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International scientists formulate a roadmap for
insect conservation and recovery
To the Editor — A growing number of
studies are providing evidence that a suite
of anthropogenic stressors — habitat loss
and fragmentation, pollution, invasive
species, climate change and overharvesting
— are seriously reducing insect and other
invertebrate abundance, diversity and
biomass across the biosphere18. These
declines affect all functional groups:
herbivores, detritivores, parasitoids,
predators and pollinators. Insects are
vitally important in a wide range of
ecosystem services9 of which some are
vitally important for food production and
security (for example, pollination and
pest control)10. There is now a strong
scientific consensus that the decline of
insects, other arthropods and biodiversity
as a whole, is a very real and serious threat
that society must urgently address1113. In
response to the increasing public awareness
of the problem, the German government is
committing funds to combat and reverse
declining insect numbers13. This funding
should act as a clarion call to other
nations across the world — especially
wealthier ones — to follow suit and
to respond proactively to the crisis by
addressing the known and suspected threats
and implementing solutions.
We hereby propose a global ‘roadmap’
for insect conservation and recovery
(Fig. 1). This entails the immediate
implementation of several ‘no-regret’
measures (Fig. 1, step 1) that will act
to slow or stop insect declines. Among the
initiatives we encourage are the following
immediate measures:
Taking aggressive steps to reduce
greenhouse gas emissions; reversing recent
trends in agricultural intensification
including reduced application of synthetic
pesticides and fertilizers and pursuing
their replacement with agro-ecological
measures; promoting the diversification
and maintenance of locally adapted land-
use techniques; increasing landscape
heterogeneity through the maintenance of
natural areas within the landscape matrix
and ensuring the retention and creation of
microhabitats within habitats which may be
increasingly important for insects during
extreme climatic events such as droughts or
heatwaves; reducing identified local threats
such as light, water or noise pollution,
invasive species and so on; prioritizing the
import of goods that are not produced at
the cost of healthy, species-rich ecosystems;
designing and deploying policies (for
example, subsidies and taxation) to induce
the innovation and adoption of insect-
friendly technologies; enforcing stricter
measures to reduce the introduction of alien
species, and prioritizing nature-based tactics
for their (long-term) mitigation; compiling
and implementing conservation strategies
for species that are vulnerable, threatened
or endangered; funding educational
and outreach programs, including those
tailored to the needs of the wider public,
farmers, land managers, decision makers
and conservation professionals; enhancing
citizen science’ or ‘community science’
as a way of obtaining more data on insect
diversity and abundance as well as engaging
the public, especially in areas where
academic or professional infrastructure is
lacking; devising and deploying measures
across agricultural and food value chains
that favour insect-friendly farming,
including tracking, labelling, certification
and insurance schemes or outcome-based
incentives that facilitate behavioural
changes, and investing in capacity building
to create a new generation of insect
conservationists and providing knowledge
and skills to existing professionals
(particularly in developing countries).
To better understand changes in insect
abundance and diversity, research should
aim to prioritize the following areas:
Quantifying temporal trends in insect
abundance, diversity and biomass by
extracting long-term datasets from existing
insect collections to inform new censuses;
exploring the relative contributions
of different anthropogenic stressors
causing insect declines within and across
different taxa; initiating long-term studies
comparing insect abundance and diversity
in different habitats and ecosystems along
a management-intensity gradient and at
the intersection of agricultural and natural
habitats; designing and validating insect-
friendly techniques that are effective,
locally relevant and economically sound in
agriculture, managed habitats and urban
environments; promoting and applying
standardized monitoring protocols globally
and establishing long-term monitoring plots
or sites based on such protocols, as well as
increasing support for existing monitoring
efforts; establishing an international
governing body under the auspices of
existing bodies (for example, the United
Nations Environment Programme (UNEP)
or the International Union for Conservation
of Nature (IUCN)) that is accountable for
documenting and monitoring the effects of
proposed solutions on insect biodiversity in
the longer term; launching public–private
partnerships and sustainable financing
initiatives with the aim of restoring,
protecting and creating new vital insect
habitats as well as managing key threats;
increasing exploration and research to
improve biodiversity assessments, with
a focus on regional capacity building in
understudied and neglected areas, and
performing large-scale assessments of the
conservation status of insect groups to help
define priority species, areas and issues.
Most importantly, we should not wait
to act until we have addressed every key
knowledge gap. We currently have enough
information on some key causes of insect
decline to formulate no-regret solutions
whilst more data are compiled for lesser-
known taxa and regions and long-term data
are aggregated and assessed. Implementation
should be accompanied by research that
examines impacts, the results of which
can be used to modify and improve the
implementation of effective measures.
Furthermore, such a ‘learning-by-doing’
approach ensures that these conservation
strategies are robust to newly emerging
pressures and threats. We must act now.
Jerey A. Harvey  1*,
Robin Heinen  1, Inge Armbrecht  2,
Yves Basset3, James H. Baxter-Gilbert4,
T. Martijn Bezemer  1, Monika Böhm  5,
Riccardo Bommarco  6,
Paulo A. V. Borges  7, Pedro Cardoso8,
Viola Clausnitzer9, Tara Cornelisse10,
Elizabeth E. Crone11, Marcel Dicke  12,
Klaas-Douwe B. Dijkstra13, Lee Dyer14,
Jacintha Ellers  15, Thomas Fartmann16,
Mathew L. Forister14, Michael J. Furlong17,
Andres Garcia-Aguayo18, Justin Gerlach19,
Rieta Gols  12, Dave Goulson  20,
Jan-Christian Habel21, Nick M. Haddad  22,
Caspar A. Hallmann23, Sérgio Henriques  5,
Marie E. Herberstein24, Axel Hochkirch25,
Alice C. Hughes26, Sarina Jepsen27,
T. Hefin Jones28, Bora M. Kaydan29,
David Kleijn30, Alexandra-Maria Klein  31,
Tanya Latty32, Simon R. Leather  33,
Sara M. Lewis11, Bradford C. Lister34,
John E. Losey35, Elizabeth C. Lowe24,
Craig R. Macadam  36,
James Montoya-Lerma37,
Christopher D. Nagano10, Sophie Ogan25,
Michael C. Orr  38, Christina J. Painting39,
Thai-Hong Pham40, Simon G. Potts41,
Aunu Rauf42, Tomas L. Roslin6,
Michael J. Samways43,
Francisco Sanchez-Bayo44, Sim A. Sar45,
Cheryl B. Schultz  46, António O. Soares  7,
Anchana Thancharoen47, Teja Tscharntke48,
Jason M. Tylianakis  49,
Kate D. L. Umbers  50, Louise E. M. Vet1,
Marcel E. Visser  1, Ante Vujic51,
David L. Wagner52,
Michiel F. WallisDeVries  53,
1. No-regret solutions
3. New research
Avoid and mitigate
alien species
Phase out
pesticide use,
and replace
with ecological
restoration and
in agriculture
Phase out
pesticide use,
and replace
with ecological
in agriculture
Phase out
pesticide use,
and replace
with ecological
Education for
awareness, citizen
science and capacity
of threatened
Reduce light,
water and
noise pollution
Reduce imports
of ecologically
harmful products
2. Prioritization
Perform large-scale assessments
of the conservation status of insect
groups to define priority species,
areas and issues, for example increase
the number of insects with informative
IUCN Red List assessments.
Immediate action
Mid-term action
Conduct new research to disentangle the
contributions of different anthropogenic
stressors driving insect declines, within
and across different taxa. Perform field
studies along a management-intensity
gradient and at the intersects of agricultural
and natural habitats. Increase explorative
research to accelerate rate of knowledge
gain in understudied areas.
5. Partnerships
Long-term action
Launch public–private partnerships and
sustainable financing initiatives with the
aim of restoring, protecting and creating
new vital insect habitats, as well as
managing key threats.
4. Existing data
Analyse current data on insect diversity that
is present, such as in private, museum and
academic insect collections. This is important
to form new censuses of past insect diversity.
This is especially important in areas where
scientific data currently do not exist.
6. Global monitoring program
Promote and apply standardized monitoring
protocols at a global level under the auspices
of an existing international governing body
(for example, the UN or IUCN). Establish
standardized sites where monitoring is
conducted over longer terms. Ensure support
for existing monitoring efforts.
Fig. 1 | Roadmap to insect conservation and recovery, calling for action at short-, intermediate- and long-term timescales. No-regret measures for immediate
utilization in insect conservation refer to actions that should be implemented as soon as possible. These solutions will be beneficial to society and biodiversity
even if the direct effects on insects are not known as of yet (that is, no-regret solutions). This encompasses utilization of insect-friendly techniques that are
effective, locally relevant and economically sound, for example, in farming, habitat management and urban development.
Catrin Westphal54, Thomas E. White  32,
Vicky L. Wilkins55, Paul H. Williams56,
Kris A. G. Wyckhuys  57, Zeng-Rong Zhu58
and Hans de Kroon23
1Netherlands Institute of Ecology (NIOO-KNAW),
Wageningen, e Netherlands. 2Departamento de
Biología, Universidad del Valle, Cali, Colombia.
3ForestGEO, Smithsonian Tropical Research Institute,
Panama City, Panama. 4Centre for Invasion
Biology, Stellenbosch University, Matieland, South
Africa. 5Institute of Zoology, Zoological Society of
London, London, UK. 6Department of Ecology,
Swedish University of Agricultural Sciences,
Uppsala, Sweden. 7cE3c-Centre for Ecology,
Evolution and Environmental Changes / Azorean
Biodiversity Group, University of Azores, Lisbon,
Portugal. 8Laboratory for Integrative Biodiversity
Research (LIBRe), Finnish Museum of Natural
History, University of Helsinki, Helsinki, Finland.
9Senckenberg Research Institute, Goerlitz, Germany.
10Center for Biological Diversity, Portland, OR, USA.
11Department of Biology, Tus University, Medford,
MA, USA. 12Laboratory of Entomology, Wageningen
University, Wageningen, e Netherlands. 13IUCN
SSC Freshwater Conservation Committee, Naturalis
Biodiversity Center, Leiden, e Netherlands.
14Biology Department, University of Nevada, Reno,
NV, USA. 15Department of Ecological Sciences,
Vrije University, Amsterdam, e Netherlands.
16Department of Biodiversity and Landscape Ecology,
Osnabrück University, Osnabrück, Germany. 17School
of Biological Sciences, e University of Queensland,
St Lucia, Queensland, Australia. 18Estacion de
Biología Chamela, Instituto de Biología, Chamela,
Jalisco, Mexico. 19IUCN SSC Terrestrial Invertebrate
Red List Authority, Cambridge, UK. 20School of
Life Sciences, University of Sussex, Brighton, UK.
21Evolutionary Zoology, Department of Biosciences,
University of Salzburg, Salzburg, Austria. 22Kellogg
Biological Station and Department of Integrative
Biology, Michigan State University, Hickory Corners,
MI, USA. 23Institute for Water and Wetland Research,
Radboud University, Nijmegen, e Netherlands.
24Department of Biological Sciences, Macquarie
University, Sydney, New South Wales, Australia.
25Department of Biogeography, Trier University, Trier,
Germany. 26Centre for Integrative Conservation,
Xishuangbanna Tropical Botanical Garden, Chinese
Academy of Sciences, Menglun, Yunnan, China.
27e Xerces Society for Invertebrate Conservation,
Portland, OR, USA. 28School of Biosciences, Cardi
University, Cardi, UK. 29Biotechnology Application
and Research Centre, Çukurova University, Balcalı,
Adana, Turkey. 30Plant Ecology and Nature
Conservation Group, Wageningen University,
Wageningen, e Netherlands. 31Albert Ludwigs
University of Freiburg, Freiburg, Germany. 32School
of Life and Environmental Science, Sydney Institute
of Agriculture, University of Sydney, Sydney, New
South Wales, Australia. 33Crop & Environment
Science, Harper Adams University, Newport, UK.
34Department of Biological Sciences, Rensselaer
Polytechnic Institute, Troy, NY, USA. 35Entomology
Department, Cornell University, Ithaca, NY, USA.
36Buglife - e Invertebrate Conservation Trust,
Peterborough, UK. 37Departamento de Biología,
Universidad del Valle, Cali, Colombia. 38Key
Laboratory for Zoological Systematics and Evolution,
Institute of Zoology, Chinese Academy of Sciences,
Beijing, China. 39School of Science, University
of Waikato, Hamilton, New Zealand. 40Vietnam
National Museum of Nature & Graduate School
of Science and Technology, Vietnam Academy of
Science and Technology, Hanoi, Vietnam. 41Centre for
Agri-Environmental Research, School of Agriculture,
Policy and Development, Reading University,
Reading, UK. 42Department of Plant Protection,
IPB University, Bogor, Indonesia. 43Department of
Conservation Ecology and Entomology, Stellenbosch
University, Matieland, South Africa. 44Department
of Environment and Energy, Canberra, Australian
Capital Territory, Australia. 45National Agricultural
Research Institute, Lae, Papua New Guinea. 46School
of Biological Sciences, Washington State University,
Vancouver, British Columbia, USA. 47Department
of Entomology, Faculty of Agriculture, Kasetsart
University, Bangkok, ailand. 48Agroecology,
Department of Crop Sciences, University of
Göttingen, Göttingen, Germany. 49Bio-protection
Centre, School of Biological Sciences, University
of Canterbury, Christchurch, New Zealand.
50School of Science and Health, Western Sydney
University, Penrith, New South Wales, Australia.
51Department of Biology and Ecology, Faculty of
Sciences, University of Novi Sad, Novi Sad, Serbia.
52Ecology and Evolutionary Biology, University of
Connecticut, Storrs, CT, USA. 53De Vlinderstichting
(Dutch Buttery Conservation) & Plant Ecology and
Nature Conservation Group, Wageningen University,
Wageningen, e Netherlands. 54Functional
Agrobiodiversity, Department of Crop Sciences,
University of Göttingen, Göttingen, Germany.
55IUCN SSC Mid Atlantic Island Invertebrate
Specialist Group, IUCN, Cambridge, UK. 56Natural
History Museum, London, UK. 57Chrysalis
Consulting, Hanoi, Vietnam. 58Zhejiang Provincial
Key Laboratory of Crop Insect Pests and Diseases,
Hangzhou, Zhejiang, China.
Published: xx xx xxxx
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Competing interests
The authors declare no competing interests.
... Whilst few studies exist on the potential impacts of invertebrate trade (e.g. 7 ), popularity as pets or for specimen collectors is known to have nearly driven various species to extinction, especially where niche markets exist 8 . For the majority of invertebrate species, researchers lack precise information, despite potential declines, making further investigation an imperative 9,10 . ...
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... Efforts to streamline monitoring programs at the European level (Potts et al., 2021) should go hand in hand with necessary and immediate action for insect conservation (Harvey et al., 2020;. Even when regional, national or even European monitoring schemes are implemented, we argue for basing conservation evidence on the data that are already available, especially to assess changes that have already happened. ...
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... Here, we argue that analyses of potential drivers of declines and hazards, as well as mitigation strategies and conservation measures [1,2], should additionally make use of the substantial body of literature and evidence from studies across space, i.e. relationships with environmental conditions or land use across sites. The existing (and growing) knowledge on effects in space exceeds the potential for detectable drivers of temporal trends within reasonable time (figure 1). ...
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Temporal trends in insect numbers vary across studies and habitats, but drivers are poorly understood. Suitable long-term data are scant and biased, and interpretations of trends remain controversial. By contrast, there is substantial quantitative evidence for drivers of spatial variation. From observational and experimental studies, we have gained a profound understanding of where insect abundance and diversity is higher—and identified underlying environmental conditions, resource change and disturbances. We thus propose an increased consideration of spatial evidence in studying the causes of insect decline. This is because for most time series available today, the number of sites and thus statistical power strongly exceed the number of years studied. Comparisons across sites allow quantifying insect population risks, impacts of land use, habitat destruction, restoration or management, and stressors such as chemical and light pollution, pesticides, mowing or harvesting, climatic extremes or biological invasions. Notably, drivers may not have to change in intensity to have long-term effects on populations, e.g. annually repeated disturbances or mortality risks such as those arising from agricultural practices. Space-for-time substitution has been controversially debated. However, evidence from well-replicated spatial data can inform on urgent actions required to halt or reverse declines—to be implemented in space.
... The fact that we cannot pinpoint an obvious direct effect of local human interference in our forest study, can only lead to the conclusion that large-scale processes such as influx of nutrients and pesticides, acidification and/or climate change contribute to insect declines . To substantiate these strong suspicions with data, it is critical that long-term monitoring of insect populations and potential environmental drivers is conducted at a multitude of locations, for FOREST HOVERFLY COMMUNITY COLLAPSE instance, through well-coordinated citizen-science programmes (Didham et al., 2020;Harvey et al., 2020;Montgomery et al., 2020). ...
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To study insect decline, an important threat to biodiversity, long‐term datasets are needed. Here we present a study of hoverfly (Diptera: Syrphidae) abundance and diversity in a Dutch forest, surrounded by other forests, and analyse the variation in insect numbers over four decades. Between 1982 and 2021, abundance decreased by 80%. Until 1990, abundance showed a strong decrease of 10.9% per year, mainly in nationally rare species with carnivorous larvae exposed to air. From 1990, abundance stabilised, whereas from 2000, a second period of strong decline of 9.0% per year occurred, mainly in very common species. Species richness also declined strongly between 1979 and 2021: the total number of species observed in five monitoring days dropped by 44% over those 43 years. The characteristic set of dry‐forest hoverfly species disappeared over four decades. The number of nationally rare species observed at the study site declined from 19 to 9 early on, in a period (1979–1984) that coincided with intense nitrogen input and acidification caused by agriculture in the same region. The more recent decline is likely also caused by factors from outside the forest, as forest management and conditions remained constant. Continued influx of nutrients and pesticides at a regional level, as well as climate change are possible causes of the decline. Research is needed to quantify their relative effects. In a Dutch forest, the abundance of hoverflies decreased by 80% between 1982 and 2021: until 1990 with 10.9% per year, in 1990–2000 numbers stabilised, and from 2000 a decline of 9.0%. Species richness declined strongly between 1979 and 2021: the total number of species observed on five monitoring days dropped by 44%. The number of nationally rare species observed declined from 19 to 9 in 1979–1984; by 2021 the characteristic set of dry‐forest species had disappeared, and only some common hoverflies remain.
The degradation of natural habitats is causing ongoing homogenization of biological communities and declines in terrestrial insect biodiversity, particularly in agricultural landscapes. Orthoptera are focal species of nature conservation and experienced significant diversity losses over the past decades. However, the causes underlying these changes are not yet fully understood. We analysed changes in Orthoptera assemblages surveyed in 1988, 2004 and 2019 on 198 plots distributed across four major grassland types in Central Europe. We demonstrated compositional differences in Orthoptera assemblages found in wet, dry and mesic grasslands, as well as ruderal habitats decreased, indicating biotic homogenization. However, mean α-diversity of Orthoptera assemblages increased over the study period. We detected increasing numbers of species with preferences for higher temperatures in mesic and wet grasslands. By analysing the temperature, moisture and vegetation preferences of Orthoptera, we found that additive homogenization was driven by a loss of species adapted to extremely dry and nitrogen-poor habitats and a parallel spread of species preferring warmer macroclimates.
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Environmental pollution is one of the major drivers of the present-day decline in global biodiversity. However, the links between the effects of industrial pollution on insect communities and the underlying species-specific responses remain poorly understood. We explored the spatial pattern in insect communities by analysing 581 samples of moths and butterflies (containing 25,628 individuals of 345 species) collected along a strong pollution gradient in subarctic Russia, and we recorded temporal changes in these communities during the pollution decline that occurred from 1992 to 2006. In the 1990s, the diversity of the Lepidoptera community was positively correlated with the distance from the copper-nickel smelter at Monchegorsk. The overall abundance of Lepidoptera did not change along the pollution gradient, although the abundance of many species decreased with increasing pollution. The responses of each individual species to pollution were associated with its life history traits. The abundances of monophagous species that fed inside live plant tissues and hibernated as imagoes or pupae were not affected by pollution, whereas the abundances of oligophagous and polyphagous species that fed externally on plants and hibernated as larvae generally declined near the smelter. Substantial decreases in aerial emissions from the smelter between 1992 and 2006 resulted in an increase in the diversity of moths and butterflies in severely polluted habitats, whereas their overall abundance did not change. This recovery of the Lepidoptera community occurred due to the reappearance of rare species that had been previously extirpated by pollution and was observed despite the lack of any signs of recovery of the vegetation in the heavily polluted sites. We conclude that the recovery trajectories of insect communities following emission control can be predicted from studies of their changes along spatial pollution gradients by using space-for-time substitution.
Despite a substantial increase in scientific, public and political interest in pollinator health and many practical conservation efforts, incorporating initiatives across a range of scales and sectors, pollinator health continues to decline. We review existing pollinator conservation initiatives and define their common structural elements. We argue that implementing effective action for pollinators requires further scientific understanding in six key areas: (i) status and trends of pollinator populations; (ii) direct and indirect drivers of decline, including their interactions; (iii) risks and co-benefits of pollinator conservation actions for ecosystems; (iv) benefits of pollinator conservation for society; (v) the effectiveness of context-specific, tailored, actionable solutions; and (vi) integrated frameworks that explicitly link benefits and values with actions to reverse declines. We propose use of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) conceptual framework to link issues and identify critical gaps in both understanding and action for pollinators. This approach reveals the centrality of addressing the recognized indirect drivers of decline, such as patterns of global trade and demography, which are frequently overlooked in current pollinator conservation efforts. Finally, we discuss how existing and new approaches in research can support efforts to move beyond these shortcomings in pollinator conservation initiatives. This article is part of the theme issue ‘Natural processes influencing pollinator health: from chemistry to landscapes’.
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Biodiversity is in crisis, and insects are no exception. To understand insect population and community trends globally, it is necessary to identify and synthesize diverse datasets representing different taxa, regions, and habitats. The relevant literature is, however, vast and challenging to aggregate. The Entomological Global Evidence Map (EntoGEM) project is a systematic effort to search for and catalogue studies with long‐term data that can be used to understand changes in insect abundance and diversity. Here, we present the overall EntoGEM framework and results of the first completed subproject of the systematic map, which compiled sources of information about changes in dragonfly and damselfly (Odonata) occurrence, abundance, biomass, distribution, and diversity. We identified 45 multi‐year odonate datasets, including 10 studies with data that span more than 10 years. If data from each study could be gathered or extracted, these studies could contribute to analyses of long‐term population trends of this important group of indicator insects. The methods developed to support the EntoGEM project, and its framework for synthesizing a vast literature, have the potential to be applied not only to other broad topics in ecology and conservation, but also to other areas of research where data are widely distributed. A systematic approach to reviewing the literature can reduce bias in the types of datasets identified to understand conservation issues. Here, we present a community‐driven evidence synthesis framework that can be adapted to gather and assess evidence from many broad topics in conservation and apply the approach to gather datasets documenting long‐term changes in insect populations.
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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.
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Insects make up the bulk of terrestrial diversity (1). Reports of insect declines, best documented in Europe and North America, suggest that 40% of insect species in temperate countries may face extinction over the next few decades (2), although this figure is probably inflated (3). Other studies have highlighted falling insect biomass in Germany and Puerto Rico (4, 5), as well as threats to many insect taxa in Europe (5) and insect pollinators worldwide (6) that support food production (7). To protect insects, it is crucial that they are considered as separate species with distinct responses to threats, with particular attention to tropical insects and their habitats. Bees and butterflies may serve as an initial focus, but conservation efforts must go far beyond these iconic species. Halting habitat loss and fragmentation, reducing pesticide use, and limiting climate change are all required if insect populations are to be preserved.
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A number of studies indicate that tropical arthropods should be particularly vulnerable to climate warming. If these predictions are realized, climate warming may have a more profound impact on the functioning and diversity of tropical forests than currently anticipated. Although arthropods comprise over two-thirds of terrestrial species, information on their abundance and extinction rates in tropical habitats is severely limited. Here we analyze data on arthropod and insectivore abundances taken between 1976 and 2012 at two midelevation habitats in Puerto Rico’s Luquillo rainforest. During this time, mean maximum temperatures have risen by 2.0 °C. Using the same study area and methods employed by Lister in the 1970s, we discovered that the dry weight biomass of arthropods captured in sweep samples had declined 4 to 8 times, and 30 to 60 times in sticky traps. Analysis of long-term data on canopy arthropods and walking sticks taken as part of the Luquillo Long-Term Ecological Research program revealed sustained declines in abundance over two decades, as well as negative regressions of abundance on mean maximum temperatures. We also document parallel decreases in Luquillo’s insectivorous lizards, frogs, and birds. While El Niño/Southern Oscillation influences the abundance of forest arthropods, climate warming is the major driver of reductions in arthropod abundance, indirectly precipitating a bottom-up trophic cascade and consequent collapse of the forest food web.
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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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We must start an ambitious and professional global programme to explore and preserve invertebrate biodiversity, says Axel Hochkirch.
Biodiversity of insects is threatened worldwide. Here, we present a comprehensive review of 73 historical reports of insect declines from across the globe, and systematically assess the underlying drivers. Our work reveals dramatic rates of decline that may lead to the extinction of 40% of the world's insect species over the next few decades. In terrestrial ecosystems, Lepidoptera, Hymenoptera and dung beetles (Coleoptera) appear to be the taxa most affected, whereas four major aquatic taxa (Odonata, Plecoptera, Trichoptera and Ephemeroptera) have already lost a considerable proportion of species. Affected insect groups not only include specialists that occupy particular ecological niches, but also many common and generalist species. Concurrently, the abundance of a small number of species is increasing; these are all adaptable, generalist species that are occupying the vacant niches left by the ones declining. Among aquatic insects, habitat and dietary generalists, and pollutant-tolerant species are replacing the large biodiversity losses experienced in waters within agricultural and urban settings. The main drivers of species declines appear to be in order of importance: i) habitat loss and conversion to intensive agriculture and urbanisation; ii) pollution, mainly that by synthetic pesticides and fertilisers; iii) biological factors, including pathogens and introduced species; and iv) climate change. The latter factor is particularly important in tropical regions, but only affects a minority of species in colder climes and mountain settings of temperate zones. A rethinking of current agricultural practices, in particular a serious reduction in pesticide usage and its substitution with more sustainable, ecologically-based practices, is urgently needed to slow or reverse current trends, allow the recovery of declining insect populations and safeguard the vital ecosystem services they provide. In addition, effective remediation technologies should be applied to clean polluted waters in both agricultural and urban environments.