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Royal Commission on Environmental Pollution Submission to: Royal Commission study on artificial light in the environment From the Royal Entomological Society It has long been of concern that increasing artificial light levels associated with urban developments such as road, security and amenity lighting have been changing the natural and semi-natural environment, not only in urban areas but increasingly in more rural areas as well. As a Society, our particular interests are insects and other invertebrates that make up the majority of living species and biomass. Apart from being of conservation interest in their own right, healthy invertebrate populations provide numerous free ecosystem services such as pollination and pest control, as well as forming a vital component of the diet of many bird and mammal species (such as bats) that have important populations in urban areas and also have very high public profiles. Despite this long-running concern about possible deleterious effects of light pollution on insects, surprisingly little substantial research has been done to understand and quantify actual effects at the population level, although there have been two useful recent reviews of the subject which contain much of what is known (Eisenbeis 2006; Frank 2006). Attraction to Light An immediate effect of much artificial lighting is that it attracts many nocturnal insects which then remain in its close vicinity. This attraction to light has benefited entomological studies for centuries as the phenomenon has been used for light trapping and providing census information, in particular for monitoring moth populations (Conrad et al. 2007). There is no doubt that very large numbers of insects are attracted to artificial lights, which then become prey to bats and birds, or perhaps more importantly are diverted from their natural behaviour patterns. Light sources are known to differ in their attractiveness to insects. As an example, high pressure mercury vapour lights with a high content of UV are very attractive, whereas high pressure sodium lights seem to catch less than half as many on average (Eisenbeis 2006) and low pressure sodium lights have virtually no attraction to most insects. This has often led to low-pressure sodium lights being recommended as a way of minimising light pollution effects on insects in sensitive areas such as parks and nature reserves, however, for reasons given below this might be very bad advice indeed. The distance insects are attracted to lights is not well understood, with estimates ranging from a few to many hundreds of metres (Eisenbeis 2006). What is not disputed is that very large numbers of insects are attracted and that this might be having important overall effects on insect abundance as well as having very serious effects on populations of rarer insect species, particularly near urban areas. In addition lighting may be acting as a very effective barrier between local breeding sites of insects. Repulsion and inhibition from artificial light Some insects are known to be strongly repelled by light. This would appear to be an advantage in this context, but as more and more of the environment is lit then there are fewer and fewer places for such species to survive and breed. 1 Much street lighting currently uses high or low pressure sodium light. Although such light is generally less attractive to insects than previous types, observations suggest that normal flight behaviour is completely inhibited in the general area of such lights, in effect sterilising large areas for nocturnal flying insects (e.g. Uffen 1994). This effect may be far more insidious than the problems associated with attraction to light and further research into this neglected area is recommended. Certainly an increase in the use of sodium lighting is not a panacea, at least as far as insect populations are concerned. Other problems with light pollution Perhaps less obvious are our concerns for the disruption of overwintering strategies of insects. Many insects in temperate regions undergo a diapause (hibernation) stage that is resistant to adverse winter conditions and development is renewed in warmer spring weather. Such cold-resistant stages pre-empt inclement weather and are induced by the short days of autumn. Day length is the most reliable environmental signal that indicates season and within limits the response is temperature insensitive, temperature being a much less dependable indication of date. The mechanism for the response to day length is partly understood and insects are sensitive to ambient light levels that extend into civil twilight and are little above those in full-moon conditions (Saunders 2002). Thus, it is not inconceivable that light from artificial sources is perceived as extended day length, indeed as continuous light conditions, and inhibits the production of overwintering forms. Such an effect would lead to local extinction and decrease biodiversity in areas around artificial lights. As far as we are aware there are no scientific studies of the effects of artificial lighting on insect overwintering, although the consequences may be very important. The effect of increased or inappropriate lighting might be having several other undesirable side effects on insect populations. For example many of the day-flying species, such as butterflies, have larvae that only emerge and feed at night. Artificial light are likely to inhibit this behaviour or make such larvae open to much higher levels of bird and mammal predation than normal. Also, some insects use light communication for signalling between the sexes. The notable British beetle species that do this are glow-worms, and concern has been expressed about light pollution levels badly affecting such species (e.g. http://www.galaxypix.com/glowworms/ ; (Lloyd 2006). Conclusions The ways that light pollution impacts on insects are varied but the effects are likely to be important for insect populations in general. From a conservation perspective rare species with isolated population near urban areas may be particularly vulnerable. However, it has recently been shown that the total population of a very biodiverse group of nocturnal insects, the moths, have declined in the UK by a third since 1968, with declines being particularly severe in the south east of Britain where light pollution is particularly intense, so light pollution may be partially implicated in a very widespread decline of some of our most abundant and widespread species as well (Conrad et al. 2006). We would therefore recommend that much more research is carried in this important area and in the meantime every effort is made to reduce unnecessary external lighting, particularly near known breeding sites for rare invertebrate species, but also more widely in both urban and rural environments. 2 References Conrad, K. F., Fox, R. & Woiwod, I. P. 2007 Monitoring biodiversity: Measuring long-term changes in insect abundance. In Insect Conservation Biology (ed. O. T. Lewis, T. R. New & A. J. A. Stewart), pp. 203-225. Wallingford: CABI. Conrad, K. F., Warren, M. S., Fox, R., Parsons, M. & Woiwod, I. P. 2006 Rapid declines in common moths underscore a biodiversity crisis. Biological Conservation 132, 279291. Eisenbeis, G. 2006 Artificial night lighting and insects: attraction of insects to streetlamps in a rural setting in Germany. In Ecological Consequences of Artificial Night Lighting (ed. C. Rich & T. Longcore), pp. 281-304. Washington: Island Press. Frank, K. D. 2006 Effects of artificial night lighting on moths. In Ecological Consequences of Artificial Night Lighting (ed. C. Rich & T. Longcore), pp. 305-344. Washington: Island Press. Lloyd, J. E. 2006 Stray light, fireflies, and fireflyers. In Ecological Consequences of Artificial Night Lighting (ed. C. Rich & T. Longcore), pp. 345-364. Washington: Island Press. Saunders, D.S. 2002 Insect Clocks 3rd edition. Elsevier, Amsterdam. Uffen, R. 1994 Report of East Region meeting, Nottingham University, 13th November 1993. Antenna 18, 80-81. 17 January 2008 Professor Jim Hardie Mr Ian Woiwod President of the Royal Entomological Society The Mansion House Chiswell Green Lane St Albans Herts AL2 3NS Plant and Invertebrate Ecology Department Rothamsted Research Harpenden Herts AL5 2JQ and Imperial College London Department of Life Sciences Silwood Park campus Ascot Berks SL5 7PY 3