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Soil salinity has been causing problems for agriculturists for millennia, primarily in irrigated lands. The importance of salinity issues is increasing, since large areas are affected by irrigation-induced salt accumulation. A wide knowledge base has been collected to better understand the major processes of salt accumulation and choose the right method of mitigation. There are two major types of soil salinity that are distinguished because of different properties and mitigation requirements. The first is caused mostly by the large salt concentration and is called saline soil, typically corresponding to Solonchak soils. The second is caused mainly by the dominance of sodium in the soil solution or on the soil exchange complex. This latter type is called “sodic” soil, corresponding to Solonetz soils. Saline soils have homogeneous soil profiles with relatively good soil structure, and their appropriate mitigation measure is leaching. Naturally sodic soils have markedly different horizons and unfavorable physical properties, such as low permeability, swelling, plasticity when wet, and hardness when dry, and their limitation for agriculture is mitigated typically by applying gypsum. Salinity and sodicity need to be chemically quantified before deciding on the proper management strategy. The most complex management and mitigation of salinized irrigated lands involves modern engineering including calculations of irrigation water rates and reclamation materials, provisions for drainage, and drainage disposal. Mapping-oriented soil classification was developed for naturally saline and sodic soils and inherited the first soil categories introduced more than a century ago, such as Solonchak and Solonetz in most of the total of 24 soil classification systems used currently. USDA Soil Taxonomy is one exception, which uses names composed of formative elements.
Confidence in the projected impacts of climate change on agricultural systems has increased substantially since the first Intergovernmental Panel on Climate Change (IPCC) reports. In Africa, much work has gone into downscaling global climate models to understand regional impacts, but there remains a dearth of local level understanding of impacts and communities’ capacity to adapt. It is well understood that Africa is vulnerable to climate change, not only because of its high exposure to climate change, but also because many African communities lack the capacity to respond or adapt to the impacts of climate change. Warming trends have already become evident across the continent, and it is likely that the continent’s 2000 mean annual temperature change will exceed +2°C by 2100. Added to this warming trend, changes in precipitation patterns are also of concern: Even if rainfall remains constant, due to increasing temperatures, existing water stress will be amplified, putting even more pressure on agricultural systems, especially in semiarid areas. In general, high temperatures and changes in rainfall patterns are likely to reduce cereal crop productivity, and new evidence is emerging that high-value perennial crops will also be negatively impacted by rising temperatures. Pressures from pests, weeds, and diseases are also expected to increase, with detrimental effects on crops and livestock.
Much of African agriculture’s vulnerability to climate change lies in the fact that its agricultural systems remain largely rain-fed and underdeveloped, as the majority of Africa’s farmers are small-scale farmers with few financial resources, limited access to infrastructure, and disparate access to information. At the same time, as these systems are highly reliant on their environment, and farmers are dependent on farming for their livelihoods, their diversity, context specificity, and the existence of generations of traditional knowledge offer elements of resilience in the face of climate change. Overall, however, the combination of climatic and nonclimatic drivers and stressors will exacerbate the vulnerability of Africa’s agricultural systems to climate change, but the impacts will not be universally felt. Climate change will impact farmers and their agricultural systems in different ways, and adapting to these impacts will need to be context-specific.
Current adaptation efforts on the continent are increasing across the continent, but it is expected that in the long term these will be insufficient in enabling communities to cope with the changes due to longer-term climate change. African famers are increasingly adopting a variety of conservation and agroecological practices such as agroforestry, contouring, terracing, mulching, and no-till. These practices have the twin benefits of lowering carbon emissions while adapting to climate change as well as broadening the sources of livelihoods for poor farmers, but there are constraints to their widespread adoption. These challenges vary from insecure land tenure to difficulties with knowledge-sharing.
While African agriculture faces exposure to climate change as well as broader socioeconomic and political challenges, many of its diverse agricultural systems remain resilient. As the continent with the highest population growth rate, rapid urbanization trends, and rising GDP in many countries, Africa’s agricultural systems will need to become adaptive to more than just climate change as the uncertainties of the 21st century unfold.
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.
In 1945, the Amazon biome was still mostly intact. The scars of ancient cultural developments in Andean and lowland Amazon had healed, and the impacts of rubber and other resource exploitation were reversible. Very few roads existed, and only in its periphery. In the 1950s and especially in the 1960s, Brazil and other Andean countries launched ambitious road building and colonization projects, largely driven by Brazilian geopolitical concerns. Interest in the Amazon became much more intense in the 1970s as forest loss began to raise worldwide concern. Construction of more and better roads continued at an exponentially growing pace in each following decade, multiplying correlated deforestation and forest degradation everywhere in the Amazon. A point of no return was reached when interoceanic roads crossed the borders of Brazilian-Andean countries in the 2000s, exposing the remaining safe havens for indigenous people and nature. It is commonly estimated that today no less than 18% of the forest has been replaced with agriculture and that more than 50% of the remaining forests are significantly degraded. Most deforested land, especially in Andean countries, is wasted or scarcely used. Oil, mining, and intense urban development, as well as intensive agriculture, spread serious water and soil contamination throughout the region. Logging, fisheries, and hunting gave rise to the successive commercial extinction of valuable species.
Theories regarding the importance of biogeochemical cycles had already been in development since the 1970s, however, in the late 1980s the dominant popular view on the environmental value of the Amazon “lungs of the planet” emerged. The confirmation of the role of the Amazon as a carbon sink added some international pressure for its protection. But, in general, the many scientific discoveries regarding the Amazon have not been helpful in improving its conservation. Instead, a combination of new agricultural technologies, anthropocentric philosophies, and economic changes has strongly promoted forest clearing.
From the 1980s to the present day, Amazon conservation efforts have increasingly diversified, and now consist of five theoretically complementary strategies: (1) the creation of more, larger and better managed protected areas, including biological corridors; (2) the protection of more and larger indigenous territories; (3) the promotion of a series of “sustainable use” options such as “community based conservation,” sustainable forestry, and agroforestry; (4) the financing of conservation through debt swaps and related financial mechanisms for mitigating climate change and; (5) the use of better legislation, monitoring, and control. Five small protected areas have existed in the Amazon since the early 1960s but, in response to the road building boom of the 1970s, several larger patches of forests were set aside with the aim of conserving viable samples of biological diversity. Today, around 25 % of the Amazon is designated as protected areas, but almost half of these areas are categorized in a way that allows human presence and resource exploitation, and there is no effective management. Another 25.3% is designated to indigenous people who may or not conserve the forest. Excluding areas of overlap, both types of protected areas cover 41.2% of the Amazon. Neither strategy has fully achieved its objective, alone or together, and development pressures and threats grow as road construction and deforestation continue relentlessly with increasing funding by multilateral and national banks and pressure from transnational enterprises.
The future will be directed by unprecedented agricultural expansion and the corresponding intensification of deforestation and forest degradation. Additionally, the Amazon basin will be impacted by new, larger hydraulic works. Mining will increase and spread. Policy makers of Amazon countries still view the region as the future for expanding conventional development, and the population continues to be indifferent.
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.
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.
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
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.
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 has 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.
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.