fossil fuels, and the potential for the economic and political disruption of supply chains, future systems will increasingly need to be local in character while still achieving adaptation to the most favorable conditions for each system and location. It is essential that biologically and economically resilient systems become productive and profitable, as well as environmentally sound and socially equitable, in order to contribute to stability of food production, security of the food supply, and food sovereignty, to the extent that this is possible. The food system cannot continue along the lines of “business as usual,” and its path will need to radically diverge from the recognized trends toward specialization and globalization of the early 21st century. The goal needs to shift from exploitation and short-term profits to conservation of resources, greater equity in distribution of benefits, and resilience in food supply, even with global climate change.
Muhammad Farooq, Ahmad Nawaz, and Faisal Nadeem
Planned crop rotation offers a pragmatic option to improve soil fertility, manage insect pests and diseases, and offset the emission of greenhouse gases. The inclusion of legume crops in crop rotations helps to reduce the use of external nitrogen inputs for legumes and other crops because legumes may fix the atmospheric nitrogen. This also helps to reduce the environmental pollution caused by volatilization and leaching of applied nitrogen. The inclusion of allelopathic crops in rotation may be useful to suppress noxious weeds due to release of the allelochemicals in the rhizosphere. The rotation of tap-rooted crops with shallow rooted crops may result in efficient and productive use of nutrient resources and conservation of soil moisture. Continuous monoculture systems may cause the loss of biodiversity. Land fallowing is an efficient agricultural management technique mostly practiced in arid regions to capture rainwater and store it in the soil profile for later use in crop production. During fallowing, tillage operations are practiced to enhance moisture conservation in the soil. Keeping soil fallow for a season or more restores soil fertility through nutrient deposits; increases organic matter, microbial carbon, and soil microbial diversity; and improves the soil’s physical properties, including aggregation stability and reduced soil compaction due to decreased traffic. In addition, fallowing of land provides biological means of pest (weeds and insects) control by disrupting the life cycle of pests and decreasing reliance on pesticides. Land fallowing can help offset the emission of greenhouse gases from agricultural fields by reducing traffic and increasing carbon sequestration within the soil. Summer fallowing may help to preserve moisture in diverse soil types in the rainfed regions of the world, although it may reduce the carbon sequestration potential of soils over the long term. Energy resources are decreasing, and the inclusion of energy crops in crop rotation may be highly beneficial. Many of the processes, factors, and mechanisms involved in crop rotation and land fallowing are poorly understood and require further investigation.
Corn ranks first among crops in quantity produced globally, owing to its high yield and to its value as a food for humans and domestic animals. While its water-use efficiency is high compared to that of other crops, the production of high corn yields requires a great deal of water; the availability of water largely determines where the crop is grown. As a high-yielding grass species, corn also requires a substantial supply of nutrients (especially nitrogen) from external sources, including manufactured fertilizers and organic materials such as animal or green manures. This, along with the need to manage soils, weeds, insects, and diseases, makes corn production environmentally consequential.
Corn captures large quantities of sunlight energy through photosynthesis, but its production requires large external inputs of energy, coming mostly (in mechanized production) from fossil fuels. So even though the crop’s high yields moderates the environmental cost per unit of grain produced, minimizing the external environmental consequences of large-scale corn production is an important goal in the quest for greater sustainability of production of this important crop.
Shu Ting Chang and Solomon P. Wasser
The word mushroom may mean different things to different people in different countries. Specialist studies on the value of mushrooms and their products should have a clear definition of the term mushroom. In a broad sense, “Mushroom is a distinctive fruiting body of a macrofungus, which produce spores that can be either epigeous or hypogeous and large enough to be seen with the naked eye and to be picked by hand.” Thus, mushrooms need not be members of the group Basidiomycetes, as commonly associated, nor aerial, nor fleshy, nor edible. This definition is not perfect, but it has been accepted as a workable term to estimate the number of mushrooms on Earth (approximately 16,000 species according to the rules of International Code of Nomenclature). The most cultivated mushrooms are saprophytes and are heterotrophic for carbon compounds. Even though their cells have walls, they are devoid of chlorophyll and cannot perform photosynthesis. They are also devoid of vascular xylem and phloem. Furthermore, their cell walls contain chitin, which also occurs in the exoskeleton of insects and other arthropods. They absorb O2 and release CO2. In fact, they may be functionally more closely related to animal cells than plants. However, they are sufficiently distinct both from plants and animals and belong to a separate group in the Fungi Kingdom. They rise up from lignocellulosic wastes: yet, they become bountiful and nourishing. Mushrooms can greatly benefit environmental conditions. They biosynthesize their own food from agricultural crop residues, which, like solar energy, are readily available; otherwise, their byproducts and wastes would cause health hazards. The spent compost/substrate could be used to grow other species of mushrooms, as fodder for livestock, as a soil conditioner and fertilizer, and in environmental bioremediation. The cultivation of mushrooms dates back many centuries; Auricularia auricula-judae, Lentinula edodes, and Agaricus bisporus have, for example, been cultivated since 600
Mushrooms can be used as food, tonics, medicines, cosmeceuticals, and as natural biocontrol agents in plant protection with insecticidal, fungicidal, bactericidal, herbicidal, nematocidal, and antiphytoviral activities. The multidimensional nature of the global mushroom cultivation industry, its role in addressing critical issues faced by humankind, and its positive contributions are presented. Furthermore, mushrooms can serve as agents for promoting equitable economic growth in society. Since the lignocellulose wastes are available in every corner of the world, they can be properly used in the cultivation of mushrooms, and therefore could pilot a so-called white agricultural revolution in less developed countries and in the world at large. Mushrooms demonstrate a great impact on agriculture and the environment, and they have great potential for generating a great socio-economic impact in human welfare on local, national, and global levels.
Assessing the environmental footprints of modern agriculture requires a balanced approach that sets the obviously negative effects (e.g., incidents with excessive use of inputs) against benefits stemming from increased resource use efficiencies. In the case of rice production, the regular flooding of fields comprises a distinctive feature, as compared to other crops, which directly or indirectly affects diverse impacts on the environment. In the regional context of Southeast Asia, rice production is characterized by dynamic changes in terms of crop management practices, so that environmental footprints can only be assessed from time-dependent developments rather than from a static view. The key for the Green Revolution in rice was the introduction of high-yielding varieties in combination with a sufficient water and nutrient supply as well as pest management. More recently, mechanization has evolved as a major trend in modern rice production. Mechanization has diverse environmental impacts and may also be instrumental in tackling the most drastic pollution source from rice production, namely, open field burning of straw. As modernization of rice production is imperative for future food supplies, there is scope for developing sustainable and high-yielding rice production systems by capitalizing on the positive aspects of modernization from a local to a global scale.
Wheat is the most widely grown food crop in the world and the dominant staple crop in temperate countries where it contributes between about 20% and 50% of the total energy intake. About 95% of the wheat grown is hexaploid bread wheat, with tetraploid durum wheat being grown in the hot dry Mediterranean climate and very small volumes of ancient species. About 80% of the dry weight of the mature grain is starchy endosperm. This is the major grain storage tissue, which is separated by milling to give white flour, the outer layers and germ together forming the bran. However, white flour and bran differ significantly in their compositions, with white flour being rich in starch (about 80% dry wt) and protein (about 10% dry wt) and the bran rich in fiber, minerals, vitamins, and phytochemicals.
Most of the wheat consumed by humankind is in the form of bread, noodles, pasta, and other processed foods, and the quality for processing is determined by two major characteristics: the grain texture (hardness) and the viscoelastic properties conferred to dough by the gluten proteins.
In addition to being a source of energy, wheat also contributes protein and a range of other essential and beneficial components, particularly dietary fiber. However, because most of these components are concentrated in the bran, it is important to increase the consumption of whole grain products or to improve the composition of white flour. Although there is concern among consumers about possible adverse effects of consuming wheat products on health, these are unlikely to affect more than a small proportion of the population, and wheat should form part of a healthy balanced diet for the vast majority.
Mainaak Mukhopadhyay and Tapan Kumar Mondal
Tea, the globally admired, non-alcoholic, caffeine-containing beverage, is manufactured from the tender leaves of the tea [Camellia sinensis (L.)] plant. It is basically a woody, perennial crop with a lifespan of more than 100 years. Cultivated tea plants are natural hybrids of the three major taxa or species, China, Assam (Indian), or Cambod (southern) hybrids based on the morphological characters (principally leaf size). Planting materials are either seedlings (10–18 months old) developed from either hybrid, polyclonal, or biclonal seeds, or clonal cuttings developed from single-leaf nodal cuttings of elite genotypes. Plants are forced to remain in the vegetative stage as bushes by following cultural practices like centering, pruning, and plucking, and they are harvested generally from the second year onward at regular intervals of 7–10 days in the tropics and subtropics, with up to 60 years as the economic lifespan. Originally, the Chinese were the first to use tea as a medicinal beverage, around 2000 years ago, and today, around half of the world’s population drink tea. It is primarily consumed as black tea (fermented tea), although green tea (non-fermented) and oolong tea (semifermented) are also consumed in many countries. Tea is also used as vegetables such as “leppet tea” in Burma and “meing tea” in Thailand.
Green tea has extraordinary antioxidant properties, and black tea plays a positive role in treating cardiovascular ailments. Tea in general has considerable therapeutic value and can cure many diseases. Global tea production (black, green, and instant) has increased significantly during the past few years. China, as the world’s largest tea producer, accounts for more than 38% of the total global production of made tea [i.e. ready to drink tea] annually, while production in India, the second-largest producer. India recorded total production of 1233.14 million kg made tea during 2015–2016, which is the highest ever production so far.
Since it is an intensive monoculture, tea cultivation has environmental impacts. Application of weedicides, pesticides, and inorganic fertilizers creates environmental hazards. Meanwhile, insecticides often eliminate the fauna of a vast tract of land. Soil degradation is an additional concern because the incessant use of fertilizers and herbicides compound soil erosion. Apart from those issues, chemical runoff into bodies of water can also create problems. Finally, during tea manufacturing, fossil fuel is used to dry the processed leaves, which also increases environmental pollution.
Dairy has intertwined with human society since the beginning of civilization. It evolves from art in ancient society to science in the modern world. Its roles in nutrition and health are underscored by the continuous increase in global consumption. Milk production increased by almost 50% in just the past quarter century alone. Population growth, income rise, nutritional awareness, and science and technology advancement contributed to a continuous trend of increased milk production and consumption globally. With a fourfold increase in milk production per cow since the 1940s, the contemporary dairy industry produces more milk with fewer cows, and consumes less feed and water per liter of milk produced. The dairy sector is diversified, as people from a wider geographical distribution are consuming milk, from cattle to species such as buffalo, goat, sheep, and camel. The dairy industry continues to experience structural changes that impact society, economy, and environment. Organic dairy emerged in the 1990s as consumers increasingly began viewing it as an appropriate way of both farming and rural living. Animal welfare, environmental preservation, product safety, and health benefit are important considerations in consuming and producing organic dairy products. Large dairy operations have encountered many environmental issues related to elevated greenhouse gas emissions. Dairy cattle are second only to beef cattle as the largest livestock contributors in methane emission. Disparity in greenhouse gas emissions per dairy animal among geographical regions can be attributed to production efficiency. Although a number of scientific advancements have implications in the inhibition of methanogenesis, improvements in production efficiency through feeding, nutrition, genetic selection, and management remain promising for the mitigation of greenhouse gas emissions from dairy animals. This article describes the trends in milk production and consumption, the debates over the role of milk in human nutrition, the global outlook of organic dairy, the abatement of greenhouse gas emissions from dairy animals, as well as scientific and technological developments in nutrition, genetics, reproduction, and management in the dairy sector.
Christiane Runyan and Jeff Stehm
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.
Eight thousand years ago, forests covered an estimated 47% of Earth’s land surface. In 2015, forests covered roughly 30% of the Earth’s land surface, a cumulative loss over the last 8,000 years of approximately 2.2 billion hectares (ha). Between 1990 and 2015, forest losses occurred at the rate of about 0.13% annually, but this rate appears to be slowing. These losses mostly occur in tropical forests (58%), followed by boreal (27%) and temperate forests (8%). Deforestation is driven by a number of direct and indirect factors and processes that vary across regions and interact in complex ways. The primary driver of deforestation is agricultural expansion (both commercial and subsistence), followed by mining, infrastructure extension, and urban expansion. Indirectly, population and economic growth increase the demand for agricultural and timber products. Global food demand will increase 70% by 2050, requiring a net increase of 70 million ha of arable land under cultivation, with approximately 80% of this expansion occurring in the tropics. Deforestation is affected by other indirect factors such as land tenure uncertainties, poor governance, low capacity of public forestry agencies, and inadequate planning and monitoring. Forest loss has a number of environmental, economic, and social implications. Environmentally, forests provide an expansive range of benefits across local, regional, and global scales, including hydrological benefits (e.g., regulating water supply and river discharge), climate benefits (e.g., precipitation recycling, regulating local and global temperature, and indirectly, by taking up atmospheric CO2 during photosynthesis), biogeochemical benefits (e.g., enhancing nutrient availability and reducing nutrient losses), and by supporting greater biodiversity as well as ecosystem stability and resiliency, to name a few. The loss of forest vegetation may negatively affect important ecosystem processes and services, and may induce bistable ecosystem dynamics. The existence of bistable ecosystem dynamics in some forest ecosystems suggests that these forests are prone to abrupt and irreversible shifts to a stable and often degraded state with no trees. In addition to environmental impacts, the long-term loss of forest resources negatively affects societies. About 8% (450 million) of the world’s population live in forest ecosystems, with an estimated 350 million people entirely dependent on forest ecosystems for their livelihoods. The forest sector, in 2011, contributed an estimated total amount of USD 600 billion to global GDP, or about 0.9% of global GDP. Understanding how to best manage forest resources to preserve their unique qualities is a challenge that will require an integrated and concentrated effort from scientists and policymakers alike. In particular, improving forest management will require being able to more accurately measure and monitor forest resources, identifying the trade-offs between competing objectives, valuing forest goods and services, and equitably balancing costs and benefits. On the policy front, approaches to strengthen land tenure and property rights, reduce corruption, improve the capacity of public agencies, and develop more inclusive governance arrangements are needed. Underlying these management and policy goals is the need to better understand the environmental processes occurring in forests—to improve their management, minimize adverse impacts, and strengthen our models of these systems, because the long-term loss of forest resources affects not only the functioning of ecosystems but also the societies whose health and livelihoods depend upon them.
Deforestation in Brazilian Amazonia destroys environmental services that are important for the whole world, and especially for Brazil itself. These services include maintaining biodiversity, avoiding global warming, and recycling water that provides rainfall to Amazonia, to other parts of Brazil, such as São Paulo, and to neighboring countries, such as Argentina. The forest also maintains the human populations and cultures that depend on it. Deforestation rates have gone up and down over the years with major economic cycles. A peak of 27,772 km2/year was reached in 2004, followed by a major decline to 4571 km2/year in 2012, after which the rate trended upward, reaching 7989 km2/year in 2016 (equivalent to about 1.5 hectares per minute). Most (70%) of the decline occurred by 2007, and the slowing in this period is almost entirely explained by declining prices of export commodities such as soy and beef. Government repression measures explain the continued decline from 2008 to 2012, but an important part of the effect of the repression program hinges on a fragile base: a 2008 decision that makes the absence of pending fines a prerequisite for obtaining credit for agriculture and ranching. This could be reversed at the stroke of a pen, and this is a priority for the powerful “ruralist” voting bloc in the National Congress. Massive plans for highways, dams, and other infrastructure in Amazonia, if carried out, will add to forces in the direction of increased deforestation.
Deforestation occurs for a wide variety of reasons that vary in different historical periods, in different locations, and in different phases of the process at any given location. Economic cycles, such as recessions and the ups and downs of commodity markets, are one influence. The traditional economic logic, where people deforest to make a profit by producing products from agriculture and ranching, is important but only a part of the story. Ulterior motives also drive deforestation. Land speculation is critical in many circumstances, where the increase in land values (bid up, for example, as a safe haven to protect money from hyperinflation) can yield much higher returns than anything produced by the land. Even without the hyperinflation that came under control in 1994, highway projects can yield speculative fortunes to those who are lucky or shrewd enough to have holdings along the highway route. The practical way to secure land holdings is to deforest for cattle pasture. This is also critical to obtaining and defending legal title to the land. In the past, it has also been the key to large ranches gaining generous fiscal incentives from the government. Money laundering also makes deforestation attractive, allowing funds from drug trafficking, tax evasion, and corruption to be converted to “legal” money. Deforestation receives impulses from logging, mining, and, especially, road construction. Soybeans and cattle ranching are the main replacements for forest, and recently expanded export markets are giving strength to these drivers. Population growth and household dynamics are important for areas dominated by small farmers. Extreme degradation, where tree mortality from logging and successive droughts and forest fires replace forest with open nonforest vegetation, is increasing as a kind of deforestation, and is likely to increase much more in the future.
Controlling deforestation requires addressing its multiple causes. Repression through fines and other command-and-control measures is essential to avoid a presumption of impunity, but these controls must be part of a broader program that addresses underlying causes. The many forms of government subsidies for deforestation must be removed or redirected, and the various ulterior motives must be combated. Industry agreements restricting commodity purchases from properties with illegal deforestation (or from areas cleared after a specified cutoff) have a place in efforts to contain forest loss, despite some problems. A “soy moratorium” has been in effect since 2006, and a “cattle agreement” since 2009. Creation and defense of protected areas is an important part of deforestation control, including both indigenous lands and a variety of kinds of “conservation units.” Containing infrastructure projects is essential if deforestation is to be held in check: once roads are built, much of what happens is outside the government’s control. The notion that the 2005–2012 deforestation slowdown means that the process is under control and that infrastructure projects can be built at will is extremely dangerous. One must also abandon myths that divert efforts to contain deforestation; these include “sustainable logging” and the use of “green” funds for expensive programs to reforest degraded lands rather than retain areas of remaining natural forests. Finally, one must provide alternatives to support the rural population of small farmers. Large investors, on the other hand, can fend for themselves. Tapping the value of the environmental services of the forest has been proposed as an alternative basis for sustaining both the rural population and the forest. Despite some progress, a variety of challenges remain. One thing is clear: most of Brazil’s Amazonian deforestation is not “development.” Trading the forest for a vast expanse of extensive cattle pasture does little to secure the well-being of the region’s rural population, is not sustainable, and sacrifices Amazonia’s most valuable resources.
Bartosz Bartkowski and Nele Lienhoop
While economic values of nonmarket ecosystem goods and services are in high demand to inform decision-making processes, economic valuation has also attracted significant criticism. Particularly, its implicit rationality assumptions and value monism gave rise to alternative approaches to economic nonmarket valuation. Deliberative monetary valuation (DMV) originated in the early 2000s and gained particular prominence after 2010, especially in the context of the United Kingdom National Ecosystem Assessment (UK NEA). It constitutes a major methodological development to overcome the limitations of conventional nonmarket valuation methods by incorporating deliberative group elements (information provision, discussion, time to reflect in a group setting) in the valuation process.
DMV approaches range from those that focus on facilitating individual preference formation for complex and unfamiliar environmental changes and stay close to neoclassical economic theory to those that try to go beyond methodological individualism and monetary valuation to include a plurality of different values. The theoretical foundation of DMV comprises a mix of economic welfare theory, on the one hand, and various strands of deliberative democratic theory and discourse ethics, on the other. DMV formats are mostly inspired by deliberative institutions such as citizens’ juries and combine those with stated preference methods such as choice experiments. While the diversity of approaches within this field is large, it has been demonstrated that deliberation can lead to more well-informed and stable preferences as well as facilitate the inclusion of considerations going beyond self-interest. Future research challenges surrounding DMV include the exploration of intergroup power relations and group dynamics as well as the theoretical status and the validity of DMV results.
P.S. Goh, A.F. Ismail, and N. Hilal
Water scarcity as an outcome of global population expansion, climate change, and industrialization calls for new and innovative technologies to provide sustainable solutions to address this alarming issue. Seawater and brackish water are abundantly available on earth for drinking water and industrial use, and desalination is a promising approach to resolving this global challenge. Recently, the considerable reduction in the cost of desalination has contributed to the growing capacity for global desalination. The desalination technologies that have been deployed worldwide for clean water production can be categorized into two main types: membrane-based and thermal-based. Technological advancement in this field has focused on the reduction of capital and operating cost, particularly the energy consumption of the systems. Seawater and brackish desalination technologies are promising solutions for water shortages.
Throughout the 1900s, the warmth of the current interglaciation was viewed as completely natural in origin (prior to greenhouse-gas emissions during the industrial era). In the view of physical scientists, orbital variations had ended the previous glaciation and caused a warmer climate but had not yet brought it to an end. Most historians focused on urban and elite societies, with much less attention to how farmers were altering the land. Historical studies were also constrained by the fact that written records extended back a few hundred to at most 3,500 years.
The first years of the new millennium saw a major challenge to the ruling paradigm. Evidence from deep ice drilling in Antarctica showed that the early stages of the three interglaciations prior to the current one were marked by decreases in concentrations of carbon dioxide (CO2) and methane (CH4) that must have been natural in origin. During the earliest part of the current (Holocene) interglaciation, gas concentrations initially showed similar decreases, but then rose during the last 7,000–5,000 years. These anomalous (“wrong-way”) trends are interpreted by many scientists as anthropogenic, with support from scattered evidence of deforestation (which increases atmospheric CO2) by the first farmers and early, irrigated rice agriculture (which emits CH4).
During a subsequent interval of scientific give-and-take, several papers have criticized this new hypothesis. The most common objection has been that there were too few people living millennia ago to have had large effects on greenhouse gases and climate. Several land-use simulations estimate that CO2 emissions from pre-industrial forest clearance amounted to just a few parts per million (ppm), far less than the 40 ppm estimate in the early anthropogenic hypothesis. Other critics have suggested that, during the best orbital analog to the current interglaciation, about 400,000 years ago, interglacial warmth persisted for 26,000 years, compared to the 10,000-year duration of the current interglaciation (implying more warmth yet to come). A geochemical index of the isotopic composition of CO2 molecules indicates that terrestrial emissions of 12C-rich CO2 were very small prior to the industrial era.
Subsequently, new evidence has once again favored the early anthropogenic hypothesis, albeit with some modifications. Examination of cores reaching deeper into Antarctic ice reconfirm that the upward gas trends in this interglaciation differ from the average downward trends in seven previous ones. Historical data from Europe and China show that early farmers used more land per capita and emitted much more carbon than suggested by the first land-use simulations. Examination of pollen trends in hundreds of European lakes and peat bogs has shown that most forests had been cut well before the industrial era. Mapping of the spread of irrigated rice by archaeobotanists indicates that emissions from rice paddies can explain much of the anomalous CH4 rise in pre-industrial time. The early anthropogenic hypothesis is now broadly supported by converging evidence from a range of disciplines.
Benjamin S. Arbuckle
The domestication of livestock animals has long been recognized as one of the most important and influential events in human prehistory and has been the subject of scholarly inquiry for centuries. Modern understandings of this important transition place it within the context of the origins of food production in the so-called Neolithic Revolution, where it is particularly well documented in southwest Asia. Here, a combination of archaeofaunal, isotopic, and DNA evidence suggests that sheep, goat, cattle, and pigs were first domesticated over a period of several millennia within sedentary communities practicing intensive cultivation beginning at the Pleistocene–Holocene transition. Resulting from more than a century of data collection, our understanding of the chronological and geographic features of the transition from hunting to herding indicate that the 9th millennium
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.
There are continuing developments in the analysis of hunger and famines, and the results of theoretical and empirical studies of hunger and food insecurity highlight cases where hunger intensifies sufficiently to be identified as famine. The varying ability of those affected to cope with the shocks and stresses imposed on them are central to the development of food insecurity and the emergence of famine conditions and to explaining the complex interrelationships between agriculture, famine, and economics.
There are a number of approaches to understanding how famines develop. The Malthusian approach, which sees population growth as the primary source of hunger and famine, can be contrasted with the free market or Smithian approach, which regards freely operating markets as an essential prerequisite for ensuring that famine can be overcome. A major debate has centered on whether famines primarily emerge from a decline in the availability of food or are a result of failure by households to access sufficient food for consumption, seeking to distinguish between famine as a problem related to food production and availability and famine as a problem of declining income and food consumption among certain groups in the population. These declines arise from the interaction between food markets, labor markets and markets for livestock and other productive farm resources when poor people try to cope with reduced food consumption. Further revisions to famine analysis were introduced from the mid-1990s by authors who interpreted the emergence of famines not as a failure in markets and the economic system, but more as a failure in political accountability and humanitarian response.
These approaches have the common characteristic that they seek to narrow the focus of investigation to one or a few key characteristics. Yet most of those involved in famine analysis or famine relief would stress the multi-faceted and broad-based nature of the perceived causes of famine and the mechanisms through which they emerge. In contrast to these approaches, the famine systems approach takes a broader view, exploring insights from systems theory to understand how famines develop and especially how this development might be halted, reversed, or prevented.
Economists have contributed to and informed different perspectives on famine analysis while acknowledging key contributions from moral philosophy as well as from biological and physical sciences and from political and social sciences. Malthus, Smith, and John Stuart Mill contributed substantially to early thinking on famine causation and appropriate famine interventions. Increased emphasis on famine prevention and a focus on food production and productivity led to the unarguable success of the Green Revolution. An important shift in thinking in the 1980s was motivated by Amartya Sen’s work on food entitlements and on markets for food and agricultural resources. On the other hand, the famine systems approach considers famine as a process governed by complex relationships and seeks to integrate contributions from economists and other scientists while promoting a systems approach to famine analysis.
Mark Eiswerth, Chad Lawley, and Michael H. Taylor
Introductions of non-native invasive species can harm ecosystems, heighten the risk of native species extinctions and population reductions, and lead to substantial economic damages on a worldwide scale. Increasingly, economists have made contributions that help other researchers, policymakers, and society better understand the economic implications of invasive species as well as the most economically efficient approaches for managing them. The complexity of invasive species management problems has pushed economists to ask novel economic questions and to develop new analytical approaches in order to address specific policy questions. There are three areas, in particular, where the economic analysis of invasive species management has led to significant innovations. First, there are substantial challenges to quantifying economic damages from invasive species for application in benefit−cost analysis. The challenges relate to defining the counterfactual state of an invaded ecosystem with and without management/policy and to the fact that, in a given ecosystem, estimates of economic damages are available for only a subset of the species and for only a subset of damages for any one species. Recent economic research has proposed innovative approaches to systematically dealing with these two issues in the context of invasive species that have implications for applied benefit−cost analysis more broadly. Second, unique among natural resource management problems, invasive species have the feature that their current and future extents are directly tied to a country’s participation in international trade. This feature has led to innovative research into the design of efficient measures to prevent or delay invasive species introductions along national borders, and into the trade-offs between these measures and the use of border controls as protectionist tools. The issues of optimal inspection policy and the use of nontariff barriers as a form of covert protectionism both have implications beyond invasive species management. Third, researchers have developed bioeconomic models that integrate economic and biological factors in order to analyze strategies to more cost-effectively reduce the damages caused by invasive species. These modeling efforts have dealt with issues related to temporal and spatial dynamics of the biological invasions, imperfect information regarding the extent of the invasion and the effectiveness of management, linkages between management applied at different stages of an invasion, and complications arising from ecosystems’ crossing over ecological thresholds due to invasions. In the face of increasingly rapid ecosystem change due to global climate change, increases in extreme weather, urban encroachment into wild lands, and other factors, many of these features of invasive species management problems are likely to become features of ecosystem management more broadly in the near future if they are not so already.
Dominic Moran and Jorie Knook
Climate change is already having a significant impact on agriculture through greater weather variability and the increasing frequency of extreme events. International policy is rightly focused on adapting and transforming agricultural and food production systems to reduce vulnerability. But agriculture also has a role in terms of climate change mitigation. The agricultural sector accounts for approximately a third of global anthropogenic greenhouse gas emissions, including related emissions from land-use change and deforestation. Farmers and land managers have a significant role to play because emissions reduction measures can be taken to increase soil carbon sequestration, manage fertilizer application, and improve ruminant nutrition and waste. There is also potential to improve overall productivity in some systems, thereby reducing emissions per unit of product. The global significance of such actions should not be underestimated. Existing research shows that some of these measures are low cost relative to the costs of reducing emissions in other sectors such as energy or heavy industry. Some measures are apparently cost-negative or win–win, in that they have the potential to reduce emissions and save production costs. However, the mitigation potential is also hindered by the biophysical complexity of agricultural systems and institutional and behavioral barriers limiting the adoption of these measures in developed and developing countries. This includes formal agreement on how agricultural mitigation should be treated in national obligations, commitments or targets, and the nature of policy incentives that can be deployed in different farming systems and along food chains beyond the farm gate. These challenges also overlap growing concern about global food security, which highlights additional stressors, including demographic change, natural resource scarcity, and economic convergence in consumption preferences, particularly for livestock products. The focus on reducing emissions through modified food consumption and reduced waste is a recent agenda that is proving more controversial than dealing with emissions related to production.
Maria L. Loureiro and Maria Alló
Vessel oil spills are very serious natural hazards that have affected coasts worldwide for many decades. Although oil spills from tankers are highly publicized, very little is known about the role played by the incentives and regulatory instruments in place to prevent them. In order to shed some light on these issues, data were collected worldwide on large oil spills from multiple databases, starting in the 1970s, and merged with other socioeconomic records. A crucial concern is that that large oil spills have been undercompensated over time with respect to the damages caused. A meta-analysis was estimated in order to assess relevant factors affecting the damage claimed in oil spills and the compensations received by the affected parties. Meta-regression results show that the legislation applied (strict unlimited liability versus limited liability) played a crucial role in both the amount claimed and the final compensation received. Also, time-trend variables are shown as determining factors for both the damages and claims that are finally paid. To correct the large gap between damage claimed and compensation scenarios, it is recommended to strengthen compensation funds, while carrying out more comprehensive assessment studies which apply valuation methods comparable with those proposed by green capital initiatives for marine ecosystem services, and which could be used successfully during the litigation process.
Reforestation is the natural or intentional restocking of existing forests and woodlands that have been harvested or depleted, and afforestation is the establishing of a forest in an area where there were no trees. For economic and practical purposes, reforestation and afforestation have similar goals and processes and thus can be treated as identical activities. Although reforestation and afforestation have a long history, large-scale reforestation and afforestation activities started with industrialization, which caused scarcity in timber and forest-based ecosystem services. In a unified economic model of reforestation and afforestation, factors influencing investments in reforestation and in afforestation on private and public lands include timber prices, unit reforestation cost, interest rate, the responsiveness of tree growth to silviculture, and the value of nontimber benefits, such as ecosystem services. Market and public policies may facilitate, enhance, or hinder reforestation and afforestation activities, and nontimber benefits are an increasingly important motive for reforestation and, especially, afforestation efforts around the world.