Whatever happened to acid rain? - Joseph Goffman
In 1963, scientists studying Hubbard Brook
Experimental Forest in New Hampshire
made a shocking discovery.
Their most recent rainfall samples were
nearly 100 times more acidic than usual.
At these levels, additional downpours
of acid rain
would destroy the region’s
marine and arboreal ecosystems
in a matter of decades.
Urgently sharing their findings
with fellow researchers,
they were determined
to answer two questions:
what was causing this deadly rainfall?
And what could be done to stop it?
Rain is never just composed of water.
Chemicals and particulates in the
atmosphere can be found in every drop,
and some compounds— like carbon dioxide—
make even regular rainfall
slightly acidic.
But this pales in comparison
to the powerful acids produced
when water interacts with oxides
of nitrogen or sulfur dioxide.
On the pH scale which measures acidity,
each whole number is 10 times
more acidic than the one above it.
And where normal rain has a pH
of roughly 5.4,
rain that’s interacted with these gases
can rank as low as 3.7.
Oxides of nitrogen and sulfur dioxide
can appear naturally
as a short-lived byproduct of
volcanic eruptions or lightning strikes.
But power plants, refineries,
and vehicles that use fossil fuels
consistently pump large quantities
into the air.
These dangerous gases travel with the wind
spreading hundreds of kilometers
from the pollution’s source.
Acting like roaming clouds of destruction,
their presence dramatically increases
the acidity of local precipitation,
creating acid rain, acid snow,
and acid fog.
These all acidify lakes and streams,
kill crops and forests,
and damage soil to inhibit future growth.
Over time, acid rain can even corrode
human structures made of stone or metal.
By the 1970s, scientists in North America
and Europe classified acid rain
as a major environmental threat.
But despite clear evidence tying
the problem to air pollution,
companies denied responsibility
and cast doubt on the research.
In the United States, corporations lobbied
against regulating pollution,
and convinced politicians
that such policies
would raise energy costs
and threaten jobs.
These obstacles led
the government to delay changes,
and mandate further research
into the issue.
But after a decade of mounting concern,
Congress finally took action.
Since the bulk of sulfur dioxide emissions
came from power plants,
the government set a limit
on the total amount of it
the electric power sector
could emit each year.
Then, they divided the permitted emissions
into a fixed number of “allowances”
distributed to each power plant.
A plant could then choose to emit as much
sulfur dioxide as they were allowed,
or reduce their emissions and sell their
unused allowances to other power plants.
This system, known as “cap and trade,”
offered power plants
the economic flexibility to keep costs low
while strictly limiting pollution.
Many critics called these allowances
licenses to pollute,
or said the government
was selling clean air.
But since the cap was set to lower
five years into the program,
it forced every utility company to reduce
emissions in the long term.
Some plants added desulfurizing
scrubbers to their smokestacks,
or switched to low-sulfur coal
and natural gas.
Oxides of nitrogen emissions
were also reduced
with relatively low-cost technologies.
These advances allowed
the power sector to grow
while the cap kept pollution
under control.
By 1985, Canada and the European Union
adopted their own solutions,
and international treaties
began circulating
to reduce air pollution worldwide.
Today, this science-driven economic
policy has largely eliminated acid rain
across the United States and Canada.
And while many ecosystems still
need time to recover,
scientists have sped up the restoration
of other areas
by reintroducing essential organisms
killed off by acid rain.
Some countries, like Russia,
India, and China
still rely heavily on high-sulfur coal
and continue to struggle
with the environmental consequences.
However, acid rain’s relatively quick
journey from major threat to minor issue
is rightly celebrated as a victory
for policies that protect the environment.
Cap and trade can’t
solve every environmental problem.
But by using scientific consensus
to guide policy,
adopting efficient technology,
and being unafraid to impose
reasonable costs for pollution,
countries can stop a growing storm
of destruction before it’s too late.
