Level of pesticide residues
Literary Review Plan
Pesticide Residues in Food: a Cause for Concern?
This literary review aimed to discover if the UK consumer should be worried about the level of pesticide residues in their food, the health effects (adverse or otherwise) and if they are unfavourable to the extent that consumers should stop buying foods which contain pesticide residues.
Information for this literary review was obtained by extensive research into the subject of pesticide residues with the use of journals, articles, books and internet sources such as the Pesticide Residue Committee website. The information used in this review aimed to be as up to date as possible, with the majority of sources published in the last 5 years.
What are Pesticide/Pesticide Residues and Why Are Pesticides Used?
The world's population needs food to survive, and the main source of food comes from plants - however these are very susceptible to pests, competition, mould, parasites, fungus and other problems that could possibly lead to lower yield or even destruction of a whole crop (Ware 1989 estimated that in developed countries 10-30% of all crops are ruined by pests and disease.) Pesticides were invented to increase the chances of a crop surviving, and growing a larger yield, and thus ensuring that as many people are fed as possible. To understand the need for pesticide it is important to define what a ‘pesticide' may be and how it might be used. Sannino, 2008 refers to The Food and Agriculture Organisation (FAO), a division of the United Nations, who define ‘a pesticide' as “a substance or a mixture of substances [usually chemicals] intended to prevent, destroy or control any pest”; however they also class “growth regulators, defoliants or desiccants” as pesticides. Pesticides can be used to prevent disease and moulds in harvests during storage and growth and avert damage to yields caused by animals and insects.
Defending harvests from damage ensures that a high level of good quality and varied food is constantly available in the UK. The introduction and invention of pesticides has meant that consumers in the UK do not have to worry about the quantity of food available - they allow for the luxury of quality and variety. Population growth peaked at 2.04% per annum towards the end of the 1960's leading to increased food demand and changes in food consumption patterns. This sparked the growth in pesticide technology and hence we eat better quality and more varied food than before the peak growth period in the 1960s (an illustration of ‘necessity as the mother of invention'). Furthermore, The Food Standard Agency (FSA, a government organisation) note that the high yields produced due to the use of pesticides provide the consumer with lower prices for their food. Hamilton 2004 highlights the benefits of pesticides on a wider scale; due to the fact that spoilage to large amounts of crops caused by many animals, insects and micro organisms, (if pesticides were not used), could lead to losses in trade and cause great harm to the economy. There are many categories of pesticide as there are many ways that crops can be destroyed - fungicides (classically made up of carbamates or similar) are used to protect plant crops against fungus, herbicides (classically made up of carbamates, 1,3,5-triazines and substituted ureas) protect against weeds and insecticides (classically made up of organophosphorates (OPs), pyrethroids, carbamates, and substituted ureas) protect against insects (Sannino 2008). Other pesticides include molluscides and bactericides. Sannino 2008 states they are categorised by way of their chemical grouping as pesticides, either consist of organic compounds or inorganic compounds; modern pesticides mainly consist of the former with some even developed from the plant-tissue themselves, with Sannino 2008 giving rotenone as an example. Hassall 1990 states that the pest and chemical structure of the pesticide can also, and usually are, used to categorise pesticides.
‘Pesticide residues' are the level of pesticide left behind on or in foods once they have been processed (and thus will be consumed with the food, however they are not found in all foods). Residues may also be found in food due to ‘spray drift' or polluted environments or, for example in meat and animal products, due to those animals consuming feed that contains pesticides. Hamilton 2008 notes that drinking water may also become contaminated with residues. If any pesticide residue is left on or in the food it will normally be a minute amount (FSA) however some, such as Weddie 1991, and many consumers, believe that the pesticide residues cause harm, (this fact is used as a marketing tool in the organic food industry and is a possible reason why many people choose to buy organic foods) (Weddie 1991). Pesticide Residues do not necessarily occur in foods because too much pesticide has been used on crops, or because the pesticide has been applied incorrectly; some pesticides are applied to food specifically as a residue to defend the food from disease, moulds, microorganisms and similar when being stored or transported. (FSA) The prevalence of pesticide residues in food and their possible affect on human health and the environment has brought about much discussion in literature; the debate about whether these residues pose a possible cause for concern is on going - this literary review aims to explore this further.
The Green Revolution and History of Pesticide
Cremlyn, 1978 tells that the utilisation of chemicals in order for crops to flourish is older than most think - in fact some basic concepts have been understood since the Ancient Greek and Roman times, for example they were then aware of the benefits of sulphur, arsenic and soda on food crops and their capabilities of skirmishing pests. The beneficial properties of fighting against pests for nicotine, soap and pyrethrum had also been utilised long before the Green Revolution and the modern era of pesticides. During the 1800's the first controlled scientific research into the beneficial affects of chemicals to prevent pest damaging crops were undertaken. Hajšlová 1999 details the advancement of the utilisation of arsenic leading to the introduction of an insecticide made up of impure copper arsenite in the last 1860's. Further advancements throughout the century where discovered, for example a fungicide containing copper sulphate which illustrated selective pesticides properties, and the utilisation and invention of organomercury pesticides in to the early 20th century. Holland 1996 regarded the 1930's as the start of the ‘modern' age of pesticide use, invention and implementation. Many important discoveries were made in this decade, including dinitro-ortho-cresikm, thiram, pentachlorophenol, TEPP and (towards the end of the decade) DDT. Hajšlová 1999 notes how DDT went on to become the most extensively employed insecticide across the glob, sparking the use of other organochlorines in pesticides. In the 1940's hormone herbicides, and carbamate herbicides and insecticides were utilised, however Sannino 2008 notes that pesticides in agriculture only became extensive and gained wide spread usage after the Second World War, coinciding with the Green Revolution and up-scaling of agricultural technology and need for more food production with population growth (which peaked during the late 1960s). The 1950's saw the birth of many more pesticides, such as urea, that remain in use in modern agriculture. The next decade saw the introduction of important compounds such as captan, glyodin, benomyl (in funigisides), tiazines, ammonia, glyposate (in herbicides) and malathion (in insecticides). At this time organic pyrethrins were also taken over by synthetic replacements that showed better action.
The Green Revolution (mainly happening throughout the 1950's, but extending into the 70s and early 80s) was designed to dramatically enhance the technology used in agriculture, and thus bring about higher yields and better quality food crops. This saw the start of the elimination of hunger for many in the developing world and dramatically changed agriculture. This ‘Green Revolution' (a phrase first coined by William Gaud in the late 1960's (Gaud 1968) was funded by The Rockefeller Foundation, the Ford Foundation and a number of Governments across the globe who saw its potential for greatness (Greathead 2008). Dr Norman Borlaug (father of the Green Revolution, (Niazi 2004)), who worked for The Rockefeller Foundation, proved that great successes could be made in agriculture and demonstrated this with his development work in Mexico in 1943. The successes there meant that Rockefeller and Borlaug sought to spread this model of development (through pesticides, mechanisation, new cultivars, irrigation and fertilisation) into other countries, firstly focussing on staple crops.
One of the first countries to roll out this model was India; De Datta 1968 noted the successes India found when implementing the new schemes, especially in respect to IR8 (a new strain of rice, latter dubbed ‘Miracle Rice') which produced ten fold the yield of traditional rice. This success was emulated throughout Asia. Barta 2007 illustrates the Green Revolution's successes in India, by stating that the cost of rice there had more than halved since the 1970s, and that by the 1990's India had tripled the average of amount of rice-grown-per-hectare. IR8 also proved a great success of reducing hunger in the Philippines, leading to their average annual rice production more than doubling between the 1960s-1980s (FAO). Conway 1998's statistics (that during the same time period cereal yields also more than doubled in less economically developed countries) also prove that the Green Revolution brought about great reduction in levels of hunger and thus increased the quality of lives for the population of those countries. However, the Philippines was one of the first to show signs of the disadvantages of the Green Revolution - IR8 needed heavy pesticide use to achieve its potential, but this led a great reduction in the number of Filipino fish and frog genus and some leafy weeds (which is environmentally unsound, however it also depleted the food supply of farmers and they occasionally utilised these as food also) (Wijaya 2008). Criticisms have also arose with some saying that food security has actually decreased for many, Spitz 1987 give the example of some land usage being moved from pulses to wheat in India, however the poor there do not use wheat as a staple and thus less are fed. Sen 1991 also saw problems with food security that he believes arose due to the Green Revolution. Sen 1991's assertions have been contested by Bowbrick 1986 who states that Sen depends on incoherent opinion, and conflicting existing hypothesis. Bowbrick 1986 also states that Sen 1991's arguments have already been disproved as they were similar to those used by the Bengal government to try and wipe out famine, however this failed in tradegy. Igbozurike 1978 stated that another problem faced was the fact that the genetically modified cultivar that had higher yields, needed a large amount of pesticides (and other agriculturally developed devices) to reach their full potential, and thus, when these devices were not part of the input, the output of the ‘higher yielding' varieties might not have actually been as large as traditional ones. Altieri 1995 feels that another disadvante of the Green Revolution is its dependence on monocultures, meaning that in developing countries a less varied diet is consumed (and this has also led to pest nuisance and soil degradation (Greathead 2008)). Frison 2008 furthers this argument by hypothesising that although the problem of starvation has been greatly alleviated by the Revolution, malnutrition has actually become worse. Chapman 2002 also believes that due to the lessen quality of the rice strains used to produce higher yields in Asian countries (as discussed earlier) these now reach a lower price when sold than the traditionally grown varieties. A further gap has arisen between big and small farmers (and thus possibly extending the gap between rich and poor) as the farming used in this scheme favours big farms, leading to a reduced number of landowners (Greathead 2008). The FAO strictly promote the opposite of this type of land ownership.
The Consultative Group on International Agricultural Research (CGIAR) was set up by The Rockefeller Foundation in 1968, and established as a global centre of food research with the aim of maintaining food security for all in 1970. The CGIAR has had to deal with concerns that the Green Revolution was unsustainable and the effects it has had on certain environments (Oasa 1987). The CGIAR implemented schemes, such as the Participatory Rural Appraisal, so that the Revolution continues in a more sustainable way and so that farmers were not cut out of the loop when it came to their land and how to improve it. These schemes were also aimed at giving the scientists involved a better perception of what needed to be done. The Green Revolution, holds many advantageous results, however, other disadvantages have also arisen. Sherer 2007 points out that the advancement of pesticides can be linked to fossil fuels, thus when the price of these rise, so does the price of crop production, and thus food. Thomas Malthus originally predicted that population growth would outstrip food supply (i.e agricultural development) (Malthus, 2005), however the Green Revolution is the main cause (along with others such as the introduction of contraception) that this did not happen. However, some, (such as Trumbull 2007, Kunstler 2005 and Peak Oil Theorists) believe that this link with fossil fuels could lead to Malthus' theory becoming fact. Similar schools of thought believe that the Green Revolution has supported population growth to such an extent that it is now causing great problems, including environmental and economic disasters (Pimentel, 1994). Following on from this argument Oasa 1987 and Ponting 2007 bring forward the evidence that as the agriculture brought about by the Green Revolution requires many inputs, (such as pesticides, feul for machines and so on), this caused many farmers to lose their land due to the fact they had to borrow money to pay for these new inputs, whereas if they had stuck with traditional methods they would still have income, employment and food supply. Following this, employment was also reduced and mechanisation took over many labourers' jobs.
The Green Revolution was indispensible to the growth of the world's population since middle of the 20th century, with the world's population approximately tripling since its development. The Green Revolution is to thank for the fact that many people are no longer starving and that the Malthusian nightmare has not materialised of population out growing food supply. Ehrlich 1968 believed that the Green Revolution was not the miracle that most thought it was, and alleged that in the next decade there would be no way that many in India would not face devastating famine and die from malnutrition. However the Green Revolution was instated in India and thankfully Ehrlich's predicted catastrophe never happened (Pollock 2008). Conway 1998's statistics show that the since the Revolution, less economically developed countries now consumed a quarter more food, and Kindall 1994 points out that the amount of grain harvested, (a staple food, without which many people would die), has increased two and a half times over.
Hajšlová 1999 sees the pesticides introduced as the “new generation of pesticides”. The 1960's also saw the arrival of research into health implications of pesticide residues in the food chain. The uses of organochlorines, such as the popular and wide-spread DDT, were reassessed in the next decade due to their negative effect on then environment. This led to some organochlorines, including DDT, being prohibited from being used in agriculture across the globe. The 70's saw further prohibition of pesticides that were thought to potentially cause other harmful effects on the body.
However, Hajšlová 1999 states that although hindsight was needed to understand the health implications of DDT and others like it, enhanced awareness and understanding, coupled with modern techniques of pesticide treatment to the land and fresh policy used when inventing new pesticides are now utilised with the aspiration of lowering the threat of negative (health and environmental) effects of pesticides.
Now there are approximately 900 utilised and prohibited chemical pesticides, thanks, in part, to the Green Revolution. Last century saw the use of pesticides increase by tremendous amounts (the EPA (The Environmental Protection Agency) states that the utilisation of pesticides increased by more than 200% in the two decades between 1960 and 1980, with approximately 1.8 billion kilograms of pesticides employed per annum across the globe.
In the 1970s 36 percent of the world's population was classed as ‘hungry', thanks in great part to the Green Revolution this number has reduced by a staggering 50 percent in only 25 years (1995) (Greathead 2008).
Third World In Desperate Need of Green Revolution - Benefits of Pesticides
Greathead 2008 notes that Sub Saharan Africa is in desperate need of a Green Revolution, however attempts to implement it their have failed due to problems associated with ease of access, manufacturing expenses, transportation, political conflict, increasing populace, tough environments and civil instability. Frison 2008 also believes that the multiplicity of soil and land types impedes its success as well as the fact that the African government are unwilling to implement a Green Revolution there. Dugger 2007 reports of recent attempts to implement Green Revolution style practises in Western Africa. This attempt seeks to introduce ‘NERICA' rice into the region which produces a 30% higher yield than normal rice there, and requires no chemical inputs such as pesticides; however the introduction of inputs can lead to this number doubling. However Dugger 2007 states that this scheme has only been victorious in Guinea as elsewhere farmers have had little access to the new rice.
Pesticide Residues and Effect of Health
Pesticides can ‘contaminate' non target organisms, such humans, in many different ways, such as through air and water pollution, through contact with the skin (as is common with workers in developing countries), or indirectly by eating and drink foods and liquids that contain pesticide residues (Department of Pesticide Regulation (2008)). Lorenz (2009) states that the level of harm caused to humans depend on the amount of contact with the pesticide. The Department of Pesticide Regulation 2008 found that due to their fat soluble and bioaccumulation characteristics, all sample of human fat taken contained some level of pesticides, with children being the most vulnerable, due to being smaller. Lorens 2009 found that contact with pesticides caused many adverse health effects, including tumours, comas, rashes, faults at birth and endocrine interference.
Miller 2004 and the World Health Organisation (WHO) approximate that three millions workers in less economically developed countries suffer adverse health affects due to pesticides per annum. However Jeyaratnam (1990) feels the number may actually much greater, and estimates more than eight times as many (although this data has not come from the WHO and thus is less trustworthy than the former estimation). McCauley LA, Anger WK, Keifer M, Langley R, Robson MG, and Rohlman D 2006 have hypothesised that many health implications, such as several cancers, are due to pesticides (however it must be noted that these negative health implications were found in subjects working directly with, and thus had direct exposure to, pesticides.) Several studies, such as those by Alavanja, 2004. and Kamel 2004, have also showed that workers using organophosphate pesticides (the more environmentally friendly alternative to organochlorine) have great risk of developing neurological defects and some cancers. The (now replaced) organochlorines have shown signs of greatly increasing the chances of the handler having diabetes (Montgomery 2008).
The level of acceptable and safe pesticide residues in food is monitored so that the ‘ADI' (acceptable daily intake) is set by dividing the NOEL (no observed adverse effect level, found by testing pesticide exposure on animals) by a large safety factor (the norm is a safety factor of one hundred) (Sannino 2008). This high safety factor would indicate that consuming the level of pesticide residues described by the ADI would not lead to concern, however much literature would contradict this. Sannino 2008 describes pesticide residues adverse affects using organochlorines (OCs) as an example, as they are no longer used on food crops due to the fact they were found to bioaccumulate in the body (owing to their properties of fat solubility). Hopper and Oehme 1989, rightly point out however that any health implications will vary greatly with dose, i.e. the level of pesticide residues consumed. Hajšlová 1999 tells that “dehydration and malnutrition” will increase the risk of harm to an individual by pesticides, and thus a healthy individual is less susceptible to illness from pesticide residues than an unhealthy one.
However Ames and Gold 1997 contradict many of these findings and state that health concerns about pesticides, and specifically cancer, and misconceived. Ames and Gold 1997 found that (with the exception of lung cancer due to smoking) cancer levels have actually fallen
Monitoring and Control of Pesticide Residues
Affects of Processing on Levels of Pesticide Residues in Food
Pesticides: Sustainability and Environmental Impact
Miller 2004 has noted that only 2% of insecticides and 5% of herbicides actually make contact with the intentioned subject (i.e. the crop), thus the rest of the pesticide that is applied will go back into the environment. This can have very negative affects on the surrounding eco-system (however the extent of these effects will be dependant on the pesticide's chemical traits and including the length of time it takes to deteriorate, how much it holds to the soil and its ability to be suspended in the water table.
The subsequent effect of soil pollution on biota is potentially devastating. Rocket 2007 believes that the occurrence of pesticides (especially DDT and pentachlorophenol) in soil hampers nitrogen fixation, and thus impedes the development of tracheophytes (such as trees). Legumes crops are also impaired, states Rocket, due to the damage towards rhizobium - this also leads to economic damage as their natural nitrogen fixing qualities mean that vast amounts of money (Fox 1997 estimated over £6.5 billion) does not have to be spent on artificial nitrogen-containing pesticides. Wells 2007 warns of the adverse affect that pesticides are having when it comes to the global bee population - bees are needed to pollinate plants and food crops thus the danger to their numbers could be potentially very hazardous. Many insecticides are lethal to the bees. Miller 2004 estimates that in the United States this has a very negative effect on the economy, due to the fact that crops are not being pollinated. Miller 2004 states that this reduction in number of bees is leading to a loss of over £100 million per annum. Palmer 2007 states that pesticide residues can act as a toxin towards animal species if they are near by, or if they wander into a crop field when pesticides have just been applied. Also if the food source of some animals, i.e. some insects, is eradicated then this will also cause adverse effects as animals could potentially go hungry, or have to be displaced. Other hazards to animal species, especially those highest in the foodchain, arrives due to the bioaccumaltion properties of some pesticides, as these animals may consume other animals that have also consumed pesticides. Miller 2004 states that many of the animals in danger of extinctionin the United States are put at higher risk due to the utilisation of pesticides.
The Green Revolution, and thus the intensive use of pesticides, has led to land being used for production that would never normally, it has also led to monocultures and pesticide resistant cultivars. These factors contribute to declining biodiversity. Davis 2003 hypothesised that the increased output of land that is already farmed will halt the expansion of harvesting other areas that have not yet been touched - thus preserving valuable green space. However Shiva 1991 disagrees, and states that much former forest has been cleared and used for agriculture, to deal with the now dilapidation land. Johnston (1986) furthers this argument by stating that a lack of pesticides in soils increases its bio-diverse worth, however many would disagree, such as Davis 2003. The amount of organic matter in the land and the amount of water the land can maintain have a directly proportional relationship (however the amount of organic matter and the level of pesticides leached has an inversely proportional relationship due to the binding properties of the matter). Lotter 2003 thus demonstrated the benefits of organic matter by noting how this is particularly beneficial in long periods without rain. Lotter 2003 states that land farmed organically produced up to forty percent more crops than those farmed using pesticides during times of drought.
Gilliom 2007 conducted a study into the water systems in the United States, where shocking results concluded that every stream tested showed signs of pesticide pollution. Kellogg 2000 furthered this and found evidence of pesticide residues in both ground water and rain. Bingham 2007 brought this research to the UK and concluded that some samples in this country actually showed levels higher than the acceptable governed level. Hogan 1973 used a ‘hydrology transport model' to assess the pollution in water structures. Hogan 1973 performed detailed investigations into pesticide runoff, with the view to forecast the level of pesticides that would contaminate top level water. Papendick 1986, speculated that soil erosion would help the movement of pesticides from their intended target, and into water. Other ways this may happen also include spray drift, leaching or surface run off. Pedersen 1997 found that the likelihood of a pesticide to pollute surrounding water depends on it many things including how it was applied, where it was applied (i.e. near a large water supply), wind, its ability to move in and interact with water and the type of crops its applied to. The level of pesticides found in water is governed by the setting of Environmental Quality Standards in Britain, (with other agencies in the U.S.A and the E.U setting other appropriate data). These Standards are put in place so that direct poisoning by a pesticide from consuming the water will not occur (Bingham 2007).
The level of pesticides in the water systems also has very unsustainable effects of fish and other water-habiting species, with Helfrich 1996 stating that insecticides cause the most damage, compared with fungicides and herbicides. Toughill 1999 states that whole water systems can be stripped of fish due to pesticides entering the body of water via surface run off. Helfich 1996 states that large amounts of fish can die due to direct contact with pesticides (such as cooper sulphite) however they can also be killed indirectly as they can be suffocated and die due to herbicides entering the water and destroying the oxygen-manufacturing weeds. Another indirect cause of damage to fish populace were noted by Helfich 1996, for example lower immune system activity, reduction in the number of plants used for guarding territory, reduction in the number of food varieties, (such as some insects) and increased incidences of rejecting nests and evading hunters. PANUPS 1999 have also found that pesticides greatly reduce zooplankton populace, which is detrimental to the likelihood of newly born fish surviving as this is their main supply of food. The time it takes for a pesticide to break down and the damage done to bodies of water and the life with in them has an inversely proportional relationship, thus in order to preserve more water systems and their inhabitants it is important that pesticides with a quick break down time are used.
Cone 2000 believes that the utilisation of pesticides is also to blame for the reduction in the number amphibians across the globe. Science Daily 2006 believes that a ‘cocktail effect' of many pesticides is seen to be harmful to development of frogs. This causes long term problems as tadpoles exposed to this cocktail of pesticides are not only slower at developing into frogs than those not, but are also reduced in body size, thus causing detrimental effects to their capability of out running food and hunters. Raloff 1998 found similar affects on tadpoles with endosulfan pollution (at concentrations deemed similar to those found in bodies of water near crop land). Science Daily 2006 also found atrazine to be particularly harmful to male of the - atrazine has been proven to feminise the males and turn many into hermaphrodites, which has damaging repercussions on levels of reproduction.
Another potential route of environmental upset is through the air - problems arise mainly due to the applications of pesticides that involve spraying. ‘Spray drift' can occur, leading to the pesticide affecting somewhere or something other than the desired target, i.e. the crop. A study of air quality in Sequoia and Kings Canyon National Park in the United States in 2006 noted that this pesticide drift creates danger to flora and fauna. Pesticides can also potentially bind themselves to dust and other materials in the air causing them to travel even further and cause more damage. Palmer 2007 does state however that this air pollution can be reduced be replacing aerial methods with pesticide application on the ground. The Netherlands utilize a system on their farms by which this type of pollution by pesticides can also be reduced. The system involves utilising a buffer zone (such as trees, which will act as a barrier to spray drift) circling any area where pesticides will be used (Science Daily 1999). Reynolds 1997 blames a level of global warming on the air pollution caused by fumigation pesticides - it states that the level of VOC (volatile organic compounds) contributes significantly contributing to the production of trioxygen (or ozone).
Ritter 2007 produced a study into POPs, (persistent organic pollutants, particles that take many years to break down). Pesticides with POP properties include DTT, endrin, mirex and chlordane. Due to POP's volatile properties they become put down in non-target areas by drifiting through the environment. The POP's capacity to bioamplify, bioaccumulate and bioconentrate, with Ritter 2007 stating concentration can increase by 70,000 fold, is one that causes concern, thus leading to some, such a DDT being banned.
Air pollution by pesticides also has a very unsustainable effect on many birds. Kerbs 1999 noted that in the United Kingdom in the 20 years between 1979 and 1999, 10 million birds were lost due to reduction of their food including plants and insects. Kerbs 1999 also estimated that in Europe over 100 different species of bird have become endangered due to the use of pesticides, finding evidence that suggests the decreasing bird numbers are linked to periods and places where and when pesticides have been extensively applied. Palmer 2007 expands on this argument, stating that although the pesticides applied to peanuts have only slightly direct adverse effects on birds and other animals, indirectly they are devastating due to elimination of their food (such as insects.) Pesticides applied as pellets can also easily be falsely identified as grain by birds and thus they might eat them and become ill, with Palmer believing that only a minute dose is needed to be lethal to smaller birds. Palmer also discovered that pesticide ‘paraquat' causes birth defects if it comes in contact with birds eggs, thus further increasing the damage to bird populace.
Another unsustainability associated with extended use of pesticides is that pests have shown signs that they are able to develop a resistance to pesticides. Even if only a small number of ‘pests' survive exposure to a pesticide, these are then able to reproduce and, as Darwin states, pass on their ‘survival of the fittest' genes to the next generation, and so on until a great level of resistance is built up. To counteract this problem the use of different types of pesticides in alternation is utilised to postpone resistance by pests (Murphy 2005).
Pest resurgence can also be a problem, due to removal of predators of the pests (Purcell et al., 1998). Ferrer et al., (1992)'s study on Diamondback Moths compared the different levels of pests using biocontrols and then using pyrethroid pesticide. The study concluded that when the pyrethroid pesticide was used pest resurgence happened - this was caused by the fact that there was a reduction in the populace of predators. However, the reverse was seen when biocontrols were used. Purcell et al., 1998 also descrives problems associated with secondary pest eruption which is caused when predators are removed from the environment by pesticides, leading to pests flourishing in the their predators kept them at bay. Miller 2004 supports these finding further, approximating that 100 of the United State's most harmful pests were formerly not seen as too damaging until the use of pesticides eradicated their predators. Purcell et al., (1998) also concluded that in the cases where these phenomenon's have happened the predators were more sensitive to the insecticides than the target pests; in some incidences this lead to a worse problem from pests than prior to pesticides being applied.
To combat the negative consequences to the environment due to the use of pesticides a number of proven substitutes exist. Wintersterstein et al., (1999) uses Iowa farm practises as examples and suggests several verified practices, including spot spraying, inspecting land for pests, lowering the rate of pesticides in the soil, physically removing the weeds with machines, revolving crops to control weeds, postponing the date of planting, and herbicide banding.
Greathead 2008 refers to the new movement of the Real Green Revolution which varies from the Green Revolution as it strives to find more sustainable agricultural applications. The original Green Revolution had a remarkable influence on agriculture and helped reduce the levels of hunger across the world significantly (Conway 1998), however from the evidence above it is apparent that these practices were particularly unsustainable with many negative societal and health effects as well as the causing problems for the environment. Greathead 2008 defines sustainable agriculture as an amalgamation of “environmental stewardship, farm profitability, and prosperous farming communities (i.e. economic, social and environmental aspects of human society)”
The Real Green Revolution looks to ‘clean up' problems caused by the original Revolution by focusing on sustaining the world's resources, including biodiversity, however this is not a small task but it will be vital to the future of agriculture and what man can produce from the earth in order to feed its population.
GM and Monsanto GM Foods
Do I believe there is a cause for concern, based on the evidence found in the above research...? Future trends.
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