Search This Blog

Tuesday, August 13, 2024

British Agricultural Revolution

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/British_Agricultural_Revolution

The British Agricultural Revolution, or Second Agricultural Revolution, was an unprecedented increase in agricultural production in Britain arising from increases in labor and land productivity between the mid-17th and late 19th centuries. Agricultural output grew faster than the population over the hundred-year period ending in 1770, and thereafter productivity remained among the highest in the world. This increase in the food supply contributed to the rapid growth of population in England and Wales, from 5.5 million in 1700 to over 9 million by 1801, though domestic production gave way increasingly to food imports in the 19th century as the population more than tripled to over 35 million.

Using 1700 as a base year (=100), agricultural output per agricultural worker in Britain steadily increased from about 50 in 1500, to around 65 in 1550, to 90 in 1600, to over 100 by 1650, to over 150 by 1750, rapidly increasing to over 250 by 1850. The rise in productivity accelerated the decline of the agricultural share of the labour force, adding to the urban workforce on which industrialization depended: the Agricultural Revolution has therefore been cited as a cause of the Industrial Revolution.

However, historians continue to dispute when exactly such a "revolution" took place and of what it consisted. Rather than a single event, G. E. Mingay states that there were a "profusion of agricultural revolutions, one for two centuries before 1650, another emphasising the century after 1650, a third for the period 1750–1780, and a fourth for the middle decades of the nineteenth century". This has led more recent historians to argue that any general statements about "the Agricultural Revolution" are difficult to sustain.

One important change in farming methods was the move in crop rotation to turnips and clover in place of fallow under the Norfolk four-course system. Turnips can be grown in winter and are deep-rooted, allowing them to gather minerals unavailable to shallow-rooted crops. Clover fixes nitrogen from the atmosphere into a form of fertiliser. This permitted the intensive arable cultivation of light soils on enclosed farms and provided fodder to support increased livestock numbers whose manure added further to soil fertility.

Term

Called “British”, the term implies that the revolution began in Britain, not that it existed solely in Britain. Other countries in Europe (including France, Prussia (Germany), and Russia), East Asia and North America followed suit in the next two centuries. The Second Agricultural Revolution was much like the Neolithic Revolution in that it occurred in many regions across the world in a short span of time.

The British origins of the revolution is the view shared by the British historians. The Dutch historians disagree. In the Netherlands between 1500 and 1650, the agricultural output per laborer rose by 80% leading to over 60% decline in manpower engaged in agriculture by 1650. From 1500 to 1750, the Dutch were faster than Britain in reducing the agricultural sector of population. The Netherlands were called "school room," or "home" of the modern agricultural revolution. Notably, one of the innovations in the British Revolution was the “Dutch” light plow. English landowners and their agents who returned from exile in the Netherlands in the 17th century introduced Dutch methods and techniques.

The term "revolution" refers to increase in yields per land and labour. Innovations in agricultural technology and methods took place gradually rather than an abrupt sweeping alteration.

Major developments and innovations

The British Agricultural Revolution was the result of the complex interaction of social, economic and farming technological changes. Major developments and innovations include:

Crop rotation

Crop Yield net of Seed
(bushels/acre)
Year Wheat Rye Barley Oats Peas
beans
Growth rate
(%/year)$
1250–1299 8.71 10.71 10.25 7.24 6.03 −0.27
1300–1349 8.24 10.36 9.46 6.60 6.14 −0.032
1350–1399 7.46 9.21 9.74 7.49 5.86 0.61
1400–1449 5.89 10.46 8.44 6.55 5.42 0.08
1450–1499 6.48 13.96 8.56 5.95 4.49 0.48
1550–1599 7.88 9.21 8.40 7.87 7.62 −0.16
1600–1649 10.45 16.28 11.16 10.97 8.62 −0.11
1650–1699 11.36 14.19 12.48 10.82 8.39 0.64
1700–1749 13.79 14.82 15.08 12.27 10.23 0.70
1750–1799 17.26 17.87 21.88 20.90 14.19 0.37
1800–1849 23.16 19.52 25.90 28.37 17.85 0.63
1850–1899 26.69 26.18 23.82 31.36 16.30
Notes:

Yields have had the seed used to plant the crop subtracted to give net yields.
Average seed sown is estimated at:

  • Wheat 2.5 bu/acre;
  • Rye 2.5 bu/acre;
  • Barley 3.5–4.30 bu/acre;
  • Oats 2.5–4.0 bu/acre;
  • Peas & beans 2.50–3.0 bu/acre.

$ Average annual growth rate of agricultural output is per agricultural worker.
Other authors offer different estimates. (1 bushel/acre = 0.06725 tonnes/hectare)

One of the most important innovations of the British Agricultural Revolution was the development of the Norfolk four-course rotation, which greatly increased crop and livestock yields by improving soil fertility and reducing fallow.

Crop rotation is the practice of growing a series of dissimilar types of crops in the same area in sequential seasons to help restore plant nutrients and mitigate the build-up of pathogens and pests that often occurs when one plant species is continuously cropped. Rotation can also improve soil structure and fertility by alternating deep-rooted and shallow-rooted plants. Turnip roots, for example, can recover nutrients from deep under the soil. The Norfolk four-course system, as it is now known, rotates crops so that different crops are planted with the result that different kinds and quantities of nutrients are taken from the soil as the plants grow. An important feature of the Norfolk four-field system was that it used labour at times when demand was not at peak levels.

Planting cover crops such as turnips and clover was not permitted under the common field system because they interfered with access to the fields. Besides, other people's livestock could graze the turnips. During the Middle Ages, the open-field system had initially used a two-field crop rotation system where one field was left fallow or turned into pasture for a time to try to recover some of its plant nutrients. Later they employed a three-year, three field crop rotation routine, with a different crop in each of two fields, e.g. oats, rye, wheat, and barley with the second field growing a legume like peas or beans, and the third field fallow. Normally from 10% to 30% of the arable land in a three crop rotation system is fallow. Each field was rotated into a different crop nearly every year. Over the following two centuries, the regular planting of legumes in the fields that were previously fallow slowly restored the fertility of some croplands. The planting of legumes helped to increase plant growth in the empty field because of the ability of the bacteria on legume roots to fix nitrogen from the air into the soil in a form that plants could use. Other crops that were occasionally grown were flax and members of the mustard family.

Convertible husbandry was the alternation of a field between pasture and grain. Because nitrogen builds up slowly over time in pasture, ploughing up pasture and planting grains resulted in high yields for a few years. A big disadvantage of convertible husbandry was the hard work in breaking up pastures and difficulty in establishing them. The significance of convertible husbandry is that it introduced pasture into the rotation.

The farmers in Flanders (in parts of France and current day Belgium) discovered a still more effective four-field crop rotation system, using turnips and clover (a legume) as forage crops to replace the three-year crop rotation fallow year. The four-field rotation system allowed farmers to restore soil fertility and restore some of the plant nutrients removed with the crops. Turnips first show up in the probate records in England as early as 1638 but were not widely used till about 1750. Fallow land was about 20% of the arable area in England in 1700 before turnips and clover were extensively grown in the 1830s. Guano and nitrates from South America were introduced in the mid-19th century, and fallow steadily declined to reach only about 4% in 1900. Ideally, wheat, barley, turnips and clover would be planted in that order in each field in successive years. The turnips helped keep the weeds down and were an excellent forage crop—ruminant animals could eat the tops and roots through a large part of the summer and winters. There was no need to let the soil lie fallow as clover would add nitrates (nitrogen-containing salts) back to the soil. The clover made excellent pasture and hay fields as well as green manure when it was ploughed under after one or two years. The addition of clover and turnips allowed more animals to be kept through the winter, which in turn produced more milk, cheese, meat and manure, which maintained soil fertility.

The mix of crops also changed: the area under wheat rose by 1870 to 3.5 million acres (1.4m ha), barley to 2.25m acres (0.9m ha) and oats less dramatically to 2.75m acres (1.1m ha), while rye dwindled to 60,000 acres (24,000 hectares), less than a tenth of its late medieval peak. Grain yields benefited from new and better seed alongside improved rotation and fertility: wheat yields increased by a quarter in the 18th century and nearly half in the 19th, averaging 30 bushels per acre (2,080 kg/ha) by the 1890s.

Dutch and Rotherham swing (wheel-less) plough

The Dutch acquired the iron-tipped, curved mouldboard, adjustable depth plough which was invented in Chinese Han dynasty from the Chinese in the early 17th century. It had the advantage of being able to be pulled by one or two oxen compared to the six or eight needed by the heavy wheeled northern European plough. The Dutch plough was brought to Britain by Dutch contractors who were hired to drain East Anglian fens and Somerset moors. The plough was extremely successful on wet, boggy soil, but was soon used on ordinary land as well.

British improvements included Joseph Foljambe's cast iron plough (patented 1730), which combined an earlier Dutch design with several innovations. Its fittings and coulter were made of iron, and the mouldboard and share were covered with an iron plate, making it easier to pull and more controllable than previous ploughs. By the 1760s Foljambe was making large numbers of these ploughs in a factory outside of Rotherham, using standard patterns with interchangeable parts. The plough was easy for a blacksmith to make, but by the end of the 18th century it was being made in rural foundries. By 1770 it was the cheapest and best plough available. It spread to Scotland, America, and France.

New crops

The Columbian exchange brought many new foodstuffs from the Americas to Eurasia, most of which took decades or centuries to catch on. Arguably the most important of these was the potato. Potatoes yielded about three times the calories per acre of wheat or barley, mainly because it took only taking 3–4 months to mature versus 10 months for wheat. On top of this, potatoes had higher nutritive value than wheat, could be grown in even fallow and nutrient-poor soil, did not require any special tools, and were considered fairly appetizing. According to Langer, a single acre of potatoes could feed a family of five or six, plus a cow, for the better part of a year, an unprecedented level of production. By 1715 the potato was widespread in the Low Countries, the Rhineland, southwestern Germany, and eastern France, but took longer to spread elsewhere.

The Royal Society of London for Improving Natural Knowledge, established in 1660, almost immediately championed the potato, stressing its value as a substitute for wheat (particularly since famine periods for wheat overlapped with bump periods for potatoes). The 1740 famines buttressed their case. The mid 18th century was marked by rapid adoption of the potato by various European countries, especially in central Europe, as various wheat famines demonstrated its value. The potato was grown in Ireland, a property of the English crown and common source of food exports, since the early 17th century and quickly spread so that by the 18th century it had been firmly established as a staple food. It spread to England shortly after it took hold in Ireland, first being widely cultivated in Lancashire and around London, and by the mid-18th century it was esteemed and common. By the late 18th century, Sir Frederick Eden wrote that the potato had become "a constant standing dish, at every meal, breakfast excepted, at the tables of the Rich, as well as the Poor."

While not as vital as the potato, maize also contributed to the boost of Western European agricultural productivity. Maize also had far higher per-acre productivity than wheat (about two and a half times), grew at widely differing altitudes and in a variety of soils (though warmer climates were preferred), and unlike wheat it could be harvested in successive years from the same plot of land. It was often grown alongside potatoes, as maize plants required wide spacing. Maize was cultivated in Spain since 1525 and Italy since 1530, contributing to their growing populations in the early modern era as it became a dietary staple in the 17th century (in Italy it was often made into polenta). It spread from northern Italy into Germany and beyond, becoming an important staple in the Habsburg monarchy (especially Hungary and Austria) by the late 17th century. Its spread started in southern France in 1565, and by the start of the 18th century it was the main food source of central and southern French peasants (it was more popular as animal fodder in the north).

Enclosure

Conjectural map of a mediaeval English manor. The part allocated to "common pasture" is shown in the north-east section, shaded green.

In Europe, agriculture was feudal from the Middle Ages. In the feudal open-field system, peasant farmers were assigned individual narrow strips of land in large fields which were used for growing crops. For the right to work this land they would pay a percentage of the yield to the aristocracy or the Catholic Church, who owned the land. A separate section of land in the same area would be "held in common" as grazing pasture. Periodically the grazing land would be rotated with the crop land to allow the land to recover.

As early as the 12th century, some fields in England tilled under the open-field system were enclosed into individually owned fields. The Black Death from 1348 onward accelerated the break-up of the feudal system in England. Many farms were bought by yeomen who enclosed their property and improved their use of the land. More secure control of the land allowed the owners to make innovations that improved their yields. Other husbandmen rented property they "share cropped" with the land owners. Many of these enclosures were accomplished by acts of Parliament in the 16th and 17th centuries.

The process of enclosing property accelerated in the 15th and 16th centuries. The more productive enclosed farms meant that fewer farmers were needed to work the same land, leaving many villagers without land and grazing rights. Many of them moved to the cities in search of work in the emerging factories of the Industrial Revolution. Others settled in the English colonies. English Poor Laws were enacted to help these newly poor.

Some practices of enclosure were denounced by the Church, and legislation was drawn up against it; but the large, enclosed fields were needed for the gains in agricultural productivity from the 16th to 18th centuries. This controversy led to a series of government acts, culminating in the General Enclosure Act of 1801 which sanctioned large-scale land reform. The process of enclosure was largely complete by the end of the 18th century.

Development of a national market

Regional markets were widespread by 1500 with about 800 locations in Britain. The most important development between the 16th century and the mid-19th century was private marketing. By the 19th century, marketing was nationwide, and the vast majority of agricultural production was for market rather than for the farmer and his family. The 16th-century market radius was about 10 miles, which could support a town of 10,000.

The next stage of development was trading between markets, requiring merchants, credit and forward sales, knowledge of markets and pricing and of supply and demand in different markets. Eventually, the market evolved into a national one driven by London and other growing cities. By 1700, there was a national market for wheat.

Legislation regulating middlemen required registration, addressed weights and measures, fixing of prices and collection of tolls by the government. Market regulations were eased in 1663 when people were allowed some self-regulation to hold inventory, but it was forbidden to withhold commodities from the market in an effort to increase prices. In the late 18th century, the idea of self-regulation was gaining acceptance. The lack of internal tariffs, customs barriers and feudal tolls made Britain "the largest coherent market in Europe".

Transportation infrastructures

High wagon transportation costs made it uneconomical to ship commodities very far outside the market radius by road, generally limiting shipment to less than 20 or 30 miles to market or to a navigable waterway. Water transport was, and in some cases still is, much more efficient than land transport. In the early 19th century it cost as much to transport a ton of freight 32 miles by wagon over an unimproved road as it did to ship it 3,000 miles across the Atlantic. A horse could pull at most one ton of freight on a macadam road, which was multi-layer stone covered and crowned, with side drainage. But a single horse could pull a barge weighing over 30 tons.

Commerce was aided by the expansion of roads and inland waterways. Road transport capacity grew from threefold to fourfold from 1500 to 1700. Railroads would eventually reduce the cost of land transport by over 95%.

Land conversion, drainage and reclamation

Another way to get more land was to convert some pasture land into arable land and recover fen land and some pastures. It is estimated that the amount of arable land in Britain grew by 10–30% through these land conversions.

The British Agricultural Revolution was aided by land maintenance advancements in Flanders and the Netherlands. With large and dense populations in Flanders and Holland, farmers there were forced to take maximum advantage of every bit of usable land; the country had become a pioneer in canal building, soil restoration and maintenance, soil drainage, and land reclamation technology. Dutch experts like Cornelius Vermuyden brought some of this technology to Britain.

Water-meadows were utilised in the late 16th to the 20th centuries and allowed earlier pasturing of livestock after they were wintered on hay. This increased livestock yields, giving more hides, meat, milk, and manure as well as better hay crops.

Rise in domestic farmers

With the development of regional markets and eventually a national market, aided by improved transportation infrastructures, farmers were no longer dependent on their local market and were less subject to having to sell at low prices into an oversupplied local market and not being able to sell their surpluses to distant localities that were experiencing shortages. They also became less subject to price fixing regulations. Farming became a business rather than solely a means of subsistence.

Selective breeding of livestock

In England, Robert Bakewell and Thomas Coke introduced selective breeding as a scientific practice, mating together two animals with particularly desirable characteristics and also using inbreeding or the mating of close relatives, such as father and daughter, or brother and sister, to stabilise certain qualities in order to reduce genetic diversity in desirable animal programmes from the mid-18th century. Arguably, Bakewell's most important breeding programme was with sheep. Using native stock, he was able to quickly select for large, yet fine-boned sheep, with long, lustrous wool. The Lincoln Longwool was improved by Bakewell, and in turn the Lincoln was used to develop the subsequent breed, named the Dishley Leicester. It was hornless and had a square, meaty body with straight top lines.

Bakewell was also the first to breed cattle to be used primarily for beef. Previously, cattle were first and foremost kept for pulling ploughs as oxen or for dairy uses, with beef from surplus males as an additional bonus, but he crossed long-horned heifers and a Westmoreland bull to eventually create the Dishley Longhorn. As more farmers followed his lead, farm animals increased dramatically in size and quality. The average weight of a bull sold for slaughter at Smithfield was reported around 1700 as 370 pounds (170 kg), though this is considered a low estimate: by 1786, weights of 840 pounds (380 kg) were reported, though other contemporary indicators suggest an increase of around a quarter over the intervening century. In 1300, the average milk cow produced 100 gallons of milk annually. By 1800, this figure rose to 566 gallons.

19th century

Besides the organic fertilisers in manure, new fertilisers were slowly discovered. Massive sodium nitrate (NaNO3) deposits found in the Atacama Desert, Chile, were brought under British financiers like John Thomas North and imports were started. Chile was happy to allow the exports of these sodium nitrates by allowing the British to use their capital to develop the mining and imposing a hefty export tax to enrich their treasury. Massive deposits of sea bird guano (11–16% nitrogen, 8–12% phosphate, and 2–3% potassium), were found and started to be imported after about 1830. Significant imports of potash obtained from the ashes of trees burned in opening new agricultural lands were imported.

By-products of the British meat industry like bones from the knackers' yards were ground up or crushed and sold as fertiliser. By about 1840 about 30,000 tons of bones were being processed (worth about £150,000). An unusual alternative to bones was found to be the millions of tons of fossils called coprolites found in South East England. When these were dissolved in sulphuric acid they yielded a high phosphate mixture (called "super phosphate") that plants could absorb readily and increased crop yields. Mining coprolite and processing it for fertiliser soon developed into a major industry—the first commercial fertiliser.

Higher yield per acre crops were planted as potatoes went from about 300,000 acres in 1800 to about 400,000 acres in 1850 with a further increase to about 500,000 in 1900. Labour productivity slowly increased at about 0.6% per year. With more capital invested, more organic and inorganic fertilisers, and better crop yields increased the food grown at about 0.5% per year—not enough to keep up with population growth.

Great Britain contained about 10.8 million people in 1801, 20.7 million in 1851 and 37.1 million by 1901. This corresponds to an annual population growth rate of 1.3% in 1801-1851 and 1.2% in 1851–1901, twice the rate of agricultural output growth. In addition to land for cultivation there was also a demand for pasture land to support more livestock. The growth of arable acreage slowed from the 1830s and went into reverse from the 1870s in the face of cheaper grain imports, and wheat acreage nearly halved from 1870 to 1900.

The recovery of food imports after the Napoleonic Wars (1803–1815) and the resumption of American trade following the War of 1812 (1812–1815) led to the enactment in 1815 of the Corn Laws (protective tariffs) to protect cereal grain producers in Britain against foreign competition. These laws were removed in 1846 after the onset of the Great Irish Famine in which a potato blight ruined most of the Irish potato crop and brought famine to the Irish people from 1846 to 1850. Though the blight also struck Scotland, Wales, England, and much of continental Europe, its effect there was far less severe since potatoes constituted a much smaller percentage of the diet than in Ireland. Hundreds of thousands died in the famine, and millions more emigrated to England, Wales, Scotland, Canada, Australia, Europe, and the United States, reducing the population from about 8.5 million in 1845 to 4.3 million by 1921.

Between 1873 and 1879 British agriculture suffered from wet summers that damaged grain crops. Cattle farmers were hit by foot-and-mouth disease, and sheep farmers by liver rot. The poor harvests, however, masked a greater threat to British agriculture: growing imports of foodstuffs from abroad. The development of the steam ship and the development of extensive railway networks in Britain and in the United States allowed U.S. farmers with much larger and more productive farms to export hard grain to Britain at a price that undercut the British farmers. At the same time, large amounts of cheap corned beef started to arrive from Argentina, and the opening of the Suez Canal in 1869 and the development of refrigerator ships (reefers) in about 1880 opened the British market to cheap meat and wool from Australia, New Zealand, and Argentina.

The Long Depression was a worldwide economic recession that began in 1873 and ended around 1896. It hit the agricultural sector hard and was the most severe in Europe and the United States, which had been experiencing strong economic growth fuelled by the Second Industrial Revolution in the decade following the American Civil War. By 1900, half the meat eaten in Britain came from abroad, and tropical fruits such as bananas were also being imported on the refrigerator ships.

Seed planting

Before the introduction of the seed drill, the common practice was to plant seeds by broadcasting (evenly throwing) them across the ground by hand on the prepared soil and then lightly harrowing the soil to cover the seed. Seeds left on top of the ground were eaten by birds, insects, and mice. There was no control over spacing, and seeds were planted too close together and too far apart. Alternatively, seeds could be laboriously planted one by one using a hoe and/or a shovel. Cutting down on wasted seed was important because the yield of seeds harvested to seeds planted at that time was around four or five.

The seed drill was introduced from China to Italy in the mid-16th century where it was patented by the Venetian Senate. Jethro Tull invented an improved seed drill in 1701. It was a mechanical seeder which distributed seeds evenly across a plot of land and at the correct depth. Tull's seed drill was expensive and fragile and therefore did not have much of an impact. The technology to manufacture affordable and reliable machinery, including agricultural machinery, improved dramatically in the last half of the 19th century.

Significance

The Agricultural Revolution was part of a long process of improvement, but sound advice on farming began to appear in England in the mid-17th century, from writers such as Samuel Hartlib, Walter Blith and others, and the overall agricultural productivity of Britain started to grow significantly only in the 18th century. It is estimated that total agricultural output grew 2.7-fold between 1700 and 1870 and output per worker at a similar rate. Despite its name, the Agricultural Revolution in Britain did not result in overall productivity per hectare of agricultural area as high as in China, where intensive cultivation (including multiple annual cropping in many areas) had been practiced for many centuries.

The Agricultural Revolution in Britain proved to be a major turning point in history, allowing the population to far exceed earlier peaks and sustain the country's rise to industrial pre-eminence. Towards the end of the 19th century, the substantial gains in British agricultural productivity were rapidly offset by competition from cheaper imports, made possible by the exploitation of new lands and advances in transportation, refrigeration, and other technologies.

The Agricultural Revolution in other countries was a turning point too. In the agrarian societies, four families produced enough food for five families, that is for themselves and one more family. Not much manpower was available for non-agricultural activity. In the course of the revolution, one family began to produce enough food for five families. Much manpower was liberated from agriculture and became available for industry. Thus the Agricultural Revolution made possible the Industrial Revolution:

Industrialization and modern economic growth are basically conditioned by the level of agricultural productivity inherited from pre-modern period... [A]n agricultural revolution and subsequent rise in agricultural productivity are often considered prerequisites for take-off of the initial spurt of industrialization.

Unprecedented population growth followed and even more explosive was the growth of the non-agricultural sector. Barrington Moore stressed the "importance of getting rid of agriculture as a major social activity" in the formation of the working class. First, "rural proletariat" appeared; later, this mass moved to cities causing unprecedented urbanization. When the percentage of manpower engaged in agriculture declined from 80 to 60, occurred great social revolutions or reformations (revolution from above). The result was not liberte, egalite, fraternite; often the result was the opposite, with stronger autocracy. But in all cases, the power shifted from land owners to industrial entrepreneurs or central-planning states, marking "revolutionary break with the past." The ten-millennia Agrarian Age was succeeded by the Industrial Age.

Today, agriculture accounts for 5% of the world product. But these 5% is the basis holding the rest 95% like a reverse pyramid. The Second Agricultural Revolution created this basis and made possible our industry and other sectors of the modern civilization. Without this basis all this civilization, with all its technological progress, would collapse. "No modern development made us independent from Earth Mother, or Pachamama that feeds, as the Inca put it."

Swing Riots

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Swing_Riots
Horse-powered threshing machine

The Swing Riots were a widespread uprising in 1830 by agricultural workers in southern and eastern England in protest of agricultural mechanisation and harsh working conditions. The riots began with the destruction of threshing machines in the Elham Valley area of East Kent in the summer of 1830 and by early December had spread through the whole of southern England and East Anglia. It was to be the largest movement of social unrest in 19th-century England.

As well as attacking the popularly-hated threshing machines, which displaced workers, the protesters rioted over low wages and required tithes by destroying workhouses and tithe barns associated with their oppression. They also burned ricks and maimed cows.

The rioters directed their anger at the three targets identified as causing their misery: the tithe system, requiring payments to support the established Anglican Church; the Poor Law guardians, who were thought to abuse their power over the poor; and the rich tenant farmers, who had been progressively lowering workers' wages and introduced agricultural machinery. If captured, the protesters faced charges of arson, robbery, riot, machine-breaking and assault. Those convicted faced imprisonment, transportation and possibly execution.

The Swing Riots had many immediate causes. The historian J. F. C. Harrison believed that they were overwhelmingly the result of the progressive impoverishment and dispossession of the English agricultural workforce over the previous fifty years leading up to 1830. In Parliament, Lord Carnarvon had said that the English labourers were reduced to a plight more abject than that of any race in Europe, with their employers no longer able to feed and employ them. A 2020 study found that the presence of threshing machines caused greater rioting and that the severity of the riots was lowest in areas with abundant employment alternatives and the highest in areas with few alternative employment opportunities.

Name and etymology

The name "Swing Riots" was derived from Captain Swing, the name attributed to the fictitious, mythical figurehead of the movement. The name was often used to sign threatening letters sent to farmers, magistrates, parsons and others. These were first mentioned by The Times on 21 October 1830.

'Swing' was apparently a reference to the swinging stick of the flail used in hand threshing.

Background

Enclosure

Early 19th-century England was almost unique among major nations in having no class of landed smallholding peasantry. The Enclosure Acts of rural England contributed to the plight of rural farmworkers. Between 1770 and 1830, about 6 million acres (24,000 km2) of common land were enclosed. The common land had been used for centuries by the poor of the countryside to graze their animals and grow their own produce. The land was now divided up among the large local landowners, leaving the landless farmworkers solely dependent upon working for their richer neighbours for a cash wage. That may have offered a tolerable living during the boom years of the Napoleonic Era, when labour had been in short supply and corn prices high, the return of peace in 1815 resulted in plummeting grain prices and an oversupply of labour. According to the social historians John and Barbara Hammond, enclosure was fatal to three classes: the small farmer, the cottager and the squatter. Before enclosure, the cottager was a labourer with land; after enclosure, he was a labourer without land.

In contrast to the Hammonds' 1911 analysis of the events, the historian G. E. Mingay noted that when the Swing Riots broke out in 1830, the heavily-enclosed Midlands remained almost entirely quiet, but the riots were concentrated in the southern and south-eastern counties, which were little affected by enclosure. Some historians have posited that the reason was that in the West Midlands, for example, the rapid expansion of the Potteries and the coal and iron industries provided an alternative range of employment to agricultural workers.

Critically, J. D. Chambers and G. E. Mingay suggested that the Hammonds exaggerated the costs of change, but enclosure really meant more food for the growing population; more land under cultivation and, on the balance, more employment in the countryside. The modern historians of the riots, Eric Hobsbawm and George Rudé, cited only three of a total of 1,475 incidents as being directly caused by enclosure. Since the late 20th century, those contentions have been challenged by a new class of recent historians. Enclosure has been seen by some as causing the destruction of the traditional peasant way of life, however miserable:

"Enclosure dissipated the haze which surrounded rural poverty and left it nakedly visible as propertyless labour"

— Hobsbawm/Rude. Captain Swing p. 16

Landless peasants could no longer maintain an economic independence and so had to become labourers. Surplus peasant labour moved into the towns to become industrial workers.

Precarious employment

In the 1780s, workers would be employed at annual hiring fairs, or ‘mops’, to serve for the whole year. During that period, the worker would receive payment in kind and in cash from his employer, would often work at his side, and would commonly share meals at the employer's table. As time passed, the gulf between farmer and employee widened. Workers were hired on stricter cash-only contracts, which ran for increasingly shorter periods. First, monthly terms became the norm. Later, contracts were offered for as little as a week. Between 1750 and 1850, farm labourers faced the loss of their land, the transformation of their contracts and the sharp deterioration of their economic situations. By the time of the 1830 riots, they had retained very little of their former status except the right to parish relief, under the Old Poor Law system.

Additionally, there was an influx of Irish farm labourers in 1829, who had come to seek agricultural work which contributed to reduced employment opportunities for other farming communities. Irish labourers would find themselves being threatened from the beginning of the riots the following year.

Poor Laws

Historically, the monasteries had taken responsibility for the impotent poor, but after their dissolution in 1536 to 1539, responsibility passed to the parishes. the Act of Settlement in 1662 had confined relief strictly to those who were natives of the parish. The poor law system charged a Parish Rate to landowners and tenants, which was used to provide relief payments to settled residents of the parish who were ill or out of work. The payments were minimal, and at times, degrading conditions were required for their receipt. As more and more people became dependent on parish relief, ratepayers rebelled ever more loudly against the costs, and lower and lower levels of relief were offered. Three "one-gallon" bread loaves a week were considered necessary for a man in Berkshire in 1795. However provision had fallen to just two similarly-sized loaves being provided in 1817 Wiltshire. The way in which poor law funds were disbursed led to a further reduction in agricultural wages since farmers would pay their workers as little as possible in the knowledge that the parish fund would top up wages to a basic subsistence level (see Speenhamland system).

Tithe System

To that mixture was added the burden of the church tithe. This was the church's right to a tenth of the parish harvest. The tithe-owner could voluntarily reduce the financial burden on the parish either by allowing the parish to keep more of their share of the harvest. Or the tithe-owner could, again voluntarily, commute the tithe payments to a rental charge. The rioters had demanded that tithes should be reduced, but this demand was refused by many of the tithe-owners.

Industrialisation

The final straw was the introduction of horse-powered threshing machines, which could do the work of many men. They spread swiftly among the farming community and threatened the livelihoods of hundreds of thousands of farmworkers. Following the terrible harvests of 1828 and 1829, farm labourers faced the approaching winter of 1830 with dread.

Riots

A letter threatening to burn Corpus Christi College, Cambridge, sent in 1830 and signed "Swing".

Starting in the south-eastern county of Kent, the Swing Rioters smashed the threshing machines and threatened farmers who owned them. The first threshing machine to be destroyed was during Saturday night, 28 August 1830 at Lower Hardres. By the third week of October, more than 100 threshing machines had been destroyed in East Kent. The riots spread rapidly and systematically - following pre-existing road networks - through the southern counties of Surrey, Sussex, Middlesex and Hampshire before they spread north into the Home Counties, the Midlands and East Anglia. Originally, the disturbances were thought to be mainly a southern and East Anglian phenomenon, but subsequent research has revealed just how widespread Swing riots really were, with almost every county south of the Scottish border involved.

In all, sixty percent of the disturbances were concentrated in the south (Berkshire 165 incidents, Hampshire 208, Kent 154, Sussex 145, Wiltshire 208); East Anglia had fewer incidents (Cambridge 17, Norfolk 88, Suffolk 40); and the Southwest, the Midlands and the North were only marginally affected.

Tactics

The tactics varied from county to county, but typically, threatening letters, often signed by Captain Swing, would be sent to magistrates, parsons, wealthy farmers or Poor Law guardians in the area. The letters would call for a rise in wages, a cut in the tithe payments and the destruction of threshing machines, or people would take matters into their own hands. If the warnings were not heeded local farm workers would gather, often in groups of 200 to 400, and would threaten the local oligarchs with dire consequences if their demands were not met. Threshing machines would be broken, workhouses and tithe barns would be attacked and the rioters would then disperse or move on to the next village. The buildings containing the engines that powered the threshing machines were also a target of the rioters and many gin gangs, also known as horse engine houses or wheelhouses, were destroyed, particularly in south−eastern England. There are also recorded instances of carriages being held up and their occupants robbed.

Other actions included incendiary attacks on farms, barns and hayricks in the dead of night, when it was easier to avoid detection. Although many of the actions of the rioters, such as arson, were conducted in secret at night, meetings with farmers and overseers about the grievances were conducted in daylight.

Despite the prevalence of the slogan "Bread or Blood", only one person is recorded as having been killed during the riots, which was one of the rioters by the action of a soldier or farmer. The rioters' only intent was to damage property. Similar patterns of disturbances and their rapid spread across the country were often blamed on agitators or on "agents" sent from France, where the revolution of July 1830 had broken out a month before the Swing Riots had begun in Kent.

Despite all of the different tactics used by the agricultural workers during the unrest, their principal aims were simply to attain a minimum living wage and to end rural unemployment.

A 2021 study that examined how information and diffusion shaped the riots found "that information about the riots traveled through personal and trade networks but not through transport or mass media networks. This information was not about repression, and local organizers played an important role in the diffusion of the riots".

Aftermath

Trials

The landowning class in England felt severely threatened by the riots and responded with harsh punitive measures. Nearly 2,000 protesters were brought to trial in 1830–1831; 252 were sentenced to death (though only 19 were actually hanged), 644 were imprisoned and 481 were transported to penal colonies in Australia. Not all rioters were farm workers since the list of those punished included rural artisans, shoemakers, carpenters, wheelwrights, blacksmiths and cobblers. One of those hanged was reported to have been charged only because he had knocked the hat off the head of a member of the Baring banking family. Many of the protesters who were transported had their sentences remitted in 1835.

Social, economic and political reform

Charles Grey, 2nd Earl Grey

Eventually, the farmers agreed to raise wages, and the parsons and some landlords reduced the tithes and rents. However, many farmers reneged on the agreements, and the unrest increased.

Many people advocated political reform as the only solution to the unrest, one of them being the radical politician and writer William Cobbett. The authorities had received many requests to prosecute him for the speeches that he had made in defence of the rural labourer, but it was for his articles in the Political Register that he was eventually charged with seditious libel. He wrote an article, The Rural War, about the Swing Riots. He blamed those in society who lived off unearned income at the expense of hard-working agricultural labourers; his solution was parliamentary reform. During his trial in July 1831 at the Guildhall, he subpoenaed six members of the cabinet, including the prime minister. Cobbett defended himself by going on the attack. He tried to ask the government ministers awkward questions supporting his case, but they were disallowed by the Lord Chief Justice. However, he was able to discredit the prosecution's case, and at great embarrassment to the government, he was acquitted.

A major concern was that the Swing Riots could spark a larger revolt. That was reinforced by the 29 July 1830 revolution in France, which overthrew Charles X, and the independence of Belgium from the Netherlands later in 1830. The support for parliamentary reform was on party lines, with the Tories against reform and the Whigs having proposed changes well before the Swing riots. The farm labourers who were involved in the disturbances did not have a vote, but it is probable that the largely landowning classes, who could vote, were influenced by the Swing Riots to support reform.

Portrait of Lord Melbourne by John Partridge. Lord Melbourne - Home Secretary of Earl Grey's Whig government

Earl Grey, during a House of Lords debate in November 1830, suggested the best way to reduce the violence was to introduce reform of the House of Commons. The Tory Prime Minister, the Duke of Wellington, replied that the existing constitution was so perfect that he could not imagine any possible alternative that would be an improvement. When that was reported, a mob attacked Wellington's home in London. The unrest had been confined to Kent, but during the following two weeks of November, it escalated massively by crossing East and West Sussex into Hampshire, with Swing letters appearing in other nearby counties.

On 15 November 1830, Wellington's government was defeated by a vote in the House of Commons. Two days later, Earl Grey was asked to form a Whig government. Grey assigned a cabinet committee to produce a plan for parliamentary reform. Lord Melbourne became Home Secretary in the new government. He blamed local magistrates for being too lenient, and the government appointed a Special Commission of three judges to try rioters in the counties of Berkshire, Buckinghamshire, Dorset, Wiltshire and Hampshire.

Parliamentary Acts

The riots were a major influence on the Whig government. They added to the strong social, political and agricultural unrest throughout Britain in the 1830s, encouraging a wider demand for political reform, culminating in the introduction of the Great Reform Act, 1832. The act was the first of several reforms that over the course of a century transformed the British political system from one based on privilege and corruption to one based on universal suffrage and the secret ballot. In domestic elections before the Great Reform Act of 1832, only about three per cent of the English population could vote. Most constituencies had been founded in the Middle Ages and so the newly-industrial northern England had virtually no representation. Those who could vote were mainly the large landowners and wealthy commoners.

The Great Reform Act was followed by the Poor Law Amendment Act 1834, ending "outdoor relief" in cash or kind and setting up a chain of designedly unwholesome workhouses covering larger areas across the country to which the poor had to go if they wanted help.

Pesticide resistance

From Wikipedia, the free encyclopedia
https://en.wikipedia.org/wiki/Pesticide_resistance
Pesticide application can artificially select for resistant pests. In this diagram, the first generation happens to have an insect with a heightened resistance to a pesticide (red) After pesticide application, its descendants represent a larger proportion of the population, because sensitive pests (white) have been selectively killed. After repeated applications, resistant pests may comprise the majority of the population.

Pesticide resistance describes the decreased susceptibility of a pest population to a pesticide that was previously effective at controlling the pest. Pest species evolve pesticide resistance via natural selection: the most resistant specimens survive and pass on their acquired heritable changes traits to their offspring. If a pest has resistance then that will reduce the pesticide's efficacy – efficacy and resistance are inversely related.

Cases of resistance have been reported in all classes of pests (i.e. crop diseases, weeds, rodents, etc.), with 'crises' in insect control occurring early-on after the introduction of pesticide use in the 20th century. The Insecticide Resistance Action Committee (IRAC) definition of insecticide resistance is 'a heritable change in the sensitivity of a pest population that is reflected in the repeated failure of a product to achieve the expected level of control when used according to the label recommendation for that pest species'.

Pesticide resistance is increasing. Farmers in the US lost 7% of their crops to pests in the 1940s; over the 1980s and 1990s, the loss was 13%, even though more pesticides were being used. Over 500 species of pests have evolved a resistance to a pesticide. Other sources estimate the number to be around 1,000 species since 1945.

Although the evolution of pesticide resistance is usually discussed as a result of pesticide use, it is important to keep in mind that pest populations can also adapt to non-chemical methods of control. For example, the northern corn rootworm (Diabrotica barberi) became adapted to a corn-soybean crop rotation by spending the year when the field is planted with soybeans in a diapause.

As of 2014, few new weed killers are near commercialization, and none with a novel, resistance-free mode of action. Similarly, as of January 2019 discovery of new insecticides is more expensive and difficult than ever.

Causes

Pesticide resistance probably stems from multiple factors:

  • Many pest species produce large numbers of offspring, for example insect pests produce large broods. This increases the probability of mutations and ensures the rapid expansion of resistant populations.
  • Pest species had been exposed to natural toxins long before agriculture began. For example, many plants produce phytotoxins to protect them from herbivores. As a result, coevolution of herbivores and their host plants required development of the physiological capability to detoxify or tolerate poisons. Secondary metabolites or allelochemicals produced by plants inhibit insect feeding, but insects have evolved enzymes to metabolize or detoxify them by converting them into non-toxic metabolites. The same enzymes may also detoxify insecticides by converting lipophic compounds into ones that are excreted or otherwise removed from the insect. Greater exposure to insect-inhibiting secondary metabolites or allelochemicals is more likely to increase pesticide resistance. One group of chemicals produced by insects to detoxify toxins are esterases which can detoxify organophosphates and pyrethroid. Conditions that affect how resistant some insects are to insecticides include exposure to different amounts of secondary metabolites or allelochemicals, which are variable among plant species and in response to herbivory pressure. The way an insect feeds on a plant impacts their exposure; insects that feed on the vascular tissue (sap sucking insects like aphids) are generally exposed to less insect-inhibiting compounds than insects that consume the leaves. Plants produce a wide range of defensive chemical compounds and generalist insects that feed on different types of plants can increase their exposure to them increasing their likelihood of developing pesticide resistance.
  • Humans often rely almost exclusively on pesticides for pest control. This increases selection pressure towards resistance. Pesticides that fail to break down quickly contribute to selection for resistant strains even after they are no longer being applied.
  • In response to resistance, managers may increase pesticide quantities/frequency, which exacerbates the problem. In addition, some pesticides are toxic toward species that feed on or compete with pests. This can paradoxically allow the pest population to expand, requiring more pesticides. This is sometimes referred to as the pesticide trap, or a pesticide treadmill, since farmers progressively pay more for less benefit.
  • Insect predators and parasites generally have smaller populations and are less likely to evolve resistance than are pesticides' primary targets, such as mosquitoes and those that feed on plants. Weakening them allows the pests to flourish. Alternatively, resistant predators can be bred in laboratories.
  • Pests with limited viable range (such as insects with a specific diet of a few related crop plants) are more likely to evolve resistance, because they are exposed to higher pesticide concentrations and has less opportunity to breed with unexposed populations.
  • Pests with shorter generation times develop resistance more quickly than others.
  • The social dynamics of farmers: Farmers following the common practices of their peers is sometimes problematic in this case. Overrelying on pesticides is a popular mistake and becomes increasingly popular as farmers conform to the practices around them.
  • Unfamiliarity with variation in regulatory enforcement can hamper policy makers' ability to produce real change in the course of resistance evolution.

Examples

Resistance has evolved in multiple species: resistance to insecticides was first documented by A. L. Melander in 1914 when scale insects demonstrated resistance to an inorganic insecticide. Between 1914 and 1946, 11 additional cases were recorded. The development of organic insecticides, such as DDT, gave hope that insecticide resistance was a dead issue. However, by 1947 housefly resistance to DDT had evolved. With the introduction of every new insecticide class – cyclodienes, carbamates, formamidines, organophosphates, pyrethroids, even Bacillus thuringiensis – cases of resistance surfaced within two to 20 years.

  • Studies in America have shown that fruit flies that infest orange groves were becoming resistant to malathion.
  • In Hawaii, Japan and Tennessee, the diamondback moth evolved a resistance to Bacillus thuringiensis about three years after it began to be used heavily.
  • In England, rats in certain areas have evolved resistance that allows them to consume up to five times as much rat poison as normal rats without dying.
  • DDT is no longer effective in preventing malaria in some places. Resistance developed slowly in the 1960s due to agricultural use. This pattern was especially noted and synthesized by Mouchet 1988.
  • In the southern United States, Amaranthus palmeri, which interferes with cotton production, has evolved resistance to the herbicide glyphosate and overall has resistance to five sites of action in the southern US as of 2021.
  • The Colorado potato beetle has evolved resistance to 52 different compounds belonging to all major insecticide classes. Resistance levels vary across populations and between beetle life stages, but in some cases can be very high (up to 2,000-fold).
  • The cabbage looper is an agricultural pest that is becoming increasingly problematic due to its increasing resistance to Bacillus thuringiensis, as demonstrated in Canadian greenhouses. Further research found a genetic component to Bt resistance.
  • The widespread introduction of Rattus norvegicus (the brown rat) combined with the widespread use of anticoagulent rodenticides such as warfarin has produced almost equally widespread resistance to vitamin K antagonist rodenticides around the world.

Consequences

Insecticides are widely used across the world to increase agricultural productivity and quality in vegetables and grains (and to a lesser degree the use for vector control for livestock). The resulting resistance has reduced function for those very purposes, and in vector control for humans.

Multiple and cross-resistance

  • Multiple-resistance pests are resistant to more than one class of pesticide. This can happen when pesticides are used in sequence, with a new class replacing one to which pests display resistance with another.
  • Cross-resistance, a related phenomenon, occurs when the genetic mutation that made the pest resistant to one pesticide also makes it resistant to others, often those with a similar mechanism of action.

Adaptation

Pests becomes resistant by evolving physiological changes that protect them from the chemical.

One protection mechanism is to increase the number of copies of a gene, allowing the organism to produce more of a protective enzyme that breaks the pesticide into less toxic chemicals. Such enzymes include esterases, glutathione transferases, aryldialkylphosphatase and mixed microsomal oxidases (oxidases expressed within microsomes).

Alternatively, the number and/or sensitivity of biochemical receptors that bind to the pesticide may be reduced.

Behavioral resistance has been described for some chemicals. For example, some Anopheles mosquitoes evolved a preference for resting outside that kept them away from pesticide sprayed on interior walls.

Resistance may involve rapid excretion of toxins, secretion of them within the body away from vulnerable tissues and decreased penetration through the body wall.

Mutation in only a single gene can lead to the evolution of a resistant organism. In other cases, multiple genes are involved. Resistant genes are usually autosomal. This means that they are located on autosomes (as opposed to allosomes, also known as sex chromosomes). As a result, resistance is inherited similarly in males and females. Also, resistance is usually inherited as an incompletely dominant trait. When a resistant individual mates with a susceptible individual, their progeny generally has a level of resistance intermediate between the parents.

Adaptation to pesticides comes with an evolutionary cost, usually decreasing relative fitness of organisms in the absence of pesticides. Resistant individuals often have reduced reproductive output, life expectancy, mobility, etc. Non-resistant individuals sometimes grow in frequency in the absence of pesticides - but not always - so this is one way that is being tried to combat resistance.

Blowfly maggots produce an enzyme that confers resistance to organochloride insecticides. Scientists have researched ways to use this enzyme to break down pesticides in the environment, which would detoxify them and prevent harmful environmental effects. A similar enzyme produced by soil bacteria that also breaks down organochlorides works faster and remains stable in a variety of conditions.

Resistance to gene drive forms of population control is expected to occur and methods of slowing its development are being studied.

The molecular mechanisms of insecticide resistance only became comprehensible in 1997. Guerrero et al 1997 used the newest methods of the time to find mutations producing pyrethroid resistance in dipterans. Even so, these adaptations to pesticides were unusually rapid and may not necessarily represent the norm in wild populations, under wild conditions. Natural adaptation processes take much longer and almost always happen in response to gentler pressures.

Management

In order to remediate the problem it first must be ascertained what is really wrong. Assaying of suspected pesticide resistance - and not merely field observation and experience - is necessary because it may be mistaken for failure to apply the pesticide as directed, or microbial degradation of the pesticide.

The United Nations' World Health Organization established the Worldwide Insecticide resistance Network in March 2016, due to increasing need and increasing recognition, including the radical decline in function against pests of vegetables.

Integrated pest management

The Integrated pest management (IPM) approach provides a balanced approach to minimizing resistance.

Resistance can be managed by reducing use of a pesticide: which may also be beneficial for mitigating pest resurgence. This allows non-resistant organisms to out-compete resistant strains. They can later be killed by returning to use of the pesticide.

A complementary approach is to site untreated refuges near treated croplands where susceptible pests can survive.

When pesticides are the sole or predominant method of pest control, resistance is commonly managed through pesticide rotation. This involves switching among pesticide classes with different modes of action to delay or mitigate pest resistance. The Resistance Action Committees monitor resistance across the world, and in order to do that, each maintains a list of modes of action and pesticides that fall into those categories: the Fungicide Resistance Action Committee, the Weed Science Society of America (the Herbicide Resistance Action Committee no longer has its own scheme, and is contributing to WSSA's from now on), and the Insecticide Resistance Action Committee. The U.S. Environmental Protection Agency (EPA) also uses those classification schemes.

Manufacturers may recommend no more than a specified number of consecutive applications of a pesticide class be made before moving to a different pesticide class.

Two or more pesticides with different modes of action can be tankmixed on the farm to improve results and delay or mitigate existing pest resistance.

Status

Glyphosate

Glyphosate-resistant weeds are now present in the vast majority of soybean, cotton, and corn farms in some U.S. states. Weeds resistant to multiple herbicide modes of action are also on the rise.

Before glyphosate, most herbicides would kill a limited number of weed species, forcing farmers to continually rotate their crops and herbicides to prevent resistance. Glyphosate disrupts the ability of most plants to construct new proteins. Glyphosate-tolerant transgenic crops are not affected.

A weed family that includes waterhemp (Amaranthus rudis) has developed glyphosate-resistant strains. A 2008 to 2009 survey of 144 populations of waterhemp in 41 Missouri counties revealed glyphosate resistance in 69%. Weed surveys from some 500 sites throughout Iowa in 2011 and 2012 revealed glyphosate resistance in approximately 64% of waterhemp samples.

In response to the rise in glyphosate resistance, farmers turned to other herbicides—applying several in a single season. In the United States, most midwestern and southern farmers continue to use glyphosate because it still controls most weed species, applying other herbicides, known as residuals, to deal with resistance.

The use of multiple herbicides appears to have slowed the spread of glyphosate resistance. From 2005 through 2010 researchers discovered 13 different weed species that had developed resistance to glyphosate. From 2010-2014 only two more were discovered.

A 2013 Missouri survey showed that multiply-resistant weeds had spread. 43% of the sampled weed populations were resistant to two different herbicides, 6% to three and 0.5% to four. In Iowa a survey revealed dual resistance in 89% of waterhemp populations, 25% resistant to three and 10% resistant to five.

Resistance increases pesticide costs. For southern cotton, herbicide costs climbed from between $50–$75 per hectare ($20–$30/acre) a few years ago to about $370 per hectare ($150/acre) in 2014. In the South, resistance contributed to the shift that reduced cotton planting by 70% in Arkansas and 60% in Tennessee. For soybeans in Illinois, costs rose from about $25–$160 per hectare ($10–$65/acre).

Bacillus thuringiensis

During 2009 and 2010, some Iowa fields showed severe injury to corn producing Bt toxin Cry3Bb1 by western corn rootworm. During 2011, mCry3A corn also displayed insect damage, including cross-resistance between these toxins. Resistance persisted and spread in Iowa. Bt corn that targets western corn rootworm does not produce a high dose of Bt toxin, and displays less resistance than that seen in a high-dose Bt crop.

Products such as Capture LFR (containing the pyrethroid bifenthrin) and SmartChoice (containing a pyrethroid and an organophosphate) have been increasingly used to complement Bt crops that farmers find alone to be unable to prevent insect-driven injury. Multiple studies have found the practice to be either ineffective or to accelerate the development of resistant strains.

Ecological genetics

From Wikipedia, the free encyclopedia

This contrasts with classical genetics, which works mostly on crosses between laboratory strains, and DNA sequence analysis, which studies genes at the molecular level.

Research in this field is on traits of ecological significance—traits that affect an organism's fitness, or its ability to survive and reproduce. Examples of such traits include flowering time, drought tolerance, polymorphism, mimicry, and avoidance of attacks by predators.

Research usually involves a mixture of field and laboratory studies. Samples of natural populations may be taken back to the laboratory for their genetic variation to be analyzed. Changes in the populations at different times and places will be noted, and the pattern of mortality in these populations will be studied. Research is often done on organisms that have short generation times, such as insects and microbial communities.

History

Although work on natural populations had been done previously, it is acknowledged that the field was founded by the English biologist E.B. Ford (1901–1988) in the early 20th century. Ford started research on the genetics of natural populations in 1924 and worked extensively to develop his formal definition of genetic polymorphism. Ford's magnum opus was Ecological Genetics, which ran to four editions and was widely influential.

Other notable ecological geneticists include R. A. Fisher and Theodosius Dobzhansky. Fisher helped form what is known as the modern synthesis of ecology, by mathematically merging the ideas of Darwin and Mendel. Dobzhansky worked on chromosome polymorphism in fruit flies. He and his colleagues carried out studies on natural populations of Drosophila species in western USA and Mexico over many years.

Philip Sheppard, Cyril Clarke, Bernard Kettlewell and A.J. Cain were all strongly influenced by Ford; their careers date from the post World War II era. Collectively, their work on lepidoptera and on human blood groups established the field and threw light on selection in natural populations, where its role had been once doubted.

Research

Inheritance and natural selection

Ecological genetics is closely tied to the concept of natural selection. Many classical ecology works have employed aspects of ecological genetics, investigating how inheritance and the environment affect individuals.

Industrial melanism in peppered moths

Industrial melanism in the peppered moth Biston betularia is a well-known example of the process of natural selection. The typical wing color phenotype of B. betularia is black and white flecks, but variant 'melanic' phenotypes with increased amounts of black also occur. In the nineteenth century, the frequency of these melanic variants increased rapidly. Many biologists proposed explanations for this phenomenon. It was demonstrated in the early 1910s, and again in many later studies, that the melanic variants were a result of dominant alleles at a single locus in the B. betularia genome. The proposed explanations, then, centered around various environmental factors that could contribute to natural selection. In particular, it was proposed that bird predation was selecting for the melanic moth forms, which were more cryptic in industrialized areas. H. B. D. Kettlewell investigated this hypothesis extensively in the early 1950s.

Uncertainty surrounding whether birds preyed on moths at all posed an initial challenge, leading Kettlewell to perform a series of experiments with captive birds. These experiments, while inititally unsuccessful, found that when a variety of insects are provided, the birds did preferentially prey on the most conspicuous moths: those with coloration unmatched to their surroundings. Kettlewell then performed field experiments using mark-recapture techniques to investigate the selective predation of moths in their natural habitat. These experiments found that, in woods near industrialized areas, melanic moth forms were recaptured at much higher rates than the traditional lighter-colored forms, while in non-industrialized woods, the reverse held true.

More recent research has further emphasized the role of genetics in the case of industrialized melanism in B. betularia. While research had already emphasized the role of alleles in determining wing-color phenotype, it was still unknown whether the melanic alleles had a single origin or had arisen multiple times independently. The use of molecular marking and chromosomal mapping in conjunction with population surveys demonstrated in the early 2010s that the melanic B. betularia variants have one single ancestral origin. Additionally, the melanic variants appear to have arisen by mutation from a typical wing-color phenotype.

Polygenic selection

Research on ecologically important traits often focuses on single alleles. However, it has been found that in many cases, phenotypes have a polygenic basis - they are controlled by many different alleles. Complex traits in particular are more likely to have a polygenic basis. Advances in genetic technology have allowed scientists to more closely investigate the genetic basis of complex traits, leading to an accumulation of evidence supporting the importance of polygenic control in understanding the evolution of these traits.

A major line of evidence can be drawn from what we about artificial selection and its influence on traits. Many experiments that have utilized artificial selection have found traits to respond quickly and steadily. If only a small amount of genes have a large influence on a particular trait, this would not be seen. The way that complex traits with continuous variation change in response to natural selection can most reasonably be explained by many alleles having a small effect on the phenotype of interest.

The prevalance of traits with a polygenic basis poses some issues when researching traits and adaptation in natural populations. Separating the effects of genes, environmental factors, and random genetic drift on traits can be difficult with complex traits.

Limitations

Work of this kind needs long-term funding, as well as grounding in both ecology and genetics. These are both difficult requirements. Research projects can last longer than a researcher's career; for instance, research into mimicry started 150 years ago and is still going strongly. Funding of this type of research is still rather erratic, but at least the value of working with natural populations in the field cannot now be doubted.

Education

From Wikipedia, the free encyclopedia https://en.wikipedia.org/wiki/Education Education is the transmissio...