Une pollution ignorée: la lumière de nuit.

Merci à la fondation Nicolat Hulot de m'avoir envoyé cette info,que je classe  dans la série l'homme  est l'animal  kamikase: nuisible et suicidaire.

La pollution lumineuse nefaste pour le regne animal , BE Etats-Unis n°68, 02/03/07

Lors d'un symposium intitule : "The Night : Why Dark Hours Are So Important", organise par la "Dark-Sky Association" dans les locaux de la "Carnegie Institution", les effets de la pollution lumineuse sur les organismes ont ete abordes. Ce symposium a regroupe plus de 100 participants durant deux jours.

Tous les animaux produisent la melatonine, une hormone qui regule le cycle cellulaire, protege les organismes superieurs contre la formation de cancer et permet d'etablir le rythme circadien. Cependant, la synthese de cette hormone est plus efficace lors de nuits totales et recurrentes. La

melatonine est d'ailleurs en vente libre aux US. dans les supermarches ou pharmacie pour ses effets sur le sommeil.

Pour comprendre comment la lumiere nocturne peut alterer le metabolisme et la reproduction, Bryanty Buchanan du College Utica de New York et son equipe ont expose des escargots et des tetards a differents niveaux de lumiere artificielle sur des periodes allant jusqu'a deux mois.

Les resultats sont sans appel. Dans des conditions classiques de lumiere, environ 40% des grenouilles se developpent normalement, contre 100% dans l'obscurite totale et seulement 15% dans des conditions de lumieres artificielles meme legeres. Selon Buchanan, la reponse a l'illumination artificielle est dose-dependante et cette constatation est identique chez l'escargot. D'un point de vue comportemental, la lumiere nocturne perturbe l'accouplement des grenouilles et les escargots restent caches sous des feuilles au lieu de se nourrir.

Ces donnees sont en accord avec les resultats obtenus par d'autres groupes avec differentes especes. Par exemple, Lorna Patrick, biologiste au "US Fish and Wildlife Service" de Floride s'interesse aux problemes rencontres par les tortues de mer sur les plages bordees par les rues illuminees.

Naturellement, apres l 'eclosion, les bebes tortues se tournent vers l'element le plus lumineux, l'ocean. Cependant, il est desormais frequent de les retrouver morts dans les rues.

George Brainard, professeur de neurologie et de pharmacologie au "Jefferson Medical College" de Philadelphie souligne que certaines etudes montrent une augmentation des cancers du sein dans les pays industrialises.
Cependant, il ajoute que pour l'instant aucune relation directe n'a ete demontree. Des recherches sont necessaires pour confirmer que si la lumiere peut etre benefique, lorsqu'elle est mal utilisee elle peut blesser.

Enfin, certains scientifiques pensent, qu'a cause de la lumiere emise sur terre, les constellations, les etoiles et les planetes resteront abstraites pour les prochaines generations.

Sources : - <http://www.nightsymposium.org/>

- <http://seattlepi.nwsource.com/national/305076_nitelight26.html>

- <http://sciencenow.sciencemag.org/cgi/content/full/2007/222/2>

- <http://www.bulletins-electroniques.com/actualites/41533.htm>

Pour en savoir plus :

<http://fr.wikipedia.org/wiki/M%C3%A9latonine>

Ce texte est traduit de ça:

Monday, February 26, 2007

Could bright nights mean lights-out for species?
Scientists discuss dangers of a lack of darkness

By MICHAEL FAMIGLIETTI
SCRIPPS HOWARD NEWS SERVICE

WASHINGTON -- Are the streetlights and security lights the Western world takes for granted causing breast cancer, killing sea turtles and blocking views of the constellations?

Last week scientists said: Well, maybe.

"There are a lot of people in the world who don't know the difference between night and day," said David Crawford, an astronomer and co-founder of the International Dark-Sky Association, at a conference on nighttime light held here.

More than 100 scientists, lighting technicians and government workers registered for the two-day conference hosted by the Carnegie Institution, a non-profit research center.

George Brainard, a professor of neurology and pharmacology at Jefferson Medical College in Philadelphia, said some research points to a rise in breast cancer for women living in industrialized countries.

The bombardment of light may prevent the brain from producing melatonin, a hormone some researchers think combats cancer, Brainard said. "Melatonin follows the pattern of dark time," he added.

But Brainard didn't declare a direct link between breast cancer and streetlights. He said additional research is needed to confirm that "if light can be beneficial, then if it's not used correctly, it can harm."

Crawford, whose organization planned the event, "The Night: Why Dark Hours Are So Important," said the growing number of bright lights stretched across the world obscures the circadian rhythm, the 24-hour cycle on which most organisms operate.

He described the problem as "obvious" because total darkness no longer exists in many places, deterring most humans and animals from their natural processes, such as adequate sleep.

"Do you see the glare and the clutter? Why do they do that?" he asked the crowd inside the dark auditorium where the meeting took place.

Lorna Patrick, a biologist with the U.S. Fish and Wildlife Service in Florida, is concerned about baby sea turtles, which she said face death when streetlights neighbor beaches.

Upon hatching, the young head for the ocean because usually it's the brightest light source, she said. But that has changed.

"We have found dead hatchlings at the bottom of streetlights," she said.

That change is one of many new problems facing animal life as lights get brighter.

"We don't really know what will happen, but there could be an impact on population," said Bryant Buchanan, who studies frogs and salamanders at Utica College in New York. He said his research found changes in the growth of frog larvae that received too much light. The larvae produce melatonin during darkness, just like humans.

As for the constellations, the stars and planets, earth light might one day block them, too.

Some scientists said future generations may see them only in textbooks.