Changes in phenology and abundance of suction‐trapped Diptera from a farmland site in the <scp>UK</scp> over four decades

Grabener, Swantje; Oldeland, Jens; Shortall, C. R.; Harrington, R.

doi:10.1111/een.12873

Cited by 20 publications

(6 citation statements)

References 55 publications

(59 reference statements)

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“…Agricultural intensification is likely to have had a negative impact on aerial insect population sizes (Benton et al 2002, Paquette et al 2013, Møller et al 2021, which has been shown to affect the foraging behaviour of another swallow species (Stanton et al 2016). In this study, we found a long-term decline in insect biomass at one of four sites (Hereford), an increase at one site (Rothamsted) and stable populations at two sites, although subsequent analyses have also identified a decline in Diptera abundance (trends in biomass were not tested) at the Rothamsted suction trap (Grabener et al 2020). Swallow population trends were also variable between the four trap sites, although there was no obvious link between trends in insects and Swallows.…”

Section: Discussionmentioning

confidence: 56%

“…Swallow diet is diverse and the response of different insect taxa to environmental change will differ: warming may alter aphid population dynamics (Bell et al 2015) but have a negative impact on Diptera associated with wet soils (Pearce-Higgins 2010, Pearce-Higgins & Morris 2023), both of which form a significant component of Swallow diets. In this study we found that Swallow chick survival was more dependent on the biomass of other insects, largely Diptera, than on aphids, and they may therefore be sensitive to declines in Diptera abundance (Grabener et al 2020). We call for further studies of the contribution that large-scale declines in insect abundance may have had upon insectivore population trends.…”

Section: Discussionmentioning

confidence: 56%

“…In this study, we found a long‐term decline in insect biomass at one of four sites (Hereford), an increase at one site (Rothamsted) and stable populations at two sites, although subsequent analyses have also identified a decline in Diptera abundance (trends in biomass were not tested) at the Rothamsted suction trap (Grabener et al . 2020). Swallow population trends were also variable between the four trap sites, although there was no obvious link between trends in insects and Swallows.…”

Section: Discussionmentioning

confidence: 99%

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Aerial insect biomass, but not phenological mismatch, is associated with chick survival of an insectivorous bird

Martay

Leech

Shortall

et al. 2023

Ibis

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Recent insect abundance declines may have affected populations of insectivorous bird species but evidence for this is limited. Here, we use spatially overlapping 29-year timeseries of aerial insect biomass and Barn Swallow Hirundo rustica numbers and breeding success from southern England to model the association between changes in invertebrate prey abundance, Swallow productivity and population trends. We found a positive statistical relationship between Swallow chick survival and the biomass of aerial insects available for chicks. In nests where at least one chick fledged, 96.7% of chicks were predicted to survive to fledging where there was high insect biomass (an average of 0.62 g/day), compared with 87.4% of chicks surviving to fledging where there was the lowest insect biomass (0.02 g/day; excluding the greatest and smallest 5% of insect biomass measurements). The amount of food available for chicks was largely a function of annual variation in insect abundance rather than the phenology of egg-laying and insect emergence. However, we did not find a correlation between annual insect abundance and subsequent Swallow population growth. In the context of concerns about declining insect abundance, this study shows how changes in insect biomass may affect the productivity of an insectivorous bird at a regional scale, but with uncertain implications for population size at that same scale.

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Section: Discussionmentioning

confidence: 56%

Section: Discussionmentioning

confidence: 56%

Section: Discussionmentioning

confidence: 99%

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Aerial insect biomass, but not phenological mismatch, is associated with chick survival of an insectivorous bird

Martay

Leech

Shortall

et al. 2023

Ibis

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“…The latter included declines of 51% in broadleaf woodland, 43% in the uplands, 44% in urban habitats and 28% in improved grassland from 1968–2016 [ 44 ]. Declines in aerial insect abundance have been reported at some English sites, but not others [ 45 , 46 ]. Overall, it appears that the putative magnitude of earthworm declines suggested by our analysis are similar to that of other declining insect groups in the UK, if less than declines reported from continental Europe.…”

Section: Discussionmentioning

confidence: 99%

Collation of a century of soil invertebrate abundance data suggests long-term declines in earthworms but not tipulids

2023

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Large-scale declines in terrestrial insects have been reported over much of Europe and across the world, however, population change assessments of other key invertebrate groups, such as soil invertebrates, have been largely neglected through a lack of available monitoring data. This study collates historic data from previously published studies to assess whether it is possible to infer previously undocumented long-term changes in soil invertebrate abundance. Earthworm and tipulid data were collated from over 100 studies across the UK, spanning almost 100 years. Analyses suggested long-term declines in earthworm abundance of between 1.6 to 2.1% per annum, equivalent to a 33% to 41% decline over 25 years. These appeared greatest in broadleaved woodlands and farmland habitats, and were greater in pasture than arable farmland. Significant differences in earthworm abundance between habitats varied between models but appeared to be highest in urban greenspaces and agricultural pasture. More limited data were available on tipulid abundance, which showed no significant change over time or variation between enclosed farmland and unenclosed habitats. Declines in earthworm populations could be contributing to overall declines in ecosystem function and biodiversity as they are vital for a range of ecosystem services and are keystone prey for many vertebrate species. If robust, our results identify a previously undetected biodiversity decline that would be a significant conservation and economic issue in the UK, and if replicated elsewhere, internationally. We highlight the need for long-term and large-scale soil invertebrate monitoring, which potentially could be carried out by citizen/community scientists.

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“…Since 2000 long‐term research in insects illustrated declines in distribution in well‐studied insects such as butterflies, bumblebees, moths, bees, and flies (Biesmeijer et al, 2006; Bourn & Thomas, 2002; Carvell et al, 2006; Conrad et al, 2006; Shortall et al, 2009). In more recent years, many case studies and reviews prove that the distribution and abundance of many other insect groups have declined by 30%–75% within a few decades (Bell et al, 2020; Dirzo et al, 2014; Fox et al, 2014; Grabener et al, 2020; Hallmann et al, 2017, 2020; Homburg et al, 2019; van Strien et al, 2019). Society realises that these insects are an essential link in the food web, and that they facilitate essential processes such as pollination and nutrient recycling (Habel & Schmitt, 2018; Raven & Wagner, 2021).…”

Section: Introductionmentioning

confidence: 99%

Forest hoverfly community collapse: Abundance and species richness drop over four decades

Barendregt

Zeegers²,

Steenis³

et al. 2022

Insect Conserv Diversity

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1. 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.2. 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.3. 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.4. The number of nationally rare species observed at the study site declined from 19 to 9 early on, in a period (1979)(1980)(1981)(1982)(1983)(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. 5. 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.

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Changes in phenology and abundance of suction‐trapped Diptera from a farmland site in the UK over four decades

Cited by 20 publications

References 55 publications

Aerial insect biomass, but not phenological mismatch, is associated with chick survival of an insectivorous bird

Aerial insect biomass, but not phenological mismatch, is associated with chick survival of an insectivorous bird

Collation of a century of soil invertebrate abundance data suggests long-term declines in earthworms but not tipulids

Forest hoverfly community collapse: Abundance and species richness drop over four decades

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