Experiences with GM crops to date

René Custers, PRRI, VIB, Belgium, and John Komen, Program for Biosafety Systems, The Netherlands

1. Introduction

The introduction of GM crops has led to one of the fastest, if not the fastest adoption of an agricultural innovation. The first GM crop – tomato with a delayed fruit ripening trait – was cultivated on a modest scale starting in 1994. In general however it is said that the large scale cultivation of GM crops started in 1996 with the introduction of herbicide tolerant soybean, better known as “Roundup Ready” soybean. From 1996 onward the cultivation of GM crops has shown a yearly double digit increase. The data from 2011 (figure 1 below) present a worldwide GM crop cultivation area of  160 million hectares, dispersed over 29 countries, and involving around 17 million farmers. As can be seen in figure 1, the largest area of GM crop production takes place in North America (USA, Canada) and South America (Argentina, Brazil), and India. Six EU countries planted a record 114,490 hectares of biotech Bt maize, up 26% from 2010, and an additional two countries planted the biotech potato “Amflora” that has modified starch content suitable for industrial purposes.

The present chapter summarizes a range of impact studies and specific case studies that have analyzed the environmental, economic and productivity impact of GM crops.

Figure 1. Biotech Crop Countries, 2011


Source:  James, 2011. ISAAA Brief No.43.


2. Recent adoptions

Whereas the first adoptions have been technology provider- and farmer driven, it is interesting to look at some of the more recent large scale introductions of GM crops. A first example is the introduction of GM herbicide tolerant sugarbeet in theUSA. The technology was already available many years ago, but the first large scale introduction in theUSAonly started in 2008. The reason for this was that the sugar industry was hesitant at first. Discussions with different stakeholders in the food and feed chains led to an agreement on the introduction of the technology. So not only technology providers and farmers were involved, but the whole of the sugar production chain. The adoption rate in the first year in the USAwas 56% and in 2009 already 95% of the sugarbeets grown in the USA were GM. This is the historically fastest adoption of GM ever (Wilson, 2009). The reason for this fast adoption is that weed control is the most important issue in sugar beet cultivation. The Roundup Ready system provides a convenient solution. Although several court cases in 2010 challenged the deregulation of GM sugarbeet in the USA, the safety of its production and resulting products were confirmed and cultivation continues at very high adoption rates. In a recent review  (Park et al., 2011) the authors estimated the potential ecconomic gain to EU farmers by growing GM herbicide-tolerant sugarbeet could be between € 73-219 million / year.

In Africa, recent adoptions involve GM insect-tolerant maize in Egypt and insect-resistant cotton in Burkina Faso. In Burkina Faso the introduction of GM crops has been government driven, as the main stakeholder in cotton production and exports. It was decided that the introduction of GM insect resistant cotton would be beneficial to the country. Three million people inBurkina Fasorely for a substantial part of their income on cotton by working for the cotton industry directly or indirectly. Moreover, insects were beginning to develop resistance to chemical insecticides.  After clearing the GM insect resistant cotton for marketing, Burkina Faso from 2008 started to grow Bt cotton for seed multiplication and initial commercialization, at around 8,500 hectares. In only a few growing seasons, adoption of GM cotton rapidly increased to around 300,000 hectares (James, 2011) or 80% of total cultivated area for cotton.

3. Impacts of GM crops in general

3.1. GM herbicide tolerant crops

In 2008, herbicide tolerance was deployed already on 63% of the worldwide GM acreage. Over the years this has led to a major shift in the use of herbicides in soybean, maize, oilseed rape and cotton. Conventional mixtures of herbicides (different herbicides used at different moments of crop cultivation, i.e., pre-emergence and post-emergence, or tank mixed herbicides) were replaced by herbicides with the active ingredient glyphosate (the active ingredient in Roundup). Glyphosate-containing herbicides are generally sprayed twice post-emergence. This major shift has led to a decline in the amount of herbicides used, but the most important impact is caused by a move to the usage of less harmful glyphosate-based herbicides, which has resulted in a decreased environmental impact (Kleter et al., 2007). These crops however do not change the way large-scale industrial agriculture is being performed, as it remains dependent on the use of herbicides.

The major impact of herbicide-tolerant crops is on farm management. Herbicide-tolerant crops in general make weed control much easier, and has enabled farmers to spend less time on it. Timing of the application becomes much less important. A major benefit of herbicide tolerant crops therefore is their agronomic convenience.

The second important impact of herbicide-tolerant crops is that it has encouraged the use of the so-called “no-till” systems of agriculture (for instance in soybean cultivation in the USA and in oilseed rape cultivation in Australia). This type of agriculture leaves the crop residues on the field after the harvest and does not plough them under in Winter. This leads to benefits in terms of decreased soil run-off and less erosion, better retention of moisture, a much better carbon sequestration, decreased use of machinery and fuel, and has led to an increase of the humus content of the soil, which is positive for soil fertility. In the subsequent growing season, the next crop is simply sown between the remains of the former crop, without any prior soil treatment. Calculations have been done to show the positive impact of this strategy in terms of the reduction of greenhouse gas emissions (Brookes and Barfoot, 2009). Their analysis points to a reduction of a total of 17.7 billion kg in carbon emissions (the equivalent to taking 7.8 million cars from the roads for 1 year), resulting from the introduction of GM crops since 1996.

Impacts on income

Herbicide-tolerant crops mean lower expenditures on herbicides, labor, machinery and fuel, but require a higher expenditure for the seeds. In the USA this has not led to any significant gains at the farm level. In South America gross margin gains are about $20 per hectare, resulting from lower GM seed fees than in the USA (Qaim, 2009).

Impacts on productivity

Herbicide-tolerant crops as such are not expected to result in a large yield increase. This would only be the case where weeds provide such a competition that the growth of the crop is hindered, or where the conventional herbicides have a negative growth effect on the crop. For Roundup Ready soybeans some have reported a negative yield effect in the initial years. This would then have been caused by a yield drag, and the fact that the genetic background of the RR soybeans was somewhat inferior to the best performing conventional varieties at that time. Over the years further breeding with the GM soybeans will have resulted in bridging any gap with the conventional varieties. More recently Roundup Ready II soybeans have been introduced. In comparison to Roundup Ready I soybeans the RR II soybeans are said to have a 5% better yield, while the trait itself is the same. The main conclusion is that for herbicide tolerance it is not as much the trait itself that determines yield, it is the superiority of the genetic background of the variety that matters most.

Emergence of herbicide tolerant weeds

In the USA, but also in Argentina, the widespread, continuous use of glyphosate-based herbicides has in certain areas led to the emergence of herbicide-tolerant weeds. In the USA glyphosate-resistant Palmer amaranth (pigweed) is a well known example (Benbrook, 2009). The emergence of herbicide-tolerant weeds is problematic and is the result of the absence of a good resistance management strategy from the very start. Common sense had predicted that the continuous use of the same herbicide on the same land, in the first place leads to a shift in weed populations (towards weeds with a limited leaf surface), and secondly to the emergence of resistant weeds. The emergence of these resistant weeds has led in some places to the additional application of additional, more harmful herbicides, either in a pre-emergence application, or in a tank mix with glyphosate. The environmental benefits of the glyphosate-tolerant crops are then significantly reduced.

The situation in the USA contrasts with the manner in which herbicide-tolerant oilseed rape is being introduced in Australia. There, herbicide resistance management has been a major priority in the introduction of glyphosate-tolerant oilseed rape. One component of the management strategy is that the GM oilseed rape is used in a crop rotation system where it only is grown on a certain piece of land once every 3 or 4 years (Weidemann, 2009).

This shows that it is not the GM technology itself that is either good or bad, but rather it is the way in which GM crops are applied in practice that will determine their contribution to sustainability, as with all agricultural advances.

3.2. GM insect resistant crops

Insect pests can cause serious crop damage. In Spain, for example, the European corn borer can cause up to 15% yield loss in maize in years with high insect infestation (Esteban Rodrigo, 2009). In cotton there is a range of insect pests of which the cotton bollworm is the most important. Traditionally, high amounts of insecticides are used in cotton to control the insect pests. In conventional maize, insecticide use is limited because it is very difficult to hit the insects, as they are hidden inside the plant.

The introduction of GM insect-tolerant varieties of maize and cotton has led to a serious decrease in the amount of insecticides used, especially in cotton. This has a beneficial environmental impact, but also a beneficial impact on farmer health risk, especially in less developed countries, where crops are often sprayed manually and farmers are not well protected against exposure to insecticides. In India and other countries this has seen the decline of insecticides in the category of the most hazardous substances (Qaim, 2009).

This introduction has also resulted in a higher harvest security. Farmers want to be sure that they will have a reasonable harvest. Buying insect-resistant crops in areas where there may be insect infestation is a form of crop insurance. In areas with insect infestation, yields have substantially increased. In areas where large amounts of insect tolerant crops have been grown over the years, overall insect pressure has decreased resulting in important benefits to conventional and organic agriculture. Thus, even non-adopters benefit from the use of these crops (see, for example, Kong-Ming et al, 2008).

The result is that farmer incomes have increased, despite the fact that the GM seeds are more expensive than the non-GM varieties.

In maize the introduction of insect tolerance has led to a decline in the presence of some carcinogenic mycotoxins. Mycotoxins are produced by fungi that may grow on the stems and cobs. Insect infestation leads to damage to these plant parts, forming perfect spots for fungi to start growing and start producing their toxins. The insect-tolerant maize has less insect damage resulting in less fungal infestation, resulting in less mycotoxin, especially the mycotoxins fumonisin (FUM), moniliformin (MON) and deoxynivalenol (DON). In field trials in Germany, GM insect-tolerant maize contained about 3-4 times less of these mycotoxins than conventional maize. The mycotoxins are not only hazardous to humans and animals that consume the maize, they are also toxic to micro-organisms used to produce bio-ethanol from maize, making the production process less efficient.

4. Other impacts of GM technology in crops

Impact on seed prices

GM seed prices are higher than for conventional seeds and the price difference is referred to as the technology fee. This technology fee can differ greatly from region to region, depending on the starting price of conventional seeds, and whether or not crops can be patented. The biotech seed companies in general calculate their technology fees such that farmers still reap a significant part of the economic benefits of the GM crops. But there are some concerns about developments in the GM seed prices. In some areas and for some crops the GM adoption rate is so high, the number of technology providers so low, and conventional, suitable alternatives becoming so rare, that farmers fear that GM seed prices can be set at any rate.


GM technology is responsible for extra costs in the development of crops. It comes on top of the costs for conventional breeding, as GM elite lines, once created, also become part of large conventional breeding schemes to produce the necessary varieties. Besides this, the GM regulatory requirements have led to additional registration costs. In Europe the average costs for generating the data for a marketing dossier and the costs attached to the dossier itself amount to € 6.8 million per dossier (Schenkelaars, 2008). This makes it difficult for small- and medium-sized companies and public organisations to become active in the development and marketing of GM crops. The current worldwide market situation reflects this. There are only very few GM crop technology providers, with one – Monsanto – being very dominant, and only very few publicly developed GM crops that have entered the market. There is a need for a broader base of technology providers, promoting greater diversity and competition; however, this is not helped by the current regulatory framework.

5. Impact case studies

5.1. Insect-tolerant maize in Spain

Spain is the main European country growing a GM crop. In 2011, Spanish farmers cultivated almost 98,000 ha of GM insect-tolerant MON810 maize. Today there are about 124 different MON810 varieties registered on the Spanish variety list, stemming from about 11 different companies (Esteban Rodrigo, 2009). Since its development and regulatory approval, the MON810 event has entered into different breeding programmes in different companies, all developing their own hybrid varieties. Each of these varieties if cultivated in the EU, will be treated as GM crops and will have to comply with the appropriate GM directives and regulatory conditions imposed.

Spanish data from 2002 to 2004 show that the MON810 varieties gave a positive yield effect in areas of insect infestation. The higher the insect pressure, the higher the positive yield difference compared with conventional maize. In regions with high insect infestation the positive yield difference was about 12% (Gómez-Barbero et al, 2008).  The adoption rate of MON810 varieties in Spain also nicely correlates with the pest pressure. The higher the pest pressure in the region, the higher the adoption rate of GM maize. This shows that farmers behave rationally and only grow GM maize when there is a high likelyhood of a benefit.

The GM insect-resistant maize in Spain is all used for animal feed, and there is no price differential between the sale price of GM and non-GM maize crops. Calculations based on data from 2002 to 2004 in Spain showed that for the farmers there was an economic benefit of growing the GM insect-resistant maize ranging from € 3 to 135 per ha (Gómez-Barbero et al, 2008). The cumulative impact on farm income in Spain until 2007 was about € 50 milion (Esteban Rodrigo, 2009).

In areas with lower insect infestation, the higher seed price is compensated for by decreased use of insecticides. This reduction in insecticide use is a positive environmental impact of the cultivation of this maize. Conventional maize growers applied on average 0.86 sprayings of insecticide per year, whereas full adopters of GM insect resistant maize applied on average 0.32 sprayings of insecticide per year (Gómez-Barbero et al, 2008).

5.2. Virus resistant papaya on Hawaii

In the 1950s papaya production on Hawaii relocated from Oahu Island to Hawaii Island as a result of a devastating infestation with papaya ringspot potyvirus (PRSV). The Puna district onHawaii Islandthen grew papaya succesfully for many years, until in 1992 the first infestations with PRSV were also detected here. By the end of 1994 about half of the plantations were infected and growers were going out of business. In parallel researchers were developing GM virus-resistant papaya. A first field trial was held onOahoIslandin 1992. The GM crop proved to be very resistant and one line was further developed for marketing. Regulatory approval was obtained in 1997 and the first GM seeds were distributed to papaya growers in May 1998.

Today, papaya production in the Puna district is flourishing. About 80% of the papaya crop is GM, while the rest is conventional. They are growing next to each other, separated only by a few meters. Because of the planting of the resistant GM variety the overall virus pressure has seriously declined, enabling the remaining conventional papaya to survive without problems.

After 10 years of large-scale continuous cultivation of the GM papaya, the resistance to PRSV is still retained.  Recently, the government of Japan approved the GM papaya for consumption, which represents a critical export market for Hawaii.

5.3. GM Insect resistant cotton in India

India has about 6.3 million cotton farmers, with a very small average holding size of about 1.5 ha.India holds 25% of the global cotton area, but its contribution to the world cotton production was way below 25% because of low yields compared to other parts of the world (Ramachandra Kaundinya Vinnakota, 2009).

Insect infestation was one of the major problems in cotton production. Lepidopteran insects like American bollworm, army worm, pink bollworm and spotted bollworm caused serious problems. Farmers on average used 6-10 sprays per growing season to control insect pests. The amount of insecticides used on cotton represented 42% ofIndia’s total agricultural insecticide use.

GM insect-resistant, Bt cotton was introduced in 2002. Since 2002 five different lines of Bt cotton have been authorized inIndia, some of which are developed by public institutions. The adoption of Bt cotton has rapidly picked up over the years. Already in 2008 about 80% of the cotton area was planted with GM varieties. The introduction of GM has resulted in a steep yield increase. According to India’s Ministry of Textiles, whereas in the 1990s the average yield was about 300 kg/ha, now the average yield is more than 550 kg/ha. Since 2005 India has become a net exporter of cotton, exporting now about 8 million bales of cotton annually.

In the first years of adoption in India there was still a large variability in the Bt cotton yields. This was due to the fact that the Bt gene was incorporated only in a few cotton varieties that were not suitable for all locations (Qaim, 2009). In some locations this led to dramatic situations for individual farmers that had invested in expensive seed, but had no return in the form of a higher yield. This is also why inIndiamuch attention has been paid to the Bt cotton seed price. When seed price is too high, the technology is not within reach of many small holder farmers. In the first years of Bt cotton adoption the seed price of this cotton was very high, more than 3 times the price of non-Bt cotton seed at that time (Ramachandra Kaundinya Vinnakota, 2009). In later years – from 2005 onwards – many Indian states have established a maximum  price for Bt cotton seed, at about 1.5 (for “Bollgard I” and other Bt seeds) to 2 times (for “Bollgard II” seeds) the price for non-Bt seeds. Looking at the rate of adoption since 2005 and the increase in yields, this has had a very positive effect.



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