Paper prepared for presentation at the Second International Conference on Coexistence between Genetically Modified (GM) and non-GM based Agricultural Supply Chains (GMCC) Montpellier (France), 14th and 15th November 2005Genetic engineering, GMO, Maize, Co-existence, Agricultural and Food Policy, L51, O32,

Angevin, F.

Gomez-Barbero, Manuel

Menrad, Klaus

Messean, A.

Reitmeier, Daniela

Rodriguez-Cerezo, Emilio

English

Research Papers in Economics

1 
 
 
ECONOMIC EFFECTS OF CO-EXISTENCE MEASURES 
IN MAIZE CROP AND SEED PRODUCTION – A CASE 
STUDY OF FRANCE 
 
 
 
D. Reitmeier
1, K. Menrad
1, M. Gómez-Barbero², F. Angevin³, 
A. Messéan³, E. Rodriguez-Cerezo² 
 
 
k.menrad@wz-straubing.de 
 
 
 
 
1 Chair of Marketing and Management of Biogenic Resources, Straubing Center of 
Science, University of Applied Sciences Weihenstephan, Straubing, Germany 
 
² European Commission-DG JRC, Institute for Prospective Technological Studies, 
Seville, Spain 
 
³ National Institute for Agronomic Research (INRA), INRA Grignon, Laboratory Eco-
Innov, Thiverval Grignon, France 
 
 
 
 
 
 
 
 
Paper prepared for presentation at the Second International Conference on 
Coexistence between Genetically Modified (GM) and non-GM based 
Agricultural Supply Chains (GMCC) 
Montpellier (France), 14
th and 15
th November 2005 
 
 
 
 
 
 
 
 
Copyright 2005 by authors. All rights reserved. Readers may make verbatim copies of this 
document for non-commercial purposes by any means, provided that this copyright notice 
appears on all such copies.  2 
Economic effects of co-existence measures in maize crop and seed 
production – A case study of France 
 
D.Reitmeier
1, K. Menrad
2, M. Gómez-Barbero
3, F. Angevin
4, A. Messéan
5 and E. Rodríguez-
Cerezo
6 * 
 
(1) University of Applied Sciences of Weihenstephan, Science Centre Straubing, Schulgasse 
16, 94315 Straubing, daniela.reitmeier@fh-weihenstephan.de 
(2) University of Applied Sciences of Weihenstephan, Science Centre Straubing, Schulgasse 
16, 94315 Straubing, klaus.menrad@fh-weihenstephan.de 
(3) European Commission-DG JRC. Institute for Prospective Technological Studies. Inca 
Garcilaso s/n, 41092 Seville. Manuel.gomez@cec.eu.int 
(4) National Institute for Agronomic Research (INRA), INRA Grignon, Laboratory Eco-
Innov, BP 01, 78 850 Thiverval Grignon, Frederique.Angevin@jouy.inra.fr 
(5) National Institute for Agronomic Research (INRA), INRA Grignon, Laboratory Eco-
Innov, BP 01, 78 850 Thiverval Grignon, messean@grignon.inra.fr 
(6) European Commission-DG JRC. Institute for Prospective Technological Studies. Inca 
Garcilaso s/n, 41092 Seville. emilio.rodriguez-cerezo@cec.eu.int  
 
Abstract 
 
The paper analyses the economic effects of specific co-existence measures (like e. g. 
increasing isolation distances between GM and non-GM plants, changing flowering time 
between varieties, non-GM buffer zones) in maize crop and seed production in selected 
regions in France. The results are based on simulations of agronomic measures and 
corresponding cost calculations for specific measures and landscape simulations. In maize 
grain production levels of adventitious presence below 0.9% can be achieved without any co-
operation between farmers in neighbouring clusters. In case fields are located in the same 
cluster, additional measures have to be taken with very differing cost effects depending on the 
specific characteristic of the measure. Additional measures should also be taken (either by the 
seed company or by the commercial GM grower) for ensuring co-existence between 
commercial GM fields and non-GM seed production clusters, while current practices would 
be sufficient for ensuring co-existence between GM and non-GM maize seed production plots 
for a threshold of 0.5% adventitious presence.  
 
Introduction 
Since April 2004, the EU system to trace and label GMOs and to label products derived from 
GMOs has been put in place. The regulations set a threshold no higher than 0.9% for the 
                                                 
* The views expressed in this paper are those of the authors and do not necessarily correspond 
to those of their respective institutions. 
 3 
adventitious presence of GM material in non-GM products (Regulation (EC) 2003/1829). In 
July 2003 the European Commission (DG Agriculture) released Commission 
Recommendation 2003/556/EC on general co-existence guidelines and asked member states 
to set up national strategies and best practices to ensure the co-existence of GM crops with 
conventional and organic farming. In the specific case of seed production, the European 
Commission decided to regulate the adventitious presence of GM seeds in conventional seeds 
under Directive 2001/18/EC rather than in a specific directive on the marketing of seeds. 
Several studies analysed the possibilities of co-existence schemes and its economic effects on 
maize production in Europe (e. g. Bock et al. 2002, Tolstrup et al. 2003). However, a lot of 
questions could not be clarified in these studies in particular with respect to production of 
certified maize seeds. Therefore thresholds for the adventitious presence of GM seeds in 
conventional seeds are still under discussion in the EU. This paper contributes case study 
analyses on co-existence measures and its economic effects in GM maize crop and seed 
production in France.  
 
Methodology 
Based on agronomic considerations geographical areas have been identified in European 
Member States which were most likely to adopt GM maize. The sources of adventitious GM 
presence in conventional maize, the levels of admixture estimated with current and additional 
farming practices and the economic effects of adapting farming practices for maize crop and 
seed production in France were analysed within the project. Different levels of initial seed 
purity were considered in order to estimate their effect on the final level of adventitious 
presence using a model of gene flow namely MAPOD®. Simulations were carried out on 
landscapes representative of two French regions: the département
1 of “Pyrénées-Atlantiques” 
in south-west France for seed production and the “Poitou-Charentes” region in western France 
for crop production. Two scenarios were built for the presence of GMOs in the landscape 
(10% and 50% share of GMOs in the relevant crop), three agricultural production systems 
(GMO-based, conventional and organic) as well as different thresholds for adventitious GM 
presence: 0.1% and 0.9% for crop production and 0.1%, 0.3% and 0.5% for seed production. 
In a first step the economic performance of the different crops is investigated by reviewing 
literature, collecting publicly available statistical information and searching databases, as well 
as contacting and interviewing experts. The costs of co-existence measures for the different 
crops, farm types and regions as suggested as outcome of agronomic analyses are calculated 
in a second step using publicly available data sources of costs of agronomic practices. When 
calculating the costs of co-existence measures labour costs as well as opportunity costs of an 
alternative use have been taken into account. If necessary, available data are modified 
according to the situation in the defined farm type and region. In order to check these 
modifications additional experts have been consulted in rarely cases.  
 
                                                 
1 French administrative district. 
 4 
Measures 
Simulations with MAPOD® were carried out to evaluate the impact of current practices as 
well as the feasibility of alternative practices. Different strategies were tested (figure 1): 
Spatial isolation: Farmers in the region studied had to maintain an isolation distance between 
GM and non-GM crops. Increasing isolation distances is an effective way of decreasing 
adventitious presence by cross-pollination.  
Time isolation: Separating flowering times is another option proposed to maize seed 
producers in France (GNIS
2, 2003). This can be achieved by providing a choice of varieties, 
some flowering earlier than others. 
Non-GM buffer zone: Sowing an area of non-GM maize all around the GM field could be an 
interesting strategy for limiting or diluting gene flow from the GM field to the non-GM field. 
Farmers can consider this area as a refuge, limiting the development of resistance (e. g. in 
case of insect-resistant maize). 
Discard width: The discard width of a non-GM field is an area of variable size around the 
edge of the field. The use of discard widths involves separately harvesting the margins and the 
central part of the field.  
Plant extra male rows: Current legal isolation distances for certified seed production for 
France are 300 meter (seed cluster < 10 ha) respectively 200 meter (seed cluster ≥ 10 ha). In 
recent years, it has become possible to reduce isolation distances by planting extra male fertile 
rows around seed production plots. These extra male rows act as “protection” for female 
plants by making foreign pollen less competitive.  
 
Figure 1: Illustration of different measures to avoid cross pollination in maize crop production 
 
 
 
Preliminary results 
 
Economic effects in maize crop production 
France is the leading maize producer in Europe (EUR 15). The Poitou-Charentes region has 
been chosen for a case study for maize crop production since it represents the third largest 
grain maize producing region and accounts for about 11% of the area under maize in France. 
                                                 
2 GNIS: Groupement National Interprofessionnel des Semences (National interprofessional association for seeds and plants). 
Non-GM 
width 
Discard 
width 
Non-GM crop: 
 
  Area 
 
  Earliness of 
flowering 
Wind 
Isolation 
distance 
Spatial layout of the field 
with respect to wind 
direction 
GM crop 5 
Furthermore, GM maize varieties are an alternative for farmers with problems controlling 
weeds and European or Mediterranean corn borer infestations. Variable production costs of 
687 €/ha and an income of 950 €/ha form the baseline for the calculation of costs of co-
existence measures in maize crop production in France resulting in a gross margin of 743 €/ha 
in the year 2004 if compensation payments were taken into consideration (Theyssier, 2004). 
Since the costs of several co-existence measures differ depending on the potential economic 
performance of the cultivated GM maize (for that no empirically sound data are available for 
France so far) it is assumed in a first case that GM maize has the same gross margin as non-
GM maize, while an economic advantage of GM maize compared to non-GM varieties is 
considered in a second case. 
There are very low opportunity costs of increasing isolation distances in maize crop 
production due to the small differences in the gross margins of alternative crops whereas the 
changing of flowering times causes substantial income losses for farmers active in maize crop 
production. The opportunity costs of discard widths on the non-GM field (which is separately 
harvested) significantly differ depending on the width of the discard width as well as the size 
of the non-GM field. High differences in the per-hectare costs can also be observed for non-
GM buffer zones around GM fields mainly depending on the GM adoption rate in a region 
and the estimated economic performance of GM maize. 
The economic effects of non-GM buffer zones were analyzed in a landscape with GM maize 
production (Figure 2). Based on the simulations of the level of adventitious presence of GM 
pollen in different fields, big variations can be observed in the additional costs of non-GM 
buffer zones, depending on the sizes of the GM fields, the width of the buffer zones as well as 
the underlying assumptions concerning the economic performance of GM maize in France. 
Significant cost savings can be achieved if the fields producing GM crops are clustered in the 
region, in particular if small-sized GM fields are concerned.  
 
Figure 2: Example of field pattern used for the landscape scale study: 10 % GM maize 
adoption 
1 2 
3 
4 
5  6 
7 
8 
9 
10 
11 12 
14 
13 
15 
16 
17 
18 
19 
20 
21 
22
24
25
26 
27
28 
29 
30 
23
 
 
Economic effects in maize seed production 
Maize seed production in Europe covered 126,311 ha in 2003 with France being the leading 
seed producer in Europe (49,822 ha). In France 50% of seed production is concentrated in the 6 
south-west region and two “départements” (Landes and Pyrénées-Atlantiques) account for 
25% of the national production
3. To estimate the economic effects of the co-existence 
measures suggested, it was assumed that a yield of 3.5 t of maize seed per hectare generates a 
total income of €3 365/ha from maize seed production in France (Hugger, 2004). Taking into 
account variable production costs of €2 177/ha and additional compensation payments, a 
gross margin of €1 488/ha (representing the situation in 2003 and 2004) was taken as the 
baseline for the cost calculations for maize seed production (Hugger, 2004). The economic 
effects of increasing isolation distances were calculated for a kind of worst-case scenario in 
which the farmer producing GM maize seed has to reduce his seed producing area and plant 
the most economic crop (i.e. wheat) as an alternative. This results in very substantial gross 
margin losses in particular if additional isolation distances exceeding 150 m are concerned. 
Substantial opportunity costs also have to be added if 18 additional male rows have to be 
cultivated in order to reach a defined threshold of GM adventitious presence. Changing the 
flowering time of the seed maize varieties cultivated also has negative effects on yield which 
are quite substantial in the case of switching from very late to late varieties (30°days). The 
income losses are significantly lower if the flowering time is switched from late to mid-early 
varieties. 
In a final step the economic effects are calculated for combinations of different measures in 
case that GM and non-GM seeds are produced in a region. The lowest per-hectare costs of 
such combinations of measures necessary to meet a defined threshold differ considerably, 
depending on the sizes of neighbouring non-GM seed production plots. In order to meet a 
threshold of 0.5% in maize seed production, substantial opportunity costs has to be assumed 
in the case of non-GM seed plots of 0.5 ha, while this threshold can be met without any 
additional costs in the case of 5 ha non-GM seed plots. The same picture emerges if a 0.3% 
threshold has to be met. The opportunity costs of additional measures to meet a 0.1% 
threshold add up to a substantial proportion of the gross margin even in the “best case” 5 ha 
non-GM seed plots.  
 
Conclusions 
The feasibility of co-existence between GM and non-GM grain maize production should be 
evaluated on a case-by-case basis. In case GM and non-GM fields are located in separate 
clusters, levels of adventitious presence below 0.9% can be achieved without any co-
operation between farmers in neighbouring clusters, whatever the proportion of GM maize in 
the landscape, be it 10% or 50%. If GM and non-GM maize are to co-exist in the same field 
cluster, various additional measures (including isolation distances, non-GM buffer zones, 
time-lag, etc.) could make it possible to attain adventitious presence rates below 0.9%. Those 
strategies could imply co-operation between farmers in the same cluster (e.g. time-lag 
strategies). The additional costs of co-existence measures (e.g. non-GM buffer zones), when 
needed, vary substantially depending on the specific characteristics of the measure (e.g. width 
                                                 
3 Source: Courtesy of GNIS. 7 
of the buffer zone), the relative sizes of GM and non-GM fields, and differences in market 
prices of GM and non-GM maize. Consequently, the level of additional costs can only be 
estimated case by case. 
Maize seed is already produced under contracts between seed companies and farmers and is 
organized by clusters of fields dedicated to seed production. .Ensuring co-existence between 
GM and non-GM maize seed production plots within a seed production cluster (seed-seed co-
existence) should be relatively easy for a threshold of 0.5%, as current practices would be 
sufficient. For a 0.3% threshold, additional measures would have to be taken, either allocating 
GM and non-GM seed plots with the right orientation (with respect to wind direction) or 
increasing isolation distance. However, this measure could lead to significant gross margin 
losses for farmers and seed companies. Ensuring co-existence between commercial GM fields 
and non-GM seed production clusters (seed-crop co-existence) is a real issue. At least for 
some of the plots within clusters (the peripheral ones), additional measures should be taken, 
either by the seed company or by the commercial GM grower. 
 
References 
Bock, A.-K.; Lheureux, K.; Libeau-Dulos, M. et al. (2002): Scenarios for co-existence of 
genetically modified, conventional and organic crops in European agriculture. Report EUR 
20394EN, Seville  
European Commission, 2003. Commission Recommendation of 23 July 2003 on guidelines 
for the development of national strategies and best practices to ensure the coexistence of 
genetically modified crops with conventional and organic farming, 2003/556/EC (notified 
under document number C(2003) 2624), Official Journal of the European Union, 29/07/2003, 
vol. 46, L189, pp 36-47. 
GNIS, 2003. Règlements techniques de la production, du contrôle et de la certification des 
semences. Tome 1: Semences de grandes cultures certifiées, commerciales, mélanges. (pp 83-
104). 
Hugger, H. (2004): Personal communication on economics of maize seed production in south 
west Germany. Regional Commission/Council of Fribourg, August 2004 
Teyssier, D. (2004): Index des prix et des normes agricoles 2004-2005, 20e édition, Paris, 
2004 
Tolstrup, K.; Andersen, S. B.; Boelt, B. et al. (2003): Report from the Danish working group 
on the co-existence of genetically modified crops with conventional and organic crops. DIAS 
report Plant production No. 94. Tjele, Denmark 
 

Personal communication on economics of maize seed production in south west Germany. Regional Commission/Council of Fribourg,

Règlements techniques de la production, du contrôle et de la certification des semences. Tome 1: Semences de grandes cultures certifiées, commerciales, mélanges.

Scenarios for co-existence of genetically modified, conventional and organic crops in European agriculture. Report EUR 20394EN, Seville European Commission,

ECONOMIC EFFECTS OF CO-EXISTENCE MEASURES IN MAIZE CROP AND SEED PRODUCTION - A CASE STUDY OF FRANCE

ECONOMIC EFFECTS OF CO-EXISTENCE MEASURES IN MAIZE CROP AND SEED PRODUCTION - A CASE STUDY OF FRANCE

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