Harrowsmith – September 2019

Harrowsmith Fall 2019 | 213

We understand the difference
between artificial light and
natural light, but animals do not.
Our artificial light lengthens the
apparent daylight, resulting in
complacency among animals late
in the season, with stressful or
deadly consequences. Consider
the changes to the ecosystem
that have been reported in the
media: the decline of insects,
songbirds and other animals, and
changes in vegetation. (Compare
a natural rural field with one in
a city—they are different.) These
have been blamed on changes
to the environment; night-long
twilight is one of those changes,
yet it is the easiest to fix.

The signs of pollution may

be subtle

Fish are predators for the

smaller fish, and near the bottom

of the aquatic food chain is

zooplankton, which are very

small animals that feed on

algae and other plants. Some

species stay deep in the dark

during the day—hiding from the

larger predatory fish—and only

rise near the surface at night

(a phenomenon known as diel

vertical migration, or diurnal

vertical migration). Shoreline

lighting fools them into thinking

it is still twilight, so they don’t

approach the surface, which

leaves algae to bloom, die and rot,

adding toxins to the water.

These lights are shielded (good), but they’re too close to the shoreline (bad).

The bright white light also enhances the growth of algae by the dock and

attracts flying insects that drive away late-evening human visitors.