why did moths change color? was Do bicycles and cars mix?
Bob Bayn, Network & Computing Services wrote:
Actually, the moth "changed color to blend in"** with the natural
color of the bark of trees instead of the lighter color of the
lichens that used to grow on the trees. The pollution levels
killed off the lichen. It wasn't just black soot painting the
I am afraid you got it wrong here. The moth in question lives on birch
trees, and their bark is naturally white, only in heavily poluted areas
they are covered in black sot and dust.
Lichens btw are usually either green, yellow or red, not white. This is
quite logical too, a white lichen would reflect all light, and have no
energy source for photosynthesis.
May be you are not old enough to remember how things were in
industrialised areas before the environmental movement of the '70s. You
actually could not dry laundry outside: it would become black before it
became dry. There was a big political drive in those days under the
title "we want to see again the blue sky over the Ruhr (an area with a
lot of coal mining and iron smelting activity in Germany).
I remember train rides along the Rhine river, where we had to keep the
windows closed because of the sulfuric stench of the water, which was so
chemical loaded that bathing in the river was deadly (it was the then
German minister for environment Klaus Toepfer (now head of environmental
protection at the UN) who was the first to do so again in a publicity
heist after major international cleanup efforts. In the 19th century
there had been strikes by servants in cities like Colone because they
were given only cheap river salmon for food. Salmon became extinct in
the river in the 20th century because of pollution, only now they are
Yes, quite a lot has been achieved in the last 30 years, but more needs
to be done. And a more considerate use of fossile fuels would be a good
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