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Intensification of agriculture and landscapes
Intensification during the European Post-War and modernization of agriculture
Agricultural intensification describes a process in which the inputs are increased in order to obtain higher outputs (Bowler 1986). This means that, while intensifying their practices, farmers use higher amounts of fertilizers, pesticides, fungicides, herbicides, oil fuel (through mechanization), in order to get higher productivity of their work and fields, hence yields. In this part, we are going to explore how and when the agricultural intensification occurred in Europe and France, what concrete changes it had in agricultural practices, and finally, how it impacted on the rural landscapes.
In order to stabilize the global food production agriculture has known its own “Green Revolution” during the 20th century in Western countries. This modernization of agriculture followed the trends of public policies and technological advances.
In France, the modernization of agriculture occurred mainly after the World War II. The aim of its policies was to find a third way between the liberal capitalism of the United States of America and the social revolution of the Soviet Union (Allaire 1988). The aim of the modernization of agriculture was not so much to improve the living standard of the rural populations but to improve the economic situation of the system overall (Daucé 2000). The intensification of agriculture thereby occurred as the industrialization of agriculture, thus its integration in the agri-food industry, which hence meant an autonomy loss for the farmers (Allaire 1988).
More advanced farming education then aimed at teaching the farmers how to enact new techniques, such as the use of chemical fertilizers and pesticides, agronomic practices or genetic improvement (Daucé 2000). This phenomenon was even enhanced since it was funded through the Marshall Plan, which as well accelerated the mechanization of farms.
Then, the agricultural intensification aimed at providing to the French nation the highest amount of food at the lowest price, supported of course by important campaigns of public policies to help its development (Gerbaux and Muller 1984). The number of farmers decreased substantially, being selected through the processes of public policies and the granting of loans (Figure 1a). As the number of farms decreased, their mean size went higher (Figure 1b).
Figure 1. Evolution of (a) number of farms in France and (b) the mean farm utilized agricultural surface in France (source: Agreste, 2016).
The role of the Common Agricultural Policy (CAP) has been important in the modernization of agriculture in European Union (Emmerson et al. 2016). Indeed, the CAP first aimed at increasing the agricultural production in order to stabilize the food supply in the Post-War era, as the Treaty of Rome settled in 1957. Three protectionist mechanisms were then operated to favor the development of European agricultural production, such as the support of price, so that the producers can live from their work, high import tariffs, in order to prioritize domestic producers, and finally encourage export with proper subsidies. This risk-free environment gave agriculture a much higher profitability than before, and secured the farmers into investing in more technologically-advanced equipment and buying or renting new land for enlargement (Bowler 1986).
The intensification of agriculture also resulted in the specialization of farms and agricultural regions (Allaire 1988). Specialization can be defined as the focus of the production of a farm, region or country, towards a little diversity of products, or outputs (Bowler 1986). A specialized farm, where a narrow range of products is made, is the opposite of a diversified farm, where products of different natures are made. On one hand, the use of chemical fertilization freed the cultivators from organic fertilization, which came from livestock manure for the most (Mazoyer and Roudart 2006). On the other hand, the high availability of cheaper food for cattle, such as cereals or protein crops coming from specialized cropping farms, allowed the breeders to feed their cattle without self-sufficiency.
At some point, farmers could not avoid specialization since they concentrated their capital investments in new equipment, which was specialized itself: for example, croppers bought larger tractors and combine harvesters whereas dairy farms got milking machines. Economies of scale then drove farmers to orient their production towards the more profitable activity (Bowler 1986). Agri-food industry then developed according to the comparative advantages of every region. In Europe, this regional specialization can be observed at the country level, e.g. with France and United Kingdom showing focus towards cereal production, and Netherlands and Ireland having increased their dairy production. Specialization is also observed at the regional scales of countries: in France, intensive livestock for meat production has developed in Brittany, while Normandy focused on grass-based dairy production, northern regions are important producers of sugar beet and potatoes, and mountain areas are oriented towards extensive livestock (Bowler 1986). This organization is even more pronounced nowadays, where specialization is organized at a global scale. For example, the protein crops which feed European cattle, such as soybean, are massively imported from the United States of America and South America. This specialization therefore contributed to develop the agri-food industry at the mass consumption era.
Since agriculture now occupies 70 % of Europe’s lands, and 59 % of France (Desriers 2007), it has strong impacts on biodiversity and its practices rule on wildlife (Hails 2002). This impact is now so considerable that it questions the sustainability of farmed ecosystems, hence the sustainability of food production (Stoate et al. 2001).
Despite a few authors already observing and informing about the decline of biodiversity due to the intensification of agriculture (Carson 1962; Dorst 1965), western countries stayed on the path of industrialization, leading the food production towards productivity and competition on global markets. Indeed, clear patterns relate agricultural intensification to the decline of farmland biodiversity since 1950’s Green Revolution (Chamberlain et al. 2000; Robinson and Sutherland 2002; Emmerson et al. 2016). This loss can be linked both to farming practices and landscape simplification (Matson et al. 1997; Stoate et al. 2001; Butler et al. 2007; Stoate et al. 2009).
Intensification of agricultural practices and their impact
Intensification of agriculture happened at the farm and landscape levels (Emmerson et al. 2016). Agricultural practices are highly dependent on the context they are used in. A practice can be optimal in one context though it is only mismanagement in another situation (Strijker 2005). Meeting the needs of high yield varieties requested new management practices (Robertson and Swinton 2005). Therefore, farmers relied increasingly on higher inputs of pesticides, herbicides, fungicides or synthetic fertilizers. The raw productivity of every farm worker has thus been enhanced a hundredfold, since the beginning of 1950’s (Mazoyer and Roudart 2006). The main objective of intensification has been to increase strongly the farming productivity.
Mechanization has been one of the most obvious form of the practice intensification, and was first the replacement of animal power by fossil fuel power in tractors (Mazoyer and Roudart 2006). Then, mechanization took a central place in the farming activities and outdated all other form of work (Binswanger 1986). Newer tractors became more and more powerful: nowadays engines are more than 10 times more powerful those from the 1950’s. Progressively, new farming activities were mechanized, with for example the expansion of the combine harvester. Breeding also knew its mechanization, with the use for example of milking machines. The impact of mechanization on productivity is substantial, since the average area per worker rose from 1 ha before the 1950’s to 200 ha nowadays.
One important step in the intensification in agriculture has been the selection of high yielding varieties. In order to meet the needs of newly selected varieties, the use of chemical or mineral fertilizers appeared more efficient than organic ones. The development of the extraction and the proceeding industry increased dramatically the availability of mineral fertilizers. (Mazoyer and Roudart 2006). The application of mineral fertilizers played a major role in the growth of yields (Strijker 2005). Since the beginning of the twentieth century, the wheat yields have indeed been multiplied by 7, while the nitrogen fertilization has doubled.
The intensification increased the cropping costs by capital amortization, since important amounts is invested in the seeds of selected varieties, in the depreciation of mechanized equipment or in the necessary mineral fertilization. Hence, farmers had to take as little risk as possible and secure the higher yield they can. The preventive and curative sprayings of pesticides, herbicides and fungicides thus become systematic in order to avoid the losses due to insects, weeds or disease.
Tillage
Tillage, as a pre-sowing mechanical weed control, can be considered as an intensive practice only when its depth is around 30 cm. In this case, it shall be named conventional, intensive or traditional tillage, as opposed to more modern tillage, such as the superficial and agronomic ones. Anyhow, it still concerns a high share of cropped lands across Europe, we shall study its effects on biodiversity as an intensive practice.
Tillage has a major impact on soil biodiversity, and cannot be neglected for agroecosystems (Giller et al. 1997; Kladivko 2001; Stoate et al. 2001). Tillage impacts not only on below ground, but also on ground-dwelling arthropod populations. Indeed, carabids can be exposed to predation or desiccation, physically hurt or even buried (Holland and Reynolds 2003). Moreover, the burying of crop residues by tillage reduces the diversity of saprophytic fauna, on which carabids could prey after the harvest (Hatten et al. 2007). It also simplifies the habitat of epigeal fauna, leaving less refuges against predation or abiotic changes. Finally, deeper tillage can induce higher mortality in carabid communities than more superficial tillage (chisel plowing) or no-till at all (Shearin et al. 2007).
Crop fertilization
The application of fertilizers has importantly augmented during the Green Revolution. The input of mineral nitrogen and phosphorus fertilization has multiple ecological effects. The deposition or leaking of fertilizers on the vegetative boundaries of cropped fields benefits the most opportunistic species: the nitrophilous annual weed species (Boatman et al. 1994; Marshall and Moonen 2002). This results in the modification of the plant composition of the edges. Indeed, the more a field is managed intensively, the more it tends to homogenize the plant community in its vicinity towards more weed species (Boutin and Jobin 1998; Willi et al. 2005). Furthermore, a reduction of the botanical diversity of grassy field margins and surroundings leads to a lower diversity in gamma arthropod community (Thomas and Marshall 1999; Bengtsson et al. 2005; Guerrero et al. 2010). Intensive mineral fertilization is also thought to contribute to the decline of butterfly and bee diversity through the reduction of floral diversity (Maes and Dyck 2005; Le Féon et al. 2010).
Pest and weed control
Overall, pesticides have a negative effect on biodiversity. This impact has been found consistently all across Europe (Geiger et al. 2010; Emmerson et al. 2016). Geiger et al. (2010) found persistent declines of diversity among plant species due to herbicides and insecticides, carabid species due to insecticides and bird species due to fungicide applications. In intensively farmed areas, the reduction of botanical diversity due to herbicides has a negative impact on weed eating arthropods diversity (Clough et al. 2007). The danger of neonicotinoids on bees has also been assessed and shown (Goulson 2014; van der Sluijs et al. 2015; Kessler et al. 2015).
Moreover, pesticides can involve contamination at large spatial scales due to the drift of active substances across landscape (Gove et al. 2007; Tuck et al. 2014). This impacts on mobile species such as butterflies, bees and birds, by affecting not only the species, but the whole food web (Donald et al. 2000; Chamberlain et al. 2000; Benton et al. 2002; Emmerson et al. 2016). For example, organic farming with no herbicides conserves or augments the floral diversity which favors bumblebee diversity, even in a intensively farmed landscape context (Rundlöf et al. 2008). If we consider the bird diversity, higher insecticide applications lead to a reduction of the richness and abundance of arthropods in the whole landscape, and thus reduce the food availability of predatory arthropods, such as carabids or spiders, and birds, hence reducing their diversity (Benton et al. 2002; Hallmann et al. 2014). Finally, higher insecticide applications tend to homogenize bird communities towards the dominance of generalist species over specialists (Chiron et al. 2014).
Intensification at landscape scale through simplification
Before heading to the description of a landscape, it is important to start with the notion of landscape. Indeed, while the landscape can be intuitively imagined in everyone’s mind. Turner and Gardner (2015) suggest: “A landscape is an area that is spatially heterogeneous in at least one factor of interest.”
This wide definition deserves to open the definition of the landscape, particularly to the notion of scales, which can of great interest for ecology. Indeed, different taxa have different perceptions of a landscape; hence, what is a landscape for a peculiar taxon, is only a habitat patch for a taxon whose mobility is wider. This definition is more practical related to this thesis than the one of the European Landscape Convention (Déjeant-Pons 2006) : “Landscape means an area, as perceived by people, whose character is the result of the action and interaction of natural and/or human factors.”
We can observe here the common differences between the landscape definitions of the American and European schools of landscape ecology. Although the American school focuses on the natural value of a landscape, i.e. its fundamental biotic and biotic components, the European school is more concerned about the interactions between the ecological and anthropogenic processes. Both perceptions are of interest related to this thesis. Indeed, there is a need of a definition which can fit various scales of ecological interpretations, and another one which can reintegrate the ecological landscape in its anthropogenic use background. This is particularly important for agricultural landscapes.
Landscape heterogeneity: composition and configuration
Landscapes can be defined through two kinds of heterogeneities: compositional and configurational (Fahrig et al. 2011), sometimes more simply brought as composition and configuration (Figure 2). Though Duelli (1997) refers to habitat diversity and heterogeneity, the notions are quite similar. The compositional heterogeneity of a landscape is its number of different land cover types. In agricultural landscapes, it will be reflected by the diversity of crops and non-cropped covers, such as grazed grasslands, hedgerows or woody groves. Compositional heterogeneity can although be weighed by the relative area covered by every of its land cover type, the same way the notion of evenness is applied to biodiversity. It is indeed the kind of ponderation made by the Shannon diversity index with biodiversity, though it is now commonly applied to landscape compositional heterogeneity as well.
Table of contents :
1. Introduction
1.1. Intensification of agriculture and landscapes
1.1.1. Intensification during the European Post-War and modernization of agriculture
1.1.2. Intensification of agricultural practices and their impact
1.1.3. Intensification at landscape scale through simplification
1.1.4. Impacts of landscape simplification on biodiversity
1.2. Beneficial insects in agricultural landscapes
1.2.1. Ecosystem services provided by biodiversity
1.2.2. Landscape, ground-dwelling insects and biological control
1.2.3. Landscape, insects and pollination
1.3. Landscape functional heterogeneity
1.3.1. Limits of the fragmentation model
1.3.2. Landscape functional heterogeneity, an intermediate framework
1.3.3. Implications for biodiversity at local scale
1.3.4. Implications for biodiversity at the landscape scale
1.4. Scope of the thesis
1.4.1. Knowledge gaps
1.4.2. Frame of study
1.4.3. Research question and hypotheses
1.4.4. Thesis plan
2. Material and methods
2.1. Study regions
2.2. Sampling methods and protocol
2.3. Statistical analyses
2.3.1. Biodiversity indicators
2.3.2. Field and landscape parameters
2.3.3. Generalized linear models (GLM)
2.3.4. Mantel correlograms: spatial correlations of carabid assemblages
2.3.5. Species distribution, traits and landscape context: RLQ multivariate analysis
3. Complementarity of grasslands and cereal fields ensures carabid regional diversity in French farmlands
3.1. Introduction
3.2. Material and Methods
3.2.1. Study regions
3.2.2. Site selection and carabid sampling
3.2.3. Data analysis
3.3. Results
3.3.1. Species richness in winter cereal and permanent grassland
3.3.2. Carabid diversity: study region context and field parameters combined effects
3.3.3. Spatial correlation of carabid assemblage in differentiated land covers
3.4. Discussion
3.4.1. Grassland and cereal crop carabid assemblages
3.4.2. Similarities in carabid assemblages between cereal fields and grasslands
3.4.3. Carabid assemblages and regional differences
3.4.4. Complementarity and discrepancy of grassland and cropland in terms of carabid assemblages
3.5. Conclusion
4 Landscape diversity and field border density enhance carabid diversity in adjacent grasslands and cereal fields
4.1 Introduction
4.2 Material and Methods
4.2.1 Study regions and landscape characteristics
4.2.2 Site selection and carabid sampling
4.2.3 Data analysis
4.3 Results
4.3.1 Major landscape and species differences between the three study regions
4.3.2 Gamma species richness, from both land cover types
4.3.3 Permanent grassland and winter cereal crop species richness
4.3.4 Common species richness
4.4 Discussion
4.4.1 Landscape diversity and edge density explain carabid species richness
4.4.2 Landscape parameters impact on carabid richness in grasslands but not in cereal crops
4.4.3 Adjacency between winter crops and grasslands drives common species richness
4.4.4 Landscape radii level explains species richness
4.4.5 Consistency of the landscape effect between study regions
4.4.6 The role of permanent grasslands and landscape diversity for the management of carabid species
4.5 Conclusion
5. Functional traits of carabid assemblages in adjacent grasslands and cereal fields
5.1. Introduction
5.2. Material and Methods
5.2.1. Study regions and landscape characteristics
5.2.2. Site selection and carabid sampling
5.2.3. Data analysis
5.3. Results
5.3.1. Life traits of common and exclusive species to paired cereal fields and grassland
5.3.2. Distribution of life traits between the two land covers
5.3.3. Landscape context influence on life traits
5.4. Discussion
5.4.1. Polyphagous species are more shared by both land covers
5.4.2. Trait occurrence is primarily determined by the land cover type
5.4.3. Landscape isolation endangers grassland specialists
5.5. Conclusion
6. Landscape and field parameters, spiders and pollinators
6.1. Introduction
6.2. Material and methods
6.2.1. Study regions
6.2.2. Site selection and insect sampling
6.2.3. Data analysis
6.3. Results
6.3.1. Spider family richness activity-density
6.3.2. Hoverfly activity-density
6.3.3. Lacewing activity-density
6.4. Discussion
6.4.1. Spider family richness was not determined by landscape parameters
6.4.2. Grasslands enhances the number of spiders
6.4.3. Pollinators density and their landscape context
6.4.4. Limits of the pollinators sampling
6.5. Conclusion
7. General discussion
7.1 Main results and hypotheses validation
7.1.1 Neighboring grassland and cereal carabid communities have species in common
7.1.2 Functional traits of carabids in grasslands and cereal crops
7.1.3 Field and landscape parameters influence on other beneficial arthropods
7.2 Managing the landscapes for beneficial diversity conservation
7.2.1 A mosaic of grasslands for enhanced potential biological control
7.2.2 Taking natural enemies’ dispersal ability into account
7.2.3 Small-scale and diversified farming as an opportunity for enhancing biological control .
7.2.4 Complementary landscape solutions
7.3 Higher biodiversity may favor potential biological control
7.3.1 Complementarity of natural enemies as an asset for biological control
7.3.2 Higher diversity involves higher resilience of the enemy community
7.3.3 Limits to enhancing natural enemy diversity
7.4 Operational recommendations, tools and public policy
7.4.1 Public policies of landscape management
7.4.2 At the farmers’ level
7.4.3 Applied recommendations for our study regions
7.4.4 Agricultural landscapes as a Common
7.5 Limits of the thesis
7.5.1 Some issues regarding our data collection and sampling
7.5.2 Differences between study regions
7.5.3 Landscape-practices interactions towards biodiversity
8. Conclusion
References
Appendices
