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Large carabid beetle declines in a United Kingdom monitoring network increases evidence for a widespread loss in insect biodiversity

Why it matters: the relevance of this research
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This paper is relevant to the following issues:

  • Biodiversity loss

  • Insect conservation

  • Habitat management

  • Ecosystem services related to food security


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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.

 

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