/ 27 April 2023

Blinding wildlife: The dark side of artificial light at night

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Artificial: A satellite image of Africa and part of Europe at night. Light pollution is not yet a major problem in most of Africa but development will change this. (Planet Observer/Universal Images Group/Getty Images)

It has been described as the “dark side of keeping the lights on” which has a range of negative effects for all life on Earth: light pollution.

The excessive glow of artificial outdoor light from streetlights, houses, factories, ports, airports, sports stadiums, car parks, billboards and car headlights, is increasing globally. 

The amount of artificial light on the Earth’s surface is surging by at least 2% a year and about 80% of the world’s population is living under a “lit sky”, a figure that is closer to 99% in Europe and North America.

Light pollution is a growing threat for wildlife in and around cities, said Ingrid Coetzee, the director of biodiversity, nature and health at ICLEI Africa. It is part of the global ICLEI network of more than 2 500 local and regional governments committed to sustainable urban development.

Although not much related research on light pollution exists in South Africa and elsewhere on the continent, it will clearly become more of a problem as development increases, she said. “Cities have an important role to play in taking practical actions that can reduce or eliminate light pollution.”

Last week, the Convention on the Conservation of Migratory Species of Wild Animals (CMS) and ICLEI’s Cities Biodiversity Centre, based in Cape Town, launched an online guide to help cities around the world reduce the effects of light pollution on insects, birds, bats and a range of other animals. 

It offers facts, successful case studies, information resources, and a checklist for cities to reduce the harmful effects of artificial lighting on wild animals. With 60% of the world’s population set to live in towns or cities by 2030, cities play a critical role in addressing light pollution, said Kobie Brand, the global director of the biodiversity centre. 

Coetzee said Africa remains one of the least light polluted continents, with the populations least affected by light pollution recorded in 2016 listed as Chad, Central African Republic and Madagascar. “This is rapidly changing with the expansion of lighting infrastructure, which is closely tied with economic development.” 

Based on the nighttime light (NTL) methodology, light pollution evidently goes together with development, urbanisation, energy consumption and rapid population growth, she said. “A growth in NTLs is expected for African countries, given their investment in developing electricity provision infrastructure for artificial lighting.”

In South Africa, light pollution stems from lighting used in the streets, commercial boards, light from commercial shopping areas and the light used in industrial areas. “Generally, the primary sites of light pollution are city centres or commercial areas, for example in and around Durban, where most of the economic activities occur. The areas used for recreational purposes also contribute to light pollution but not as much as built-up and commercial areas.”

Similarly, in Gauteng maps of light intensity indicate that the commercial hubs of Johannesburg’s city centre and Sandton are “noticeably the most light intense places” in the province, along with industrial centres that operate for 24 hours a day, such as

ArcelorMittal and Sasolburg in the south. 

“In Nigeria, the urban peripheries of Port Harcourt are fast developing, with a notable increased illumination and poor lighting installations, including unshielded light fixtures, outdoors.”

According to the guide, many species from migratory birds and bats to marine turtles are being hammered. The increasing use of lighting has “modified the natural environment dramatically” affecting wild animals, plants and the functioning of entire ecosystems. There is, however, a lack of information on how artificial light at night affects most species. 

“As they are nocturnal, bats are particularly susceptible to light pollution which can disrupt their foraging, commuting, drinking, roosting and migrating behaviours,” it said. 

Light pollution can affect adult female marine turtles when they come ashore to nest and hatchling turtles may be unable to find their way to the sea or to disperse successfully to the open ocean under conditions where light pollution is present. 

“Light pollution is implicated, alongside other drivers such as pesticide use, in the massive global decline in insects. The physiology, behaviour and fitness of diurnal and nocturnal insects can all be affected, with knock-on effects on pollination and food webs.”

Light pollution most severely affects birds, particularly those which migrate at night. Every year, it contributes to the deaths of millions of birds from collisions with buildings and other infrastructure. Light pollution can alter birds’ behaviours, including migration, foraging and vocal communication. It affects their activity levels and energy expenditures.

Migratory birds travel thousands of kilometres to their wintering grounds, as well as on their way back to their breeding areas. “In South Africa, many of these breeding grounds are wetlands,” Coetzee said. “These journeys are repeated every year, requiring precise orientation and high energy consumption, as an ecological adaptation to different environmental conditions and as a way to exploit food resources available at different times of the year.”

Most of Africa’s apex predators are nocturnal, said a new study published in the South African Journal of Science. “Lions have been shown to have a higher hunting success during moonless nights, particularly when attacking humans, and given increases in habitat destruction, compounded by increased human population increases and expansion, human-lion encounter rates may increase.” 

Road networks are expanding on the continent and there is a growing realisation that artificial light at night from cars may act as an “overlooked pollutant”. Two studies in Tanzania reported that 79% and 63% of all recorded roadkills (excluding birds) were of nocturnal animals, while a study in South Africa reported that 100% and 61% of amphibian and mammal roadkills, respectively, were from nocturnal species. “… Vehicular movement and ‘blinding’ by headlights may pose a particular risk for Africa’s nocturnal species.” 

The effect of artificial light at night on other major groups of organisms in Africa such as birds, insects and plants are “virtually unknown”, but may be expected as is the case elsewhere, and crucially also may alter the ecosystem services they underpin, like pollination.

The extent to which artificial light at night enables environmental crime is unknown and may be significant. “Intertidal poaching for abalone is prevalent across much of the western coast of southern Africa, and skyglow from cities, as well as light emissions from coastal towns, may help orientate poaching activity at night and enable navigation. 

“Similarly, skyglow and point source lights from outside of major protected areas may enable the orientation and navigation for poachers pursuing large game, such as rhinos. In the Kruger National Park, the moon phase plays a role in rhino poaching incidents, with poachers preferring nights with better light conditions.”

From 1992 to 2018, protected areas in Africa were affected by increasingly severe artificial lights, Coetzee said. More than 80% of protected areas experienced aggravated light pollution as of 2018. “Protected areas showed clearer signs of increasing light pollution, depending on their proximity to cities, where increased and more intense human activity occurs, with a maximum effect distance of approximately 245km.”

Two protected areas in Africa have received recognition for their dark skies. Namibia’s

NamibRand Nature Reserve was declared Africa’s first International Dark-Sky Reserve

by the International Dark Sky Association, reaching the “Gold” tier level. In South Africa, in 2019, the !Ae! Hai Kalahari Heritage Park was declared an International Dark-Sky Sanctuary. “In addition to its environmental protection value, dark skies therefore also have value for ecotourism,” Coetzee said.

New international light pollution guidelines for wildlife are slated to be adopted by CMS Parties at the 14th meeting of the CMS Conference of the Parties in Samarkand, Uzbekistan, in October. 

“Both the city guide and the upcoming international guidelines are a response to the increasing worldwide recognition of this growing problem and will enable governments and cities to take concrete steps to curb light pollution and help save migratory species of wild animals,” she said.