Use barriers or vegetation to reduce artificial light
Overall effectiveness category Awaiting assessment
Number of studies: 1
Background information and definitions
Artificial light disrupts the natural sea finding behaviour of sea turtle hatchlings as hatchlings orient towards the lowest horizon with the brightest lights. As a result, high sea walls or trees can be used to block artificial inland lighting and in doing so mitigate the impact of artificial lighting on sea turtle hatchlings (Limpus & Kamrowski 2013).
Limpus C. & Kamrowski R.L. (2013) Ocean-finding in marine turtles: the importance of low horizon elevation as an orientation cue. Behaviour, 150, 863–93.
Supporting evidence from individual studies
A replicated, site comparison study (years not provided) on a sandy beach in Orissa, India (Karnad et al. 2009) found that when casuarina Casaurina equisetifolia plantations were in close proximity to the high tide line, more olive ridley Lepidochelys olivacea sea turtle hatchlings oriented themselves towards the sea compared to when plantations were further away from the tide line, or there was no light barrier. Fewer hatchlings oriented towards land and showed significant seaward orientation when casuarina were planted 50 m from the high tideline (0 of 10 hatchlings/trial oriented landwards) compared to when plantations were 500 m from the high tideline (4 of 10 hatchlings/trial) or where there was no light barrier (high intensity artificial lights visible: 5 of 10 hatchlings/trial; spaced out artificial lights visible: 2 of 10 hatchlings/trial). The 5 km beach was divided into areas with illumination and casuarina planted 50 m, or 500 m from the high tide line; no light barrier and lighting from well-spaced light from a highway; and no light barrier and high intensity artificial light. During the night, newly emerged hatchlings were placed in the middle of a 1.5 m circular arena with artificial light sources and the seaward horizon visible (nine trials/area, 10 hatchlings/trial). Hatchlings were allowed to orient, move to the edge of the arena and their direction of travel was recorded.Study and other actions tested