Predatory carabid beetles are important components of many terrestrial habitats and food webs, but ECN's long-term carabid monitoring has, along with other studies, revealed widespread declines. Here we present the findings of researchers who used ECN carabid beetle data to investigate these trends. Their research, and their recommendations for changes to wood and hedge management that may benefit carabid beetles, was published in the 2016 paper Large carabid beetle declines in a United Kingdom monitoring network increases evidence for a widespread loss in insect biodiversity (Brooks et al.).

The paper present trends in the abundance of carabid (or ground) beetles at 11 terrestrial ECN sites over a 15 year period.

Reference

Brooks, DR., Bater, JE., Clark, SJ., Monteith, DT., Andrews, C., Corbett, SJ., Beaumont, DA. and Chapman, JW. (2012). Large carabid beetle declines in a United Kingdom monitoring network increases evidence for a widespread loss in insect biodiversity. Journal of Applied Ecology, 49 (5), 1009-1019. DOI: 10.1111/j.1365-2664.2012.02194.x

Why this research matters

This paper is relevant to the following issues:

• Biodiversity loss
• Insect conservation
• Habitat management
• Ecosystem services related to food security

In brief

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In more detail

The authors of this paper assessed ECN data on carabid beetles, collected from 11 sites over the period 1994 to 2008. Sites covered pasture, field margins, chalk downland, woodland and hedgerows in the lowlands, moorland and pasture in the uplands, and grassland, heaths and bogs in montane locations.

The data revealed substantial overall declines in carabid beetle abundance. Three-quarters (75%) of the species studied declined. Half of the declining species were estimated to be experiencing population reductions of more than 30% (averaged over 10-year periods). Declines of this magnitude are of conservation concern and are comparable to those reported for butterflies and moths.

Carabid beetles are important components of terrestrial food webs, and so changes may affect other species in an ecosystem (such as the prey species that carabids feed on). Some carabid species eat seeds and there is evidence that in farmland, carabids help to control weeds by eating weed seeds. Forms of natural biocontrol are important when considering future strategies for food production.

Overall trends masked differences between regions and habitats. The biggest declines were seen at montane sites (52%), northern moorland sites (31%) and western pasture sites (31%). In contrast, there was a 48% increase in species numbers at the southern downland site. Populations were generally stable in upland pasture, woodland and hedgerow sites.

The authors discuss possible factors influencing the observed trends. Climatic changes could account for some of the observed changes, but localised changes in habitats may also be important. For example, the height of the vegetation sward may be important (it affects temperature at the soil surface).

The authors suggest that management of 'microhabitat' conditions may be important in conservation of carabids. In particular, since woods and hedgerows are important overwintering refuges for many carabids, there may be scope to manage these habitats to benefit the beetles.

This is the published abstract of the research paper

1. Carabid beetles are important functional components of many terrestrial ecosystems. Here, we describe the first long-term, wide-scale and quantitative assessment of temporal changes in UK carabid communities, to inform nationwide management aimed at their conservation.
2. Multivariate and mixed models were used to assess temporal trends over a 15-year period, across eleven sites in the UK Environmental Change Network. Sites covered pasture, field margins, chalk downland, woodland and hedgerows in the lowlands, moorland and pasture in the uplands, and grassland, heaths and bogs in montane locations.
3. We found substantial overall declines in carabid biodiversity. Three-quarters of the species studied declined, half of which were estimated to be undergoing population reductions of > 30%, when averaged over 10-year periods. Declines of this magnitude are recognized to be of conservation concern. They are comparable to those reported for butterflies and moths and increase the evidence base showing that insects are undergoing serious and widespread biodiversity losses.
4. Overall trends masked differences between regions and habitats. Carabid population declines (10-year trend, averaged across species) were estimated to be 52% in montane sites, 31% in northern moorland sites and 28% in western pasture sites (with at least 80% of species declining in each case). Conversely, populations in our southern downland site had 10-year increases of 48% on average. Overall, biodiversity was maintained in upland pasture, and populations were mostly stable in woodland and hedgerow sites.
5. Synthesis and applications. Our results highlight the need to assess trends for carabids, and probably other widespread and ubiquitous taxa, across regions and habitats to fully understand losses in biodiversity. Land management should be underpinned by a consideration of how wide-scale environmental drivers interact with habitat structure. The stability of population trends in woodlands and hedgerows of species that are declining elsewhere puts these habitats at the fore-front of integrated landscape management aimed at preserving their ecosystem services.