Summary Ecological Consequences of Artificial Night Lighting Text based on:: Catherine Rich, Travis Longcore, Editors Island Press, 2006 ISBN 1-55963-129-5 Images: Google Image Search Effects of Artificial Light: - Orientation and Attraction/Repulsion - Reproduction - Communication - Competition - Predation - Ecosystem disruption Complex Ecosystem Effects of Artificial Light An ecological system is a complex web of relationships between animals and their surroundings. Living things respond in a variety of ways to impacts on the environment. Some examples of the effect of light at night are well known - moths gathering around a street lamp, or the harvesting of fish with spotlights - but the long term impacts and changes to the ecosystem are not well understood. These changes can have a dramatic effect on humans - as for example the negative impact of light at night on the salmon fishery. Terrestrial Mammals Terrestrial Mammals Possible effects: - disruption of foraging behaviour - increased risk of predation - disruption of biological clocks, affecting mating success and group-mediated anti-predator vigilance - increased road deaths due to blinding and disorientation - disruption of dispersal movements and corridors Increased highway lighting is not effective in reducing deer-car collisions. Terrestrial Mammals Many mammals (small carnivores, rodents) are nocturnal. These are affected by light at night. Night-adapted animals have a rod-based retina, which provides the necessary sensitivity for night vision but blinds the animal in bright light. Light (moonlight) increases the risk of predation, so small mammals stay hidden. A light level of 0.2 lux was sufficient to suppress melatonin production in rats and enhance tumor production. Bats Bats Insects are attracted to lights, bats then gather in the lights to feed on these insects. Moths evade bats by detecting their ultrasound, but moths do not use this warning in bright light, so they are an easy target. Bats In several mountain valleys in switzerland, the lesser horseshoe bat became locally extinct after streetlights were installed. They were replaced by pipistrelle bats, who feed at streetlights Migrating Birds Migrating Birds Migrating Birds Migrating birds tend to move toward light and are reluctant to leave the lighted area. - delays migration - mortality due to exhaustion and collision with structures. Floodlit structures attract and kill birds, particularly in misty weather. Sea Turtles Sea Turtles Hatching turtles are disoriented by artificial light, causing them to go inland instead of to the sea. Artificial light also aids predation of the hatchlings. A number of measures have been taken with some success. These include shielding of luminaires, reducing light output, installing motion detectors and light curfews, and LED lighting embedded in roadways. All coastal buildings must now have a lighting plan. However, problems continue with population growth and lighting further inland that creates sky glow. Local lighting controls are not a complete solution. Reptiles Gecko Reptiles Rattlesnakes and water snakes hunt in the dark of the new moon. These species have declined in areas of heavy light pollution. Gecko mating is curtailed in artificial light. Frogs and Toads Frogs and Toads Frogs and toads have extremely sensitive night vision, and can see in light levels of 10^-6 to 10^-5 lux. (Moonlight is typically about 1 lux). They are nocturnal, so light at night affects them and their predator-prey relationship. Some species are attracted to light, which acts as an 'evolutionary trap'. Mating behaviour (chorusing) and fertility (in toads) are inhibited under artificial light. After exposure to bright light (along a highway, for example) frog night vision can take hours to restore to night vision sensitivity. Salamanders Newt Salamanders Salamanders are are aquatic animals. Newts rely on the day-night transition to initiate foraging, and rely on the characteristics of natural light for navigation. Artificial light interferes with both these activities, and may be one factor in their population decline. Fishes Sea Trout Fishes Some fish species are attracted to light, and fishing vessels use high-intensity lamps to attract their prey. Mercury-vapour lamps have been used to attract fish into special channels around dams and power stations. Other fish species avoid light. In Scotland, lights from a tennis court eliminated sea trout from a nearby river. Fishes Juvenile rainbow trout are inhibited from foraging by moonlight or artificial light. Darkness is essential for fish to avoid predation. Harbour seals have learned to use artificial light to outmigrating smolts. Salmon fry are inhibited from migration by light levels in excess of 1 lux. Several species are inhibited from spawning (laying eggs) by light at night Insects and Streetlamps Insects are critically important as pollinators and members of food webs in an ecosystem. Lamp Effects on beetles, moths, flies, caddisflies: Fixation or Capture Insect cannot escape near zone of the light. Crash Barrier Flight path is interrupted so insects cannot migrate Vacuum Cleaner Insects are removed from the area local to the lamp. Insects and Streetlamps Insects and Streetlamps Radius of attraction: 400 to 600 metres under full darkness, 40 to 60 metres under full moon. In dark zones, the attraction has been 2000 to 11000 insects per night. In a rural village with lighting, 400 to 1600 insects per night per lamp. Approximately 1/3 of the insects are killed or incapacitated. In order, worst to best, are high-pressure mercury, highpressure sodium and low-pressure sodium lamps. Insect attraction can be reduced with a UV filter. Insects and Streetlamps Mayflies Moths Moths Areas around artificial lights function as bat, bird, gecko and spider feeding stations. Some bats live only a few days, so any disruption of their behaviour has an effect on the population. Light interferes with dispersal, which inhibits resistance to habitat fragmentation. Light greater than 0.05 lux inhibits mating in one species of moth. Moths Lamp with ultraviolet component (mercury vapour, LED) is a strong attractant. Low pressure sodium vapour rarely attracts moths. Individual lamps attract more strongly than an aggregate of lamps. One lamp trap collected 50,000 moths in a single evening. A typical catch rate is 4 to 10,000 insects per year. Artificial light can inhibit moth parasites. Fireflies Artificial light swamps the luminescent mating communications of fireflies. Continuous light (due to skyglow) may affect the timing of development from pupa to fly. Artificial light inhibits the resettlement of fragmented habitat (light barrier effect). Freshwater Habitats Plankton Daphnia Freshwater Habitats Zooplankton are at the bottom of the food chain, so their health impacts the marine ecosystem. Nocturnal marine organisms respond to light of full moon (0.05 to 0.1 lux). Zooplankton rise to the surface at night. Artificial light suppresses zooplankton migration. Cued by low light, stream insects (eg, caddisfly larvae) migrate downstreamat night while foraging. Plant Responses to Artificial Lighting Plant Responses to Artificial Lighting There are four photoreceptor families. These have different spectrum responses in order to control the timing of growth (eg, germination) under various conditions (direct sun, open sky, shade). Photoperiodism: some plants are sensitive to the length of the day. Daylight extension inhibits the flowering of some plants and encourages it in others. A brief exposure to light will inhibit the cockleburr from flowering. Some trees exposed to lighting exhibited late season growth followed by severe winter dieback. Security lighting around prisons prevents soybeans from growing, within 30 metres of the source. Minimizing the Impact of Artificial Light on an Ecosystem Turn lights off when they are not needed Reduces the impact on nocturnal insects, animals and on plants. Limit the extent of lighting Minimizes environmental impact and sky glow Use new lighting methods: Example: buried LED lamps in coastal highway Consider the impact of spectrum Example: some insects are particularly sensitive to ultraviolet LPA Guideline How do we incorporate ecological concerns in the LPA Guideline? We assume ecology has relevance in the urban environment. Option 1: Appendix of significant length with images Option 2: Brief mention with a few examples. Tone and Orientation: Positive, eg, light pollution abatement measures will also aid the ecology of birds, insects and marine animals.