NIGHT SKY AND DARK ENVIRONMENTS: BEST MANAGEMENT PRACTICES FOR ARTIFICIAL LIGHT AT NIGHT ON BLM-MANAGED LANDS TECHNICAL NOTE 457 24 Although there is evidence of human health effects with exposure to artificial light, the economic costs of these effects are not known. Costs could include those to treat diseases, lost worker productivity due to disrupted sleep resulting in fatigue, and any related industrial or transportation accidents. It should be noted that known health effects are primarily from indoor lighting and thus would likely not apply to outdoor lighting on BLM-managed lands. Effects on plant and animal species and associated ecosystems from ecological light pollution could also have negative economic effects where humans depend on these species and ecosystems for services such as food, clean water, flood abatement, etc. Quantifying the economic cost of effects associated with ecological light pollution on wildlife species and resulting damage to ecological systems is difficult and has not been undertaken. A direct and quantifiable economic effect of light pollution is wasted energy. Unshielded and incorrectly directed luminaires cast light where it is not needed, using energy to illuminate areas unnecessarily. The estimated cost of this wasted light is $3.3 billion annually, and the wasted energy generates 21 million tons of carbon dioxide per year (IDA 2012b). Finally, some effects cannot be measured in monetary terms. The cost of diminished night skies to our culture and history cannot be measured, nor can its effect on aesthetic and wilderness values. One cannot calculate the value of the diminishment or loss of species and ecosystems negatively affected by light pollution. Similarly, the cost to humanity of losing dark skies is immeasurable. 3.4 Exposure Mechanisms: How Artificial Light at Night Affects Animals and Plants The loss of naturally dark environments is an increasing concern for ecological systems. Effects of this type are often referred to as ecological light pollution rather than astronomical light pollution (Longcore and Rich 2004). Nighttime light can have biological effects on a wide variety of animals and plants spanning all major taxonomic levels—invertebrates, fish, amphibians, reptiles, birds, and mammals (Longcore and Rich 2004; Gaston et al. 2013). Gaston et al. (2013) identified six major ways that artificial light at night can affect animals and plants: 1. Temporal niche partitioning effects: Light-induced activity or suppression of activity of animals at times outside of their normal activity patterns. 2. Dark repair and recovery effects: Light-induced suppression of biological repair mechanisms in organisms. 3. Photoperiodism and circadian rhythm effects: The alteration of behaviors that are dependent on light and dark cycles. 4. Effects from enhanced visual perception: Enhanced vision of animals at night. 5. Effects on spatial orientation and navigation: The inability of animals to orient or navigate properly at night. 6. Photosynthesis effects: The induction of photosynthesis in plants at night; a type of photoperiodism due to artificial light. Influences on photosynthesis are specific to plants, while repair and recovery effects and photoperiodism and circadian rhythm effects can occur in both plants and animals. It should be noted that effects on photosynthesis are not the only effects on plants (see Section 3.5.2). While this technical note primarily addresses direct effects on certain species, understanding the broader ecological context is important. The influences of artificial light into naturally dark environments may be various as types of light pollution interact and also interact with other influences (e.g., noise). Furthermore, numerous and complex ecological interactions occur between the elements of ecosystems. Therefore, direct effects to one species may cause indirect effects to other species through changes in resource competition, predator-prey dynamics, or other mechanisms.
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