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Recent reports of local extinctions of arthropod species 1 , and of massive declines in arthropod biomass 2 , point to land-use intensification as a major driver of decreasing biodiversity. However, to our knowledge, there are no multisite time series of arthropod occurrences across gradients of land-use intensity with which to confirm causal relationships. Moreover, it remains unclear which land-use types and arthropod groups are affected, and whether the observed declines in biomass and diversity are linked to one another. Here we analyse data from more than 1 million individual arthropods (about 2,700 species), from standardized inventories taken between 2008 and 2017 at 150 grassland and 140 forest sites in 3 regions of Germany. Overall gamma diversity in grasslands and forests decreased over time, indicating loss of species across sites and regions. In annually sampled grasslands, biomass, abundance and number of species declined by 67%, 78% and 34%, respectively. The decline was consistent across trophic levels and mainly affected rare species; its magnitude was independent of local land-use intensity. However, sites embedded in landscapes with a higher cover of agricultural land showed a stronger temporal decline. In 30 forest sites with annual inventories, biomass and species number-but not abundance-decreased by 41% and 36%, respectively. This was supported by analyses of all forest sites sampled in three-year intervals. The decline affected rare and abundant species, and trends differed across trophic levels. Our results show that there are widespread declines in arthropod biomass, abundance and the number of species across trophic levels. Arthropod declines in forests demonstrate that loss is not restricted to open habitats. Our results suggest that major drivers of arthropod decline act at larger spatial scales, and are (at least for grasslands) associated with agriculture at the landscape level. This implies that policies need to address the landscape scale to mitigate the negative effects of land-use practices.
Contribution of individual years to overall trends a, To assess the contribution of individual years to the overall trend, we repeated the linear mixed models for overall biomass, abundance and number of species, and excluded one year each time. The distribution of t and z values for the effect of the year from subset models (white), and from the full models including all years (black), are shown (11 models for grasslands and 10 models for forests). Grey bars denote effect of the year 2008 (the year with the strongest effect on overall trend estimates). b, In addition, we tested whether the observed effect of year differed from a random expectation by randomizing the order of years 100× for forests and grasslands before modelling. The distribution of t and z values for the effect of the year from models with randomly ordered years (white) and models with the years ordered correctly (black) are shown (101 models each for grasslands and forests). Vertical dashed lines indicate levels of significance with P < 0.05. The results in a show that both weaker and stronger temporal trends could be detected when single years were excluded from the analysis, compared to the full model including all years. Results in b show that models with the years ordered randomly produced effects of the year that were normally distributed around zero, and only the models with years ordered correctly generated strong temporal trends. For a more detailed discussion, see Supplementary Information section 3.
Effect of tree mortality on arthropod trends a, The relative change in the number of arthropod species between the first two and the final two study years was similar for managed (n = 19) and unmanaged (n = 9) forest sites (z = 0.648, P = 0.517, derived from a linear mixed model with relative difference in species number as response, harvesting category as fixed and region as random effect). Dots show raw data per site. Boxes represent data within the 25th and 75th percentile, black lines show medians, and whiskers show 1.5× the interquartile range. b, When considering actual tree mortality between forest inventories in 2009 and 2016, declines in the number of arthropod species were weaker at sites with higher tree mortality (z = 2.536, P = 0.011, derived from a linear mixed model with relative difference in species number as response, tree mortality as fixed and region as random effect). Dots show raw data per site. The blue line visualizes the significant relationship between the change in the number of arthropod species and tree mortality based on the linear mixed model, and the shaded area represents confidence intervals. This suggests that changes in habitat conditions and heterogeneity linked to tree mortality—such as increasing canopy openness, herb cover or deadwood availability—moderated declines in the number of arthropod species. More research is needed to identify mechanistic relationships. Tree mortality included both natural mortality and timber harvesting. Forest sites had a stand age of, on average, 116 years (minimum of 30 years and maximum of 180 years) and therefore did not include overmature stands. Owing to stand age and because management was abandoned 20 to 70 years before this study started, natural tree mortality was low even in unmanaged stands. We expect increasingly positive effects of natural tree mortality and associated increased structural diversity and heterogeneity⁴⁰ on arthropod trends with increasing stand age, but further research is required. In Germany, harvesting is usually conducted as shelterwood cutting. In our sites, the harvested amount over the course of our study reached a maximum of 1% of the standing volume per year. More intense harvesting systems (such as clear cutting), which lead to less heterogeneous habitat conditions, may not have similar moderating effects on arthropod declines.
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Nature | Vol 574 | 31 October 2019 | 671
Arthropod decline in grasslands and forests
is associated with landscape-level drivers
Sebastian Seibold1,2*, Martin M. Gossner3, Nadja K. Simons1,4, Nico Blüthgen4, Jörg Müller2,5,
Didem Ambarlı1,6, Christian Ammer7, Jürgen Bauhus8, Markus Fischer9, Jan C. Habel1,10,
Karl Eduard Linsenmair11, Thomas Nauss12, Caterina Penone9, Daniel Prati9, Peter Schall7,
Ernst-Detlef Schulze13, Juliane Vogt1, Stephan Wöllauer12 & Wolfgang W. Weisser1
Recent reports of local extinctions of arthropod species1, and of massive declines in
arthropod biomass2, point to land-use intensication as a major driver of decreasing
biodiversity. However, to our knowledge, there are no multisite time series of
arthropod occurrences across gradients of land-use intensity with which to conrm
causal relationships. Moreover, it remains unclear which land-use types and arthropod
groups are aected, and whether the observed declines in biomass and diversity are
linked to one another. Here we analyse data from more than 1million individual
arthropods (about 2,700species), from standardized inventories taken between 2008
and 2017 at 150grassland and 140forest sites in 3regions of Germany. Overall gamma
diversity in grasslands and forests decreased over time, indicating loss of species
across sites and regions. In annually sampled grasslands, biomass, abundance and
number of species declined by 67%, 78% and 34%, respectively. The decline was
consistent across trophic levels and mainly aected rare species; its magnitude was
independent of local land-use intensity. However, sites embedded in landscapes with a
higher cover of agricultural land showed a stronger temporal decline. In 30forest sites
with annual inventories, biomass and species number—but not abundance—decreased
by 41% and 36%, respectively. This was supported by analyses of all forest sites sampled
in three-year intervals. The decline aected rare and abundant species, and trends
diered across trophic levels. Our results show that there are widespread declines in
arthropod biomass, abundance and the number of species across trophic levels.
Arthropod declines in forests demonstrate that loss is not restricted to open habitats.
Our results suggest that major drivers of arthropod decline act at larger spatial scales,
and are (at least for grasslands) associated with agriculture at the landscape level. This
implies that policies need to address the landscape scale to mitigate the negative
eects of land-use practices.
Much of the debate surrounding the human-induced biodiversity crisis
has focused on vertebrates
, but population declines and extinctions
may be even more substantial in small organisms such as terrestrial
. Recent studies have reported declines in the biomass of
flying insects
, and in the diversity of insect pollinators
, butterflies
and moths
, hemipterans
and beetles
. Owing to the associated
negative effects on food webs
, ecosystem functioning and ecosystem
, this insect loss has spurred an intense public debate. However,
time-series data relating to arthropods are limited, and studies have
so far focused on a small range of taxa11,13,14, a few types of land use and
—or even on single sites
. In addition, many studies lack species
or high temporal resolution
. It therefore remains unclear
whether reported declines in arthropods are a general phenomenon
that is driven by similar mechanisms across land-use types, taxa and
functional groups.
The reported declines are suspected to be caused mainly by human
land use
. Locally, farming practices can affect arthropods directly by
application of insecticides
, mowing
or soil disturbance, or indirectly
via changes in plant communities through the application of herbi-
cides or fertilizer
. Forestry practices can also affect local arthropod
Received: 8 February 2019
Accepted: 16 September 2019
Published online: 30 October 2019
1Terrestrial Ecology Research Group, Department of Ecology and Ecosystem Management, Technical University of Munich, Freising, Germany. 2Field Station Fabrikschleichach, Department of
Animal Ecology and Tropical Biology, Julius-Maximilians-University Würzburg, Würzburg, Germany. 3Forest Entomology, Swiss Federal Research Institute WSL, Birmensdorf, Switzerland.
4Ecological Networks, Department of Biology, Technical University of Darmstadt, Darmstadt, Germany. 5Bavarian Forest National Park, Grafenau, Germany. 6Department of Agricultural
Biotechnology, Faculty of Agricultural and Natural Sciences, Düzce University, Düzce, Turkey. 7Silviculture and Forest Ecology of the Temperate Zones, University of Göttingen, Göttingen,
Germany. 8Institute of Forest Sciences, Faculty of Environment and Natural Resources, University of Freiburg, Freiburg, Germany. 9Institute of Plant Sciences, University of Bern, Bern,
Switzerland. 10Evolutionary Zoology, Biosciences, Salzburg University, Salzburg, Austria. 11Department of Animal Ecology and Tropical Biology, Julius-Maximilians-University Würzburg,
Würzburg, Germany. 12Faculty of Geography, Philipps-University Marburg, Marburg, Germany. 13Max Planck Institute for Biogeochemistry, Jena, Germany. *e-mail:
Content courtesy of Springer Nature, terms of use apply. Rights reserved
... However, these represent only a small fraction of Earth's biodiversity. Several reports have raised the possibility that insects are in sharp decline, in both abundance and species diversity (6)(7)(8)(9)(10)(11). It is therefore important to evaluate progress in insect population genomics and to consider how this field can contribute to insect conservation. ...
... They are important sources of food for a huge range of vertebrates and play a vital role in a wide range of ecosystem functions, most notably decomposition and plant pollination. Several recent reports have highlighted insect declines, indicating that losses could exceed even those found in other taxonomic groups (6)(7)(8)(9)(10)(11). Large numbers of species may therefore face extinction before they are known. ...
... Reports of insect declines focus mainly on population trends, finding declines in total biomass, abundance, range size, and species richness (6)(7)(8)(9)(10)(11). One of the most comprehensive studies, focusing on flying insects in 63 sites in northwestern Germany, indicated a 75% reduction in biomass over 27 years (8). ...
Insects constitute vital components of ecosystems. There is alarming evidence for global declines in insect species diversity, abundance, and biomass caused by anthropogenic drivers such as habitat degradation or loss, agricultural practices, climate change, and environmental pollution. This raises important concerns about human food security and ecosystem functionality and calls for more research to assess insect population trends and identify threatened species and the causes of declines to inform conservation strategies. Analysis of genetic diversity is a powerful tool to address these goals, but so far animal conservation genetics research has focused strongly on endangered vertebrates, devoting less attention to invertebrates, such as insects, that constitute most biodiversity. Insects’ shorter generation times and larger population sizes likely necessitate different analytical methods and management strategies. The availability of high-quality reference genome assemblies enables population genomics to address several key issues. These include precise inference of past demographic fluctuations and recent declines, measurement of genetic load levels, delineation of evolutionarily significant units and cryptic species, and analysis of genetic adaptation to stressors. This enables identification of populations that are particularly vulnerable to future threats, considering their potential to adapt and evolve. We review the application of population genomics to insect conservation and the outlook for averting insect declines. Expected final online publication date for the Annual Review of Animal Biosciences, Volume 11 is February 2023. Please see for revised estimates.
... Worldwide concerns have been raised about the widespread decline of arthropods (Sánchez-Bayo and Wyckhuys 2019), associated mainly with landscape simplification and agricultural intensification at the landscape level (Tscharntke et al. 2005;Seibold et al. 2019;van Klink et al. 2020). In recent years in Uruguay, there has been a 138% increase of agricultural land availability, primarily associated with increasing soybean acreage (MGAP-DIEA 2016). ...
... Recently, concerns have been raised about the widespread decline of arthropods (Sánchez-Bayo and Wyckhuys 2019); therefore, maintaining the diversity of entomofauna in agroecosystems should be a priority. The positive association of predator richness obtained between non-Bt refuges and Bt soybean crops showed the importance of complying with these areas to conserve species-rich assemblages of generalist predators and mitigate their decline in agroecosystems, mostly associated with habitat loss by landscape simplification and agricultural intensification (Seibold et al. 2019). ...
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Soybean plants that express various insecticidal proteins of the bacterium Bacillus thuringiensis have been widely adopted globally in many crop systems. This technology effectively controls the main defoliating pest species in most countries and reduces insecticide spray requirements. However, widespread use of Bt crops also generates high selection pressure against pest populations, leading to resistance concerns. Refuge areas are established to delay this phenomenon, but little is known about their other ecological functions. We evaluated the role of non-Bt soybean refuge areas regarding the abundance and richness of predator species in Bt soybean and non-Bt fields. For 2 years, herbivore and predatory arthropods were sampled in 28 soybean fields (RR/Bt) and their non-Bt soybean refuge areas (RR/noBt) in Uruguay, throughout the whole crop cycle. Landscape crop diversity (1 km radius) was characterized by its richness and evenness. Arthropod abundance and richness were analyzed using general linear mixed models. The abundance and richness of predators (Araneae, Coccinellidae, Heteroptera and Chrysopidae) found in Bt soybean were positively associated with the values recorded in refuge areas, independently of the diversity of the surrounding landscape. This relationship was not affected by changes in the distance between sampling points (within 800 m). The abundance of stink bugs and leaf-feeding caterpillars in Bt soybean was positively associated with refuge area values. Our results reinforce the importance of refuge areas, not only due to their role in resistance management, but also as preservation areas of beneficial fauna within a landscape approach to Integrated Pest Management in agroecosystems.
... Land use/cover change (LUCC), mainly caused by human activities, has altered the configuration and composition of regional landscape elements, disrupted ecological processes and ultimately changed HQ (Aguilar et al., 2019;Zhang et al., 2020a). For example, a significant increase in built-up land converted from cropland can cause landscape fragmentation and homogenization (Zhu et al., 2021), endangering the survival of species (Seibold et al., 2019). Landscape fragmentation refers to the process of convergence from simple to complex landscapes due to disturbances caused by natural or human factors (De Montis et al., 2017). ...
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Landscape fragmentation due to urban sprawl and industrialization has caused habitat loss and threatened global biodiversity. However, the magnitude, spatial pattern, and mechanisms of how landscape fragmentation leads to habitat loss remain unclear. The Yellow River Basin (YRB) and the Yangtze River Economic Belt (YZREB) are important ecological security barriers that play a decisive role in landscape connectivity and biodiversity conservation in China. From a comparative perspective, this study analyzes the temporal-spatial changes of land cover in the YRB and the YZREB from 2005 to 2018 and simulates the land use pattern in 2031 using a patch-level simulation (PLUS) model. Then the degree and tendency of landscape fragmentation during 2005-2031 are measured based on the entire region and a 10 km grid, respectively. The habitat quality (HQ) is measured using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. The temporal-spatial evolution characteristics of HQ are analyzed across multiple dimensions, including the entire region, urban agglomerations and watersheds (upstream, midstream, and downstream). Finally, spatial econometric models are applied to examine the spatial dependence of HQ and quantify the spatial impact of landscape fragmentation on HQ in the YRB and YZREB based on 10 km grids. Results show that: (1) there would be a significant trend of landscape fragmentation and habitat degradation in both the YRB and YZREB during 2005-2031. (2) HQ in the YRB and YZREB has the spatial distribution characteristics of being low in coastal areas and urban agglomerations but high in inland areas and mountainous forest areas. (3) The spatial distribution and spatial relationship of landscape fragmentation and HQ in YRB and YZREB differ significantly in multi-spatiotemporal dimensions. The findings could provide support for landscape planning and biodiversity conservation strategies in China and other developing countries.
... Following the pathways described above, we predict that ecosystem services provided by mobile animal species that use the whole landscape to meet their feeding and habitat requirements 23 , such as aboveground regulating ecosystem services relying on arthropods (for example, pollination and pest control) or cultural ecosystem services (for example, birdwatching), will be most strongly influenced by the direct 'spill-over' of these organisms [26][27][28] (Fig. 1, arrow 2) but that the direction of these effects will vary depending on the ecology of ecosystem service providers. By contrast, ecosystem services provided by less mobile species, such as provisioning ecosystem services linked to plants or regulating belowground ecosystem services that rely on soil biodiversity, will be more affected by local biodiversity, and thus the indirect 'dispersal' effects of a diverse surrounding species pool (Fig. 1, arrows 1 and 3). ...
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The impact of local biodiversity loss on ecosystem functioning is well established, but the role of larger-scale biodiversity dynamics in the delivery of ecosystem services remains poorly understood. Here we address this gap using a comprehensive dataset describing the supply of 16 cultural, regulating and provisioning ecosystem services in 150 European agricultural grassland plots, and detailed multi-scale data on land use and plant diversity. After controlling for land-use and abiotic factors, we show that both plot-level and surrounding plant diversity play an important role in the supply of cultural and aboveground regulating ecosystem services. In contrast, provisioning and belowground regulating ecosystem services are more strongly driven by field-level management and abiotic factors. Structural equation models revealed that surrounding plant diversity promotes ecosystem services both directly, probably by fostering the spill-over of ecosystem service providers from surrounding areas, and indirectly, by maintaining plot-level diversity. By influencing the ecosystem services that local stakeholders prioritized, biodiversity at different scales was also shown to positively influence a wide range of stakeholder groups. These results provide a comprehensive picture of which ecosystem services rely most strongly on biodiversity, and the respective scales of biodiversity that drive these services. This key information is required for the upscaling of biodiversity-ecosystem service relationships, and the informed management of biodiversity within agricultural landscapes.
... Insects are currently declining in many parts of the world (Hallmann et al. 2021;Sánchez-Bayo and Wyckhuys 2021;Seibold et al. 2019;Wagner et al. 2021). The main explanations for insect decline are the loss of habitat through increasing urbanization, climate change, landscape homogenization, high use of pesticides and fertilization and intensive farming methods for example frequent mowing (IPBES 2019;Dicks et al. 2021;Mupepele et al. 2019;Potts et al. 2010). ...
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... The widespread use of chemicals in agriculture and horticulture constitutes a pervasive and substantial source of pollution (14,15). Agrochemicals, in particular pesticides, have been linked to reductions in pollinator abundance and diversity (16)(17)(18), and subtle and sub-lethal mechanisms of toxicity are increasingly being recognized as affecting pollinator health and their ability to orient and forage (19)(20)(21)(22)(23). Yet aside from chemical toxicity, little is known about the influence of agrochemicals on the mutualistic interaction between plants and pollinators. Foliar applications of agrochemicals are common practice in horticulture and in recent decades gained popularity in agriculture (24). ...
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The main objective of this study was to examine how different stand types influenced the tendency of visitors for varying recreational activities (i.e., hiking, trekking, camping and hunting) from 1993 to 2018 in the surrounding areas of Uluyayla Natural Recreation Site in Bartin, northern Turkey. A total of 627 visitors were selected on a voluntary basis, and questioned in the form of questionnaire. Most of the participants were in the age of 21–40 years old, and they were mostly (62.4%) male. Most of the participants (82.7%) lived in cities, while 62.8% of them were tourists when visiting the site. In determining the preferences of the visitors regarding the stand types for different recreational activities, several images of each stand were shared with them, and they were asked which stand type they would prefer for a given recreation activity (i.e., hiking, tracking, camping and hunting). A range of options from 1 to 5 in Likert’s scale was used in evaluating the given responses. The degree of positive and negative effects was examined via trend analysis. It was found that stand type had influence on the preferences of visitors regarding the recreational activities. In general, unmanaged and moderately treated stands were more preferred by visitors for the recreational purposes, compared to the previously managed stands. On the other hand, visitors’ preference for the activities were different during two periods (i.e., 1993–2005 and 2006–2018). For each recreational activity, there was an increasing trend from 1993 to 2018. There had been a continuous increase for hunting since 1996, and for trekking and camping after 1999. The increases between 1993–1996 and 1996–1999 were likely due to the increasing awareness of the society as a result of the training and consciousness raising activities for nature conservation. The demand on the recreational activities continuously increased in unmanaged and moderately treated stands, while no significant changes were examined in the previously managed stands. The study points out that forest planning and management should consider different needs of visitors for recreational infrastructure.
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1.The successional dynamics of forests – from canopy openings to regeneration, maturation and decay – influence the amount and heterogeneity of resources available for forest‐dwelling organisms. Conservation has largely focused only on selected stages of forest succession (e.g. late‐seral stages). However, to develop comprehensive conservation strategies and to understand the impact of forest management on biodiversity, a quantitative understanding of how different trophic groups vary over the course of succession is needed. 2.We classified mixed mountain forests in Central Europe into nine successional stages using airborne LiDAR. We analysed α‐ and β‐diversity of six trophic groups encompassing approximately 3,000 species from three kingdoms. We quantified the effect of successional stage on the number of species with and without controlling for species abundances and tested whether the data fit the more‐individuals hypothesis or the habitat heterogeneity hypothesis. Furthermore, we analysed the similarity of assemblages along successional development. 3.The abundance of producers, first‐order consumers and saprotrophic species showed a U‐shaped response to forest succession. The number of species of producer and consumer groups generally followed this U‐shaped pattern. In contrast to our expectation, the number of saprotrophic species did not change along succession. When we controlled for the effect of abundance, the number of producer and saproxylic beetle species increased linearly with forest succession, whereas the U‐shaped response of the number of consumer species persisted. The analysis of assemblages indicated a large contribution of succession‐mediated β‐diversity to regional γ‐diversity. 4. Synthesis and applications. Depending on the species group, our data supported both the more‐individuals hypothesis and the habitat heterogeneity hypothesis. Our results highlight the strong influence of forest succession on biodiversity and underline the importance of controlling for successional dynamics when assessing biodiversity change in response to external drivers such as climate change. The successional stages with highest diversity (early and late successional stages) are currently strongly underrepresented in the forests of Central Europe. We thus recommend that conservation strategies aim at a more balanced representation of all successional stages. This article is protected by copyright. All rights reserved.
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Global declines in insects have sparked wide interest among scientists, politicians, and the general public. Loss of insect diversity and abundance is expected to provoke cascading effects on food webs and to jeopardize ecosystem services. Our understanding of the extent and underlying causes of this decline is based on the abundance of single species or taxo-nomic groups only, rather than changes in insect biomass which is more relevant for ecological functioning. Here, we used a standardized protocol to measure total insect biomass using Malaise traps, deployed over 27 years in 63 nature protection areas in Germany (96 unique location-year combinations) to infer on the status and trend of local entomofauna. Our analysis estimates a seasonal decline of 76%, and midsummer decline of 82% in flying insect biomass over the 27 years of study. We show that this decline is apparent regardless of habitat type, while changes in weather, land use, and habitat characteristics cannot explain this overall decline. This yet unrecognized loss of insect biomass must be taken into account in evaluating declines in abundance of species depending on insects as a food source, and ecosystem functioning in the European landscape.
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1. For managed temperate forests, conservationists and policymakers favour fine-grained uneven-aged management over more traditional coarse-grained even-aged management, based on the assumption that within-stand habitat heterogeneity enhances biodiversity. There is, however, little empirical evidence to support this assumption. We investigated for the first time how differently grained forest management systems affect the biodiversity of multiple above- and below-ground taxa across spatial scales. 2. We sampled 15 taxa of animals, plants, fungi and bacteria within the largest contiguous beech forest landscape of Germany and classified them into functional groups. Selected forest stands have been managed for more than a century at different spatial grains. The even-aged (coarse-grained management) and uneven-aged (fine-grained) forests are comparable in spatial arrangement, climate and soil conditions. These were compared to forests of a nearby national park that have been unmanaged for at least 20 years. We used diversity accumulation curves to compare γ-diversity for Hill-numbers 0D (species richness), 1D (Shannon diversity) and 2D (Simpson diversity) between the management systems. Beta diversity was quantified as multiple-site dissimilarity. 3. Gamma diversity was higher in even-aged than in uneven-aged forests for at least one of the three Hill-numbers for six taxa (up to 77%), while eight showed no difference. Only bacteria showed the opposite pattern. Higher γ-diversity in even-aged forests was also found for forest specialists and saproxylic beetles. 4. Between-stand β-diversity was higher in even-aged than in uneven-aged forests for one third (all species) and half (forest specialists) of all taxa, driven by environmental heterogeneity between age-classes, while α-diversity showed no directional response across taxa or for forest specialists. 5. Synthesis and applications. Comparing even-aged and uneven-aged forest management in Central European beech forests, our results show that a mosaic of different age-classes is more important for regional biodiversity than high within-stand heterogeneity. We suggest reconsidering the current trend of replacing even-aged management in temperate forests. Instead, the variability of stages and stand structures should be increased to promote landscape scale biodiversity.
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1. Along with the global decline of species richness goes a loss of ecological traits. Associated biotic homogenization of animal communities and narrowing of trait diversity threaten ecosystem functioning and human well-being. High management intensity is regarded as an important ecological filter, eliminating species that lack suitable adaptations. Belowground arthropods are assumed to be less sensitive to such effects than aboveground arthropods. 2. Here, we compared the impact of management intensity between (grassland vs. forest) and within land-use types (local management intensity) on the trait diversity and composition in below- and aboveground arthropod communities. 3. We used data on 722 arthropod species living above ground (Auchenorrhyncha and Heteroptera), primarily in soil (Chilopoda and Oribatida) or at the interface (Araneae and Carabidae). 4. Our results show that trait diversity of arthropod communities is not primarily reduced by intense local land use, but is rather affected by differences between land-use types. Communities of Auchenorrhyncha and Chilopoda had significantly lower trait diversity in grassland habitats as compared to forests. Carabidae showed the opposite pattern with higher trait diversity in grasslands. Grasslands had a lower proportion of large Auchenorrhyncha and Carabidae individuals, whereas Chilopoda and Heteroptera individuals were larger in grasslands. Body size decreased with land-use intensity across taxa, but only in grasslands. The proportion of individuals with low mobility declined with land-use intensity in Araneae and Auchenorrhyncha, but increased in Chilopoda and grassland Heteroptera. The proportion of carnivorous individuals increased with land-use intensity in Heteroptera in forests and in Oribatida and Carabidae in grasslands. 5. Our results suggest that gradients in management intensity across land-use types will not generally reduce trait diversity in multiple taxa, but will exert strong trait filtering within individual taxa. The observed patterns for trait filtering in individual taxa are not related to major classifications into above- and belowground species. Instead, ecologically different taxa resembled each other in their trait diversity and compositional responses to land-use differences. These previously undescribed patterns offer an opportunity to develop management strategies for the conservation of trait diversity across taxonomic groups in permanent grassland and forest habitats. This article is protected by copyright. All rights reserved.
Evidence of declines in insect populations has recently received considerable scientific and societal attention. However, the lack of long-term insect monitoring makes it difficult to assess whether declines are geographically widespread. By contrast, bird populations are well monitored and often used as indicators of environmental change. We compared the population trends of European insectivorous birds with those of other birds to assess whether patterns in bird population trends were consistent with declines of insects. We further examined whether declines were evident for insectivores with different habitats, foraging strata, and other ecological preferences. Bird population trends were estimated for Europe (1990-2015) and Denmark (1990-2016). On average, insectivores declined over the study period (13% across Europe and 28% in Denmark), whereas omnivores had stable populations. Seedeaters also declined (28% across Europe; 34% in Denmark), but this assessment was based on fewer species than for other groups. The effects of insectivory were stronger for farmland species (especially grassland species), for ground feeders, and for cold-adapted species. Insectivory was associated with long-distance migration, which was also linked to population declines. However, many insectivores had stable populations, especially habitat generalists. Our findings suggest that the decline of insectivores is primarily associated with agricultural intensification and loss of grassland habitat. The loss of both seed and insect specialists indicates an overall trend toward bird communities dominated by diet generalists. © 2019 Society for Conservation Biology.
Land-use intensification is a major driver of biodiversity loss. Alongside reductions in local species diversity, biotic homogenization at larger spatial scales is of great concern for conservation. Biotic homogenization means a decrease in β-diversity (the compositional dissimilarity between sites). Most studies have investigated losses in local (α)-diversity and neglected biodiversity loss at larger spatial scales. Studies addressing β-diversity have focused on single or a few organism groups (for example, ref. 4), and it is thus unknown whether land-use intensification homogenizes communities at different trophic levels, above- and belowground. Here we show that even moderate increases in local land-use intensity (LUI) cause biotic homogenization across microbial, plant and animal groups, both above- and belowground, and that this is largely independent of changes in α-diversity. We analysed a unique grassland biodiversity dataset, with abundances of more than 4,000 species belonging to 12 trophic groups. LUI, and, in particular, high mowing intensity, had consistent effects on β-diversity across groups, causing a homogenization of soil microbial, fungal pathogen, plant and arthropod communities. These effects were nonlinear and the strongest declines in β-diversity occurred in the transition from extensively managed to intermediate intensity grassland. LUI tended to reduce local α-diversity in aboveground groups, whereas the α-diversity increased in belowground groups. Correlations between the β-diversity of different groups, particularly between plants and their consumers, became weaker at high LUI. This suggests a loss of specialist species and is further evidence for biotic homogenization. The consistently negative effects of LUI on landscape-scale biodiversity underscore the high value of extensively managed grasslands for conserving multitrophic biodiversity and ecosystem service provision. Indeed, biotic homogenization rather than local diversity loss could prove to be the most substantial consequence of land-use intensification.
Environmental changes strongly impact the distribution of species and subsequently the composition of species assemblages. Although most community ecology studies represent temporal snap shots, long-term observations are rather rare. However, only such time series allow the identification of species composition shifts over several decades or even centuries. We analyzed changes in the species composition of a southeastern German butterfly and burnet moth community over nearly 2 centuries (1840-2013). We classified all species observed over this period according to their ecological tolerance, thereby assessing their degree of habitat specialisation. This classification was based on traits of the butterfly and burnet moth species and on their larval host plants. We collected data on temperature and precipitation for our study area over the same period. The number of species declined substantially from 1840 (117 species) to 2013 (71 species). The proportion of habitat specialists decreased, and most of these are currently endangered. In contrast, the proportion of habitat generalists increased. Species with restricted dispersal behavior and species in need of areas poor in soil nutrients had severe losses. Furthermore, our data indicated a decrease in species composition similarity between different decades over time. These data on species composition changes and the general trends of modifications may reflect effects from climate change and atmospheric nitrogen loads, as indicated by the ecological characteristics of host plant species and local changes in habitat configuration with increasing fragmentation. Our observation of major declines over time of currently threatened and protected species shows the importance of efficient conservation strategies.
Cereal fields are central to balancing food production and environmental health in the face of climate change. Within them, invertebrates provide key ecosystem services. Using 42 years of monitoring data collected in Southern England, we investigated the sensitivity and resilience of invertebrates in cereal fields to extreme weather events and examined the effect of long-term changes in temperature, rainfall and pesticide use on invertebrate abundance. Of the 26 invertebrate groups examined, eleven proved sensitive to extreme weather events. Average abundance increased in hot/dry years and decreased in cold/wet years for Araneae, Cicadellidae, adult Heteroptera, Thysanoptera, Braconidae, Enicmus and Lathridiidae. The average abundance of Delphacidae, Cryptophagidae and Mycetophilidae increased in both hot/dry and cold/wet years relative to other years. The abundance of all 10 groups usually returned to their long-term trend within a year after the extreme event. For five of them sensitivity to cold/wet events was lowest (translating into higher abundances) at locations with a westerly aspect. Some long-term trends in invertebrate abundance correlated with temperature and rainfall, indicating that climate change may affect them. However, pesticide use was more important in explaining the trends, suggesting that reduced pesticide use would mitigate the effects of climate change. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.