Context
In fragmented landscapes, edge influence (EI) can be an important driver of ecological change. Multiple edges can interact so that distance to the nearest edge is not an accurate predictor of ...EI, an issue referred to as ‘interactive EI’. This is especially important in conservation corridors, since their linear nature puts multiple edges in close proximity.
Objectives
We assess how corridor width, an important design variable in conservation corridors, influences EI on arthropod diversity.
Methods
Arthropods were sampled along the edges of grassland corridors of different widths, and from nearby protected areas (PAs) as reference. The influence of corridor width on edge-related change in arthropod diversity was assessed. This was done at the scale of single corridors, and in comparison to nearby PAs.
Results
Corridor width influences EI strength. This was apparent at the local scale, and for those species associated with the corridor interior. At the landscape scale, distance to the nearest edge was more important for the similarity of corridors to PAs than corridor width. This was driven by edge specialists rather than grassland interior species.
Conclusions
Interactive EI influences local edge responses, especially for species which avoid edges. Future assessments should incorporate processes operating across larger scales into edge responses. We show that there is much greater conservation value in larger corridors for grassland specialists than smaller corridors, and for a given area of set-aside conservation land, we support the establishment of a few wide corridors over many narrow corridors in production landscapes.
Habitat loss threatens insect diversity globally. However, complementary vegetation types in remaining habitat increases opportunities for species survival. We assess the extent to which indigenous ...forest patches moderate the impact of exotic commercial afforestation on grassland butterflies. Butterflies were sampled in grassland along uncorrelated gradients of landscape-scale indigenous forest and plantation cover, while controlling for variation in local vegetation composition. We separately assessed responses by butterfly groups differing in habitat preference, larval diet, and mobility. There was no effect of landscape- or local-scale variables on species richness, but there was a strong interactive effect of forest and plantation cover on butterfly assemblage structure. The effect varied according to species traits. When forest cover was high, assemblages did not differ at different levels of plantation cover. However, plantation cover significantly influenced assemblage structure when forest cover was low. Grassland with limited forest cover in the protected area supported unique assemblages with high frequency of less mobile, specialized species with herbaceous larval host plants, whereas grassland with low forest cover near plantations had a prevalence of mobile, generalist species. A positive association between forest cover and butterflies with woody larval host plants suggests that indigenous forest patches improved the suitability of fragmented grassland for a subset of butterflies, emphasising the value of natural heterogeneity in transformed areas. However, certain butterfly traits associated with large, open grassland were under-represented in grassland between plantations, underscoring the importance of open areas in the broader landscape to conserve the full diversity of species.
Landscape ecological networks (ENs) consist of landscape-scale conservation corridors that connect areas of high natural value within a production mosaic with protected areas (PAs). In South Africa, ...ENs have been implemented on a large spatial scale to offset the negative impacts of plantation forestry on indigenous grasslands. We focus on corridor width as a factor for conserving dung beetle and ant diversity within an EN. We also investigate the importance of natural environmental heterogeneity (elevation, vegetation type) and habitat quality (soil hardness, invasive alien plant density). We sampled dung beetles and ants in 30 corridors of different sizes, and at ten sites in a nearby PA. In addition, we also analysed dung beetles according to their feeding guild. Tunnelling dung beetle species richness increased with corridor width. Rolling dung beetle species richness was higher in the PA than in the corridors of the EN. The dung beetle assemblage within the EN differed from that within the PA. Corridors of various widths differed in ant composition but not in species richness. Furthermore, the PA and the EN differed in environmental variables, which contributed to differences in dung beetle species richness and assemblage composition. Within the EN, environmental heterogeneity across the landscape was more important than corridor width for driving species diversity of both dung beetles and ants. When planning future ENs, wide corridors (>280 m) that encompass as much natural heterogeneity across the landscape as possible will best conserve the range of local insect species.
Habitat degradation is a major concern in transformed landscapes, as it reduces complexity by removing species, interactions, and ultimately biodiversity. Degradation is also of concern for ...ecological networks (ENs) composed of an interconnected system of conservation corridors among South Africa's commercial forestry compartments. These corridors are predominantly grasslands, and used as rangeland, so managed to optimize grazing conditions. Yet, how this management approach influences biodiversity remains unknown. Here, we studied how butterfly assemblages respond to local differences in rangeland quality (low, high and reference sites), and how this effect compared to that of local environmental variables (e.g. rockiness and bare ground), meso environmental gradients (e.g. topographic position and aspect), and landscape composition (i.e. proportion of different land cover types in the surrounding matrix). We calculated species richness and composition, Shannon's diversity index (H′), and the Butterfly Conservation Index (BCIn) representing the proportion of sensitive and range-restricted butterfly species per site. Rangeland quality was considered less important for butterflies than other environmental variables, but it was also significantly confounded with other environmental variables. At the landscape scale, proportion of grassland in the landscape matrix influenced butterfly assemblage composition, while proportion of thicket had a significant positive effect on BCIn. Moreover, the effect of elevation on assemblage composition emphasizes the value of maintaining environmental gradients within these conservation corridors. At the meso spatial scale, butterfly species richness and diversity (H′) declined with increased dominance by a single plant species, which usually occurs late in a normal fire cycle. This suggests a reliance by butterflies on recurring natural disturbances for long-term persistence. We recommend moderate patch burning and grazing, as well as occasional hot burns to reduce thicket in Afromontane grassland. This approach would improve local scale vegetation patterns, and increase heterogeneity across the landscape for conserving these butterflies into the future.
•Butterfly assemblages responded inconclusively to rangeland quality.•Butterflies responded conclusively to fire and its effect on plant's dominance structure.•Grassland corridors should represent a range in elevation and topographic positions.•Burning and grazing at moderate levels help sustain grassland butterflies.
To ensure integrity of protected areas we need to understand how species respond to anthropogenic borders. We investigate, from a metacommunity perspective, the direct and indirect mechanisms by ...which transformed areas affect distribution patterns of ground-living arthropod assemblages inhabiting an extensive protected area adjacent to fruit orchards in an important biosphere reserve. Arthropods and environmental variables were sampled along transects perpendicular to natural-orchard edges. Influence of distance from orchard boundary, degree of impermeability of the boundary, orchard habitat quality (local scale land-use intensity), and edge-induced changes in local environmental variables on arthropod species richness and composition in non-crop habitats were assessed. Arthropod groups were assessed in terms of habitat fidelity: species associated with natural habitat (stenotopic species), those within crop habitat (cultural species), and those showing no preference for either habitat (ubiquitous species). Spillover resulted in higher cultural species richness near edges, but not higher overall species richness. Environmental filtering was important for stenotopic species composition, which was influenced by edge-induced changes in environmental variables. Ubiquitous species composition was determined by orchard impermeability. Increased orchard habitat quality was associated with higher cultural and ubiquitous species richness. The effects of orchards on assemblages in natural habitats can be variable, but predictable when using species habitat specificity in conjunction with a metacommunity framework. High intensity orchards may act as sink habitats, especially for species that readily disperse between crop and natural habitats. Here we recommend that local buffer strips are > 85 m wide, which will reduce the influence of cultural species spillover on sensitive natural ecosystems.
•Diverse herbaceous cover crops promoted vineyard arthropod diversity.•It favoured all taxa, feeding guilds and organisms in different microhabitats.•No effect was detected for agrochemicals used in ...a sensitive integrated approach.•Individual management practices influenced arthropods more than overall farm regime.
Agricultural intensification threatens biodiversity, requiring a shift to agroecological farming. Identifying locally-specific management practices that can effectively enhance biodiversity can help guide farmland conservation efforts. We assess the effect of management practices and environmental variables on arthropod diversity under varying vineyard management regimes in a South African biosphere reserve. We also determine whether the implementation of these practices and their combined effect on arthropods differ between integrated and organic vineyards. Arthropod morphospecies richness and evenness were assessed for different taxonomic groups (spiders, beetles, and true bugs), in different positions in the crop (ground level, on cover crops, and on vine foliage) and for different feeding guilds (herbivores, detritivores, and predators). Percentage herbaceous vegetation cover had a consistent positive effect on morphospecies richness across taxa, microhabitats, and guilds. Other vegetation-related variables, such as volume of plant litter, plant species richness, and plant height positively influenced several of the biodiversity responses. We did not detect any negative effect of agrochemicals used in an integrated approach, or a strong effect of overall farming approach (organic vs. integrated) on the species richness or evenness of any of the focal taxa, sampled positions, or guilds. These results indicate that the maintenance of dense and diverse cover crops is a strategic way to enhance vineyard arthropod diversity where other management practices are already implemented sensitively. This highlights that minimal adjustment of management practices can greatly benefit farmland biodiversity conservation and is in keeping with the ethos of the concept of a biosphere reserve.
Understanding the effects of agricultural practices on farmland biodiversity requires a landscape perspective, as local-scale processes can be influenced by the structure of the surrounding ...landscape. We assess whether amount of natural vegetation in the landscape interacts with two local-scale variables, in-crop vegetation cover and farming approach (organic vs. integrated), to influence vineyard arthropods within the Cape Floristic Region. Responses were assessed for overall arthropods and three sub-categories based on arthropod species affinity to vineyards, natural vegetation (fynbos), or both systems. There were no significant interactions between local and landscape variables that affected the species richness of arthropods. However, there was a main effect of increased in-crop herbaceous vegetation that increased the species richness of overall arthropods and ubiquitous arthropods. Furthermore, interactions between the amount of natural vegetation and local-scale processes influenced composition of arthropod assemblages. Assemblages among integrated vineyards were similar in composition irrespective of landscape context, whereas they were dissimilar among organic vineyards in landscapes with different levels of natural vegetation. Our results suggest a relatively lower homogenising effect of organic farming than non-organic farming on landscape-scale biodiversity and that maintaining non-crop vegetation in vineyards benefits arthropod diversity. These findings emphasise the importance of considering the interplay between local management and the surrounding landscape in promoting biodiversity in a farming and conservation mosaic. This is especially important where landscapes vary greatly in complexity, as in many agricultural regions worldwide.
Environmental degradation is a global phenomenon with a high likelihood of influencing human quality of life. Effective management responses are needed to achieve societal goals of sustainability. We ...develop here a new monitoring protocol (Management Check: MATCH) that comprehensively evaluates management outcomes at the operational level. Using the Driver-Pressure-State-Impact-Response (DPSIR) framework, we identified pressures influencing ecosystem integrity inside conservation corridors and commercial compartments of a timber production landscape mosaic. They were 1) domestic livestock grazing (the only exogenous pressure), 2) fire management, 3) invasive alien plants (IAPs), and potential soil erosion from two sources: 4) roads, and 5) harvested timber compartments. We assessed the effects of these on wetland and stream buffers. Environmental incidents accounted for more serious management issues (e.g. oil spills). Management responses were systematically unpacked into point-form questions, which formed the building blocks of our monitoring protocol. We assessed management in twelve plantations in KwaZulu-Natal, South Africa. Answers were compared with Best Operational Practice (BOP), and reworked into a Weighted Index of Compliance (WIC) per section. We found that there was poor management of livestock grazing, but good management of IAPs, roads, and timber compartments. Management of wetland and stream buffers was very good. Fire management presented problems linked to lack of direct effects, measurable at the spatial and temporal scales of operations. We discuss operational outcomes within their respective legislative frameworks, and suggest ways of improving management operations, where needed. MATCH is the first monitoring protocol to comprehensively assess environmental management of commercial forestry at the operational level, and to clearly translate operational activities into measurable progress towards strategic goals. In doing so, MATCH breaks down silos and builds bridges for efficient environmental management in dynamic socio-ecological systems. Moreover, the principles developed here can be applied to build tools that help manage major risks in other economic sectors too. Overall, MATCH strengthened strategic and informed action, which is necessary at multiple levels of an organization, to combat major societal risks, such as environmental degradation.
•Management responses were identified for environmental pressures in forestry.•MATCH is a qualitative assessment of management compared with best practice.•Weighted Indices of Compliance (WIC) rated management efficiency for each pressure.•Management of each pressure was interpreted within their legislative frameworks.•Using MATCH, we can identify management gaps, and report ongoing progress.
Complementarity is crucial when prioritizing sites for biodiversity conservation. Networks of conservation corridors (CCs) can contribute to regional representativeness by complementing biodiversity ...features included in existing protected areas (PAs). We ask whether criteria important for CC management and design are effective at prioritizing complementary sites, and how the consideration of species represented in PAs influence criteria performance. We focused on species turnover of generalist and specialist dragonflies across 88 riverine sites. Criteria assessed included site-level estimates of dragonfly species richness, estimates of local habitat quality and corridor width. Measures of local habitat quality were based on either dragonfly indicator species or proportion of alien vegetation. Results showed that CCs complement dragonfly diversity in PAs by contributing unrepresented generalist species. Of the criteria, corridor width was the most efficient at prioritizing complementary sites, while prioritization based on dragonfly indicator species or species richness underperformed. When aiming to prioritize CC sites that also complement sites situated in established PAs, wide corridors with low levels of alien vegetation should be favoured.
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•We assessed parasitoid assemblages in vineyards and adjacent remnant vegetation.•Remnants maintained rich and distinct parasitoid assemblages in vineyard landscapes.•Parasitoid ...spillover between remnant natural vegetation and vineyards was limited.•Inhospitable surrounding vineyards isolated parasitoids in remnants.•Conserving remnants and improving matrix quality can maintain parasitoid diversity.
The maintenance of remnant natural vegetation in agricultural landscapes is an important component of conservation programmes that promote farmland sustainability. Demonstrating the biodiversity value of remnant vegetation can support conservation initiatives in production landscapes. We assessed the diversity and assemblage structure of hymenopteran parasitoids in fragments of native scrubland (fynbos) within vineyard landscapes in the Cape Floristic Region of South Africa. We also aimed to detect positive effects of adjacent fynbos on vineyard parasitoids, such as elevated diversity at vineyard edges adjoining fynbos or evidence of parasitoid spillover into vineyards. Fynbos remnants had significantly higher parasitoid abundance and richness than neighboring vineyards, and supported assemblages distinct from those within vineyards. Parasitoid diversity in vineyards was not influenced by distance to remnant vegetation. Additionally, evidence for spillover was limited, as there were abrupt changes in assemblage structure at fynbos/vineyard boundaries. Surrounding vineyards therefore seem to have an isolating effect on parasitoids in remnants. This emphasises the need to increase the permeability of the vineyard matrix. Yet, our results show that remnants are important for retaining parasitoid diversity and provide refugia for certain species within the disturbed agricultural environment. Approaches that combine natural remnant conservation with arthropod-friendly activities in vineyards would be an effective way to support diverse and functional parasitoid assemblages at the landscape scale. Conservation of this diversity will be crucial for maintaining long-term ecological resilience in agricultural landscapes.
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