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Political shift away from the EU has left the UK deciding whether or not to retain the original European Commission legislation, maintaining tight restrictions on the cultivation and commercialisation of GM crops. However, due to falling yields, alongside decreasing environmental sustainability of UK agricultural practice, the government is under pressure to introduce new legislation, allowing for a restructure of the agriculture industry in favour of GM technology. Through a review of published data and articles, the efficacy of GM crops to ensure consistent crop production, since their commercialisation and in their current state, was assessed. This looked at factors including pesticide and herbicide resistance, changes in chemical use and overall economic benefits provided by the GM crops. This was then used to determine whether the UK should encourage domestic GM commercialisation, alongside a survey to identify whether there is in fact an internal market for GM produce at a consumer level. This survey showed that opinion of certain demographics within the population had swayed in support of GM integration and this could be bolstered further through providing the public with up-to-date data as part of strategic marketing. As the two main barriers to UK integration of GM crops, EU law conformity and public opinion are no longer obstacles; now is the best time to reshape the UK agricultural sector for a sustainable, productive future.

























List of Figures

Figure 1- Comparison of the Total farm income per year in Million £ against the total cultivated land area of the UK over the same time period. The data was data directly from DEFRA reports 2011-2016 as published on the GOV.UK website.  (Original Graph) 7

Figure 2. The composition of UK agricultural industry based on the total land area grown of each crop, measured as the ‘Total supply”. Data taken from an ONS report dated 2015; so the percentages may have varied but it is likely that any variation was not significantly disproportionate. 9

Figure 3. A comparative analysis of Bt transgenic cotton crops against conventional cotton crop in terms of actual yield and pesticide costs. Pesticide cost can also be considered a substitute value for the amount of pesticide used, as the cost is based upon how much was applied. The countries chosen are the 5 major producers of Bt cotton. The data was taken from (Brookes and Barfoot, 2017) (Original graph) 15

Figure 4. Global-scale comparison between major producers of Herbicide Tolerant (HT) crops, measured by Aggregate income benefit in US$; a measure of the added benefit of growing GM crops instead of conventional crops of the same type. (A) shows the HT Maize market dominated by the US, mainly through the use of glyphosate. (B) the HT cotton industry is similarly dominated by the US, as most other major producers of GM cotton tend to focus on pest resistance through using Bt cotton variants. (C) HT soybean is more distributed, with Argentina and Brazil also major producers. Data taken from (Brookes and Barfoot, 2017). (Original graph) 17

Figure 5. Graphical representations of the demographics reached and that successfully responded to the survey. Shown as percentages of the total survey sample, 205 people. (A) By sex; Male, Female and Other(B) By ‘Highest qualification level achieved', used as a measure for individuals likely level of specialist knowledge. (C) By age group; any responses below the age of 18 had to be discarded due to ethical limitations with collecting data from minors. (The survey questions can be viewed in the Appendix). 24

Figure 6. The frequency of responses for each option of the 5 questions found to have significantly different mean answers following a Paired Sample T test (Table 4). Each figure displays how many people chose each level of agreement with each of the 5 statements both before and after they were provided with an informational section in the Survey. The rationale behind this was to determine whether the public's level of support or opposition towards GM crops could be altered or influenced through informational marketing. A, B. C. D,E relate the statements the data represents the responses for. The Statements themselves are displayed on each figure. 29

Chapter 1. Introduction

1.1 Background

Genetically modified (GM) crops have heralded a new era in agriculture since their initial commercialization in 1996. In the 20 years since, the total hectares of GM crops grown commercially has risen from just 1.7 million in 1996 to 185.1 million in 2016 (ISAAA, 2016), a 11,000% rise. However, this rapid growth in GM development has plateaued in the 2000's due to biotechnology splitting opinion in the international community. While many regions, particularly the US, South America and parts of Asia were quick to commercialized and develop these crops, many influential countries were sceptical about potential health and environmental side effects. The greatest example of this is the EU which has very strict regulations and restrictions, set in place by the European Commission, dictating which GM crops and products can be imported and grown within the EU. Many countries that have accepted GM technology have reached maximum capacity, either in arable land availability or through a limitation in essential resources. This saturation, along with the unwillingness of remaining anti-GM countries to change their laws has caused the recent plateau in growth. The GM crops themselves come in two general forms; Herbicide Tolerant (HT) and Insecticide Resistant (IR) the most common of which are Glyphosate and Bt (Bacillus Thuringiensis) respectively. Four main crops dominate the GM market; Canola, Maize, Cotton and Soybean, but only cotton and maize have both HT and IR variants. Soybean is the most widespread and successful of the four, as 77% of the global soybean crops grown are GM (Kaphengst et al, 2011) with the next most successful being cotton (49%); but this difference is far more substantial when the difference in total hectares grown is considered, with the ratio standing at 90 million to 30 million respectively.

As the global population continues to grow at an accelerated rate, food security continues to decline, which is why it may be time for the EU and others to reconsider their position on GM agriculture and imports.  More specifically, this thesis will consider whether the UK in particular should reconsider its regulatory position following ‘Brexit' as it is no longer subject to constraints put in place by the European Commission. As part of this, the use of GM crops to control pests and weeds will be reviewed, looking at human impacts, environmental impacts and assessing whether the change from conventional crop types to GM has benefitted food security for the respective countries. Further to this, the current agronomic status in the UK will be reviewed to see whether legislative change is advisable and realistic. A survey will be used to assess public opinion in the UK to determine whether there is a potential market for GM produces; reviewing the possible changes in public opinion since initial protests in 1997 against imported GM animal feeds cultivated by Monsanto.

1.2 Current legislation in the UK

The UK government was one of few within the EU that wanted a less restrictive stance on GMO technology; however, pre-Brexit it had to abide by EU regulations as set by the European Commission. Now, the government is debating whether to maintain current policy or to draw up new legislation allowing for greater integration of GM crops into UK agriculture as well as import practices. As it stands, the EU has a strict framework for the import and cultivation of GMOs. The fundamentals aims of the framework is to ‘protect human and animal health and the environment' through high standard safety assessments as well as ‘clear labelling' and ‘traceability' of GMOs on the market.

As a result of the restrictions, very few GMOs are cultivated across Europe; aside from Spain, which grows roughly 53,000 hectares of Bt Maize (ISAAA, 2016).  The majority of GM crops in the EU are not food crops; instead they are GM flower crops, such as carnations in the Netherlands, modified to blossom different colours (Directive 2001/18/EC; European Commission). Applications to cultivate or import GM products are lengthy and require ‘purposes' granted by the European commission through the European Food Safety Authority (EFSA). These are only assessed and granted on a case-by-case basis and even if granted, only extend for a 10-year period before reassessment is required. In 2015, the EU introduced an ‘opt-out' clause to appease member states that wanted more independent control over their own internal regulations. This gave each member nation control over assessing and granting their own applications for GMO cultivation. Despite this, over two-thirds of the members of the EU chose to completely ban all GM crops. Further to cultivation, imports of GM goods are very strict; the only significant import is at low-levels in feed for livestock.

1.3 Agriculture and food security in the UK

In order to assess whether GM crops would be suitable to be cultivated in the UK and if it is even necessary, the current state of the UK's agricultural sector has to be considered. The main elements to consider in this case are productivity, income, the types of crop grown, chemical usage and the total land area that has been agriculturally cultivated thus far.

Fig 1 summarises the total land use for agriculture between 2008 and 2016 along with the total farm income across the same period. It shows that while the total land area used for the cultivation of crops has remained relatively consistent since 2008, the total farm income has fallen to its lowest in 10 years (DEFRA, 2016; DEFRA, 2011). This is linked to a trend of falling productivity, measured at -2.3% between 2015-2016, a significantly greater reduction than the -0.4% the previous year (DEFRA, 2015).  This fall in productivity is associated with many factors, importantly static input volumes. The fall in in productivity is a result of reduced production function, which relates the ‘output of a production system to the inputs used in production' (Dawe & Dobermann, 2004). This effectively means that the relative agricultural inputs; pesticides, fertilisers, labour and plant protection products are becoming less effective and having a reduced impact on crop yield or the productivity of the yield. It has been noted that it is possible to have reduced productivity without an actual reduction in yield as the quality of the yield can be affected. A normal solution to an output-based issue would be to increase inputs, however, this is more complicated for agriculture as pesticides and fertilisers have significant restrictions. Many of the regulations currently in place are derivatives of EU regulations as Brexit is still being negotiated. These restrict the type and quantity of pesticides used, with bans having been introduced in recent years, notably that of neonicotinoids in April 2018 due to concerns about their effect on bee populations (Cresswell, Desneux & van Engelsdorp, 2012). Another restriction is that of ‘Maximum Residue Level' (MRL), determining the maximum amount of plant protection products (herbicides; insecticides; fungicides) that can be applied to food crops. This is to protect the health of the consumers of the crop produce, as pesticides chemicals can be toxic if digested in high enough quantities. In terms of fertiliser there is a loading limit of how much nitrogen can be applied to the land, otherwise nitrogen vulnerable zones can be created. For organic manure in the UK, this limit is 250kg per hectare of total manure; 170kg in livestock manure (GOV.UK, 2017).

As a result of these limitations, the farmers are unable to simply increase pesticide and fertiliser use or use new pesticides. Which is the basis of this thesis' rationale; the agriculture industry has reached a metaphorical ceiling, where the current methods of farming have reached their maximum capacity. 71% of the UK land area has already been cultivated which is almost all the suitable land area, and chemical usage has taken its toll on the ecosystem leading to imposing restrictions and ban being implemented. The UK's food security has declined drastically over the past two decades, declining from 87% to 68% (DEFRA); with the UK's population expected to rise by 5.5% to 69.2 million by 2026 (ONS, 2017), so it is essential that productivity is increased to meet the

Crop Type Fungicide (Tonnes) Herbicide (Tonnes) Insecticide (Tonnes) Growth Regulators (Tonnes) Seed Treatments

Wheat 3138.5 3477.8 27.6 2008.6 116.6

Winter Barley 310.7 715.7 3.7 347.4 20.3

Spring Barley 357.5 711.7 1.7 95.2 14.2

Ware Potatoes 1177.6 386.77 101.27 58.74 23.65

Seed Potatoes 102.5 31.7 4.2 NA 8.1

future demand. As a result, alternatives must be considered, of which GM crops are one of the most substantial.

Figure 2 shows the breakdown of the UK crop production based on crop type; with the majority of crop species being composed of Wheat (46%), Barley (20%) and Potatoes (16%). This has important implications for both the environmental impacts as well as potential domestic commercialisation of GM crop variants. Chemical use, including herbicides, fungicides and insecticides varies with crop type, due to the varying nature of the pests and weeds that affect them. Summarised in the Table 1 are the relative amounts of these different chemicals applied across the 3 main UK crops; wheat, barley and potatoes. Wheat is the cause of the majority of chemical application, particularly through fungicide, herbicide and growth regulators (FERA, 2016). These can all have many environmental impacts, including contamination of foodstuffs and surface waters through leaching, and particularly toxicity towards non-target organisms, such as beneficial soil microorganisms (Aktar et al, 2009). Therefore, it is important to consider the different crops in question, as changes to chemical use would be a key factor when considering which potential GM crop strains could or should be commercialised. Looking at the structure of the agricultural sector is also important in terms of infrastructure. For example, if GM crops were to be grown commercially in the UK, it would most achievable by using existing infrastructure and expertise by growing GM variants of crops already grown in the UK, such as potatoes. However, this is limited in the short term by the range of GM lines available, particularly in the case of wheat where field tests have been carried out, as recently as march 2017, but there are as yet no commercial GM wheat crops available. This is also the case for barley, however, potatoes and oilseed rape do have commercial GM variants on the global market.

1.4 Ecosystem status

With 72% of UK land area dedicated to agriculture, the effects of agricultural practice, particularly pesticide and fertiliser use, are unsurprisingly very significant. Currently, over 50% of the UK's sensitive rural areas are over the critical threshold for eutrophication and acidification (DEFRA). A major cause of this is agricultural run-off, which is washed off fields, containing fertiliser and pesticide contaminants. In particular, fertiliser elements that enter water bodies during rainfall-events cause severe eutrophication, with 60% of nitrates and 25% of phosphorous being found to have farming origins (Holden et al, 2017). The other impacts that agriculture has had on the UK ecosystem include biodiversity loss, soil degradation and reduced water quality. Tillage has had major impacts of soil quality and erosion in the UK. It disrupts the structure of the soil, reducing water retention and it exposes the organic compounds in the soil leading to higher levels of aeration increasing the rate of decomposition of these compounds, reducing soil organic carbon (FAO, 2014). As a result of static and falling yields in recent years, tillage levels have increased in efforts to boost yields by exposing more organic carbon and nutrients, leading to reduced soil fertility, with an estimated annual cost of £1.2Bn, mainly due to loss in soil organic nutrients (47% of the cost) (Graves et al, 2015).

Chapter 2. Methods

The aim of this thesis is to review the use of GM crops to reduce pests and weeds and the effects of commercialisation of these crops on humans, the environment and global food security. This included yield and income benefits to the farmers and the economy, potential human health benefits and costs and in terms of the environment; chemical pollution, soil degradation This was done through a literature review of peer-reviewed studies and published articles, as well as government based data publications and bodies such as DEFRA, FAO and ONS, considering the benefits and consequences of the GM crops; including reduced ecological footprint and pesticide resistance respectively. Secondly, to consider and determine whether GM crops should be commercially grown in the UK, a survey will be conducted to analyse whether there would be a market for GM products as well as whether the general public would support a change in legislation. The results from the survey will be compared between multiple different demographic groups; including age, sex and education. This will provide a more in-depth understanding of key areas and demographics that are against GM agriculture. By providing up to date information and statistics about the effects of GM crops in comparison to their wild type relatives, it will provide a basis to measure to what extent public opinion might be a barrier to the GM commercialisation. This will be done by analysing the significance of changes in the responses to the same questions; before and after being provided with the information. The survey was developed using Qualtrics and distributed through multiple channels within the University and through social media including The data collected from the survey was analysed and visualised using a combination of programs, including Microsoft Excel, SPSSstatistics and Qualtrics Reports. A number of tests will be carried out, including paired and independent sample T tests, following tests for normality, to determine and identify any significant differences in the data; to be reported. Following the literature review and the survey, an overall conclusion will be drawn as to whether GM commercialisation legislation should be altered, furthermore, to what extent, for example, what GM crop types could be introduced. Also taken into consideration will be the potential valuation of benefits derived from GM crops in terms of unseen economic benefits. This overall conclusion will draw on relevant study on the current status of UK agriculture and food security, also reviewing in comparison, alternatives to GM that could improve food security and reduce the ecological footprint of agriculture.

Chapter 3. Control of insect pests

3.1 Timeline summary

GM crops have a relatively short timeline' being significantly developed in the late 1970s and 80s by a small number of firms, notably including Monsanto; releasing their ‘Roundup' herbicide in 1976. The main component of Roundup being Glyphosate, which has since become very controversial due to its ability to cause a large selection pressure for glyphosate resistance in non-target species. The first GM crop to be developed was GM tobacco in 1983 by scientists. However, the first to enter the market was the ‘Flavr Savr' tomato, which was commercialised in the US in 1994 by Calgene. In the UK in 1997, protests broke out following GM soy imports and since then strict restrictions have remained in place preventing growth and import of almost all GM crops, in both the UK and the EU.

3.2 Control of Insect Pests

There has been a significant rise in demand over the past few decades for effective control of insect pests, both for agricultural productivity and human health. This demand has grown as a result of the increasing resistance in pest populations to traditional insecticides. Since insecticides were introduced in the 1940's, over 400 species of insects and mites were resistant to at least one insecticide by 1983 (Georghiou & Mellon, 1983); further estimated to be over 1000 by 2003 (Miller, 2004). One example of significant insecticide resistance is that of arthropods to Neonicotinoids; the 7 species with over 10 reported cases had a total 495 reported cases between them (Bass et al, 2015). The most prominent of these was B. tabaci, the Cotton Whitefly, which is a major agricultural pest that also transmits multiple plant viruses.

As a result, new, more effective methods have been developed, including but not limited to natural predator release (biocontrol), mating disruption and in the case of GM the spraying of biopesticides (such as Bt) alongside the development of transgenic crops which are resistant to insect pests. As mentioned, one of the most common methods of conferring insect resistance to GM crops is by creating transgenic Bt (Bacillus thuringiensis) crop variants. These transgenic crops produce insecticidal crystal (Cry) proteins such as Cry1Ac endotoxin (Fitt., 2003), derived from B. thuringiensis, which produce spores. These spores are taken up by the insects and then dissolve in the gut, killing the insect within days. This reduces the need for synthetic insecticides, reducing the selection pressure for resistance to develop in the pest population. Bt crops have been increasingly successful when used in combination with other IPM (integrated pest management) plans. For example, it can be successfully combined with biological control; using natural enemies as in the case of Green Aphids (M. persicae) (Tian et al, 2015). These aphids had developed resistance to Cry1Ab and or Cry1C, so would normally lead to the application of insecticides; however, the Bt has no impact on the prey quality of the Aphids so that if their natural predators, Coleomegilla maculate or Eueodes americanus (Tian et al, 2015) were to be introduced, the Aphids would still be a suitable prey, allowing them to feed on and subsequently suppress the population. Another element of these IPM systems is the ‘Refuge Strategy', which is mandated in the US (Tabasknik, 2008). This is designed to delay the development of resistance to Bt proteins in pest populations; alongside using a range of Bt proteins to spread to selection pressure. This strategy involves maintaining ‘refuge' populations of susceptible pests, based on the premise that the few insect pests that develop resistance will mate with an insect from the refuge population, preventing the resistance mutation rapidly spreading through the population. Bt Maize and Bt Cotton are two of the most common types and were grown, with 24.3 million hectares of GM cotton grown globally, the majority in India and the US (10.8 million acres in India, 4.4 million in the US) (Witjaksono et al, 2014).

IR crops have had a significant, positive impact, both on yield and the economic benefits. IR Maize produced an aggregate income benefit to farmers of US$45.9bn between 1996-2015, while over the same time period IR Cotton produced US$50bn in aggregate income benefit (Across the 18 major GM cultivating countries globally; data compiled from; Brookes and Barfoot, 2017; ISAAA Brief, 2016) (See summary table in the Appendix). Using Bt cotton as an example, figure 3A shows the impact on yield (Kg per hectare) for both conventional cotton crops and Bt cotton crops across the 5 major Bt cotton producing countries (Brookes and Barfoot, 2017). It shows that for all 5 countries represented the yield per hectare was greater than conventional cotton crops in the same environments. Further to this, pesticide costs per hectare were also much lower in every country, most noticeably China. This is due to reduced requirement for pesticides, in this case insecticide. This benefits both the environment; preventing damage to biodiversity through damage to non-target species. This demonstrates the superiority of Bt cotton over traditional cotton crops; further support by a study in US corn farms. While investigating the effects of Bt proteins (Cry1A.105 + Cry2Ab2 and just Cry1Ab) on ‘Heliocoverpa zea' a major pest of sweet corn, it was found that in almost every case, the yield and marketability of Bt expressing transgenic crops was significantly greater than conventional counterparts, independent of the frequency of spraying of pesticides on the conventional crops (Shelton et al, 2013). This highlights the benefit of IR crops for reducing pesticide use as well as increasing yield, along with the associated benefits for the environment. Crops that express transgenic Bt toxins greatly reduce pesticide use, resulting in lower selection pressures to develop resistance among pests and have potential for far greater development. Crops expressing two Bt toxins can delay resistance to Bt significantly, so they can be made significantly more effective than conventional farming practices; especially when incorporated with biocontrol.

Chapter 4. Control of weeds

Similar to IR GM crops, herbicide tolerant (HT) crops have produced huge economic benefits to the farmers and countries that cultivate them.

Figure 4 (A, B, C) shows the aggregate income benefit gained from 3 of the largest herbicide tolerant GM crops, between 1996 and 2015 (Brookes and Barfoot, 2017). The countries shown are all included in the top 18 GM growing countries globally. 4a and 4b show the vast gap in economic returns between the US and the other countries commercially cultivating HT Maize and HT cotton. In the US, GM Maize

was studied and exhibited yield between 5.6%-24.6% than the isogenic lines (Pellegrino et al, 2018). These crops also resulted in lower concentrations of mycotoxins, thricotecens and fumonisin. Furthermore, biomass decomposition was faster in these crops, increasing biogeochemical nutrient cycling of nitrogen and carbon, benefitting the soil composition. However, 4C shows a different market dynamic, with HT soybean as a far more competitive market; Argentina and Brazil also being major producers alongside the US. The total income benefits to the growers of these three GM crop types alone was US$52.3bn between 1996-2015 (calculated from dataset; Brookes and Barfoot, 2017) While there were significant yield gains for some of the countries; US maize (24.6%), Filipino Maize (15%), Argentine Cotton (9%), Mexican Cotton (18%) and Bolivian Soybean (15%), the majority of the income benefits were derived from cost savings. Using GM maize as an example, the farmers reduced fixed costs through reduced herbicide applications; on average each crop required 9.8% less herbicide than isogenic, conventional crop lines (Perry et al, 2016). However, the reduction in chemical use is less profound than insecticide use on IR crops.

Glyphosate, the component of Monsanto's original ‘Roundup' herbicide, is the most common herbicide applied to HT crops. Herbicide tolerant GM crops account for 56% of global glyphosate use; 125, 384 tonnes were applied in total in the US in 2014, 113,356 tonnes of which were applied on agricultural land (Benbrook, 2016). Glyphosate is a broad-spectrum herbicide, disrupting the Shikimic acid pathway, which produces proteins vital for plant growth as well as some other microorganisms (NPIC, 2018). Therefore, rather than using a combination of conventional, specific herbicides to target all the different weed pest species, glyphosate is applied across the whole crop on the assumption that it will target and kill all weeds in the crop area while the transgenic crop plants expressing Glyphosate tolerance. However, this is has had serious implications for resistance around the world. Glyphosate resistance has been recorded in 6 continents in 32 species, with at least 15 weed species in the US, where the majority of global glyphosate is applied on GM Maize and Soybean crops (Paraquat information centre, 2018). The main methods of resistance are non-synonymous single mutations of two codons of EPSPS; producing an enzyme resistant to glyphosate, and target-gene duplication following by sequestration of the glyphosate salts by transporter mechanisms (Sammons and Gaines, 2014). This resistance has led to the development of ‘Superweeds', which can completely take over crop space, forcing it to be abandoned. However, due to a lack of alternatives and the dependency of many farmers on glyphosate, the quantity applied by farmers continues to grow (NASS, 2016), despite the concerns.

There are further concerns about potential toxic effects of the residues of glyphosate, namely AMPA; the primary metabolite. When tested by the US department of Agriculture in 2011, it was found that residues over 1.9ppm for glyphosate and 2.3ppm for AMPA were found in 90.3% and 95.7% of Soybean samples respectively (Myers et al, 2016). These residues are becoming more prominent due to ‘harvest aid' (late season) spraying of glyphosate between 1 and 2 weeks before harvest. This is having raised concerns in particular since the WHO reclassified glyphosate as “probably carcinogenic to humans” (IARC,2018). However, this decision has in turn been criticised. Herbicide tolerant GM crops have been very successful for controlling weed populations since its commercialisation, but its efficacy is declining due to increasing resistance in weed population as a result of the lack of diversity and large quantities in which the herbicides are applied.

Chapter 5. Environmental Effects

Many concerns have been raised about the impacts, direct and indirect on the environment, including the effects on chemical residues in soil and water, the spread of resistance and biodiversity. These concerns have been the basis for many countries including the UK not adopting GM technology on a commercial level. Contrary to these concerns, many studies have actually documented the benefits that GM crops confer to the environment. Notably, since commercialisation in 1996, the ecological footprint associated with pesticide use has been reduced 18.6% as a result of overall pesticide application declining by over 6191 million kilograms by 2015 (Brookes and Barfoot, 2017). This reduction was supported by a meta-analysis on the impact of GM crops, which determined the overall pesticide use by GM crops to be 37% lower than for conventional crop types of the same varieties (Klumper et al, 2014). In China, Bt crops resulted in 78,000 tonnes less pesticide in 2001; and this has been a consistent trend across many regions, reducing pest resistance and chemical pollution as well as toxic pesticide poisoning of farmers and anyone else handling high quantities of pesticide (Pray et al, 2002). The use of Bt GM crops in particular are particularly beneficial to human health; found to significantly reduced the incidence of pesticide poisoning (Hossain et al, 2004). In terms, of Biodiversity, GM (Bt) cotton in particular has demonstrated no substantial negative effects on biodiversity and insect abundance; showing no significant changes following cultivation in the Philippines (Yorobe et al, 2006). In some countries these crops have actually had beneficial impacts on insect diversity and abundance, as in Australia and the US, increasing the population abundance of beneficial insects through targeting predators that also act as pests (Carpenter et al, 2002).

However, these benefits are not equally shared or exhibited across all regions and crop types. The effect on the environment depends largely on the strategies used and the type of crop (and associated pesticides), for example whether the genetic modification is herbicide tolerance or insect resistance, and if the modifications are stacked or not. Stacking mutations as part of a ‘pyramid' strategy has a significant effect on delaying resistance spreading to pest populations. In a study comparing the effects of single Bt modifications against two-gene modifications on resistance in P.xylostella larvae, this was measured over 30 generations. The larvae placed on the two-gene plants exhibited no significant resistance at any point during the trial, whereas the mean survival of larvae on the single gene treated plants was over 50% after just 21 generations (Zhao et al, 2005). However, another important observation was that growing both single gene plants and two-gene modified plants concurrently led to an increased rate of resistance of the larvae towards the two-gene crop plants; in this case, after 24 generations, the mean survival of larvae on one replicate of the two-gene plants was over 60%.

A further example of differences between the multiple types of GM crops is the total impact on pesticide use, which varies greatly between crop types. On average, IR crops reduce pesticide use significantly greater than HT crops, highlighted by the difference between HT maize and IR maize. Between 1998 and 2011, herbicide tolerant maize farmers used 1.2% less pesticide, as opposed to IR maze farmers who reduced pesticide use by 11.2% in comparison (Perry et al, 2016). GM crops, both HT and IR based can impact on soil microbial communities, which are vital organisms in nutrient cycling. Although the level of impact has been debated, with evidence being produced that Bt crops have no effect (Griffiths et al, 2005; Naef & Defago, 2006), contrary to this, many studies have also found that Bt crops (including cotton and maize) alter microbial diversity and can reduce density, particularly in AM (Arbuscular Mycorrhizal) Fungi (Blackwood & Buyer, 2004; Lamarche & Hamelin, 2007). Furthermore, glyphosate was found to inhibit nitrogenase activity; limiting nitrogen cycling in the soil and influencing population structure in rhizobium soil communities. Glyphosate is also a strong chelating agent; which locks up organic nutrients, which prevents it from being cycled.

Chapter 6. Toxicity to humans

Pesticides in general are responsible for an estimated 500,000 pesticide poisonings a year, resulting in 5,000 deaths, as reported by the WHO (Phipps & Park, 2002). So, reducing overall pesticide use is beneficial for human health.  There are many misconceptions about the effects of GM crops and produce on human health, largely due to scaremongering and misinformation in the media by writers who do not understand scientific rigour and methodology in testing. In fact, through genetic modification, crops can be made to be more nutritious, which particularly beneficial in the developing world where malnutrition are commonplace. ‘Golden rice' was developed to counteract Vitamin A deficiency in countries where the staple food is rice; vitamin A deficiency is attributed to 2 million childhood deaths annually (Key, Ma & Drake, 2008). They can also be modified to remove allergenic chemicals and compounds produced in the resulting food, making them edible for individuals previously unable to eat them (Bawa & Anilakumar, 2012). While the debate about GM crops and the link to human health is on-going, there have been many studies that glyphosate residues in high doses are implicit in causing kidney damage, liver enlargement and inflammation in mice and rats following administration (Torretta et al, 2018). As previously mentioned, late harvest spraying of glyphosate to increase yield, up to only one week before harvest can lead to increased residues in the final produce, including consumables. However, this is a result of spraying strategies, not a result of GM crops themselves. Other synthetic pesticides not applied to conventional, unmodified crop types are equally toxic to farmers and pesticide handlers when accumulated in high-dose quantities with at least 98 having been identified as endocrine disrupting chemicals in humans (Damalas & Koutroubas, 2016; Ewence et al, 2015). Overall, there has been no confirmed link between GM crops and toxicity to humans; there has been evidence of associated chemical use becoming toxic in certain quantities (i.e glyphotsate) however, the level of toxicity is not significantly greater than that of conventional crop farming (Bawa & Anilakumar, 2012).

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