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Vol. 11 No. 1 - January 2005

Scotobiology – The Biology of Darkness

By: Tony Bidwell and Peter Goering

The development of plants, particularly those in temperate zones varies with season and most plants detect season by the duration of darkness. Hence “short-day plants” require long nights, and “long day plants” require short nights. Short-day plants normally bloom in the autumn when the days are shorter. Long nights initiate the onset of flowering, and later, as nights lengthen, the onset of dormancy, which enables plants to withstand the vigours of winter. If short-day/long-night plants are illuminated even briefly during a long night, they detect this as two short “nights”, under continuous night-time light pollution plants respond as if there were no night. In either case flowering and development are compromised. The effects of successive nightly illumination are cumulative, flowering and dormancy – and hence survival – of short day-plants

Birds suffer huge losses due to light pollution. There has been a tremendous increase in the number of brightly illuminated tall infrastructure, including buildings, power plants, chimneys, telecommunication towers and wind generators. Birds are disoriented by bright lights, and either fly toward them or are unable to see structures behind them. The behaviour of many animals, including mammals, amphibious and insects can be seriously affected by light pollution.

The effects of light pollution are also considerable at the community and ecosystem level. Disturbance of plant and animal life-cycles within a community affects the survival of otherwise unaffected members. Light pollution from cities and highways is sufficiently widespread to affect very large areas, and the effects on individual organisms can disrupt the population balance and thus the integrity of whole communities.

Human health is more severely affected by light pollution than is generally realized. Human hormone regulation, physiology and behaviour have evolved in a diurnal pattern of night and day. The normal operation of sleep/wake cycles, hormone cycles, the immune system and other biochemical behaviour, depends on the daily alternation of light and dark. For example the immune system functions more strongly during the day to protect the body against invasion, while antibody production is highest at daytime. At night, the killer cells that attack tumour and establish invasion are more active. Night-time light pollution imbalances the different activities of the immune systems, to the serious detriment of health, and disrupts circadian hormone cycles with resulting emotional, physical and psychological change.

Light pollution may become a major ecological and human health issue if we continue to ignore the evidence of its increasing impacts. A hopeful aspect of the problem is that much light pollution is unnecessary and could be easily controlled. The lights on high structures to prevent airplane collisions are of course essential, but their effects may be ameliorated by using specific wavelengths or flashing lights. The light pollution from internal illumination of large buildings could be reduced by curtains and floodlighting of buildings and statues could be dramatically reduced.

A major reduction of light pollution can be achieved with shaded/focused street, highway area and advertising lightings; less powerful, downward-focussed street can provide adequate lighting without skyward pollution. Finally, reducing light pollution would also lower the environment impacts associated with electricity generation.

More work in the science of scotobiology needed to understand the impacts of light pollution, and to promote practical solutions.

Tony Bidwell is at the Queen’s University, Wallace, Canada (E-mail: ts@ns.sympatico.ca)

Peter Goering is at Muskoka Heritage Foundation Toronto, Canada (E-mail: goeringp@sympatico.ca)

(This article is condensed from ‘Global Change Newsletter’ published by IGBP Secretariat, Stockholm, Sweden.)


This article has been reproduced from the archives of EnviroNews - Newsletter of ISEB India.


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