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

In the paper

“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).”

In the paper

“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.”

In the paper

“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).”

In the paper

“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].”

What the sources say

• Not checked yetcites [45] I Steffan-Dewenter, 2002, Scale-dependent effects of landscape context on three pollinator guilds, Ecology source

In the paper

“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).”

In the paper

“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).”

In the paper

“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.”

In the paper

“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).”

In the paper

“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).”

In the paper

“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).”

In the paper

“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.”

In the paper

“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.”

In the paper

“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.”

What the sources say

• Not checked yetcites [1] E Öckinger, 2007, Semi-natural grasslands as population sources for pollinating insects in agricultural landscapes, Journal of Applied Ecology source
• Not checked yetcites [2] J Ollerton, 2011, How many flowering plants are pollinated by animals?, Oikos source
• Not checked yetcites [3] WJ Mattson, 1975, Phytophagous insects as regulators of forest primary production, Science source
• Not checked yetcites [4] LH Yang, 2014, Insects as drivers of ecosystem processes, Current Opinion in Insect Science source

In the paper

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

What the sources say

• Not checked yetcites [7] C van Swaay, 2013, The European grassland butterfly indicator: 1990–2011, EEA Technical Reports
• Not checked yetcites [8] D Goulson, 2008, Decline and conservation of bumble bees, Annual Review of Entomology source
• Not checked yetcites [9] SG Nilsson, 2008, Long-term land-use changes and extinction of specialised butterflies, Insect Conservation and Diversity source
• Not checked yetcites [10] R Winfree, 2009, A meta-analysis of bees’ responses to anthropogenic disturbance, Ecology source
• Not checked yetcites [11] SG Potts, 2010, Global pollinator declines: trends, impacts and drivers, Trends in Ecology and Evolution source
• Not checked yetcites [12] A Ilyinykh, 2011, Analysis of the causes of declines in Western Siberian outbreaks of the nun moth Lymantria monacha, BioControl source
• Not checked yetcites [13] J Ollerton, 2014, Extinctions of aculeate pollinators in Britain and the role of large-scale agricultural changes, Science source
• Not checked yetcites [14] BA Woodcock, 2016, Impacts of neonicotinoid use on long-term population changes in wild bees in England, Nature Communications source
• Not checked yetcites [15] KF Conrad, 2002, Long-term decline in abundance and distribution of the garden tiger moth (Arctia caja) in Great Britain, Biological Conservation source
• Not checked yetcites [16] KF Conrad, 2006, Rapid declines of common, widespread British moths provide evidence of an insect biodiversity crisis, Biological Conservation source

In the paper

“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)).”

In the paper

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

In the paper

“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.”

In the paper

“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.”

What the sources say

• Not checked yetcites [29] U Bosch, 1994, Naturkundliche Untersuchungen zum Naturschutzgebiet Die Spey—III. Nachgewiesene Schmetterlinge (Macrolepidoptera), Natur am Niederrhein (NF)
• Not checked yetcites [30] C Schmidt, 1995, Naturkundliche Untersuchungen zum Naturschutzgebiet Die Spey—VI. Die Köcherfliegen (Insecta, Trichoptera), Natur am Niederrhein (NF)
• Not checked yetcites [31] M Hellenthal, 2007, Schwebfliegen (Diptera, Syrphidae) des Wahnbachtals im Bergischen Land (Nordrhein-Westfalen, Deutschland), Volucella
• Not checked yetcites [28] CR Shortall, 2009, Long-term changes in the abundance of flying insects, Insect Conservation and Diversity source

In the paper

“For example, populations of European grassland butterflies are estimated to have declined by 50% in abundance between 1990 and 2011 [7].”

What the sources say

• Not checked yetcites [7] C van Swaay, 2013, The European grassland butterfly indicator: 1990–2011, EEA Technical Reports

In the paper

“Climate change is a well-known factor responsible for insect declines [15, 18, 21, 37].”

What the sources say

• Not checked yetcites [15] KF Conrad, 2002, Long-term decline in abundance and distribution of the garden tiger moth (Arctia caja) in Great Britain, Biological Conservation source
• Not checked yetcites [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 yetcites [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 yetcites [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, Osmia rufa (Hymenoptera: Megachilidae), Environmental Entomology source

In the paper

“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).”

In the paper

“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).”

What the sources say

• Not checked yetcites [54] A Gelman, 1992, Inference from iterative simulation using multiple sequences, Statistical Science source

In the paper

“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.”

In the paper

“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.”

In the paper

“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.”

In the paper

“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).”

In the paper

“Data for other well-studied taxa such as bees [8–14] and moths [15–18] suggest the same trend.”

What the sources say

• Not checked yetcites [8] D Goulson, 2008, Decline and conservation of bumble bees, Annual Review of Entomology source
• Not checked yetcites [9] SG Nilsson, 2008, Long-term land-use changes and extinction of specialised butterflies, Insect Conservation and Diversity source
• Not checked yetcites [10] R Winfree, 2009, A meta-analysis of bees’ responses to anthropogenic disturbance, Ecology source
• Not checked yetcites [11] SG Potts, 2010, Global pollinator declines: trends, impacts and drivers, Trends in Ecology and Evolution source
• Not checked yetcites [12] A Ilyinykh, 2011, Analysis of the causes of declines in Western Siberian outbreaks of the nun moth Lymantria monacha, BioControl source
• Not checked yetcites [13] J Ollerton, 2014, Extinctions of aculeate pollinators in Britain and the role of large-scale agricultural changes, Science source
• Not checked yetcites [14] BA Woodcock, 2016, Impacts of neonicotinoid use on long-term population changes in wild bees in England, Nature Communications source
• Not checked yetcites [15] KF Conrad, 2002, Long-term decline in abundance and distribution of the garden tiger moth (Arctia caja) in Great Britain, Biological Conservation source
• Not checked yetcites [16] KF Conrad, 2006, Rapid declines of common, widespread British moths provide evidence of an insect biodiversity crisis, Biological Conservation source
• Not checked yetcites [17] R Fox, 2013, The decline of moths in Great Britain: a review of possible causes, Insect Conservation and Diversity source

In the paper

“Amongst other methods, the geostatistical approach is considered a superior interpolation method in order to derive weather variables to trap locations [41].”

What the sources say

• Not checked yetcites [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

In the paper

“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).”

In the paper

“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.”

In the paper

“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.”

In the paper

“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.”

What the sources say

• Not checked yetcites [10] R Winfree, 2009, A meta-analysis of bees’ responses to anthropogenic disturbance, Ecology source
• Not checked yetcites [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 yetcites [24] R Dirzo, 2014, Defaunation in the Anthropocene, Science source
• Not checked yetcites [25] JA Thomas, 2016, Butterfly communities under threat, Science source

In the paper

“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.”

In the paper

“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.”

What the sources say

• Not checked yetcites [28] CR Shortall, 2009, Long-term changes in the abundance of flying insects, Insect Conservation and Diversity source

In the paper

“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].”

What the sources say

• Not checked yetcites [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 yetcites [27] JA Thomas, 2004, Comparative losses of British butterflies, birds, and plants and the global extinction crisis, Science source
• Not checked yetcites [67] CA Hallmann, 2014, Declines in insectivorous birds are associated with high neonicotinoid concentrations, Nature source

In the paper

“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.”

What the sources say

• Not checked yetcites [7] C van Swaay, 2013, The European grassland butterfly indicator: 1990–2011, EEA Technical Reports
• Not checked yetcites [25] JA Thomas, 2016, Butterfly communities under threat, Science source
• Not checked yetcites [26] JC Habel, 2015, Butterfly community shifts over 2 centuries, Conservation Biology
• Not checked yetcites [27] JA Thomas, 2004, Comparative losses of British butterflies, birds, and plants and the global extinction crisis, Science source
• Not checked yetcites [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 yetcites [8] D Goulson, 2008, Decline and conservation of bumble bees, Annual Review of Entomology source
• Not checked yetcites [9] SG Nilsson, 2008, Long-term land-use changes and extinction of specialised butterflies, Insect Conservation and Diversity source
• Not checked yetcites [10] R Winfree, 2009, A meta-analysis of bees’ responses to anthropogenic disturbance, Ecology source
• Not checked yetcites [11] SG Potts, 2010, Global pollinator declines: trends, impacts and drivers, Trends in Ecology and Evolution source
• Not checked yetcites [12] A Ilyinykh, 2011, Analysis of the causes of declines in Western Siberian outbreaks of the nun moth Lymantria monacha, BioControl source

In the paper

“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.”

What the sources say

• Not checked yetcites [9] SG Nilsson, 2008, Long-term land-use changes and extinction of specialised butterflies, Insect Conservation and Diversity source
• Not checked yetcites [66] M Warren, 2001, Rapid responses of British butterflies to opposing forces of climate and habitat change, Nature source

In the paper

“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.”

In the paper

“However, we have not exhaustively analysed the full range of climatic variables that could potentially impact insect biomass.”

In the paper

“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).”

In the paper

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

In the paper

“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.”

In the paper

“This considerably exceeds the estimated decline of 58% in global abundance of wild vertebrates over a 42-year period to 2012 [56, 57].”

What the sources say

• Not checked yetcites [56] WWF International. Living Planet Report 2016: Risk and resilience in a new era. Gland, Switzerland. 2016;.
• Not checked yetcites [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

In the paper

“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.”

In the paper

“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).”