blooming earlier in spring, may
benefit some organisms but could
prove disastrous for others.Toxic controls
The introduction of pesticides, such
as DDT, to increase crop harvests
proved to be an environmental
disaster: they eradicated useful
invertebrates as well as harmful
ones; they caused cancers in
humans; and rendered birds of prey
infertile. Rachel Carson’s 1962 book
Silent Spring highlighted many of
these issues, and caused a partial
rethink of pesticide use. The work
of several other ecologists has
resulted in legislative controls to
mitigate the environmental impact.
When Gene Likens and his
team investigated why previously
fish-rich lakes had died, they found
that the culprit was acid rain,caused by emissions of sulfur
dioxide and nitrogen oxide from
industrial chimneys. As a
result, legislation to control the
emissions was passed in the US
and Europe. After US chemists
Frank Rowland and Mario Molina
showed that chlorofluorocarbons
(CFCs) destroy atmospheric ozone,
the use of CFCs was banned
worldwide in 1989.
Light pollution, which affects
beach-nesting turtles, bats, and
migrating birds, has proved harder
to control. The International Dark-
Sky Association is at the forefront
of campaigns for environmentally
responsible lighting.Diminished resources
Garrett Hardin, an American
ecologist, warned of the dangers
of overpopulation in 1968, when theglobal population was 3.6 billion.
By 2018, it had swollen to 7.6 billion,
and although the growth rate
has slowed considerably, the
ever-increasing consumption
of natural resources has led to
depleted stocks of wood, fossil
fuels, minerals, and even fish. The
collapse of the once bountiful cod
fishery off Newfoundland in 1992
highlighted the vulnerability of our
food chain to overfishing and led
the Canadian government to
impose an indefinite moratorium
on fishing on the Grand Banks.
Clean water is one of the most
fundamental requirements for
society but almost 1 billion people
do not have access to it. A lethal
combination of climate change
and population growth in some
developing regions threatens
to increase this number. ■THE HUMAN FACTOR
1997
Charles Moore finds
a mass of floating
debris that becomes
known as the “Great
Pacific Ocean
Garbage Patch.”1988
The International
Dark Sky
Association
is founded in order
to prevent light
pollution.2003
Camille Parmesan
and Gary Yohe
publish evidence for
the climate-change
phenomenon of
“spring creep.”2008
Maude Barlow wins
Canada’s highest
environmental
honor for her
campaign for global
access to clean water.1999
High mortality rates
in frogs are traced to
viruses exacerbated
by the trade in live
amphibians.2003
Research finds that
ocean acidity
has surged since
industrialization
began.2014
Naomi Klein blames
large corporations
for depleting natural
resources and the
climate crisis.229
1992
Canada halts
its cod fishing
industry due
to excessively
depleted fish stocks.US_228-229_Ch_8_Human_Impacts_Intro.indd 229 12/11/18 6:25 PM