There Is a Light That Never Goes Out! Reversing the Glow-Worm’s Decline

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The glow-worm Lampyris noctiluca (Linnaeus, 1767) (Coleoptera: Lampyridae) is thought to be declining in the UK. Average glowing counts at 19 sites in Essex, south-east England, changed from ca. 20 glow-worms per km of transect in 2001 to ca. 5 glow-worms per km in 2018. Local-scale factors in addition to climate change drove greater reduction in numbers at some sites than others. There is a clear signal of climate warming and drying effects on glow-worm numbers, but a substantially greater proportion of variation in glowing female counts is explained by local-scale site factors, such as unmanaged scrub encroachment. Management that increased site populations included scrub clearance on a seawall flood defense embankment and coppicing in an ancient woodland. No significant declines were noted in Essex woodlands, or in linear habitats such as a disused railway line or river corridor. The prognosis for Essex populations depends on how the climate and site management factors interact. Sustained favorable management of sites by coppicing and scrub cutting may buffer populations against declines caused by climate drying and warming and benefit other insects such as butterflies.

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The effects of lagomorph grazing on the Orthoptera of a small hill at Lound Lakes (Suffolk, UK) were studied during the summer of 2020. The transect counts of Orthoptera revealed low sward height due to high rabbit Oryctolagus cuniculus (Linnaeus, 1758) grazing on the high slopes which led to the general absence of tall grass species such as the Common Green Grasshopper Omocestus viridulus (Linnaeus, 1758) and Roesel's Bush-cricket Roeseliana roeselii (Hagenbach, 1822). Only nymphs and Field Grasshopper Chorthippus brunneus (Thunberg, 1815) adults were found in any number on the higher slopes, perhaps utilising the short swards and bare earth as basking habitat. The lower slopes and pastures supported tall-grass Orthoptera due to the absence of rabbit grazing and tussocky grassland.
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Results from glow-worms surveys on 15 sites across southern and central England were used to assess the current status of L. noctiluca in the region and to study the influence of ecological and climatic factors on glow-worm numbers and phenology. The surveys also provide an indication of L. noctiluca's habitat requirements, as well as offering a method of estimating total population sizes.
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A small area of ancient woodland in Essex, England was coppiced. Glow-worms Lampyris noctiluca were observed in the cut area in the first four seasons after winter coppicing, whereas significantly lower numbers were recorded in an uncut control. The highest abundance was observed in the second season after coppicing, only for numbers to decline as the area became overgrown with bramble Rubus fruticosus and shading from the maturing canopy occurred. Coppicing may promote the conservation of glow-worms in ancient woodland.
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The response of glow-worms Lampyris noctiluca to winter scrub clearance on a sea wall flood defence in Essex, England was monitored. The number of glowing adult females did not show a significant difference in the two seasons (one life cycle) after scrub clearance, or at a control site with no clearance.
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Artificial lights raise night sky luminance, creating the most visible effect of light pollution-artificial skyglow. Despite the increasing interest among scientists in fields such as ecology, astronomy, health care, and land-use planning, light pollution lacks a current quantification of its magnitude on a global scale. To overcome this, we present the world atlas of artificial sky luminance, computed with our light pollution propagation software using new high-resolution satellite data and new precision sky brightness measurements. This atlas shows that more than 80% of the world and more than 99% of the U.S. and European populations live under light-polluted skies. The Milky Way is hidden from more than one-third of humanity, including 60% of Europeans and nearly 80% of North Americans. Moreover, 23% of the world's land surfaces between 75°N and 60°S, 88% of Europe, and almost half of the United States experience light-polluted nights.
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Light pollution has been proposed as a factor in the decline of Lampyris noctiluca because it has the potential to interfere with reproductive signaling and has been shown to impact the ability of males to locate light lures in a suburban environment. To compare and test the replicability of this effect in a natural setting and population, imitation females were set out under light polluted and control conditions at varying light pollution intensities in an undisturbed British chalk grassland. Very low levels of light pollution were found to interfere with phototaxis: no males were attracted at either 0.3 or 0.18 lux background lighting versus 33 males collected at paired dark controls. These background illumination levels are much lower than that of 1.5 lux which is recommended by local city councils in Britain to light footpaths. A survey of female L. noctiluca numbers and distribution showed a trend towards female clumping that was not statistically significant. We also found no evidence of light interfering with female signaling behavior.
1. The glow-worm Lampyris noctiluca (Linnaeus, 1767) (Coleoptera: Lam-pyridae) is thought to be declining in the United Kingdom. Yet, much of the evidence for this is anecdotal, with a shortage of standardised long-term data to investigate temporal changes in abundance. 2. We present an 18-year time series of standardised transect surveys for glowing adult females at 19 sites within southeast England (Essex) from 2001 to 2018. 3. We used generalised additive mixed models (GAMMs) to control for varying sampling effort, temporal autocorrelation, non-stationarity of seasonal phenology and non-linearity of temporal trajectories across sites. 4. We found a significant long-term reduction in counts of glowing female glow-worms, after accounting for a significant shift in seasonal phenology across years, and a negative effect of warmer climatic conditions on glow-worm abundance. Average glowing counts in southeast England declined by ca. −3.5% per annum from 2001 to 2018, and this result held true even after a range of sensitivity tests to account for potential methodological artefacts in citizen science data collection. 5. Temporal trajectories in abundance were strikingly out of phase across the 19 sites, suggesting that local-scale factors in addition to climate are driving greater reduction in numbers at some sites than others. 6. These standardised surveys present the first quantitative evidence that numbers of glow-worms could well be declining in the United Kingdom. There is a clear signal of climate warming and drying effects on glow-worm numbers, but a substantially greater proportion of variation in glowing female counts is explained by local-scale site factors, such as unmanaged scrub encroachment. Conservation strategies that can mitigate local population losses could be an essential buffer against climate-driven declines in southeast England.
With the subtitle, 'The full fascinating story of Britain's landscape', the emphasis of this volume is on the earlier post-glacial history of both natural and man-made features in rural Britain. Whilst chapters recount the development of fields systems, heathland, moorland, grassland and wetlands, most attention is paid to woods and wood-pastures, and their significance in both the natural environments and the economic and social life of the rural populations. Chapters are devoted to the history of hedgerows and walls, the extinction and introduction of animal species, and the changing fortunes of the elm. In addition to a chapter on conservation, conservation sections are included in most other chapters, highlighting the need for changes in current policies towards the agricultural and silvicultural uses of the countryside. -J.Sheail
Mitigation for a development initiated a ten-year study of the European glow-worm (L. noctiluca) including field survey, pitfall trapping, captive breeding and translocation methodologies. Preliminary results indicated a field ratio of sixty-three larvae for each adult female. The species is relatively resilient to disturbance and breeds readily in captivity. L. noctiluca has possibly been introduced to railways with ballast. Substrate (including turf) collection may be a suitable translocation method but pitfall trapping of larvae provides a more readily assayable technique. Habitat management should provide a mosaic of open areas suitable for courtship display, well- drained substrate for the laying and hatching of eggs and moister vegetation to encourage mollusc prey.
Sea wall flood embankments protect a large area of coastal land in eastern England (particularly in the county of Essex) from tidal flooding. These important defences also provide grassland habitats for scarce insects in Essex, including several declining bumblebees (Bombus spp.). The grassland of many sea walls is mown once annually to maintain the structural integrity of the defences; however, cutting also exerts an influence over insect populations. Many sea walls are mown in midsummer (July and August) which can lead to high mortality of insects in the sward and also remove forage resources for bumblebees in particular. A review was undertaken of recent case studies investigating the response of insect populations to various sea wall mowing regimes in Essex in eastern England. This review highlighted the importance of rotational mowing regimes for limiting damage to populations of the rare moth Gortyna borelii lunata; it seems that cutting sea wall grassland in strips allows this insect to persist on flood defences. Other small-scale studies indicated that leaving a strip of unmown grassland on the folding (or berm) on the landward side of a sea wall is essential for promoting high abundance and species richness of bumblebees and butterflies. It is possible that conservation management for insects may conflict with the annual mowing that may be needed to maintain high floristic diversity. Leaving sections of sea walls unmown for insects, particularly on the folding, may lead to a decline in the floristic diversity of the sward due to the build up of litter and development of tussocky grassland. Implementing a system of rotational mowing which incorporates unmown grassland on the folding could be a key step toward more environmentally sustainable sea wall maintenance regimes in Essex. It is also clear that more research is needed into the effects of sea wall mowing on insect abundance and diversity, as there have been very few replicated studies in the east of England.
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Glowing, Glowing, Gone? The Plight of the Glow-Worm in Essex. Corby: British Naturalists' Association
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