Forest gardening
Forest gardening is a low-maintenance sustainable plant-based food production and agroforestry system based on woodland ecosystems, incorporating fruit and nut trees, herbs and perennial vegetables which have yields directly useful to humans. Making use of companion planting, these can be intermixed to grow in a succession of layers, to build a woodland habitat. Forest gardening is a prehistoric method of securing food in tropical areas. In the 1980s, Robert Hart coined the term "forest gardening" after adapting the principles and applying them to temperate climates. Forest gardens are the world's oldest form of land use and most resilient agroecosystem, they originated in prehistoric times along jungle-clad river banks and in the wet foothills of monsoon regions. In the gradual process of families improving their immediate environment, useful tree and vine species were identified and improved whilst undesirable species were eliminated. Superior foreign species were selected and incorporated into the gardens.
Forest gardens are still common in the tropics and known by various names such as: home gardens in Kerala in South India, Zambia and Tanzania. These are called agroforests and, where the wood components are short-statured, the term shrub garden is employed. Forest gardens have been shown to be a significant source of income and food security for local populations. Robert Hart adapted forest gardening for the United Kingdom's temperate climate during the 1980s, his theories were developed by Martin Crawford from the Agroforestry Research Trust and various permaculturalists such as Graham Bell, Patrick Whitefield, Dave Jacke and Geoff Lawton. Forest gardens, or home gardens, are common in the tropics, using intercropping to cultivate trees and livestock on the same land. In Kerala in south India as well as in northeastern India, the home garden is the most common form of land use and is found in Indonesia. One example combines coconut, black pepper and pineapple; these gardens exemplify polyculture, conserve much crop genetic diversity and heirloom plants that are not found in monocultures.
Forest gardens have been loosely compared to the religious concept of the Garden of Eden. The BBC's Unnatural Histories claimed that the Amazon rainforest, rather than being a pristine wilderness, has been shaped by humans for at least 11,000 years through practices such as forest gardening and terra preta; this was explored in the bestselling book 1491 by author Charles C. Mann. Since the 1970s, numerous geoglyphs have been discovered on deforested land in the Amazon rainforest, furthering the evidence about Pre-Columbian civilizations. On the Yucatán Peninsula, much of the Maya food supply was grown in "orchard-gardens", known as pet kot; the system takes its name from the low wall of stones. The North American ecosystem was managed by the first nations' use of fire to burn underbrush to encourage large game. Large Oak forests harvested for acorns disappeared. Prairie and grasslands were managed by the first nations. In many African countries, for example Zambia, Zimbabwe and Tanzania, gardens are widespread in rural and urban areas and they play an essential role in establishing food security.
Most well known are the Chagga gardens on the slopes of Mt. Kilimanjaro in Tanzania; these are an excellent example of an agroforestry system. In many countries, women are the main actors in home gardening and food is produced for subsistence. In North-Africa, oasis layered gardening with palm trees, fruit trees and vegetables is a traditional type of forest garden. In Nepal, the Ghar Bagaincha "home garden", refers to the traditional land-use system around a homestead, where several species of plants are grown and maintained by household members and their products are intended for the family consumption; the term “home garden” is considered synonymous to the kitchen garden. However, they differ in terms of function, diversity and features. In Nepal, 72% of households have home gardens of an area 2–11% of the total land holdings; because of their small size, the government has never identified home gardens as an important unit of food production, they thus remain neglected from research and development.
However, at the household level the system is important, as it is an important source of quality food and nutrition for the rural poor and, therefore, is an important contributor to the household food security and livelihoods of farming communities in Nepal. The gardens are cultivated with a mixture of annual and perennial plants that can be harvested on a daily or seasonal basis. Biodiversity that has an immediate value is maintained in home gardens as women and children have easy access to preferred food. Home gardens, with their intensive and multiple uses, provide a safety net for households when food is scarce; these gardens are not only important sources of food, fuel, spices, flowers, construction materials and income in many countries, but they are important for the in situ conservation of a wide range of unique genetic resources for food and agriculture. Many uncultivated, as well as neglected and underutilised species could make an important contribution to the dietary diversity of local communities.
In addition to supplementing diet in times of difficulty, home gardens promote who
Ecological succession
Ecological succession is the process of change in the species structure of an ecological community over time. The time scale can be decades, or millions of years after a mass extinction; the community begins with few pioneering plants and animals and develops through increasing complexity until it becomes stable or self-perpetuating as a climax community. The "engine" of succession, the cause of ecosystem change, is the impact of established species upon their own environments. A consequence of living is the sometimes subtle and sometimes overt alteration of one's own environment, it is a phenomenon or process by which an ecological community undergoes more or less orderly and predictable changes following a disturbance or the initial colonization of a new habitat. Succession may be initiated either by formation of new, unoccupied habitat, such as from a lava flow or a severe landslide, or by some form of disturbance of a community, such as from a fire, severe windthrow, or logging. Succession that begins in new habitats, uninfluenced by pre-existing communities is called primary succession, whereas succession that follows disruption of a pre-existing community is called secondary succession.
Succession was among the first theories advanced in ecology. Ecological succession was first documented in the Indiana Dunes of Northwest Indiana and remains at the core of ecological science. Precursors of the idea of ecological succession go back to the beginning of the 19th century; the French naturalist Adolphe Dureau de la Malle was the first to make use of the word succession concerning the vegetation development after forest clear-cutting. In 1859 Henry David Thoreau wrote an address called "The Succession of Forest Trees" in which he described succession in an oak-pine forest. "It has long been known to observers that squirrels bury nuts in the ground, but I am not aware that any one has thus accounted for the regular succession of forests." The Austrian botanist Anton Kerner published a study about the succession of plants in the Danube river basin in 1863. Henry Chandler Cowles, at the University of Chicago, developed a more formal concept of succession. Inspired by studies of Danish dunes by Eugen Warming, Cowles studied vegetation development on sand dunes on the shores of Lake Michigan.
He recognized that vegetation on dunes of different ages might be interpreted as different stages of a general trend of vegetation development on dunes. He first published this work as a paper in the Botanical Gazette in 1899. In this classic publication and subsequent papers, he formulated the idea of primary succession and the notion of a sere—a repeatable sequence of community changes specific to particular environmental circumstances. From about 1900 to 1960, understanding of succession was dominated by the theories of Frederic Clements, a contemporary of Cowles, who held that seres were predictable and deterministic and converged on a climatically determined stable climax community regardless of starting conditions. Clements explicitly analogized the successional development of ecological communities with ontogenetic development of individual organisms, his model is referred to as the pseudo-organismic theory of community ecology. Clements and his followers developed a complex taxonomy of successional pathways.
Henry Gleason offered a contrasting framework as early as the 1920s. The Gleasonian model was much less deterministic than the Clementsian, it differs most fundamentally from the Clementsian view in suggesting a much greater role of chance factors and in denying the existence of coherent bounded community types. Gleason argued that species distributions responded individualistically to environmental factors, communities were best regarded as artifacts of the juxtaposition of species distributions. Gleason's ideas, first published in 1926, were ignored until the late 1950s. Two quotes illustrate the contrasting views of Gleason. Clements wrote in 1916: The developmental study of vegetation rests upon the assumption that the unit or climax formation is an organic entity; as an organism the formation arises, grows and dies. Furthermore, each climax formation is able to reproduce itself, repeating with essential fidelity the stages of its development. While Gleason, in his 1926 paper, said: An association is not an organism, scarcely a vegetational unit, but a coincidence.
Gleason's ideas were, in fact, more consistent with Cowles' original thinking about succession. About Clements' distinction between primary succession and secondary succession, Cowles wrote: This classification seems not to be of fundamental value, since it separates such related phenomena as those of erosion and deposition, it places together such unlike things as human agencies and the subsidence of land. A more rigorous, data-driven testing of successional models and community theory began with the work of Robert Whittaker and John Curtis in the 1950s and 1960s. Succession theory has since become more complex. J. Connell and R. Slatyer attempted a codification of successional processes by mechanism. Among British and North American ecologists, the notion of a stable climax vegetation has been abandoned, successional processes have come to be seen as much less deterministic, with important roles for historical contingency and for alternate pathways in the actual development of communities.
Debates continue as to the general predictability of successional dynamics and the relative im
Vancouver
Vancouver is a coastal seaport city in western Canada, located in the Lower Mainland region of British Columbia. As the most populous city in the province, the 2016 census recorded 631,486 people in the city, up from 603,502 in 2011; the Greater Vancouver area had a population of 2,463,431 in 2016, making it the third-largest metropolitan area in Canada. Vancouver has the highest population density in Canada with over 5,400 people per square kilometre, which makes it the fifth-most densely populated city with over 250,000 residents in North America behind New York City, San Francisco, Mexico City according to the 2011 census. Vancouver is one of the most ethnically and linguistically diverse cities in Canada according to that census. 30% of the city's inhabitants are of Chinese heritage. Vancouver is classed as a Beta global city. Vancouver is named as one of the top five worldwide cities for livability and quality of life, the Economist Intelligence Unit acknowledged it as the first city ranked among the top-ten of the world's most well-living cities for five consecutive years.
Vancouver has hosted many international conferences and events, including the 1954 British Empire and Commonwealth Games, UN Habitat I, Expo 86, the World Police and Fire Games in 1989 and 2009. In 2014, following thirty years in California, the TED conference made Vancouver its indefinite home. Several matches of the 2015 FIFA Women's World Cup were played in Vancouver, including the final at BC Place; the original settlement, named Gastown, grew up on clearcuts on the west edge of the Hastings Mill logging sawmill's property, where a makeshift tavern had been set up on a plank between two stumps and the proprietor, Gassy Jack, persuaded the curious millworkers to build him a tavern, on July 1, 1867. From that first enterprise, other stores and some hotels appeared along the waterfront to the west. Gastown became formally laid out as a registered townsite dubbed Granville, B. I.. As part of the land and political deal whereby the area of the townsite was made the railhead of the Canadian Pacific Railway, it was renamed "Vancouver" and incorporated shortly thereafter as a city, in 1886.
By 1887, the Canadian Pacific transcontinental railway was extended westward to the city to take advantage of its large natural seaport to the Pacific Ocean, which soon became a vital link in a trade route between the Orient / East Asia, Eastern Canada, Europe. As of 2014, Port Metro Vancouver is the third-largest port by tonnage in the Americas, 27th in the world, the busiest and largest in Canada, the most diversified port in North America. While forestry remains its largest industry, Vancouver is well known as an urban centre surrounded by nature, making tourism its second-largest industry. Major film production studios in Vancouver and nearby Burnaby have turned Greater Vancouver and nearby areas into one of the largest film production centres in North America, earning it the nickname "Hollywood North"; the city takes its name from George Vancouver, who explored the inner harbour of Burrard Inlet in 1792 and gave various places British names. The family name "Vancouver" itself originates from the Dutch "Van Coevorden", denoting somebody from the city of Coevorden, Netherlands.
The explorer's ancestors came to England "from Coevorden", the origin of the name that became "Vancouver". Archaeological records indicate that Aboriginal people were living in the "Vancouver" area from 8,000 to 10,000 years ago; the city is located in the traditional and presently unceded territories of the Squamish and Tseil-Waututh peoples of the Coast Salish group. They had villages in various parts of present-day Vancouver, such as Stanley Park, False Creek, Point Grey and near the mouth of the Fraser River. Europeans became acquainted with the area of the future Vancouver when José María Narváez of Spain explored the coast of present-day Point Grey and parts of Burrard Inlet in 1791—although one author contends that Francis Drake may have visited the area in 1579; the explorer and North West Company trader Simon Fraser and his crew became the first-known Europeans to set foot on the site of the present-day city. In 1808, they travelled from the east down the Fraser River as far as Point Grey.
The Fraser Gold Rush of 1858 brought over 25,000 men from California, to nearby New Westminster on the Fraser River, on their way to the Fraser Canyon, bypassing what would become Vancouver. Vancouver is among British Columbia's youngest cities. A sawmill established at Moodyville in 1863, began the city's long relationship with logging, it was followed by mills owned by Captain Edward Stamp on the south shore of the inlet. Stamp, who had begun logging in the Port Alberni area, first attempted to run a mill at Brockton Point, but difficult currents and reefs forced the relocation of the operation in 1867 to a point near the foot of Dunlevy Street; this mill, known as the Hastings Mill, became the nucleus. The mill's central role in the city waned after the arrival of the Canadian Pacific Railway in the 1880s, it remained important to the local economy until it closed in the 1920s. The settlement which came to be called Gastown grew around
Forest ecology
Forest ecology is the scientific study of the interrelated patterns, flora and ecosystems in forests. The management of forests is known as forestry and forest management. A forest ecosystem is a natural woodland unit consisting of all plants and micro-organisms in that area functioning together with all of the non-living physical factors of the environment; the forest ecosystem is important. Forest ecology is one branch of a biotically-oriented classification of types of ecological study. Thus, forests are studied at a number of organizational levels, from the individual organism to the ecosystem. However, as the term forest connotes an area inhabited by more than one organism, forest ecology most concentrates on the level of the population, community or ecosystem. Logically, trees are an important component of forest research, but the wide variety of other life forms and abiotic components in most forests means that other elements, such as wildlife or soil nutrients, are the focal point. Thus, forest ecology is a diverse and important branch of ecological study.
Forest ecology studies share characteristics and methodological approaches with other areas of terrestrial plant ecology. However, the presence of trees makes their study unique in numerous ways. Since trees can grow larger than other plant life-forms, there is the potential for a wide variety of forest structures; the infinite number of possible spatial arrangements of trees of varying size and species makes for a intricate and diverse micro-environment in which environmental variables such as solar radiation, relative humidity, wind speed can vary over large and small distances. In addition, an important proportion of a forest ecosystem's biomass is underground, where soil structure, water quality and quantity, levels of various soil nutrients can vary greatly. Thus, forests are highly heterogeneous environments compared to other terrestrial plant communities; this heterogeneity in turn can enable great biodiversity of species of both animals. Some structures, such as tree ferns may be keystone species for a diverse range of other species.
A number of factors within the forest affect biodiversity. For example, the wild turkey thrives when uneven heights and canopy variations exist and its numbers are diminished by aged timber management. Forest management techniques that mimic natural disturbance events can allow community diversity to recover for a variety of groups including beetles. In 2017, the biologist Dr. Roberto Cazzolla Gatti and his colleagues tested a global correlation between vascular plant species richness and average forest canopy height, they found a significant correlation between H and S both at global and macro-climate scales, with the strongest confidence in the tropics. The authors of this study suggested that the higher the forest canopy, the bigger the number of species a forest can host. Forests accumulate large amounts of standing biomass, many are capable of accumulating it at high rates, i.e. they are productive. Such high levels of biomass and tall vertical structures represent large stores of potential energy that can be converted to kinetic energy under the right circumstances.
Two such conversions of great importance are fires and treefalls, both of which radically alter the biota and the physical environment where they occur. In forests of high productivity, the rapid growth of the trees themselves induces biotic and environmental changes, although at a slower rate and lower intensity than instantaneous disturbances such as fires. Woody material referred to as coarse woody debris, decays slowly in many forests in comparison to most other organic materials, due to a combination of environmental factors and wood chemistry. Trees growing in arid and/or cold environments do so slowly. Thus, tree trunks and branches can remain on the forest floor for long periods, affecting such things as wildlife habitat, fire behavior, tree regeneration processes. Lastly, forest trees store large amounts of water because of their large size and anatomical/physiological characteristics, they are therefore important regulators of hydrological processes those involving groundwater hydrology and local evaporation and rainfall/snowfall patterns.
Thus, forest ecological studies are sometimes aligned with meteorological and hydrological studies in regional ecosystem or resource planning studies. More the duff or leaf litter can form a major repository of water storage; when this litter is removed or compacted and flooding are exacerbated as well as deprivation of dry season water for forest organisms. The ecological potential of a particular species is a measure of its capacity to compete in a given geographical area, ahead of other species, as they all try to occupy a natural space. For some areas it has been quantified, as for instance by Hans-Jürgen Otto, for central Europe, he takes three groups of parameters: Related to site requirements: Tolerance to low temperatures, tolerance to dry climate, frugality. Specific qualities: Shade tolerance, height growth, longevity, regeneration capacity. Specific risks: Resistance to late freezing, resistance to wind/ice storm, resistance to fire, resist
The New York Times
The New York Times is an American newspaper based in New York City with worldwide influence and readership. Founded in 1851, the paper has won more than any other newspaper; the Times is ranked 17th in the world by circulation and 2nd in the U. S; the paper is owned by The New York Times Company, publicly traded and is controlled by the Sulzberger family through a dual-class share structure. It has been owned by the family since 1896. G. Sulzberger, the paper's publisher, his father, Arthur Ochs Sulzberger Jr. the company's chairman, are the fourth and fifth generation of the family to helm the paper. Nicknamed "The Gray Lady", the Times has long been regarded within the industry as a national "newspaper of record"; the paper's motto, "All the News That's Fit to Print", appears in the upper left-hand corner of the front page. Since the mid-1970s, The New York Times has expanded its layout and organization, adding special weekly sections on various topics supplementing the regular news, editorials and features.
Since 2008, the Times has been organized into the following sections: News, Editorials/Opinions-Columns/Op-Ed, New York, Sports of The Times, Science, Home and other features. On Sunday, the Times is supplemented by the Sunday Review, The New York Times Book Review, The New York Times Magazine and T: The New York Times Style Magazine; the Times stayed with the broadsheet full-page set-up and an eight-column format for several years after most papers switched to six, was one of the last newspapers to adopt color photography on the front page. The New York Times was founded as the New-York Daily Times on September 18, 1851. Founded by journalist and politician Henry Jarvis Raymond and former banker George Jones, the Times was published by Raymond, Jones & Company. Early investors in the company included Edwin B. Morgan, Christopher Morgan, Edward B. Wesley. Sold for a penny, the inaugural edition attempted to address various speculations on its purpose and positions that preceded its release: We shall be Conservative, in all cases where we think Conservatism essential to the public good.
We do not believe that everything in Society is either right or wrong. In 1852, the newspaper started a western division, The Times of California, which arrived whenever a mail boat from New York docked in California. However, the effort failed. On September 14, 1857, the newspaper shortened its name to The New-York Times. On April 21, 1861, The New York Times began publishing a Sunday edition to offer daily coverage of the Civil War. One of the earliest public controversies it was involved with was the Mortara Affair, the subject of twenty editorials in the Times alone; the main office of The New York Times was attacked during the New York City Draft Riots. The riots, sparked by the beginning of drafting for the Union Army, began on July 13, 1863. On "Newspaper Row", across from City Hall, Henry Raymond stopped the rioters with Gatling guns, early machine guns, one of which he manned himself; the mob diverted, instead attacking the headquarters of abolitionist publisher Horace Greeley's New York Tribune until being forced to flee by the Brooklyn City Police, who had crossed the East River to help the Manhattan authorities.
In 1869, Henry Raymond died, George Jones took over as publisher. The newspaper's influence grew in 1870 and 1871, when it published a series of exposés on William Tweed, leader of the city's Democratic Party—popularly known as "Tammany Hall" —that led to the end of the Tweed Ring's domination of New York's City Hall. Tweed had offered The New York Times five million dollars to not publish the story. In the 1880s, The New York Times transitioned from supporting Republican Party candidates in its editorials to becoming more politically independent and analytical. In 1884, the paper supported Democrat Grover Cleveland in his first presidential campaign. While this move cost The New York Times a portion of its readership among its more progressive and Republican readers, the paper regained most of its lost ground within a few years. After George Jones died in 1891, Charles Ransom Miller and other New York Times editors raised $1 million dollars to buy the Times, printing it under the New York Times Publishing Company.
However, the newspaper was financially crippled by the Panic of 1893, by 1896, the newspaper had a circulation of less than 9,000, was losing $1,000 a day. That year, Adolph Ochs, the publisher of the Chattanooga Times, gained a controlling interest in the company for $75,000. Shortly after assuming control of the paper, Ochs coined the paper's slogan, "All The News That's Fit To Print"; the slogan has appeared in the paper since September 1896, has been printed in a box in the upper left hand corner of the front page since early 1897. The slogan was a jab at competing papers, such as Joseph Pulitzer's New York World and William Randolph Hearst's New York Journal, which were known for a lurid and inaccurate reporting of facts and opinions, described by the end of the century as "yellow journalism". Under Ochs' guidance, aided by Carr
Soil conservation
Soil conservation is the prevention of soil loss from erosion or prevention of reduced fertility caused by over usage, salinization or other chemical soil contamination. Slash-and-burn and other unsustainable methods of subsistence farming are practiced in some lesser developed areas. A sequel to the deforestation is large scale erosion, loss of soil nutrients and sometimes total desertification. Techniques for improved soil conservation include crop rotation, cover crops, conservation tillage and planted windbreaks, affect both erosion and fertility; when plants trees, die they decay and become part of the soil. Code 330 defines standard methods recommended by the U. S. Natural Resources Conservation Service. Farmers have practiced soil conservation for millennia. In Europe, policies such as the Common Agricultural Policy are targeting the application of best management practices such as reduced tillage, winter cover crops, plant residues and grass margins in order to better address the soil conservation.
Political and economic action is further required to solve the erosion problem. A simple governance hurdle concerns how we name and value the land and what we call it and this can be changed by cultural adaptation. Contour ploughing orients furrows following the contour lines of the farmed area. Furrows move right to maintain a constant altitude, which reduces runoff. Contour ploughing was practiced by the ancient Phoenicians, is effective for slopes between two and ten percent. Contour ploughing can increase crop yields from 10 to 50 percent as a result of greater soil retention. Terracing is the practice of creating nearly level areas in a hillside area; the terraces form a series of each at a higher level than the previous. Terraces are protected from erosion by other soil barriers. Terraced farming is more common on small farms and in underdeveloped countries, since mechanized equipment is difficult to deploy in this setting. Keyline design is an enhancement of contour farming, where the total watershed properties are taken into account in forming the contour lines.
Tree and ground-cover are effective perimeter treatment for soil erosion prevention, by impeding surface flows. A special form of this perimeter or inter-row treatment is the use of a “grass way” that both channels and dissipates runoff through surface friction, impeding surface runoff and encouraging infiltration of the slowed surface water. Windbreaks are sufficiently dense rows of trees at the windward exposure of an agricultural field subject to wind erosion. Evergreen species provide year-round protection. Cover crops such as legumes plant, white turnip and other species are rotated with cash crops to blanket the soil year-round and act as green manure that replenishes nitrogen and other critical nutrients. Cover crops help suppress weeds. Soil-conservation farming involves no-till farming, “green manures” and other soil-enhancing practices; such farming methods attempt to mimic the biology of barren lands. They can revive damaged soil, minimize erosion, encourage plant growth, eliminate the use of nitrogen fertilizer or fungicide, produce above-average yields and protect crops during droughts or flooding.
The result is lower costs that increase farmers' profits. No-till farming and cover crops act as sinks for nitrogen and other nutrients; this increases the amount of soil organic matter. Repeated plowing/tilling degrades soil, killing its beneficial earthworms. Once damaged, soil may take multiple seasons to recover in optimal circumstances. Critics argue that no-till and related methods are impractical and too expensive for many growers because it requires new equipment, they cite advantages for conventional tilling depending on the geography and soil conditions. Some farmers claimed that no-till complicates weed control, delays planting and that post-harvest residues for corn, are hard to manage. Salinity in soil is caused by irrigating with salty water. Water evaporates from the soil leaving the salt behind. Salt breaks down causing infertility and reduced growth; the ions responsible for salination are: sodium, calcium and chlorine. Salinity is estimated to affect about one third of the earth’s arable land.
Soil salinity adversely affects crop metabolism and erosion follows. Salinity occurs in areas with shallow saline water tables. Over-irrigation deposits salts in upper soil layers as a byproduct of soil infiltration; the best-known case of shallow saline water table capillary action occurred in Egypt after the 1970 construction of the Aswan Dam. The change in the groundwater level led to high salt concentrations in the water table; the continuous high level of the water table led to soil salination. Use of humic acids may prevent excess salination given excessive irrigation. Humic acids can eliminate them from root zones. Planting species that can tolerate saline conditions can be used to lower water tables and thus reduce the rate of capillary and evaporative enrichment of surface salts. Salt-tolerant plants include saltbush, a plant found in much of North America and in the Mediterranean regions of Europe; when worms excrete egesta in the form of casts, a balanced selection of minerals and plant nutrients is made into a form accessible for root uptake.
Earthworm casts are five times richer in available nitrogen, seven times richer in available phosphates and eleven times richer in available potash than the surroundi
Slash-and-burn
Slash-and-burn agriculture called fire-fallow cultivation, is a farming method that involves the cutting and burning of plants in a forest or woodland to create a field called a swidden. The method begins by cutting down the trees and woody plants in an area; the downed vegetation, or "slash", is left to dry right before the rainiest part of the year. The biomass is burned, resulting in a nutrient-rich layer of ash which makes the soil fertile, as well as temporarily eliminating weed and pest species. After about three to five years, the plot's productivity decreases due to depletion of nutrients along with weed and pest invasion, causing the farmers to abandon the field and move over to a new area; the time it takes for a swidden to recover depends on the location and can be as little as five years to more than twenty years, after which the plot can be slashed and burned again, repeating the cycle. In India, the practice is known as jhoom. Slash-and-burn can be part of shifting cultivation, an agricultural system in which farmers move from one cultivable area to another.
It may be part of transhumance, the moving of livestock between seasons. A rough estimate is. In 2004, it was estimated that in Brazil alone, 500,000 small farmers each cleared an average of one hectare of forest per year; the technique is not sustainable for large human populations. Methods such as Inga alley cropping and slash-and-char have been proposed as alternatives which would cause less environmental degradation. A similar term is assarting, the clearing of forests for the purpose of agriculture. Assarting does not include burning. Slash-and-burn cultivation has been practiced throughout much of the world, in grasslands as well as woodlands. During the Neolithic Revolution, which included agricultural advancements, groups of hunter-gatherers domesticated various plants and animals, permitting them to settle down and practice agriculture, which provides more nutrition per hectare than hunting and gathering; this happened in the river valleys of Mesopotamia. Due to this decrease in food from hunting, as human populations increased, agriculture became more important.
Some groups could plant their crops in open fields along river valleys, but others had forests blocking their farming land. In this context, humans used slash-and-burn agriculture to clear more land to make it suitable for plants and animals. Thus, since Neolithic times, slash-and-burn techniques have been used for converting forests into crop fields and pasture. Fire was used before the Neolithic as well, by hunter-gatherers up to present times. Clearings created by the fire were made for many reasons, such as to draw game animals and to promote certain kinds of edible plants such as berries. Slash-and-burn fields are used and owned by a family until the soil is exhausted. At this point the ownership rights are abandoned, the family clears a new field, trees and shrubs are permitted to grow on the former field. After a few decades, another family or clan may use the land and claim usufructuary rights. In such a system there is no market in farmland, so land is not bought or sold on the open market and land rights are traditional.
In slash-and-burn agriculture, forests are cut months before a dry season. The "slash" is permitted to dry and burned in the following dry season; the resulting ash fertilizes the soil and the burned field is planted at the beginning of the next rainy season with crops such as upland rice, cassava, or other staples. Most of this work is done by hand, using such basic tools such as machetes, axes and makeshift shovels; the old American civilizations, like the Inca and Aztecs used this old agricultural technique. Large families or clans wandering in the lush woodlands long continued to be the most common form of society through human prehistory. Axes to fell trees and sickles for harvesting grain were the only tools people might bring with them. All other tools were made from materials they found at the site, such as fire stakes of birch, long rods, harrows made of spruce tops; the extended family conquered the lush virgin forest and cultivated their selected swidden plots, sowed one or more crops, proceeded on to forests, noted in their wanderings.
In the temperate zone, the forest regenerated in the course of a lifetime. So swidden was repeated several times in the same area over the years, but in the tropics the forest floor depleted. It was not only in the moors, as in Northern Europe, but in the steppe, prairie and barren desert in tropical areas where shifting cultivation is the oldest type of farming. Cultivation is similar to slash-and-burn.. Southern European Mediterranean climates have favored evergreen and deciduous forests. With slash-and-burn agriculture, this type of forest was less able to regenerate than those north of the Alps. Although in northern Europe one crop was harvested before grass was allowed to grow, in southern Europe it was more common to exhaust the soil by farming it for several years. Classical authors mentioned large forests, with Homer writing about "wooded Samothrace," Zakynthos and other woodlands; these authors indicated. Although parts of Europe aside from the north remained wooded, by the Roman Iron and early Viking Ages, forests were drastically reduced and settlements moved.
The reasons for this pattern of mobility, the transition to stable
