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Cited by 3,499Plant and animal studiesEcology and Vegetation Dynamics StudiesEntomological Studies and Ecology

More than 75 percent decline over 27 years in total flying insect biomass in protected areas

Open access
Hallmann, Caspar A., Sorg, Martin, Jongejans, Eelke, Siepel, Henk, Hofland, Nick, Schwan, Heinz, Stenmans, Werner, Müller, Andreas +4 more·2017·PLOS ONE
DOI 10.1371/journal.pone.0185809PMC PMC5646769
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Abstract

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 taxonomic 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 mid-summer 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.

AI snapshot

Written from the paper’s full text.

TL;DR

Using standardized Malaise traps across 63 protected areas in Germany from 1989–2016, this study estimates a 76.7% seasonal decline and 81.6% mid-summer decline in total flying insect biomass. The decline occurred across habitat types and was not explained by measured weather, land-use, or habitat variables.

Key findings

  • The basic model estimated an annual trend coefficient of −0.063 (sd = 0.002), i.e. a 6.1% annual decline, yielding a seasonally weighted decline of 76.7% [74.8–78.5%] over 27 years and a mid-summer decline of 81.6% [79.7–83.4%].
  • The decline was similar across habitat clusters and across the 26 locations sampled in more than one year, where re-estimated decline was 76.2% [73.9–78.3%].
  • Weather, land-use, and habitat variables did not explain the overall decline; the final model’s annual trend was even more negative (log(λ) = −0.081, sd = 0.006), and fixing the temporal trend to zero projected stable or approximately 8% higher biomass over the study period.
  • Nutrient-rich grasslands, margins, and wasteland contained 43% more insect biomass than nutrient-poor heathland, sandy grassland, and dunes, but the rate of decline was similar.

Methods

  • Standardized Malaise traps were deployed in 63 protected areas in western Germany between 1989 and 2016, producing 96 unique location-year combinations, 1,503 trap samples, 53.54 kg of invertebrates, and 16,908 trap exposure days; catches were emptied on average every 11.2 days (sd = 6.3).
  • Biomass was measured from alcohol-wet samples using a standardized protocol; weather data came from 169 stations within 100 km and were interpolated to trap locations, while land-use and habitat variables were derived from aerial photographs and plant inventories.
  • A Bayesian mixed-effects model modeled sample biomass as the sum of latent daily biomass, with covariates for season, year, weather, land use, habitat, and interactions; parameters were estimated via MCMC in JAGS, and models were compared using DIC and R².

Limitations

  • The paper states that most locations were sampled in only one year, with repeated sampling at only 26 of 63 locations, so the data do not represent longitudinal records at single sites and could not derive location-specific trends.
  • The paper states that land-use change was evaluated from coarse temporal aerial-photograph data and not management regimes, and that the full range of climatic variables and agricultural intensification, including pesticide use, could not be incorporated.
  • Evident from the text: the study is observational and does not identify causal drivers; traps were in protected areas of limited size, with 94% of locations enclosed by agricultural fields, and biomass was not resolved to species-level trends.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1371/journal.pone.0185809

Cites

55 of 55 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 74 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    Flying insect biomass in the sampled protected areas in Germany declined seasonally by 76% over the 27 years from 1989 to 2016.

    “Our analysis estimates a seasonal decline of 76%, and mid-summer decline of 82% in flying insect biomass over the 27 years of study.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The seasonal insect biomass profiles from the sampled location-year combinations are random samples representative of the state of entomofauna in protected areas in western Germany.
    • Rests on an assumption: Malaise trap catches provide a representative measure of total flying insect biomass at a location.
    • Rests on an assumption: The sampled protected areas are representative of Western European low-altitude nature protection areas embedded in a human-dominated landscape.
  • Findingown data

    The decline in flying insect biomass was apparent regardless of habitat type.

    “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.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The seasonal insect biomass profiles from the sampled location-year combinations are random samples representative of the state of entomofauna in protected areas in western Germany.
    • Rests on an assumption: Malaise trap catches provide a representative measure of total flying insect biomass at a location.
    • Rests on an assumption: The sampled protected areas are representative of Western European low-altitude nature protection areas embedded in a human-dominated landscape.
  • Findingown data

    Flying insect biomass in the sampled protected areas in Germany declined by 82% in mid-summer over the 27 years from 1989 to 2016.

    “Our analysis estimates a seasonal decline of 76%, and mid-summer decline of 82% in flying insect biomass over the 27 years of study.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The seasonal insect biomass profiles from the sampled location-year combinations are random samples representative of the state of entomofauna in protected areas in western Germany.
    • Rests on an assumption: Malaise trap catches provide a representative measure of total flying insect biomass at a location.
    • Rests on an assumption: The sampled protected areas are representative of Western European low-altitude nature protection areas embedded in a human-dominated landscape.
  • Findingown data

    Changes in weather, land use, and habitat characteristics cannot explain the overall decline in flying insect biomass.

    “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.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The seasonal insect biomass profiles from the sampled location-year combinations are random samples representative of the state of entomofauna in protected areas in western Germany.
    • Rests on an assumption: Malaise trap catches provide a representative measure of total flying insect biomass at a location.
    • Rests on an assumption: The sampled protected areas are representative of Western European low-altitude nature protection areas embedded in a human-dominated landscape.
  • Findingown data

    Projections of the final model with the annual trend coefficient fixed to zero suggest insect biomass would have remained stable or increased by approximately 8% (mean rate = 1.075, 0.849-1.381) over the study period.

    “Projections of our final model, while fixing the coefficient for the temporal annual trend log(λ) to zero, suggest insect biomass would have remained stable, or even increased by approximately 8% (mean rate = 1.075, 0.849–1.381) over the course of the study period.”
    Quote in the paperSubstantial claim
  • May combine two claims. 26
  • Classified as probably not a substantial claim. 24

  • May combine two claims.

    Findingown data

    Grassland and surface water did not change much in extent over the last three decades.

    “On average, cover of arable land decreased, coverage of forests increased, while grassland and surface water did not change much in extent over the last three decades (S3 Fig).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Over the study period, mean temperature increased by 0.5°C.

    “Over the course of the study period, some temporal changes occurred in the means of the weather variables (S2 Fig), most notably an increase by 0.5°C in mean temperature and a decline 0.2 m/sec in mean wind speed.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    On average, cover of arable land decreased over the last three decades.

    “On average, cover of arable land decreased, coverage of forests increased, while grassland and surface water did not change much in extent over the last three decades (S3 Fig).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Land use elements at 200m radius better predicted insect biomass than elements at 500 and 1000m radius.

    “Preliminary analysis of the relationship between log biomass and landuse variables, on a subset of the trap locations, indicated that land use elements at 200m radius better predicted insect biomass than elements at 500 and 1000m radius, similar to findings elsewhere for wild bees [45].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [45] I Steffan-Dewenter, 2002, Scale-dependent effects of landscape context on three pollinator guilds, Ecology source

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    The overall model fit improved compared to the basic model (R2 = 65.4%), explaining within- and between-year variation in insect biomass but not the overall decline (log(λ) = −0.058, sd = 0.002).

    “The overall model fit improved as compared to our basic model (R2 = 65.4%, Table 3), explaining within and between year variation in insect biomass, but not the overall decline (log(λ) = −0.058, sd = 0.002).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The marginal net effect of temporal changes showed a positive contribution to biomass growth rate of arable land, herb species richness, and Ellenberg Nitrogen.

    “The marginal net effect of changes in each covariate over time (see Analysis), showed a positive contribution to biomass growth rate of temporal developments in arable land, herb species richness, and Ellenberg Nitrogen, while negative effects of developments of tree species richness and forest coverage (Fig 5).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Over the study period, mean wind speed declined by 0.2 m/sec.

    “Over the course of the study period, some temporal changes occurred in the means of the weather variables (S2 Fig), most notably an increase by 0.5°C in mean temperature and a decline 0.2 m/sec in mean wind speed.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Including interactions between the annual trend coefficient and land use variables increased the model fit slightly and revealed significant interactions for all variables except coverage of surface water.

    “However, including interactions between the annual trend coefficient and land use variables increased the model fit slightly (Table 3), and revealed significant interactions for all variables except coverage of surface water (S2 Table).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    Coverage of forests increased over the last three decades.

    “On average, cover of arable land decreased, coverage of forests increased, while grassland and surface water did not change much in extent over the last three decades (S3 Fig).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    Ellenberg values did not affect the insect biomass trend coefficient (log(λ) = −0.059, sd = 0.003) and only marginally improved the model fit (R2 = 61.9%).

    “However, Ellenberg values did not affect the insect biomass trend coefficient (log(λ) = −0.059, sd = 0.003, S3 Table) and only marginally improved the model fit (R2 = 61.9%, Table 3).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The basic model including an annual rate of decline outperformed the null-model (ΔDIC = 822.62 units), and between-plot variation and residual variation decreased by 44.3% and 9.7% respectively after incorporating an annual rate of decline.

    “Firstly, our basic model (including an annual rate of decline) outperformed the null-model (without an annual rate of decline; ΔDIC = 822.62 units; Table 3), while at the same time, between-plot variation (i.s. σsite) and residual variation (v) decreased by 44.3 and 9.7% respectively, after incorporating an annual rate of decline into the models.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingnone given

    The reserves in which the traps were placed are of limited size in a typical fragmented West-European landscape, and almost all locations (94%) are enclosed by agricultural fields.

    “The reserves in which the traps were placed are of limited size in this typical fragmented West-European landscape, and almost all locations (94%) are enclosed by agricultural fields.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Insects play a central role in pollination, herbivory and detrivory, nutrient cycling, and providing a food source for higher trophic levels.

    “Loss of insects is certain to have adverse effects on ecosystem functioning, as insects play a central role in a variety of processes, including pollination [1, 2], herbivory and detrivory [3, 4], nutrient cycling [4] and providing a food source for higher trophic levels such as birds, mammals and amphibians.”
    Quote in the paperSubstantial claim0 of 4 sources checked
    • cites [1] E Öckinger, 2007, Semi-natural grasslands as population sources for pollinating insects in agricultural landscapes, Journal of Applied Ecology source

      Not checked in the free run.

    • cites [2] J Ollerton, 2011, How many flowering plants are pollinated by animals?, Oikos source

      Not checked in the free run.

    • cites [3] WJ Mattson, 1975, Phytophagous insects as regulators of forest primary production, Science source

      Not checked in the free run.

    • cites [4] LH Yang, 2014, Insects as drivers of ecosystem processes, Current Opinion in Insect Science source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Current data suggest an overall pattern of decline in insect diversity and abundance.

    “Current data suggest an overall pattern of decline in insect diversity and abundance.”
    Quote in the paperSubstantial claim0 of 10 sources checked
    • cites [7] C van Swaay, 2013, The European grassland butterfly indicator: 1990–2011, EEA Technical Reports

      Not checked in the free run.

    • cites [8] D Goulson, 2008, Decline and conservation of bumble bees, Annual Review of Entomology source

      Not checked in the free run.

    • cites [9] SG Nilsson, 2008, Long-term land-use changes and extinction of specialised butterflies, Insect Conservation and Diversity source

      Not checked in the free run.

    • cites [10] R Winfree, 2009, A meta-analysis of bees’ responses to anthropogenic disturbance, Ecology source

      Not checked in the free run.

    • cites [11] SG Potts, 2010, Global pollinator declines: trends, impacts and drivers, Trends in Ecology and Evolution source

      Not checked in the free run.

    • cites [12] A Ilyinykh, 2011, Analysis of the causes of declines in Western Siberian outbreaks of the nun moth <italic>Lymantria monacha</italic>, BioControl source

      Not checked in the free run.

    • cites [13] J Ollerton, 2014, Extinctions of aculeate pollinators in Britain and the role of large-scale agricultural changes, Science source

      Not checked in the free run.

    • cites [14] BA Woodcock, 2016, Impacts of neonicotinoid use on long-term population changes in wild bees in England, Nature Communications source

      Not checked in the free run.

    • cites [15] KF Conrad, 2002, Long-term decline in abundance and distribution of the garden tiger moth (<italic>Arctia caja</italic>) in Great Britain, Biological Conservation source

      Not checked in the free run.

    • cites [16] KF Conrad, 2006, Rapid declines of common, widespread British moths provide evidence of an insect biodiversity crisis, Biological Conservation source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data

    Trend coefficients of herb richness over time were comparable between Poisson and negative binomial models but differed in magnitude.

    “Trend coefficients of richness over time between a Poisson mixed effects model and a negative binomial model were comparable but differed in magnitude (Poisson GLMM: −0.034 (se = 0.003), vs NB GLMM −0.027 (se = 0.006)).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    The trend adequately describes the direction of change over time for herb richness despite imperfect fit.

    “Although the fit is not perfect in the case of herb richness, we believe our trend adequately describes direction of change over time.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Study design and conductreasoning

    Sampling was standardized in trap construction, size, design, colors, netting, ground sealing, orientation, and slope, and none of the traps differed in these field aspects.

    “The sampling was standardized in terms of trap construction, size and design (identical parts), colors, type of netting and ground sealing, trap orientation in the field as well as slope at the trap location. Hence none of the traps differed in any of these field aspects.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Malaise trap catches provide a representative measure of total flying insect biomass at a location.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Malaise traps collect a much wider diversity of insect species than suction traps and are considered superior for collecting flying insects.

    “Malaise traps are known to collect a much wider diversity of insect species (e.g. [29–31]) as compared to suction traps (e.g. [28]) and are therefore considered superior as a method of collecting flying insects.”
    Quote in the paperNot a substantial claim0 of 4 sources checked
    • cites [29] U Bosch, 1994, Naturkundliche Untersuchungen zum Naturschutzgebiet Die Spey—III. Nachgewiesene Schmetterlinge (Macrolepidoptera), Natur am Niederrhein (NF)

      Not checked in the free run.

    • cites [30] C Schmidt, 1995, Naturkundliche Untersuchungen zum Naturschutzgebiet Die Spey—VI. Die Köcherfliegen (Insecta, Trichoptera), Natur am Niederrhein (NF)

      Not checked in the free run.

    • cites [31] M Hellenthal, 2007, Schwebfliegen (Diptera, Syrphidae) des Wahnbachtals im Bergischen Land (Nordrhein-Westfalen, Deutschland), Volucella

      Not checked in the free run.

    • cites [28] CR Shortall, 2009, Long-term changes in the abundance of flying insects, Insect Conservation and Diversity source

      Not checked in the free run.

    • Rests on an assumption: Malaise trap catches provide a representative measure of total flying insect biomass at a location.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    European grassland butterfly populations declined by 50% in abundance between 1990 and 2011.

    “For example, populations of European grassland butterflies are estimated to have declined by 50% in abundance between 1990 and 2011 [7].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [7] C van Swaay, 2013, The European grassland butterfly indicator: 1990–2011, EEA Technical Reports

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Climate change is a well-known factor responsible for insect declines.

    “Climate change is a well-known factor responsible for insect declines [15, 18, 21, 37].”
    Quote in the paperNot a substantial claim0 of 4 sources checked
    • cites [15] KF Conrad, 2002, Long-term decline in abundance and distribution of the garden tiger moth (<italic>Arctia caja</italic>) in Great Britain, Biological Conservation source

      Not checked in the free run.

    • cites [18] R Fox, 2014, Long-term changes to the frequency of occurrence of British moths are consistent with opposing and synergistic effects of climate and land-use changes, Journal of Applied Ecology source

      Not checked in the free run.

    • cites [21] M Morecroft, 2002, Effects of drought on contrasting insect and plant species in the UK in the mid-1990s, Global Ecology and Biogeography source

      Not checked in the free run.

    • cites [37] M Fliszkiewicz, 2012, Influence of winter temperature and simulated climate change on body mass and fat body depletion during diapause in adults of the Solitary bee, <italic>Osmia rufa</italic> (Hymenoptera: Megachilidae), Environmental Entomology source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    Temporal changes in weather variables either do not affect insect biomass (wind speed) or are expected to positively affect it (temperature).

    “Yet, these changes either do not have an effect on insect biomass (e.g. wind speed) either are expected to positively affected insect biomass (e.g. increased temperature).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    All parameters in all models attained potential scale reduction factor values below 1.02.

    “Parameter convergence was assessed by the potential scale reduction factor [54] (commonly ), that measures the ratio of posterior distributions between independent MCM chains (in all models, all parameters attained values below 1.02).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [54] A Gelman, 1992, Inference from iterative simulation using multiple sequences, Statistical Science source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Study design and conductown data

    Total insect biomass of each catch was obtained based on a standardized measurement protocol by first subtracting fluid content.

    “Trap catches were stored in 80% ethanol solution, prior to weighing, and total insect biomass of each catch (bottle) was obtained based on a standardized measurement protocol by first subtracting fluid content.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Malaise trap catches provide a representative measure of total flying insect biomass at a location.

  • Classified as probably not a substantial claim. May combine two claims.

    Premisereasoning

    The extent to which total insect biomass has declined and the relative contribution of each proposed factor to the decline remain unresolved.

    “Hence, to what extent total insect biomass has declined, and the relative contribution of each proposed factor to the decline, remain unresolved yet highly relevant questions for ecosystem ecology and conservation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data

    Biomass data were collected and archived using a standardized protocol across 63 unique locations between 1989 and 2016, yielding 96 unique location-year combinations.

    “Biomass data were collected and archived using a standardized protocol across 63 unique locations between 1989 and 2016 (resulting in 96 unique location-year combinations) by the Entomological Society Krefeld.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Malaise trap catches provide a representative measure of total flying insect biomass at a location.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    Herb species richness showed severe overdispersion in a Poisson mixed-effects model (residual deviance/df = 2.16).

    “Although a Poisson distribution fitted tree and shrub species adequately, (residual deviance/ degree of freedom = 0.94 and 1.04 respectively), severe overdispersion was found for herb species richness (residual deviance/ degree of freedom = 2.16).”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Data for bees and moths suggest the same declining trend as for other well-studied taxa.

    “Data for other well-studied taxa such as bees [8–14] and moths [15–18] suggest the same trend.”
    Quote in the paperNot a substantial claim0 of 10 sources checked
    • cites [8] D Goulson, 2008, Decline and conservation of bumble bees, Annual Review of Entomology source

      Not checked in the free run.

    • cites [9] SG Nilsson, 2008, Long-term land-use changes and extinction of specialised butterflies, Insect Conservation and Diversity source

      Not checked in the free run.

    • cites [10] R Winfree, 2009, A meta-analysis of bees’ responses to anthropogenic disturbance, Ecology source

      Not checked in the free run.

    • cites [11] SG Potts, 2010, Global pollinator declines: trends, impacts and drivers, Trends in Ecology and Evolution source

      Not checked in the free run.

    • cites [12] A Ilyinykh, 2011, Analysis of the causes of declines in Western Siberian outbreaks of the nun moth <italic>Lymantria monacha</italic>, BioControl source

      Not checked in the free run.

    • cites [13] J Ollerton, 2014, Extinctions of aculeate pollinators in Britain and the role of large-scale agricultural changes, Science source

      Not checked in the free run.

    • cites [14] BA Woodcock, 2016, Impacts of neonicotinoid use on long-term population changes in wild bees in England, Nature Communications source

      Not checked in the free run.

    • cites [15] KF Conrad, 2002, Long-term decline in abundance and distribution of the garden tiger moth (<italic>Arctia caja</italic>) in Great Britain, Biological Conservation source

      Not checked in the free run.

    • cites [16] KF Conrad, 2006, Rapid declines of common, widespread British moths provide evidence of an insect biodiversity crisis, Biological Conservation source

      Not checked in the free run.

    • cites [17] R Fox, 2013, The decline of moths in Great Britain: a review of possible causes, Insect Conservation and Diversity source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The geostatistical approach is considered a superior interpolation method to derive weather variables to trap locations.

    “Amongst other methods, the geostatistical approach is considered a superior interpolation method in order to derive weather variables to trap locations [41].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [41] W Luo, 2008, A comparison of spatial interpolation methods to estimate continuous wind speed surfaces using irregularly distributed data from England and Wales, International Journal of Climatology source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    Repeated weightings of four samples using the measurement procedure had an average deviation from the mean of 0.4 percent.

    “In a series of 84 weightings of four different samples repeating this measurement procedure, an average deviation from the mean value of the measurement results of 0.4 percent was observed (unpublished results).”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Malaise trap catches provide a representative measure of total flying insect biomass at a location.

  • May combine two claims.

    Study design and conductown data

    Most locations (59%, n = 37) were sampled in only one year, 20 locations in two years, five locations in three years, and one in four years.

    “Most locations (59%, n = 37) were sampled in only one year, 20 locations in two years, five locations in three years, and one in four years, yielding in total 96 unique location-year combinations of measurements of seasonal total flying insect biomass.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    Because trap locations are all in lowland areas with little altitude variation, large error in weather interpolations at trap locations is not expected.

    “However, as our trap locations are all situated in lowland areas with little altitude variation, we do not expect a large error in our interpolations at trap locations.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    The number of studies on insect trends with sufficient replication and spatial coverage is limited and restricted to certain well-studied taxa.

    “However, the number of studies on insect trends with sufficient replication and spatial coverage are limited [10, 23–25] and restricted to certain well-studied taxa.”
    Quote in the paperSubstantial claim0 of 4 sources checked
    • cites [10] R Winfree, 2009, A meta-analysis of bees’ responses to anthropogenic disturbance, Ecology source

      Not checked in the free run.

    • cites [23] E Fuentes-Montemayor, 2011, The effectiveness of agri-environment schemes for the conservation of farmland moths: assessing the importance of a landscape-scale management approach, Journal of Applied Ecology source

      Not checked in the free run.

    • cites [24] R Dirzo, 2014, Defaunation in the Anthropocene, Science source

      Not checked in the free run.

    • cites [25] JA Thomas, 2016, Butterfly communities under threat, Science source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The posterior distribution of the trend coefficient did not confound any other variable.

    “For all models, we confirmed that the posterior distribution of the trend coefficient did not confound any other variable by plotting the relevant posterior samples and computing pairwise correlation coefficients.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    In the comparable study, 12.2m high suction traps were deployed at four locations in the UK over 1973-2002 and showed a biomass decline at one of the four sites only.

    “In that study, 12.2m high suction traps were deployed at four locations in the UK over the time period 1973–2002, and showed a biomass decline at one of the four sites only.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [28] CR Shortall, 2009, Long-term changes in the abundance of flying insects, Insect Conservation and Diversity source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    Agricultural intensification, including the disappearance of field margins and new crop protection methods, has been associated with an overall decline of biodiversity in plants, insects, birds and other species in the current landscape.

    “Agricultural intensification, including the disappearance of field margins and new crop protection methods has been associated with an overall decline of biodiversity in plants, insects, birds and other species in the current landscape [20, 27, 67].”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [20] TG Benton, 2002, Linking agricultural practice to insect and bird populations: a historical study over three decades, Journal of Applied Ecology source

      Not checked in the free run.

    • cites [27] JA Thomas, 2004, Comparative losses of British butterflies, birds, and plants and the global extinction crisis, Science source

      Not checked in the free run.

    • cites [67] CA Hallmann, 2014, Declines in insectivorous birds are associated with high neonicotinoid concentrations, Nature source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    Recently reported declines in butterflies, wild bees and moths are in parallel with a severe loss of total aerial insect biomass, suggesting that the flying insect community as a whole has been decimated over the last few decades.

    “Our results demonstrate that recently reported declines in several taxa such as butterflies [7, 25–27, 58], wild bees [8–14] and moths [15–18], are in parallel with a severe loss of total aerial insect biomass, suggesting that it is not only the vulnerable species, but the flying insect community as a whole, that has been decimated over the last few decades.”
    Quote in the paperSubstantial claim0 of 10 sources checked
    • cites [7] C van Swaay, 2013, The European grassland butterfly indicator: 1990–2011, EEA Technical Reports

      Not checked in the free run.

    • cites [25] JA Thomas, 2016, Butterfly communities under threat, Science source

      Not checked in the free run.

    • cites [26] JC Habel, 2015, Butterfly community shifts over 2 centuries, Conservation Biology

      Not checked in the free run.

    • cites [27] JA Thomas, 2004, Comparative losses of British butterflies, birds, and plants and the global extinction crisis, Science source

      Not checked in the free run.

    • cites [58] M Kuussaari, 2007, Contrasting trends of butterfly species preferring semi-natural grasslands, field margins and forest edges in northern Europe, Journal of Insect Conservation source

      Not checked in the free run.

    • cites [8] D Goulson, 2008, Decline and conservation of bumble bees, Annual Review of Entomology source

      Not checked in the free run.

    • cites [9] SG Nilsson, 2008, Long-term land-use changes and extinction of specialised butterflies, Insect Conservation and Diversity source

      Not checked in the free run.

    • cites [10] R Winfree, 2009, A meta-analysis of bees’ responses to anthropogenic disturbance, Ecology source

      Not checked in the free run.

    • cites [11] SG Potts, 2010, Global pollinator declines: trends, impacts and drivers, Trends in Ecology and Evolution source

      Not checked in the free run.

    • cites [12] A Ilyinykh, 2011, Analysis of the causes of declines in Western Siberian outbreaks of the nun moth <italic>Lymantria monacha</italic>, BioControl source

      Not checked in the free run.

    • Rests on an assumption: Malaise trap catches provide a representative measure of the total flying insect biomass in the protected areas studied.

  • May combine two claims.

    Interpretationown data

    While the gradual decline of rare insect species has been known for some time, the results illustrate an ongoing and rapid decline in the total amount of airborne insects active in space and time.

    “While the gradual decline of rare insect species has been known for quite some time (e.g. specialized butterflies [9, 66]), our results illustrate an ongoing and rapid decline in total amount of airborne insects active in space and time.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [9] SG Nilsson, 2008, Long-term land-use changes and extinction of specialised butterflies, Insect Conservation and Diversity source

      Not checked in the free run.

    • cites [66] M Warren, 2001, Rapid responses of British butterflies to opposing forces of climate and habitat change, Nature source

      Not checked in the free run.

    • Rests on an assumption: Malaise trap catches provide a representative measure of the total flying insect biomass in the protected areas studied.

  • May combine two claims.

    Interpretationreasoning

    The decline in insect biomass, being evident throughout the growing season and irrespective of habitat type or landscape configuration, suggests large-scale factors must be involved.

    “The decline in insect biomass, being evident throughout the growing season, and irrespective of habitat type or landscape configuration, suggests large-scale factors must be involved.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The study has not exhaustively analysed the full range of climatic variables that could potentially impact insect biomass.

    “However, we have not exhaustively analysed the full range of climatic variables that could potentially impact insect biomass.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    Some temporal changes in climatic variables in the study area have taken place, but these either were not of influence or changed in a manner that should have increased insect biomass.

    “While some temporal changes in climatic variables in our study area have taken place, these either were not of influence (e.g. wind speed), or changed in a manner that should have increased insect biomass (e.g temperature).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationown data

    Whatever the causal factors responsible for the decline, they have a far more devastating effect on total insect biomass than has been appreciated previously.

    “Whatever the causal factors responsible for the decline, they have a far more devastating effect on total insect biomass than has been appreciated previously.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Malaise trap catches provide a representative measure of the total flying insect biomass in the protected areas studied.

  • May combine two claims.

    Study design and conductown data

    The estimated rate of decline in total biomass resembles the true rate of decline and is not an artifact of site selection.

    “We are however confident that our estimated rate of decline in total biomass resembles the true rate of decline, and is not an artifact of site selection.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    The decline in average airborne insect biomass of 76% (up to 82% in midsummer) over 27 years in protected nature areas in Germany considerably exceeds the estimated decline of 58% in global abundance of wild vertebrates over a 42-year period to 2012.

    “This considerably exceeds the estimated decline of 58% in global abundance of wild vertebrates over a 42-year period to 2012 [56, 57].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [56] WWF International. Living Planet Report 2016: Risk and resilience in a new era. Gland, Switzerland. 2016;.

      Not checked in the free run.

    • cites [57] G Ceballos, 2017, Biological annihilation via the ongoing sixth mass extinction signaled by vertebrate population losses and declines, Proceedings of the National Academy of Sciences source

      Not checked in the free run.

    • Rests on an assumption: Malaise trap catches provide a representative measure of the total flying insect biomass in the protected areas studied.

  • Probably not a substantial claim: may not pass S2 (checkable), S4 (based). May combine two claims.

    Interpretationnone given

    The major and hitherto unrecognized loss of insect biomass reported here for protected areas adds a new dimension to the discussion because it must have cascading effects across trophic levels and numerous other ecosystem effects.

    “The major and hitherto unrecognized loss of insect biomass that we report here for protected areas, adds a new dimension to this discussion, because it must have cascading effects across trophic levels and numerous other ecosystem effects.”
    Quote in the paperNot a substantial claim
    • Rests on an assumption: Malaise trap catches provide a representative measure of the total flying insect biomass in the protected areas studied.

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductown data

    The present dataset spans 27 years and 63 sites, but the number of repetitions (multiple years of seasonal distributions at the same locations) was lower (n = 26).

    “Although the present dataset spans a relatively large number of years (27) and sites (63), the number of repetitions (i.e. multiple years of seasonal distributions at the same locations) was lower (n = 26).”
    Quote in the paperSubstantial claim
45 of 45

  • The authors state this as an assumption.

    The seasonal insect biomass profiles from the sampled location-year combinations are random samples representative of the state of entomofauna in protected areas in western Germany.

    “However, the data do permit an analysis at a higher spatial level, i.e. by treating seasonal insect biomass profiles as random samples of the state of entomofauna in protected areas in western Germany.”

  • The paper relies on this without support.

    Malaise trap catches provide a representative measure of total flying insect biomass at a location.

    “In the present study, we consider the total biomass of flying insects to assess the state of local entomofauna as a group.”

  • The paper relies on this without support.

    The sampled protected areas are representative of Western European low-altitude nature protection areas embedded in a human-dominated landscape.

    “Here, we investigate total aerial insect biomass between 1989 and 2016 across 96 unique location-year combinations in Germany, representative of Western European low-altitude nature protection areas embedded in a human-dominated landscape (S1 Fig).”

  • The authors state this as an assumption.

    The mass of each sample is normally distributed about the sum of the latent expected daily mass.

    “The mass m of each sample j, at site s in year k, is assumed to be distributed normally about the sum of the latent expected daily mass (zt, s, k), with variance :”

  • The authors state this as an assumption.

    Location-specific random effects are normally distributed about zero.

    “The random term (us) denotes the location-specific random effect assumed to be distributed normally about zero .”

  • The paper relies on this without support.

    Malaise trap catches provide a representative measure of the total flying insect biomass in the protected areas studied.

    “Our results document a dramatic decline in average airborne insect biomass of 76% (up to 82% in midsummer) in just 27 years for protected nature areas in Germany.”
    “malaise traps as used in the present study target insects flying close to the ground surface (up to 1 meter), with a much wider diversity of taxa.”
6 of 6

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Final-model trend estimate differs between text and Table 4

    Minor

    The Results report a mean of −0.081 and standard deviation of 0.006 for log(λ), while Table 4 reports −0.080 and 0.007.

  • Table 2 omits habitat clusters from the final model

    Minor

    Table 2 leaves the final-model cells blank for both habitat-cluster terms, but Table 4 reports coefficients for both in the final model.

  • Table 2 omits nitrogen from the final model

    Minor

    Table 2 leaves the final-model cell blank for nitrogen, whereas Table 4 reports an Ellenberg nitrogen coefficient in the final model.

3 of 3

Cites

Flagged first, then by citations

1 of the 56 references couldn’t be matched to a known paper.

Research works printed but not linked: 7

  1. U Bosch, 1994, Naturkundliche Untersuchungen zum Naturschutzgebiet Die Spey—III. Nachgewiesene Schmetterlinge (Macrolepidoptera), Natur am Niederrhein (NF), 9, 40
  2. C Schmidt, 1995, Naturkundliche Untersuchungen zum Naturschutzgebiet Die Spey—VI. Die Köcherfliegen (Insecta, Trichoptera), Natur am Niederrhein (NF), 10, 62
  3. M Hellenthal, 2007, Schwebfliegen (Diptera, Syrphidae) des Wahnbachtals im Bergischen Land (Nordrhein-Westfalen, Deutschland), Volucella, 8, 219
  4. H Schwan, 1993, Naturkundliche Untersuchungen zum Naturschutzgebiet Die Spey (Stadt Krefeld, Kreis Neuss)—I. Untersuchungsstandorte und Methoden, Natur am Niederrhein (NF), 8, 1
  5. M Sorg, 1990, Entomophage Insekten des Versuchsgutes Höfchen (BRD, Burscheid).- Teil 1. Aphidiinae (Hymenoptera, Braconidae), Pflanzenschutz-Nachrichten Bayer, 43, 29
  6. M Sorg, 2013, Ermittlung der Biomassen flugaktiver Insekten im Naturschutzgebiet Orbroicher Bruch mit Malaise Fallen in den Jahren 1989 und 2013, Mitteilungen aus dem Entomologischen Verein Krefeld, 2013, 1
  7. N Cressie, 1993, Statistics for spatial data: Wiley series in probability and statistics, Wiley-Interscience New York, 15, 16

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Related

Authors
Hallmann, C. A., Sorg, M., Jongejans, E., Siepel, H., Hofland, N., Schwan, H., Stenmans, W., Müller, A., Sumser, H., Hörren, T., Goulson, D., & de Kroon, H.
Affiliations
  • Radboud University Nijmegen (NL)
  • University of Sussex (GB)
Corresponding author
Hallmann, Caspar A.
ORCID
Venue
PLOS ONE
Publisher
Public Library of Science (PLoS)
Published
2017-10-18
Volume
12
Issue
10
Pages
e0185809
ISSN
1932-6203 (ISSN-L)
DOI
10.1371/journal.pone.0185809
PMC
PMC5646769
OpenAlex
W2766208183
Semantic Scholar
332d4e7950ea583b7755f37fadf8c536d35876c1
Cited by
3,499
References
56
Citations by year
2026: 289 · 2025: 397 · 2024: 367 · 2023: 434 · 2022: 425 · 2021: 513 · 2020: 463 · 2019: 387 · 2018: 200 · 2017: 12 · 2016: 6
FWCI
252.10
Type
journal article
Language
en
Open access
Licence
Locations
  • PLoS ONE (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, cc-by)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Sussex Research Online (University of Sussex) (submittedVersion, cc-by)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Figshare (submittedVersion, cc-by)
  • Radboud Repository (Radboud University) (submittedVersion)
  • Radboud Repository (Radboud University) (submittedVersion, other-oa)
Funders
  • Nederlandse Organisatie voor Wetenschappelijk Onderzoek (840.11.001, 841.11.007)
  • Triodos Foundation
Topics
  • Life Sciences › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Plant and animal studies
  • Physical Sciences › Environmental Science › Nature and Landscape Conservation › Ecology and Vegetation Dynamics Studies
  • Life Sciences › Agricultural and Biological Sciences › Ecology, Evolution, Behavior and Systematics › Entomological Studies and Ecology
Keywords
flying insects, insect fauna, long-term monitoring, protected areas, seasonal decline, ecosystem services, food webs, land use, weather effects, habitat characteristics, Malaise trap
MeSH terms
Animals, Conservation of Natural Resources, Flight, Animal, Insecta, Models, Theoretical, Seasons, Time Factors, Sample Size, Biomass

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-06.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-06.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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