Amount Of Semi-natural Habitats Research Articles

Ecological network design based on optimizing ecosystem services:case study in the Huang-Huai-Hai region, China

In modern agricultural landscapes, constructing ‘ecological networks’ is regarded as an efficient way to conserve biodiversity and maintain ecosystem services. Here we aimed to develop an approach to design ecological corridor by employing the ecological source - resistance surface - ecological corridor framework in combination with semi-natural habitat planning and ecosystem service trade-off assessment. ‘Ecological source patches’ were identified based on a ‘Remote Sensing Ecological Index’ (RSEI) to objectively classify ecological and environmental conditions. Our resulting spatial resistance surface was further modified used based on the ‘Cultivated Land Use Intensity’ index, to derive a high accuracy and rationality of ecological corridor extraction in agriculture landscape. While planning the ecological network, key nodes and resulting semi-natural habitat (SNH) distribution were identified using Linkage Mapper tools and circuit theory. We constructed ecological network scenarios with different amounts of semi-natural habitats and calculated resulting regional ecosystem service values (ESV) using an equivalence factor method to explore optimal spatial layouts. The results showed, while regional ecosystem service values generally increased in line with semi-natural habitat area contained within the ecological network, ecological networks with forests covering 10% of the total area were predicted as an optimal scenario balancing ecosystem services with agricultural yield in the study region. Networks with mixed forest and grassland cover totaling 20% of the area represented an alternative choice that strongly enhanced regional ecosystem services while may still allowing for high agricultural productivity. In constructing corridors, identifying, restoring and protecting key ecological nodes using targeted management and habitat restoration, while protecting existing wetlands and other water bodies that support regional water cycle and supply services, should be prioritized. Regional policy measures furthermore need to promote targeted ecological network planning to help improve the overall sustainability of agricultural production.

Conservation-relevant plant species indicate arthropod richness across trophic levels: Habitat quality is more important than habitat amount

The massive declines in terrestrial arthropods reported across Europe call for effective methods to monitor and promote biodiversity in human-dominated landscapes. Previous studies vary in their support for the suitability of plants as indicators of arthropod diversity, while the potential of subsets of conservation-relevant plant species to estimate arthropod richness remains to be tested. Moreover, the relative importance of plant species richness compared to other factors driving arthropod richness, such as land-use intensity, habitat amount and landscape configuration, is poorly understood. We conducted a multi-scale field study in Southern Germany, sampling vascular plants and terrestrial arthropods in four local land-use types (forest, grassland, arable field, settlement) across large-scale gradients of climate and land-use intensity. We obtained an extensive arthropod dataset using Malaise traps as sampling method and DNA metabarcoding for species identification. We compared the correlation of three sets of plant species richness (total, red-listed and biotope-indicator plants) with arthropod richness, including different trophic and taxonomic groups. Using mixed-effect models, we assessed the partial effects of plant species richness, habitat amount and landscape configuration on local arthropod richness while controlling for climate and land-use effects, and explored the environmental drivers of plant species richness. Arthropod species numbers of all trophic groups strongly responded to species numbers of plants that indicate protected habitats, while red-listed plant species richness was a key determinant for the richness of red-listed arthropods and butterflies. In most cases, plant species richness and temperature were stronger drivers of arthropod richness than the amount of surrounding semi-natural habitat and landscape configuration. While total plant species richness was highest in settlements, the richness of biotope-indicator plants was highest in forests and positively influenced by the amount of semi-natural habitat and edge density. The number of red-listed plant species increased with edge density at the landscape scale but was independent of habitat amount. We conclude that the richness of conservation-relevant plant species provides a powerful indicator of arthropod diversity, and underpins the potential of such plant lists for monitoring habitat quality. Our study highlights the importance of openings in forests for conservation of plants and arthropods as well as of preserving and restoring fragments of high-quality biotopes in agricultural and urban areas where the amount of semi-natural habitat is limited.

Landscape-level honey bee hive density, instead of field-level hive density, enhances honey bee visitation in blueberry

ContextTo date, managing honey bees and wild bees within crop fields remains challenging. Landscape structure is often overlooked when studying the pollination contribution of honey bees. Increasing our understanding on how to predict honey bee visitation in crops is crucial for sustainable management of agroecosystems.ObjectivesWith this study we investigated which landscape and field-level variables determine honey bee and wild bee visitation, and whether honey bee or wild bee visitation influence crop pollination.MethodsSixteen highbush blueberry fields were surveyed for honey bees, wild bees, and crop pollination in Washington, USA. Additionally, within a radius of 1000 m around each field all honey bee hives were located and the surrounding landscape was characterized.ResultsHoney bee hive numbers in the landscape positively correlate with the proportion of blueberry in the landscape. Honey bee visitation was best predicted by landscape-level hive density within a radius of 1000 m, whereas semi-natural habitat and field-level hive density did not impact honey bee visitation. The amount of semi-natural habitat and blueberry within a radius of 1000 m had a positive and negative impact, respectively, on wild bee visitation. Honey bee visitation had a positive effect on blueberry seed set.ConclusionWe conclude that honey bee visitation is determined by the number of honey bee hives in the surrounding landscape. Hence, field-level hive density recommendations miss contributions from other hives in the landscape. Furthermore, semi-natural habitat did not impact honey bee visitation and contributes to diversifying pollinator diets and provides wild bee habitat.

Spatial configuration and landscape context of wildflower areas determine their benefits to pollinator α- and β-diversity

Wildflower areas have become a staple tool within agro-environmental schemes (AES) to counteract pollinator declines. While their role in providing food resources to resident flower-visiting insects is unambiguous, the conservation effectiveness in a landscape context is less clear. Particularly, how multiple vs. single wildflower area utilization differs between simple and complex landscapes is understudied. We examined colonisation and community dynamics of wild bees and hoverflies in 33 newly established wildflower areas across a gradient of landscape complexity (amount of semi-natural habitat) and connectivity (presence of additional wildflower areas) for seven weeks during three consecutive years (one year during and two after establishment). We recorded more than 25% of the wild bee and hoverfly species of Hesse in an area of approx. 10 ha, substantiating the general benefit of wildflower areas to pollinators. While alpha-diversity increased with landscape complexity in isolated wildflower areas, the opposite pattern was observed for connected areas. The low alpha-diversity in complex landscapes indicated a dilution effect between connected sites. The inverse relationship between alpha and beta diversity among wildflower areas within landscapes suggests interspecific trade-offs between local resource conditions and landscape context. Accordingly, the establishment of multiple wildflower areas within AES is advisable to increase connectivity of suitable habitats in simple landscapes. Moreover, adjusting local conditions (plant diversity) to landscape context likely optimizes conservation effectiveness in modern agroecosystems.

Large-scale versus small-scale agriculture: Disentangling the relative effects of the farming system and semi-natural habitats on birds’ habitat preferences in the Ethiopian highlands

While the Western World is facing an inexorable decline of its farmland biodiversity following continuous intensification of production modes, agricultural landscapes in Africa are still largely dominated by small-scale subsistence farming operated by smallholders, mostly harbouring high biodiversity. However, as most African countries are confronted to an unprecedented population growth and a rapid economic development, efforts to intensify food production are widespread, with concomitant potentially negative effects on biodiversity. We conducted a study in a highly contrasted agricultural landscape of the Ethiopian highlands comprising two distinct farming systems: large-scale farming relying on modern, combine machinery and technology (e.g. enhanced crop varieties, application of herbicides, pesticides and synthetic fertilizers) vs small-scale traditional farming. Our objective was to disentangle the effects upon avian biodiversity of the operating farming system and the extent of semi-natural habitat features in the wider landscape. We performed a model selection approach to assess habitat selection by the overall bird community as well as the wintering, endemic and open habitat species, respectively. Our results show that habitat preferences of birds in the Ethiopian highlands were mainly driven by the amount of semi-natural habitats within the landscape, with varying effects depending on the farming system itself. While large-scale farming had overall more negative effects on birds, some typical open habitat species were mostly restricted to these wide-open landscapes. Our findings thereby suggest that both farming systems could coexist as long as semi-natural habitats are preserved and agricultural management maintained in its current practices. We emphasize the urgent need to conduct further studies integrating the socio-economic aspects in order to better predict future impacts of agricultural intensification processes on African farmland biodiversity.

Effects of field margin type and landscape composition on predatory carabids and slugs in wheat fields

Abstract Semi-natural vegetation can affect the colonization of crop fields by invertebrates as a source habitat and by the supplementation of resources. Such effects have been studied at the scale of field margins or at the wider landscape scale, but rarely in combination. Variation in their response to local and landscape factors between crop pests and their natural enemies can have consequences for biological pest control. We studied Arion spp. and Deroceras reticulatum as major slug pests in Europe and beyond, and predatory carabids as their potential antagonists. Predatory carabids and slugs were sampled in 18 wheat fields bordered by different habitat types (arable fields, woody or herbaceous semi-natural vegetation) along a gradient of landscape composition (amount of semi-natural habitats in 1 km radius). Species richness of predatory carabids increased with the amount of semi-natural habitats in the landscapes around wheat fields. No effects of landscape composition or adjacent habitat type were observed for predatory carabid activity-density and Deroceras reticulatum. In contrast, Arion spp. had highest numbers in structurally poor landscapes, but only if fields were bordered by woody vegetation. Thus, Arion spp. thrived best in situations where predatory carabid species richness was lowest, indicating that carabids may contribute to the natural control of slug populations. The divergent patterns between carabids and the two slug species demonstrate that more studies of multiple pest species are needed in order to develop comprehensive landscape management strategies for conservation biological control.

Relationships among ecological traits of wild bee communities along gradients of habitat amount and fragmentation

Amount of semi‐natural habitats (permanent grasslands, woodlands and hedgerows) and their level of fragmentation are among the main determinants of wild bee diversity in agricultural landscapes. However, their impact on the distribution of bee ecological traits has received little attention. In this study, we aimed to explore whether changes in the distribution of bee ecological traits along gradients of habitat amount and fragmentation were due to a direct effect of landscape context on multiple traits (‘response traits’) or to a correlation of response traits with other ecological traits not involved in the response of bee species to landscape context. In two study regions in southwest France and southeast Australia, we used a RLQ analysis (three‐table ordination method) to link bee traits with habitat amount and fragment isolation measured at the landscape scale. We found that bee ecological traits shifted at the community‐level in association with landscape gradients, whereas species‐level associations among bee traits and phylogenetic clustering in bee communities were of only minor importance in determining such shifts. We found that traits such as body size and nest location were closely linked to habitat amount and fragmentation. We also observed regionally‐specific relationships among ecological traits, suggesting that the regional species pool can play an important role in determining the response of bee communities to habitat amount and fragmentation. Our findings suggest that improved knowledge about how trait‐based responses mediate the impact of landscapes on wild bee communities will allow better prediction and understanding of subsequent effects on ecosystem functioning.

Scale-dependent effects of landscape composition and configuration on natural enemy diversity, crop herbivory, and yields.

(1) Land-use intensification in agricultural landscapes has led to changes in the way habitats and resources are distributed in space. Pests and their natural enemies are influenced by these changes, and by the farming intensity of crop fields. However, it is unknown whether the composition of landscapes (amount and diversity of land cover types) or their configuration (spatial arrangement of cover types) are more important for natural enemy diversity, and how they impact crop damage and yields. In addition, effects of interactions between local farming practices (organic vs. conventional) and landscape variables are unclear. (2) Here, we make use of a data set where landscape composition and configuration were uncorrelated across multiple spatial scales. Natural enemies, crop damage, and yields were sampled in 35 organic and conventional crop fields. Out of seven broad natural enemy taxa, five were positively affected by a complex landscape configuration. In contrast, only carabids were positively affected by the amount of seminatural habitat around fields. Increasing diversity of land cover types had positive effects on some, but negative effects on other taxa. Effect sizes varied among taxa but increased with increasing spatial scale, defined by circular areas of increasing radius around fields. (3) The diversity of aerial, but not of ground-dwelling enemies was higher in fields under organic than conventional management. Interactions of local and landscape variables were important for birds, but not other enemies. Bird richness was higher in organic fields in simple landscapes, but not in landscapes with complex configuration or high land cover diversity. (4) Crop damage decreased with landscape diversity, but increased in conventional fields with complex configuration. Yields increased with both parameters in conventional fields only, and were higher on average in organic compared to conventional fields. Enemy diversity was positively related to crop damage, indicating positive density-dependence of enemies on pests. However, the diversity of aerial enemies was also positively related to yields. (5) Our results suggest that the effectiveness of agrienvironmental schemes for managing natural enemy diversity, crop damage and yields could be enhanced by optimizing the effects of distinct landscape parameters, particularly landscape configuration and diversity, across scales.

Incidental impacts from major road construction on one of Asia’s most important wetlands: the Inner Gulf of Thailand

Large-scale infrastructure development projects can have devastating impacts upon biodiversity. We investigated the impacts of roads on land-use change in a coastal area of South-east Asia, an area of high biodiversity subject to intense human pressure. The objectives of this study were (1) to examine impacts of major roads on rates of land-use change and habitat conversion in and around the Inner Gulf of Thailand, a large wetland of international importance; and (2) to evaluate the conversion rate of salt-pans (a critical habitat for several species of threatened shorebirds) between 1990 and 2011. Nine land-use types were categorised into two groups: seminatural and human-dominated. Proportions of each land-use type at different distances from major roads were determined using GIS data. More than 40% of the area was used for aquaculture during the entire study period. The amount of seminatural habitats was positively correlated with distance from major roads. Agriculture and urban areas showed the greatest changes in area (decreasing and increasing, respectively). Habitats that changed from seminatural to human-dominated were negatively correlated with distance from major roads. Most of the converted salt-pans were lost to aquaculture. To protect important wetlands from further biodiversity loss: (1) new major road construction should be avoided or minimised; and (2) land-use strategies that both satisfy short-term human needs and maintain ecosystem capacity to provide services in the long term should be adopted.

Mass‐flowering crops increase richness of cavity‐nesting bees and wasps in modern agro‐ecosystems

AbstractConsiderable uncertainties exist on how increased biofuel cropping affects biodiversity. Regarding oilseed rape, the most common biofuel crop in the EU, positive responses of flower‐visiting insects to plentiful nectar and pollen seem apparent. However, previous investigations on this insect guild revealed conflicting results, potentially because they focused on different taxonomic groups representing a narrow range of ecological traits and considered only short time periods. Here, using trap nests in landscapes with independent gradients in area of oilseed rape and seminatural habitats, we assessed the whole community of cavity‐nesting bees and wasps, including early‐ and late‐emerging species. Our study's temporal resolution allowed determination of flowering and postflowering effects of oilseed rape on these species' richness, abundance, and mortality. Species richness of cavity‐nesting bees and wasps significantly increased with oilseed rape, although nesting activity was considerably higher after mass flowering. In addition to increasing richness independently of oilseed rape, the amount of seminatural habitat in the landscape was the sole positive driver of insect abundance once the community's dominant species was accounted for as a covariate. Thus, growth of the co‐occurring species' community is not stimulated by the resource pulse provided by oilseed rape early in the year, but by persistent resources provided by seminatural habitats after mass flowering. Early individuals of bivoltine species' first generations accumulated in seminatural habitats when these habitats were scarce, but became increasingly diluted when habitat availability increased. Once established, later foraging females generally benefited from the resource availability of seminatural habitats when initializing the second generation. We conclude that mass‐flowering crops, despite covering only a short interval of the community's main activity phase, benefit bee and wasp species richness. However, seminatural habitats are crucial in maintaining viable communities of flower‐visiting insects at the landscape scale, mitigating potential negative effects of high land‐use intensities in modern agro‐ecosystems.

Landscape composition influences the activity density of Carabidae and Arachnida in soybean fields

The distribution and abundance of semi-natural and crop habitats within agricultural landscapes is likely to greatly influence population dynamics of ground-dwelling arthropods. We investigated the influence of landscape heterogeneity and composition on the pitfall trap catch of Carabidae, Araneae, and Opiliones in soybean fields. Although we hypothesized that each predator group would increase with landscape heterogeneity and the amount of semi-natural habitat; we found variation in the response of the study organisms. The activity density of Araneae supported our hypothesis, increasing in soybean fields in landscapes with an abundance of forests and grasslands. The diversity of Carabidae in soybean fields increased in landscapes with an abundance of grassland habitat but the activity density of Carabidae declined. This decline was driven extensively by the species Poecilus chalcites which was less abundant in fields located within grassland-rich landscapes. Opiliones declined with increasing landscape heterogeneity but increased within forested landscapes. The spatial scale at which taxa responded to landscape composition also varied. Our hypothesis was that dispersal capacity would influence the spatial scale at which ground-dwelling arthropods responded to landscape structure. We found that Carabidae, which generally disperse by walking, responded to smaller spatial scales than linyphiid spiders, which frequently balloon. However, Lycosidae and Opiliones which also disperse mainly by walking as adults responded at larger spatial scales. These data suggest that understanding taxon-specific relationships to landscape variables should be considered in analyses of arthropod response to landscape structure.

Intensification of agriculture, landscape composition and wild bee communities: A large scale study in four European countries

The impacts of agricultural practices and landscape composition on bee communities were investigated in 14 sites located in four Western European countries (Belgium, France, the Netherlands and Switzerland). Standardized interviews with farmers assessed agricultural practices in terms of agricultural inputs (nitrogen fertilization and pesticides), livestock density and crop types. The proportion of semi-natural habitats was calculated for each site. We showed negative effects of agricultural intensification on species richness, abundance and diversity of wild bees. By contrast, bee species richness increased with the amount of semi-natural habitats in the landscape. Using a co-inertia analysis, we found an opposition between two types of agricultural specialization: towards crop production or towards animal husbandry. Species richness, abundance and diversity of wild bees were greater in sites turned towards crop production. In these sites, flowering crops provided abundant food resources for bees whereas, in the other group of sites, intensive animal husbandry led to landscapes dominated by forage crops rather than flower-rich permanent grasslands. We also showed that bumblebees seemed to be less sensitive to agricultural intensification than solitary bees.

Providing foraging resources for bumblebees in intensively farmed landscapes

Habitat loss and the intensification of farming practices have caused severe declines in the range and abundance of many bumblebee species in the UK. This study examines the long-term effectiveness of four different management strategies to enhance and restore bumblebee foraging habitat on arable field margins in two regions with markedly contrasting landscape structure, farming systems and amount of semi-natural habitat. Bumblebees were monitored on 120 field margins in July and August, together with estimates of flower abundance and the vegetation composition. There were no differences in the abundance and diversity of the bumblebee assemblage between the two regions (East Anglia and the West Midlands), despite a greater abundance of flowers and flowering species on the lighter soils of the West Midlands. Very few bumblebees were recorded on intensively managed cereal field margins due to the lack of dicot species. Conservation headlands supported a significantly greater number of flowering dicots, but the majority of these were annuals which did not provide good forage for bumblebees. From an agronomic and ecological perspective, the removal of field margins from the cropping system was the best strategy for providing foraging habitat for bumblebees. Non-crop habitat resulting from natural regeneration provided good foraging habitat for bumblebee species, but most of the key forage species were pernicious weeds of agriculture ( Cirsium spp.). Sowing non-crop field margins with wildlife seed mixtures had the potential for providing the best foraging habitat for bumblebees, so long as preferred forage species were introduced (e.g. Trifolium pratense). Further research is required to refine and target this management prescription for bumblebee conservation in the wider countryside.