Introduction

The creation of urban environments has significant impacts on animals and insects throughout the world (Niemelä et al.,Chapter 2; Catterall, Chapter 8; Nilon, Chapter 10; van der Ree, Chapter 11; Natuhara and Hashimoto, Chapter 12; Hochuli et al., Chapter 13; McIntyre and Rango, Chapter 14). During recent decades both landscape and urban ecologists have been confronted with a new phenomenon associated with cities and towns: ‘light pollution’. Fast-growing outdoor lighting as a threat to astronomy was first described by Riegel (1973). Astronomers need dark sky conditions to discriminate the faint light of astronomical sources from the sky background, which is due to a natural glow (airglow, scattered star light, etc.) and artificial light scattered in the Earth's atmosphere. Since the invention of electric light and especially since World War II the outdoor lighting level has increased steeply and the natural darkness around human settlements has disappeared almost totally. Unwanted skylight produced by artificial night lighting is spreading from urban areas to less populated landscapes, generating a modern sky glow.

The primary cause of this new phenomenon is the excessive growth of artificial lighting in the environment. It is related primarily to general population growth, industrial development and increasing economic prosperity, but there has also been a technical shift to lamps with higher and higher luminous efficiency. For example, the light output efficacy of an old-fashioned incandescent lamp is 10–20 lumens/watt and for a modern low-pressure sodium vapour lamp it is nearly 200 lumens/watt.