Demographic effects of artificial nighttime lighting on animal populations

Abstract

Artificial lighting, especially but not exclusively through street lights, has transformed the nighttime environment in much of the world. Impacts have been identified across multiple levels of biological organization and process. The influences, however, on population dynamics, particularly through the combined effects on the key demographic rates (immigration, births, deaths, emigration) that determine where individual species occur and in what numbers, have not previously been well characterized. The majority of attention explicitly on demographic parameters to date has been placed on the attraction of organisms to lights, and thus effectively local immigration, the large numbers of individuals that can be involved, and then to some extent the mortality that can often result. Some of the most important influences of nighttime lighting, however, are likely more subtle and less immediately apparent to the human observer. Particularly significant are effects of nighttime lighting on demography that act through (i) circadian clocks and photoperiodism and thence on birth rates; (ii) time partitioning and thence on death rates; and (iii) immigration/emigration through constraining the movements of individuals amongst habitat networks, especially as a consequence of continuously lit linear features such as roads and footpaths. Good model organisms are required to enable the relative consequences of such effects to be effectively determined, and a wider consideration of the effects of artificial light at night is needed in demographic studies across a range of species.Résumé : L'éclairage artificiel, surtout, mais non seulement via les lumières de rues, a transformé l'environnement nocturne sur une grande partie de la planète. On a identifié des impacts à plusieurs échelles sur l'organisation et les procédés biologiques. Cependant, les influences sur la dynamique des populations, surtout suite aux effets combinés sur les taux démographiques clés (immigration, naissances, morts, émigration) déterminant où les espèces individuelles se retrouvent et en quels nombres, n'ont jamais été caractérisées, jusqu'à ce jour. Jusqu'à maintenant, la majeure partie de l'attention explicite donnée aux paramètres démographiques a été appliquée sur l'attraction des organismes par les lumières, et ainsi effectivement sur la migration locale, les grands nombres d'individus impliqués, et jusqu'à un certain point la mortalité qui en résulte fréquemment. Cependant, certaines des influences les plus importantes de l'éclairage nocturne sont vraisemblablement plus subtiles et moins immédi-atement apparentes pour l'observateur humain. D'importance particulière, on note les effets de l'illumination nocturne exercés sur la démographie, selon (i) les rythmes circadiens ainsi que le photopériodisme et conséquemment sur les taux de naissance; (ii) la répartition du temps et conséquemment les taux de mortalité ; et (iii) l'immigration/émigration par les contraintes exercées sur les mouvements des individus dans les réseaux d'habitats, surtout comme co...

The biological impacts of artificial light at night: the research challenge

“…A challenge in determining the influence of ALAN on populations is that while it can potentially influence each of the key demographic parameters (births, deaths, immigration, emigration), it is difficult to study each of these effects for a single study species [78]. Those species for which births and deaths are relatively easy to measure are commonly those for which immigration and emigration are hard to determine, and vice versa.…”

Artificial light at night alters trophic interactions of intertidal invertebrates

“…On temperate rocky shores, the dogwhelk Nucella lapillus (Linnaeus 1758) exerts strong top‐down controls on biodiversity by preying on limpets, barnacles and mussels, releasing canopy‐forming algae from space competition and indirectly facilitating the establishment of canopy‐affiliated taxa as a result (Crothers ; Hughes & Burrows ). Dogwhelks are widely distributed across the North Atlantic, often in close proximity to urban centres (Crothers ), indicating that many populations are likely exposed to artificial light at night year‐round (Gaston & Bennie ). Dogwhelks have well‐developed lens eyes (Richter et al .…”

Experimental illumination of natural habitat—an experimental set-up to assess the direct and indirect ecological consequences of artificial light of different spectral composition

“…Moreover, many effects reported are collected in urban areas where artificial light is not the only component of anthropogenic disturbance, and where the behaviour of species in the absence of artificial light is unknown. Most importantly, very little information is present on what the eventual, longterm consequences are at the population level [22]. On many occasions, population effects may directly emerge, for example, as a result of mass mortality by direct effects of light.…”