Global emissions of Artificial Lighting At Night (ALAN) are projected to increase by 6% each year, with ecological impacts to coastal marine and estuarine ecosystems. Estuaries and coastal wetlands provide vital ‘ecosystem services’ by contributing to fisheries, water quality, carbon sequestration, coastal protection and pollution control.(1) 

Cumbria is home to some of the most important estuary habitats and coastal landscapes in the UK and Europe, designated for special protection.  Yet with limited powers and an absence of a framework to assess the cumulative impacts of lighting(2), are we properly assessing the potential impacts from new lighting on our estuaries and coastlines? 

The complex lightscape of estuarine habitats is expected to be especially sensitive to ALAN.  A detailed literature review looked at the research on the impacts of ALAN on individual species-to-communities, and how this could then impact at the ecosystem estuary-coastal scale via its alteration of food webs and energy flows.(1) 

One of the classic examples demonstrating the detrimental impacts of ALAN is on newly hatched sea turtles that orient and move toward artificial lights, rather than toward moonlight and starlight reflecting off the water’s surface.(3) This behaviour was implicated in the decline in sea turtle numbers, likely through both failure to reach the sea and enhanced predation pressure by birds, reptiles and mammals. 

In Atlantic salmon, fry exposed to a moderate level of ALAN meant to mimic street lights were smaller and dispersed later than fry held under normal light/dark cycles.(4) Additionally, the timing of fry dispersal from emergence to feeding territories was compromised. Instead of dispersing at night, ALAN-affected fry dispersed throughout the day, an activity that could lead to reduced survival via increased predation or inferior feeding territories.

One of the most likely responses of wading birds may be an increase in activity throughout the night under ALAN(5), which may exert additional pressures on fish and aquatic invertebrates with knock-on repercussions to aquatic ecosystems, especially estuaries. For example, predation-induced reductions in densities of herbivorous fish and invertebrates may release aquatic primary producers from grazing pressure and lead to an increase in primary productivity, in turn affecting water quality. 

The trends of growing levels of artificial lighting affecting coastal regions demands future research that quantifies ALAN effects on individual organisms and importantly, how individual responses scale-up to community and ecosystem responses.

Sensitive freshwater-coastal habitats are already facing stresses as a consequence of climate change, such as altered flow regimes, storm event erosion and deterioration of water quality. Reducing the likelihood of significant impacts to these coastal ecosystems will be critically dependent on human activities that reduce other sources of stress and enhance adaptive capacity, including minimising the impacts of light pollution. 

(1). https://link.springer.com/article/10.1007/s12237-018-0479-3

(2). https://www.friendsofthelakedistrict.org.uk/powers-to-limit-light-pollution

(3). https://ir.law.fsu.edu/cgi/viewcontent.cgi?article=1183&=&context=jluel&=&sei-redir=1&referer=https%253A%252F%252Fwww.bing.com%252Fsearch%253Fq%253Dcoastal%252Bprotection%252Bof%252Bsea%252Bturtles%252Bin%252Bflorida.%252Bjournal%252Bof%252Bland%252Buse%252B%252526%252Benvironmental%252Blaw%2526form%253DEDGEAR%2526qs%253DPF%2526cvid%253D8b6e18e1d8244e7798b0d169733aa2d8%2526cc%253DGB%2526setlang%253DenGB%2526plvar%253D0#search=%22coastal%20protection%20sea%20turtles%20florida.%20journal%20land%20use%20%26%20environmental%20law%22

(4). https://www.sciencedirect.com/science/article/abs/pii/S000632071200417X

(5). https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12036