The Ecology of ALAN (Let there be light, but not too much and definitely not blue …)

Dr John Thorogood1

1FRC Environmental, Maroochydore, Queensland


Obviously light affects animal behaviour. Some go to sleep at night, others appear startled by flash-photography, yet others are attracted by light (moths to a flame, baitfish to an illuminated jetty). Importantly, humans and animals perceive light differently, with some animals having lesser or greater sensitivity to light at either end of the spectrum (red to ultra-violet). For example both turtles and seabirds have a greater sensitivity than humans to blue and ultra-violet light.

The Sea Turtle Sensitive Area Code (A Model Code for Local Government) released in May 2019 and the National Light Pollution Guidelines released in January 2020 reflect (pun absolutely intended) a growing awareness of how anthropogenic light can influence the behaviour of wildlife.

An example relevant to our burgeoning coastal communities is the potential effect of light on nesting turtles and emergent hatchlings. Studies from around the world have shown that light can deter females from coming ashore to nest and can disorient hatchlings.

The potential consequences are potentially ecologically significant. Whilst these effects are understood in principle, they are commonly not well understood in practice. Or to put it another way, it’s now widely accepted that too much light can have deleterious effects on turtle nesting and hatchling behaviour, but determining how much light is too much, is often a challenge for ecologists, resource managers and planners.

Industrial lighting from Gladstone’s aluminium refinery has been shown to impact hatchling sea-finding behaviour 18 km away and lighting at a well-known dive resort on the Great Barrier Reef has been shown to disorient emerging hatchlings; whilst studies of the impact of urban lighting on nest-site selection on the Sunshine Coast have been inconclusive, with the ‘most popular’ nesting beaches on the Sunshine Coast being also some of the most illuminated.

By way of example, at Yaroomba on the Sunshine Coast, developer Sekisui House has recently gained planning approval for a development that will incorporate a beach-front 5-star hotel and conference centre. Concerned that the development would impact on the nesting of critically-endangered loggerhead turtles, and despite the suite of focused conditions of approval imposed by Council, the Sunshine Coast Environment Council Inc. appealed the approval in the Queensland Planning and Environment Court. In response, Sekisui House developed a comprehensive Sea Turtle Management Plan and Sea Turtle Lighting Management Plan, ultimately convincing the Court that the proposed development would not pose a significant threat to turtles. Factors the developer relied on included the set-back of development from the dunes together with the height of the dunes, a raft of controls relating to the type, location and use of lighting, and over a decade’s data showing that Yaroomba Beach was used on average by only a very small number of nesting turtles each year.

Other south-east Queensland local governments are also picking-up on the need to better manage lighting on the coast, both with respect to their own infrastructure and in respect of development approvals. On the Gold Coast, lighting specification for the expanding network of ‘Oceanways’ (shared coastal paths to landward of the dunes) is consciously taking into account the need to avoid ecological impacts by using luminaires that minimise light-spill and that can be programmed to dim outside of periods of peak usage.

This paper explores both the theory and practical application of the ecology of ALAN using a series of case studies.


Dr John Thorogood is a Senior Principal Ecologist at frc environmental. Over 30 years of ‘hands on’ experience has positioned john as one of the industry’s most highly respected aquatic ecologists.

John and the frc environmental team are recognised as the ‘go to’ aquatic specialists by clients such as Brisbane City Council, BMD, Gladstone Port Authority, LendLease, Mount Isa Mines, NSW Dpt. Public Works, Origin Energy, Port of Brisbane, Santos, SEQWater, Stanwell Corporation, Stockland, Sunwater, Qld. Dept. State Development, Veolia and Walker Corporation.

Whilst continuing to enjoy a ‘hands-on’ approach to consulting practice, John is increasingly sought after for his insight, strategic advice and approvals-related expertise.