Effects Of Agricultural Intensification Research Articles

Effects of Agricultural Intensification on Mediterranean Diets: A Narrative Review.

Mediterranean diets (MedDiets) are linked to substantial health benefits. However, there is also growing evidence that the intensification of food production over the last 60 years has resulted in nutritionally relevant changes in the composition of foods that may augment the health benefits of MedDiets. To synthesize, summarize, and critically evaluate the currently available evidence for changes in food composition resulting from agricultural intensification practices and their potential impact on the health benefits of MedDiets. We summarized/synthesized information from (i) systematic literature reviews/meta-analyses and more recently published articles on composition differences between conventional and organic foods, (ii) desk studies which compared food composition data from before and after agricultural intensification, (iii) recent retail and farm surveys and/or factorial field experiments that identified specific agronomic practices responsible for nutritionally relevant changes in food composition, and (iv) a recent systematic literature review and a small number of subsequently published observational and dietary intervention studies that investigated the potential health impacts of changes in food composition resulting from agricultural intensification. There has been growing evidence that the intensification of food production has resulted in (i) lower concentrations of nutritionally desirable compounds (e.g., phenolics, certain vitamins, mineral micronutrients including Se, Zn, and omega-3 fatty acids, α-tocopherol) and/or (ii) higher concentrations of nutritionally undesirable or toxic compounds (pesticide residues, cadmium, omega-6 fatty acids) in many of the foods (including wholegrain cereals, fruit and vegetables, olive oil, dairy products and meat from small ruminants, and fish) that are thought to contribute to the health benefits associated with MedDiets. The evidence for negative health impacts of consuming foods from intensified conventional production systems has also increased but is still limited and based primarily on evidence from observational studies. Limitations and gaps in the current evidence base are discussed. Conclusions: There is now substantial evidence that the intensification of agricultural food production has resulted in a decline in the nutritional quality of many of the foods that are recognized to contribute to the positive health impacts associated with adhering to traditional MedDiets. Further research is needed to quantify to what extent this decline augments the positive health impacts of adhering to a traditional MedDiet.

Agriculturally intensified landscapes are associated with reduced body condition of lady beetles

ContextAgricultural intensification is contributing to a global species decline. Underlying mechanisms include toxic effects of pesticides on non-target organisms and reductions in habitat and food availability. However, the effects of agricultural intensification on body condition, particularly of ecosystem service-providing arthropods, are poorly understood.ObjectivesHere, we investigated whether variations in the body condition of common lady beetle species (Coleoptera: Coccinellidae) can be explained by the composition and configuration of the surrounding landscape. Assuming strong seasonal variation in food availability in intensively farmed regions, we included the entire period of lady beetle activity in our study.MethodsLady beetles were collected from April to September 2011 in 30 landscapes in southern Wisconsin, USA. We examined how body size, body density, and lipid content of the beetles responded to the percentage of intensive cropland, habitat diversity, and edge density in the surrounding landscape.ResultsThe strongest predictor of body condition was the percentage of intensive cropland. For every 10% increase in cropland, body density decreased by about 3.9% and lipid content by 6.4%. Landscape diversity and edge density correlated with body condition of individual species.ConclusionsIn agriculturally intensified landscapes, lady beetles with reduced body condition may produce fewer offspring, have lower survival rates, and exert less effective pest control. Thus, our results suggest a mechanistic link between landscape patterns and observed declines in lady beetle populations. Our results also show that the expansion of monocultures affects even common cropland-associated species such as Harmonia axyridis, suggesting a long-term decline in biocontrol services in simplified agricultural landscapes.

Assessing Stress Response in Lizards from Agroecosystems with Different Management Practices.

Despite the importance of reptiles in agroecosystems, little is known about the effects of agricultural intensification and pesticide use on these animals. We compared antioxidant and haematological biomarkers in the wild Italian wall lizards Podarcis siculus from three olive groves representing a gradient of management intensity. Lizards from the conventional grove showed induced antioxidant defences relative to those from the organic field. However, this induction did not avoid the occurrence of oxidative stress in males from intensively managed olive groves, who showed TBARS levels 58%-133% higher than males from the other sites. Haematological responses also suggested increased stress in females from the intensively managed olive groves, with a heterophil-to-lymphocyte ratio 5.3 to 14.8-fold higher than in the other sites. The observed stress responses of lizards along the studied gradient of agricultural management suggest their potential usefulness as non-destructive biomarkers to environmental stressors associated with agricultural intensification.

Modelling vadose zone flows and groundwater dynamics of alluvial aquifers in Eastern Gangetic Plains of India: evaluating the effects of agricultural intensification

Modelling vadose zone flows and groundwater dynamics of alluvial aquifers in Eastern Gangetic Plains of India: evaluating the effects of agricultural intensification

Agriculture intensification reduces plant taxonomic and functional diversity across European arable systems

Abstract Agricultural intensification is one of the main drivers of species loss worldwide, but there is still a lack of information about its effect on functional diversity of arable weed communities. Using a large‐scale pan European study including 786 fields within 261 farms from eight countries, we analysed differences in the taxonomic and functional diversity of arable weeds assemblages across different levels of agricultural intensification. We estimated weed species frequency in each field, and collected species' traits (vegetative height, SLA and seed mass) from the TRY plant trait database. With this information, we estimated taxonomic (species richness), functional composition (community weighted means) and functional diversity (functional richness, evenness, divergence and redundancy). We used indicators of agricultural management intensity at the individual field scale (e.g. yield, inputs of nitrogen fertilizer and herbicides, frequency of mechanical weed control practices) and at the landscape scale surrounding the field (i.e. number of crop types, mean field size and proportion of arable land cover within a radius of 500 m from the sampling points). The effects of agricultural intensification on species and functional richness at the field scale were stronger than those of intensification at the landscape scale, and we did not observe evidence of interacting effects between the two scales. Overall, assemblages in more intensified areas had fewer species, a higher prevalence of species with ruderal strategies (low stature, high leaf area, light seeds), and lower functional redundancy. Maintaining the diversity of Europe's arable weed communities requires some simple management interventions, for example, reducing the high intensity of field‐level agricultural management across Europe, which could be complemented by interventions that increase landscape complexity. A free Plain Language Summary can be found within the Supporting Information of this article.

Effects of agricultural intensification on nestling condition and number of young fledged of barn swallows (Hirundo rustica)

Farmland bird populations have declined with increasing agricultural intensification possibly due to putative reductions in prey insects and effects of pesticide exposure. Presence of agriculture may be especially relevant for aerial insectivorous songbirds whose primary diet is flying insects. Here, we investigated the effects of agricultural land use on nestling body condition, an important determinant of post-fledging survival, for barn swallows (Hirundo rustica), an aerial insectivore breeding within an agro-ecosystem in southern Ontario, Canada. Our scale-of-effect analysis revealed that nestling and pre-fledging body condition varied most strongly with the proportion of row crop within 100 m of the natal barn. Unexpectedly, this correlation was positive for both nestling body condition (2016 only) and for pre-fledging condition (2016 and 2017). We found a weak positive effect of row crop on number of young fledged. We speculate that the positive effects of agricultural row-cropping on condition and number of young fledged was due to higher prey availability and/or more open foraging habitat around barns surrounded by row crops. Alternatively, higher nestling condition in high agriculture environments could reflect an insurance policy to increase survival during the post-fledging period. Our results suggest that, in our southern Ontario study area, the degree of agricultural conversion does not negatively influence individual nestling condition and number of young produced for barn swallows. We recommend future research on this species to examine reproductive success in more intense agricultural landscapes and possible effects of pesticide exposure.

The effect of adjacent habitat on native bee assemblages in a perennial low-input agroecosystem in a semiarid anthropized landscape

The decline of pollination services in some regions has stimulated much research on the effects of agricultural intensification on bees. In addition to the characteristics of agricultural plots, bee assemblages in them are influenced by the adjacent habitats. Perennial, fruit-oriented nopal (Opuntia spp.) orchards cover large surfaces in Mexico, North Africa, South America and southern U.S.A. and produce tens of thousands of flowers, but their value as habitat for bees was unknown. To document bee assemblages in nopal orchards in the Llanos de Ojuelos, southern Mexican Plateau, and to assess the influence of adjacent habitats on them, we surveyed bees in nopal orchards adjacent to cropland (Cr-orchards) and adjacent to natural shrubland patches (Sh-orchards), and in remnants of natural shrubland. We used color traps and manual capture from flowers during the 2016 and 2017 peaks of Opuntia blooming periods. We hypothesized that Sh-orchards would harbor richer and larger native bee assemblages than Cr-orchards, and that assemblages´ similarity between these Sh-orchards and shrublands would be greater than between Cr-orchards and shrublands. We collected 3823 individuals of 45 different bee taxa; 90% of all taxa, in nopal orchards. Our results partially support the premise that proximity of natural habitats to agricultural plots is positive for their bee overall abundance, but distance from shrublands did not impoverish bee species richness. Mean similarity values between Cr-orchards, Sh-orchards, and shrublands were not significantly different, as result of shrubland patches being very variable. As a result of their perennial condition and limited agricultural practices, nopal orchards provide shelter, forage, and nest substrate for native bee species, albeit perhaps less in Cr-orchards than in Sh-orchards, and likely facilitate bee movement between orchards and, or shrublands through a matrix of annual croplands. In doing so, this agroecosystem enhances regional bee community resilience in the context of an anthropized landscape.

Weed species structural and functional composition of okra fields and field periphery under different management intensities along the rural-urban gradient of two West African cities

In urban and peri-urban agricultural production systems of Sub-Saharan African cities, diverse and functional complex weed communities may help to maintain biodiversity and ecosystem services and therefore indirectly support crop performance. However, effects of agricultural intensification and urbanisation on important weed diversity in the West African region had received so far little attention, although in Burkina Faso and Ghana up to 90 per cent of the population depends on agriculture as a main source of income generation. Hence, our research focussed on the analysis of changes in weed assemblages’ structure and function of okra fields that were cultivated under different management intensities and were embedded into the rural, peri-urban and urban environment of two West African cities: Ouagadougou (Burkina Faso) and Tamale (Ghana). We found a strong relationship between gender and market orientation of okra cultivation. Market orientation of okra farmers was also a major driver in shaping weed species assemblages and led to the development of a distinct weed assemblage in urban areas that even showed higher diversity in weeds’ function. Morphological plant traits (life form, seed properties) were most affected by agricultural practises; distribution pattern of ecological traits (seed dispersal mode, pollination vector) seemed to be influenced additionally by environmental characteristics with less entomophilous but more ornithochorous weed species on okra fields within urban areas. Our results revealed that the management of okra was highly variable and that this variation was influenced by farmers’ socioeconomic background leading to changes in soil properties. These in turn may alter the functional diversity of beneficial weed communities beyond changes in species richness by potentially harming the provisioning of ecosystem services such as pest control and pollination.

Scale dependent drivers of wild bee diversity in tropical heterogeneous agricultural landscapes.

SummaryFactors associated with agricultural intensification, for example, loss of seminatural vegetation and pesticide use has been shown to adversely affect the bee community. These factors may impact the bee community differently at different landscape scales. The scale dependency is expected to be more pronounced in heterogeneous landscapes. However, the scale‐dependent response of the bee community to drivers of its decline is relatively understudied, especially in the tropics where the agricultural landscape is often heterogeneous. This study looked at effects of agricultural intensification on bee diversity at patch and landscape scales in a tropical agricultural landscape. Wild bees were sampled using 12 permanent pan trap stations. Patch and landscape characteristics were measured within a 100 m (patch scale) and a 500 m (landscape scale) radius of pan trap stations. Information on pesticide input was obtained from farmer surveys. Data on vegetation cover, productivity, and percentage of agricultural and fallow land (FL) were collected using satellite imagery. Intensive areas in a bee‐site network were less specialized in terms of resources to attract rare bee species while the less intensive areas, which supported more rare species, were more vulnerable to disturbance. A combination of patch quality and diversity as well as pesticide use regulates species diversity at the landscape scale (500 m), whereas pesticide quantity drove diversity at the patch scale (100 m). At the landscape scale, specialization of each site in terms of resources for bees increased with increasing patch diversity and FL while at the patch scale specialization declined with increased pesticide use. Bee functional groups responded differentially to landscape characteristics as well as pesticide use. Wood nesting bees were negatively affected by the number of pesticides used but other bee functional groups were not sensitive to pesticides. Synthesis and Applications: Different factors affect wild bee diversity at the scale of landscape and patch in heterogeneous tropical agricultural systems. The differential response of bee functional groups to agricultural intensification underpins the need for guild‐specific management strategies for wild bee conservation. Less intensively farmed areas support more rare species and are vulnerable to disturbance; consequently, these areas should be prioritized for conservation to maintain heterogeneity in the landscape. It is important to conserve and restore seminatural habitats to maintain complexity in the landscapes through participatory processes and to regulate synthetic chemical pesticides in farm operations to conserve the species and functional diversity of wild bees.

The use of fluctuating asymmetry as a measure of farming practice effects in rodents: A species-specific response

The effects of agricultural intensification on vertebrate populations could vary depending on whether species are habitat specialists or habitat generalists. Organic farming practices are generally considered to be less intensive and more environmental friendly than conventional farming practices and, as a result, these two managements may impact on habitat specialists and habitat generalists in different ways. The effect of environmental and/or genetic stress on populations can be assessed using fluctuating asymmetry (FA) and body condition of animals. We predicted that populations of a specialist species, the Pampean grassland mouse (Akodon azarae) would have higher levels of FA and poorer body condition on conventional farms compared to populations of A. azarae on organic farms. In contrast, we predicted that populations of generalist species, the corn mouse (Calomys musculinus) and the small vesper mouse (Calomys laucha) would not show differences in FA or body condition between conventional and organic farms. We examined the expression of FA in the hind foot and used the scaled mass index as a surrogate for body condition. As predicted, we found higher FA in the habitat specialist (A. azarae) on conventional farms compared to organic farms, and found no differences in FA among the two generalist species (C. musculinus and C. laucha). However, we found no differences in body condition for the three studied species between the two managements. Our results suggest that the effect of farming practices on small mammals varies between habitat specialists and habitat generalists. The results of this study provide important insights for the study of asymmetries, both from biological and methodological perspectives. Our results support the idea that the level of FA may be used as an index to assess the effects of farming practices on vertebrate populations.

Impacts of agricultural intensification on bird communities: New insights from a multi-level and multi-facet approach of biodiversity

Following the multiplicity of studies dealing with the effects of agricultural intensification on bird diversity, one of the lessons drawn is that these effects depend on both the taxonomic group, the component of diversity, the aspect of intensification, and the spatial scale. This often leads to disparate results among studies suggesting that the investigation of agriculture-biodiversity relationships suffers from scale-dependence, information redundancy, non-linearity problems, and thus, unpredictability.Here, we propose a multi-scale and multi-facet approach to clarify the impacts of agricultural intensification on biodiversity and possible mitigating actions. Our study is based on bird and agricultural practice surveys of 199 agricultural fields in three agricultural regions of France. Using landscape characteristics and agricultural practice variables, we disentangled four main gradients of agricultural intensification on our study sites: landscape opening (farmland expansion), landscape homogenization (decrease in crop and land cover diversity), chemical intensification (fertilizer, insecticide, and fungicide), and tillage vs. herbicide.We tested whether and how these gradients interacted with each other at field, farm and regional levels in shaping taxonomic diversity (alpha, gamma and beta diversity) and ecological responses of bird communities (relative proportion of specialist vs. generalist species, trophic categories).Landscape homogenisation and opening affected the taxonomic and ecological responses of birds at field and farm levels, but not at the regional level, highlighting the scale-dependence of agriculture–biodiversity relationships. At field and farm levels, landscape opening had a positive effect on beta diversity, and community specialization by enabling the existence of farmland specialists, while heterogeneous landscapes promoted generalists.Chemical intensification had negative impacts, especially at the farm level and on almost all facets of diversity. However, some bird species seemed to tolerate higher levels of both chemical and tillage intensification.Some important interaction effects between landscape and agricultural practices, which are often disregarded, were also revealed, such that landscape homogenization in interaction with tillage reduction was correlated with higher specialization.The field level appeared mostly relevant for explaining community variations by habitat and resource availability. Meanwhile at the coarsest scale, i.e., the Small Agricultural Region, only some possible dispersal limitations were likely to occur. Finally, our results highlight the farm level (intermediate scale) as a relevant unit for management and agricultural policies, since the community responded to both landscape and agricultural practices intensification at this level. In particular, we emphasize the necessity to conserve both heterogeneous and homogeneous agricultural landscapes under extensive practices; the former promotes taxonomic diversity, when the latter favors specialized farmland biodiversity.

Agriculture intensifies soil moisture decline in Northern China.

Northern China is one of the most densely populated regions in the world. Agricultural activities have intensified since the 1980s to provide food security to the country. However, this intensification has likely contributed to an increasing scarcity in water resources, which may in turn be endangering food security. Based on in-situ measurements of soil moisture collected in agricultural plots during 1983–2012, we find that topsoil (0–50 cm) volumetric water content during the growing season has declined significantly (p < 0.01), with a trend of −0.011 to −0.015 m3 m−3 per decade. Observed discharge declines for the three large river basins are consistent with the effects of agricultural intensification, although other factors (e.g. dam constructions) likely have contributed to these trends. Practices like fertilizer application have favoured biomass growth and increased transpiration rates, thus reducing available soil water. In addition, the rapid proliferation of water-expensive crops (e.g., maize) and the expansion of the area dedicated to food production have also contributed to soil drying. Adoption of alternative agricultural practices that can meet the immediate food demand without compromising future water resources seem critical for the sustainability of the food production system.

Different patterns in species richness and community composition between trees, plants and epiphytic lichens in semi-natural pastures under agri-environment schemes

Agri-environment schemes (AES) have been established to counteract negative effects of agricultural intensification on e.g. semi-natural pastures and meadows. The efficiency of most AESs have, however, been poorly evaluated. We evaluated the success of a Swedish AES for the management of semi-natural pastures by comparing species richness and composition of vascular plants (except trees), epiphytic lichens and trees among pastures receiving higher (high value pastures) and lower levels of AES paymens (general value pastures). There was no difference in the number of tree species among high and general value pastures, even though AES regulations allow a maximum of 60 and 100 trees/ha in general and high value pastures, respectively. High value pastures had, however, a higher number of plant and epiphytic lichen species than common value pastures. Moreover, a higher number of pasture specialist plant species were indicative of high value pastures than of general value pastures. No lichen species indicating high value pastures are associated with habitats with low canopy cover (such as e.g. pastures). Finally, tree identity was an important factor for explaining the number and composition of epiphytic lichen species. Our study highlights that species groups can respond differently to agri-environment schemes and other conservation measures. Even though the effects are the desired on the diversity of one assessed taxon, this is not always the case for non-target organism groups.

Efectos de la intensificación agrícola sobre la estructura y diversidad del paisaje en la región sojera de Uruguay

Effects of agricultural intensification on landscape structure and diversity on the Uruguayan soybean region: In recent decades, driven by the worldwide growing demand for food and biofuels, agriculture has grown exponentially at the expense of natural ecosystems. The same phenomenon is happening in Uruguay, with greater intensity on the west region of the country during the last decade, driven by the soybean crop. The objective of our study was to assess the territorial changes occurred at the landscape level, associated with agricultural intensification, on a department (political division) on the western region of Uruguay, between 1990 and 2009. Crop areas increased 27% during this period, advancing over native forest (BN) and grasslands/ rangelands (CN) areas. The BN decreased 30% mainly through the loss of small fragments (<10 ha). The CN was reduced by a 23%, mostly through the disappearance of fragments up to 50 ha. In relation to connectivity, average distances between patches of CN have changed from 168 m to 192 m, whereas in BN they have gone from 365 m to 255 m in 2009. This last observation is consistent with a more disperse distribution in 1990, that will become more compact by 2009 through the disappearance of small peripheral patches. The fragmentation of CN showed a slightly increment in the period, while a decrease was observed in BN, possibly caused by the disappearance of small fragments (less than 10 ha). Between 1990 and 2009, 2000 fragments of BN <10 ha and 2500 fragments from 1-100 CN have disappeared, becoming in most cases on soybean crops. The effects of this process on agricultural production has been quantified but the impact on landscape's capacity to sustain biodiversity and provide a wide range of ecosystem goods and services, is still poorly understood.

Evaluation of empirical models coupled with EUTROMOD for water quality prediction in Kansas reservoirs

Agricultural land use contributes high nutrient and sediment loads to nearby streams, lakes, and reservoirs, which can lead to excessive algal growth and increased siltation. Future intensification of agricultural production could further aggravate water quality concerns. To objectively evaluate the effects of agricultural intensification on future water quality, modeling tools must be able to quantitatively predict the degree to which land use change will affect the trophic state of water bodies. This study evaluated the water quality model EUTROMOD as well as several national and regional in-lake empirical water quality models as predictive tools for analyzing and estimating water quality in 28 Kansas reservoirs of varying size and watershed land use. Model-predicted nutrient loading was used with several in-lake empirical models to predict values for total nitrogen (TN), total phosphorus (TP), and chlorophyll a concentrations. Predicted values were then compared to long-term water quality measurements obtained from the Kansas lake and reservoir monitoring program. All models over-predicted concentrations of TN and TP in Kansas reservoirs; however, predictions from the Bachmann TN and Canfield-Bachmann TP in-lake empirical models were most closely coupled to observed trends and had the least error. Two possible sources of model bias were identified: the sedimentation coefficient in the in-lake empirical models and the nutrient loading estimates from the watershed model. Areas of further research are suggested for determining the dominant source of model bias and improving quantitative predictions of water quality in the Midwest, USA.

Agricultural intensification in the Bang Phluang Irrigation Scheme, Prachinburi Sub-basin, Thailand, and its impacts on water management

Thailand has embarked on river basin–focused policies to improve technical infrastructure for and participation in water management. The Bang Phluang Irrigation Scheme in Thailand's eastern region was started in 1971 to provide irrigation water, to control floods and to prevent salt-water intrusion. Farmers have increased the number of rice harvests and introduced fish and shrimp cultures. Agricultural intensification, however, has led to competition for water and to conflicts among farmers. The paper analyzes, within the context of policy and institutional change, the effects of agricultural intensification on water use, water management, conflicts, and conflict resolution.

Effects of agricultural intensification and temperature on immune response to phytohemagglutinin in Tree Swallows (Tachycineta bicolor)

Lower immune response usually translates into lower fitness. Environmental quality can play a key role in shaping immune responses in the wild, as it influences both resource availability and costly maintenance functions. The aim of this study is to evaluate the effect of habitat quality on proinflammatory response to phytohemagglutinin (PHA) in Tree Swallows (Tachycineta bicolor (Vieillot, 1808)) under contrasting agricultural practices. Specifically, we tested the hypothesis that lower quality habitat (intensive agricultural practices and low temperature) negatively impairs immune responses. To do so, we compared the response to PHA of adult female and nestling Tree Swallows nesting in intensive vs. nonintensive agricultural landscapes over 3 years (2008–2010). In accordance with our predictions, we found that habitat quality affected adult female responses to PHA. The response of adult females was significantly higher in nonintensive agricultural areas than in intensive ones. The level of agricultural intensity, however, had no influence on the response to PHA of nestlings. Our results suggest that female adults can buffer the negative impact of a low-quality habitat on their nestlings. Furthermore, our results suggest that under limiting conditions, individuals may have to trade between immunity and other functions such as parental effort.

Seasonal patterns in Tree Swallow prey (Diptera) abundance are affected by agricultural intensification

In many parts of the world, farmland bird species are declining at faster rates than other birds. For aerial insectivores, this decline has been related to a parallel reduction in the abundance of their invertebrate prey in agricultural landscapes. While the effects of agricultural intensification (AI) on arthropod communities at the landscape level have been substantially studied in recent years, seasonal variation in these impacts has not been investigated. To assess the contention that intensive cultures negatively impact food resources for aerial insectivorous birds, we analyzed the spatiotemporal distribution patterns of Diptera, the main food resource for breeding tree swallows Tachycineta bicolor), across a gradient of AI in southeastern Quebec, Canada. Linear mixed models computed from a data set of 5000 samples comprising >150,000 dipterans collected over three years (2006-2008) suggest that both Diptera abundance and biomass varied greatly during swallow breeding season, following a quadratic curve. Globally, AI had a negative effect on Diptera abundance (but not biomass), but year-by-year analyses showed that in one of three years (2008), dipterans were more abundant in agro-intensive landscapes. Analyses also revealed a significant interaction between the moment in the season and AI: In early June, Diptera abundances were similar regardless of the landscape, but differences increased as the season progressed, with highly intensive landscapes harboring fewer prey, possibly creating an "ecological trap" for aerial insectivores. While global trends in our results are in agreement with expectations (negative impact of Al on insect abundance), strong discrepancies in 2008 highlight the difficulty of predicting the abundance of insect communities. Our study indicates that predicting the effects of AI may prove more challenging than generally assumed, even when large data sets are collected, and that temporal variation within a season is important to take into consideration. While further work is required to assess the direct impacts of these seasonal trends in Diptera abundance on bird breeding success and post-fledging survival, management strategies in agricultural landscapes may need to consider the phenology of breeding birds and their dipteran prey in order to mitigate the potentially negative effects of AI late in the breeding season.

Agricultural intensification exacerbates female-biased primary brood sex-ratio in tree swallows

Impacts of agriculture practices are documented at every ecosystem level from landscape structure to biodiversity. Birds are especially affected by agricultural modifications as shown by the decline of farmland species in Europe and North America. Few studies have assessed the effects of such modifications on individual characteristics directly influencing population dynamics. Several bird studies showed that sex-ratio may be adaptive and that mother condition affects the production of sons and daughters. However, little is known about the connections between environmental and individual characteristics on sex allocation. Here we quantified the variation in primary sex-ratio in tree swallows (Tachycineta bicolor) nesting in contrasted environments associated with agricultural intensification in southern Quebec, Canada. We found that intensive agricultural practices affected female sex-ratio allocation in this area, resulting in more biased sex-ratio towards daughters throughout most of the hatching period. Yet, this bias towards daughters was reduced as the season progressed in the most intensively cultivated areas, suggesting that tree swallows have problems foreseeing the difficult growth and postfledging conditions that their nestlings will experience in such environments. Our results thereby support the hypothesis that intensive agricultural areas act as an ecological trap in our study system. We also found that effects of agricultural intensification on sex allocation differed among years and affected the relationships between sex-ratio allocation and hatching date. Our results suggest that agricultural intensification modifies female sex allocation in tree swallows, but the importance of the effects might vary among years and depend on timing of breeding.

Agricultural intensification and biodiversity partitioning in European landscapes comparing plants, carabids, and birds

Effects of agricultural intensification (AI) on biodiversity are often assessed on the plot scale, although processes determining diversity also operate on larger spatial scales. Here, we analyzed the diversity of vascular plants, carabid beetles, and birds in agricultural landscapes in cereal crop fields at the field (n = 1350), farm (n = 270), and European-region (n = 9) scale. We partitioned diversity into its additive components alpha, beta, and gamma, and assessed the relative contribution of beta diversity to total species richness at each spatial scale. AI was determined using pesticide and fertilizer inputs, as well as tillage operations and categorized into low, medium, and high levels. As AI was not significantly related to landscape complexity, we could disentangle potential AI effects on local vs. landscape community homogenization. AI negatively affected the species richness of plants and birds, but not carabid beetles, at all spatial scales. Hence, local AI was closely correlated to beta diversity on larger scales up to the farm and region level, and thereby was an indicator of farm- and region-wide biodiversity losses. At the scale of farms (12.83-20.52%) and regions (68.34-80.18%), beta diversity accounted for the major part of the total species richness for all three taxa, indicating great dissimilarity in environmental conditions on larger spatial scales. For plants, relative importance of alpha diversity decreased with AI, while relative importance of beta diversity on the farm scale increased with AI for carabids and birds. Hence, and in contrast to our expectations, AI does not necessarily homogenize local communities, presumably due to the heterogeneity of farming practices. In conclusion, a more detailed understanding of AI effects on diversity patterns of various taxa and at multiple spatial scales would contribute to more efficient agri-environmental schemes in agroecosystems.