From functional diversity to human well-being: A conceptual framework for agroecosystem sustainability

[EN] CONTEXT: Agricultural intensification contributes to global food security and well-being by supplying the food demand of a growing human population. However, ongoing land-use change and intensification seriously affect the abundance, diversity and distribution of species, besides many other impacts, thereby threatening the functioning of ecosystems worldwide. Despite the accumulating evidence that the current agricultural model is unsustainable, we are far from understanding the consequences of functional diversity loss for functioning and ecosystem service supply and the potential long-term threats to food security and human well-being. OBJECTIVE: In this review, we propose a conceptual framework to understand the relationships between functional diversity and human well-being that also considers agroecosystem health. To this end, we identify the most commonly assumed relationships linking functional diversity to regulating and provisioning agroecosystem services and their importance for human well-being, emphasising the most serious knowledge gaps in the in-dividual pathways of the conceptual framework. METHODS: A consortium formed by an international panel of experts from different disciplines including functional diversity, ecosystem services and human health compiled 275 articles. Members of the consortium proposed literature to exemplify each specific aspect of the conceptual framework in the text, in accordance with his/her field of expertise. The guideline for all experts was to focus mostly in current literature (38% of the references are from the last 5 years and 66% from the last decade), with special interest in reviews and synthesis articles (42% of the references), as well as meta-analyses and global studies (10% of the references). RESULTS AND CONCLUSIONS: The factors that influence agroecosystem health are extremely complex, involving both services and disservices related to land-use management and environmental conditions. The global human population needs sustainable and resilient agroecosystems and a concerted effort is needed to fundamentally redesign agricultural practices to feed the growing human population without further jeopardising the quality of life for future generations. We highlight the potential effects of land-use change and ecological intensification on the functional diversity of plant and animal communities, and the resulting consequences for ecosystem services and ultimately human health. SIGNIFICANCE: The resulting conceptual model is developed for researchers as well as policy makers high- lighting the need for a holistic approach to understand diversity impacts on human well-being. Finally, we document a major knowledge gap due to the lack of any studies focusing on the full pathway from diversity to human well-being.S

Blind spots in global soil biodiversity and ecosystem function research

Soils harbor a substantial fraction of the world’s biodiversity, contributing to many crucial ecosystem functions. It is thus essential to identify general macroecological patterns related to the distribution and functioning of soil organisms to support their conservation and consideration by governance. These macroecological analyses need to represent the diversity of environmental conditions that can be found worldwide. Here we identify and characterize existing environmental gaps in soil taxa and ecosystem functioning data across soil macroecological studies and 17,186 sampling sites across the globe. These data gaps include important spatial, environmental, taxonomic, and functional gaps, and an almost complete absence of temporally explicit data. We also identify the limitations of soil macroecological studies to explore general patterns in soil biodiversity-ecosystem functioning relationships, with only 0.3% of all sampling sites having both information about biodiversity and function, although with different taxonomic groups and functions at each site. Based on this information, we provide clear priorities to support and expand soil macroecological research.This manuscript developed from discussions within the German Centre of Integrative Biodiversity Research funded by the German Research Foundation (DFG FZT118). CAG and NE acknowledge funding by iDiv (DFG FZT118) Flexpool proposal 34600850. C.A.G., A.H.B., J.S., A.C., N.G.R., S.C., L.B., M.C.R., F.B., J.O., G.P., H.R.P.P., M.W., T.W., K.K., and N.E. acknowledge funding by iDiv (DFG FZT118) Flexpool proposal 34600844. N.E. acknowledges funding by the DFG (FOR 1451) and the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement no. 677232). Finally we would like to acknowledge the contribution of all the authors that provided their datasets for analysis within this paper. Open access funding provided by Projekt DEAL

Modélisation graphique de la biodisponibilité des métaux pour le ver de terre

Soil organisms like earthworms are exposed to trace metals in contaminated soils. Only a fraction of total metal content in the environment can interact with soil organisms and lead to toxicological effects. Risk assessment of contaminated soils needs to measure the extent of this interaction between metals and organisms (i.e. bioavailability). Bioavailability is how- ever a complex process that cannot be measured directly. A three-step definition had been given: 1) environmental availability designates the metal pools in soil that can potentially be uptake by the organism, 2) environmental bioavailability reflects the process of uptake of the contaminant by the organism and 3) toxicological bioavailability indicates the effects of the contaminant on the organism. A number of chemical and biological methods exist to measure each of these steps but none of them was proven to be fully generic in realistic envi- ronmental contexts. In situ, soils are often lowly contaminated by multiple contaminants and the causal relationships between chemical and biological indicators in such conditions have to be established. In this thesis we propose a graphical model (structural equation model: SEM) to address the causal hypotheses implied by the three-step definition of bioavailability. A laboratory exposure experiment was designed to test a SEM of metal bioavailability to earthworm. We chose a target earthworm species, A. caliginosa, commonly found in temper- ate soils. An analysis of literature data was conducted to verify metal bioaccumulation in A. caliginosa was representative of other earthworm species. We further selected a wide panel of soils to explore a realistic gradient of metal exposure. Specific chemical and biological methods were selected to reflect each step of metal bioavailability in the model. Environ- mental availability was assessed by experimental (extractions) and theoretical (modeling) procedures. Metal quantifications in earthworms and in three subcellular compartments were conducted to constitute observed variables of environmental bioavailability. Finally, for toxicological bioavailability, biomarkers reflecting different processes by which metals exert their effects on earthworms were quantified. The strength of the relationships between single observed variables was investigated over the panel of soils. The results showed indicator- and metal-specific relationships and further highlighted the challenges of relating chemical and biological indicators when considering low levels of bioavailability. The conceptual SEM was then confronted to our empirical observations. The results identified sets of chemical and biological indicators verifying the causal assumptions of the three-step definition of bioavail- ability in field-contaminated soils. This study shows the relevance of the SEM approach, that goes beyond the imperfections of single observed variables to reflect complex theoretical en- tities, and represents a powerful and comprehensive framework to investigate bioavailability in realistic environmental context.Evaluer le risque environnemental que repr ́esente la contamination du sol par des ́el ́ements en trace m ́etalliques est un enjeu important. Lorsque l’on cherche `a faire le lien entre l’exposition aux m ́etaux et ses impacts sur un organisme, il est n ́ecessaire de prendre en compte la biodisponibilit ́e du contaminant plutoˆt que sa teneur totale dans le sol. Cepen- dant, la biodisponibilit ́e est un concept dont il est difficile de rendre compte par une unique mesure chimique ou biologique. Dans la litt ́erature, les indicateurs les plus utilis ́es ne sont en fait pas hi ́erarchis ́es, apparaissent non g ́en ́eriques, et leur analyse peut ˆetre fauss ́ee par des facteurs confondants. La biodisponibilit ́e peut ˆetre d ́ecrite comme un processus a` trois ́etapes : (i) la disponibilit ́e des m ́etaux dans le sol, (ii) leur absorption par l’organisme et (iii) les effets des m ́etaux sur l’organisme. La mod ́elisation graphique (tel que le SEM: mod`ele par ́equations structurelles) repr ́esente un cadre d’analyse pertinent pour tester les hypoth`eses de causalit ́e qui sous-tendent cette d ́efinition et a` terme parvenir a` identifier des jeux d’indicateurs pertinents pour mesurer la biodisponibilit ́e. Dans cette th`ese, un mod`ele SEM d ́ecrivant la biodisponibilit ́e des m ́etaux pour le ver de terre a ́et ́e d ́evelopp ́e. Pour le tester, nous avons r ́ealis ́e une exp ́erience d’exposition de vers de terre en conditions controˆl ́ees. L’esp`ece de ver Aporrectodea caliginosa a ́et ́e choisie car elle est fr ́equemment trouv ́ee dans les sols temp ́er ́es. Nous avons de plus v ́erifi ́e sa repr ́esentativit ́e quant a` la bioaccumulation des m ́etaux en la comparant `a d’autres esp`eces a` partir des donn ́ees de la litt ́erature. Un large panel de sols contamin ́es in situ et non contamin ́es a ́et ́e choisi afin de cr ́eer un gradient d’exposition r ́ealiste aux m ́etaux (Cd, Pb et Zn). La disponibilit ́e des m ́etaux dans le sol a ́et ́e mesur ́ee par des m ́ethodes exp ́erimentales (extractions) et th ́eoriques (mod ́elisation). Les m ́etaux absorb ́es par les animaux ont ́et ́e quantifi ́es apr`es exposition dans les vers entiers et dans trois fractions subcellulaires. Enfin des biomarqueurs de diff ́erents niveaux d’organisation biologique ont permis d’ ́evaluer les effets des m ́etaux sur les vers de terre. Nos r ́esultats montrent que les relations entre indicateurs consid ́er ́es individuellement ́etaient d ́ependantes de l’indicateur et du m ́etal consid ́er ́e. De plus, nous avons montr ́e les difficult ́es qui ́emergent lorsque l’on cherche a` relier indicateurs chimiques et biologiques de biodisponibilit ́e dans des sols mod ́er ́ement contamin ́es par plusieurs m ́etaux. Enfin, le mod`ele SEM a ́et ́e confront ́e aux donn ́ees et a permis d’identifier des jeux d’indicateurs chimiques et biologiques qui v ́erifiaient les hypoth`eses d’une chaˆıne de causalit ́e entre disponibilit ́e, absorp- tion et effets, et ce dans le contexte de sols faiblement contamin ́es in situ. Cette ́etude montre la pertinence de l’approche SEM qui permet d’aller au-del`a de mesures uniques repr ́esentant imparfaitement le concept de biodisponibilit ́e et de fournir un cadre d’analyse synth ́etique pour ́evaluer la biodisponibilit ́e dans un contexte environnemental r ́ealiste

Transfer and bioaccumulation of pesticides in terrestrial arthropods and food webs: State of knowledge and perspectives for research

International audienceArthropods represent an entry point for pesticide transfers in terrestrial food webs, and pesticide accumulation in upper chain organisms, such as predators can have cascading consequences on ecosystems. However, the mechanisms driving pesticide transfer and bioaccumulation in food webs remain poorly understood. Here we review the literature on pesticide transfers mediated by terrestrial arthropods in food webs. The transfer of pesticides and their potential for bioaccumulation and biomagnification are related to the chemical properties and toxicokinetic of the substances, the resistance and detoxification abilities of the contaminated organisms, as well as by their effects on organisms’ life history traits. We further identify four critical areas in which knowledge gain would improve future predictions of pesticides impacts on terrestrial food webs. First, efforts should be made regarding the effects of co-formulants and pesticides mixtures that are currently understudied. Second, progress in the sensitivity of analytical methods would allow the detection of low concentrations of pesticides in small individual arthropods. Quantifying pesticides in arthropods preys, their predators, and arthropods or vertebrates at higher trophic level would bring crucial insights into the bioaccumulation and biomagnification potential of pesticides in real-world terrestrial food webs. Finally, quantifying the influence of the trophic structure and complexity of communities on the transfer of pesticides could address several important sources of variability in bioaccumulation and biomagnification across species and food webs. This narrative review will inspire future studies aiming to quantify pesticide transfers in terrestrial food webs to better capture their ecological consequences in natural and cultivated landscape

Relationships between metal compartmentalization and biomarkers in earthworms exposed to field-contaminated soils

Partitioning tissue metal concentration into subcellular compartments relecting 'toxicologically available' pools may provide good descriptors of the toxicological efects of metals on organisms. Here we investigated the relationships between internal compartmentalization of Cd, Pb and Zn and biomarker responses in a model soil organism: the earthworm. The aim of this study was to identify metal fractions reflecting the toxic pressure in an endogeic, naturally occurring earthworm species (Aporrectodea caliginosa) exposed to realistic field-contaminated soils. After a 21 days exposure experiment to 31 field contaminated soils, Cd, Pb and Zn concentrations in earthworms and in three subcellular fractions (cytosol, debris and granules) were quantified. Different biomarkers were measured: the expression of a metallothionein gene (mt), the activity of catalase (CAT) and of glutathione-s-transferase (GST), and the protein, lipid and glycogen reserves. Biomarkers were further combined in an integrated biomarker index (IBR). The subcellular fractionation provided better predictors of biomarkers than the total internal contents hence supporting its use when assessing toxicological bioavailability of metals to earthworms. The most soluble internal pools of metals were not always the best predictors of biomarker responses. metallothionein expression responded to increasing concentrations of Cd in the insoluble fraction (debris + granules). Protein and glycogen contents were also mainly related to Cd and Pb in the insoluble fraction. On the other hand, GST activity was better explained by Pb in the cytosolic fraction. CAT activity and lipid contents variations were not related to metal subcellular distribution. The IBR was best explained by both soluble and insoluble fractions of Cd and Pb. This study further extends the scope of mt expression as a robust and specific biomarker in an ecologically representative earthworm species exposed to field-contaminated soils. The genetic lineage of the individuals, assessed by DNA barcoding with cytochrome c oxidase subunit I, did not inuence mt expression

The Way Soil Organisms Look Can Help Us Understand Their Importance. Frontiers for young minds.

International audienceThere is a multitude of life forms on our planet. This is especially true under our feet, in the soil. Earthworms, spiders, and millipedes are only a few examples of the vast number of soil organisms. Once you look what lives in soils, you realize the tremendous diversity of shapes and colors. But what if we take the time to describe all their characteristics: color, size, shape, number of legs, type of wings, lifespan, and climate preferences? All these characteristics, called traits, help us to understand what types of organisms can be found in a particular ecosystem, what they feed on, and how far they can travel. Scientists use this information to understand the different roles of organisms in soils, and to restore degraded soils. Analyzing traits can reveal the importance of soil organisms and the fundamental roles they play for human societies

Role of organic matter on trace metal availability in contaminated soils: case of high biomass perennial crops vs annual crops

Soils of contaminated agrosystems are still potential arable surfaces for the production of non-alimentary cropsprovided that such cropping systems do not increase risks for the environment in order to integrate them in asustainable agriculture development. Effects of changing land management from annual to perennial on soilproperties have been widely studied over the last decades, but the case of contaminated agricultural soils remainslittle documented in particular concerning the effects on the dynamic of soil trace elements.Among the non-alimentary crops, the use of energy crops like miscanthus, a C4 perennial plant, must bestudied in particular to evaluate their environmental impacts as they are known to modify the soil organic matterpools. In this work we aimed at assessing changes in soil trace metal availability when annual crops are replacedby a perennial cropping system in a metal contaminated soil, with the hypothesis that exogenous organic carbonoriginating from the plant induced changes in the soil metal speciation. For this, we used the soil surface horizonsof a smelter impacted parcel in the North of France, whose one part was cultivated in miscanthus three years agoand the other part was left with the previous land use i.e. cropping rotations. We quantified the carbon fluxesoriginating from miscanthus in the various granulo-densimetric fractions of the soil under miscanthus by C13measurements, and compared the chemical extraction and the physical localisation of both organic carbon andof two trace metal, Cu and Zn in the various soil size fractions of both soils under miscanthus and under annualcrops. Results showed an incorporation of organic carbon from miscanthus in the coarse organic fractions whichwas related to an increase in the metal localisation in the coarse grain fractions observed for Cu but not for Zn.Comparison of metal availabilities between the two cropping systems showed no difference for Zn availabilitywhile copper availability was shown to decrease. This decrease in copper availability was related to an incresae inCu localisation towards finest soil fractions between soil under annual system and miscanthus soil, while resultsfor Zn localisation showed no changes.Our results show that soil particulate organic matter is first impacted by the new perennial crop system andthat depending on the trace metal, this impact can involve or not a change in metal localisation in the soilgranulometric fractions related to changes in metal availability

Is there a relationship between earthworm energy reserves and metal availability after exposure to eld contaminated soils?

Avec les remerciements pour Jodie ThénardGeneric biomarkers are needed to assess environmental risks in metal polluted soils. We assessed the strength of the relationship between earthworm energy reserves and metal availability under conditions of cocktail of metals at low doses and large range of soil parameters. Aporrectodea caliginosa was exposed in laboratory to a panel of soils differing in Cd, Pb and Zn total and available (CaCl2 and EDTA-extractable) concentrations, and in soil texture, pH, CEC and organic-C. Glycogen, protein and lipid contents were recorded in exposed worms. Glycogen contents were not linked to the explaining variables considered. Variable selection identified CaCl2 extractable metals concentrations and soil texture as the main factors affecting protein and lipid contents. The results showed opposite effects of Pb and Zn, high inter-individual variability of biomarkers and weak relationships with easily extractable metals. Our results support the lack of genericity of energy reserves in earthworms exposed to field-contaminated soils

Relationships between metal compartmentalization and biomarkers in earthworms exposed to field-contaminated soils

Partitioning tissue metal concentration into subcellular compartments relecting 'toxicologically available'pools may provide good descriptors of the toxicological efects of metals on organisms. Here we investigatedthe relationships between internal compartmentalization of Cd, Pb and Zn and biomarker responses in a model soil organism: the earthworm. The aim of this study was to identify metal fractions reflecting the toxic pressure in an endogeic, naturally occurring earthworm species (Aporrectodea caliginosa) exposed torealistic field-contaminated soils.After a 21 days exposure experiment to 31 field contaminated soils, Cd, Pb and Zn concentrationsin earthworms and in three subcellular fractions (cytosol, debris and granules) were quantified. Differentbiomarkers were measured: the expression of a metallothionein gene (mt), the activity of catalase (CAT) andof glutathione-s-transferase (GST), and the protein, lipid and glycogen reserves. Biomarkers were furthercombined in an integrated biomarker index (IBR).The subcellular fractionation provided better predictors of biomarkers than the total internal contentshence supporting its use when assessing toxicological bioavailability of metals to earthworms. The mostsoluble internal pools of metals were not always the best predictors of biomarker responses. metallothioneinexpression responded to increasing concentrations of Cd in the insoluble fraction (debris + granules). Proteinand glycogen contents were also mainly related to Cd and Pb in the insoluble fraction. On the other hand,GST activity was better explained by Pb in the cytosolic fraction. CAT activity and lipid contents variationswere not related to metal subcellular distribution. The IBR was best explained by both soluble and insolublefractions of Cd and Pb.This study further extends the scope of mt expression as a robust and specific biomarker in an ecologicallyrepresentative earthworm species exposed to field-contaminated soils. The genetic lineage of the individuals,assessed by DNA barcoding with cytochrome c oxidase subunit I, did not inuence mt expression