Call Michael J Swassing, ISA Certified Arborist (206)841-5954
Global Warming, Local Landscaping
People embrace
organic landscaping for a variety of reasons. Some are focused at the
most local level, the health and safety of their own families in their
own yards. Others are thinking globally. Almost all have some
combination of the two and everything in between.
But for now,
lets look at local and global air pollution impacts of different
landscape designs. Most people are aware of the noise pollution impacts
of leaf blowers. Less so the air pollution impacts, which are very
large, both with dust kicked up and the exhaust from the two stroke
engine.
Exhaust from small engines has forty times the smog
emissions of a new automobile engine idling. So every time you hear a
lawn mower in your neighborhood, think of forty cars lined up in front
of the house running. Or one car idling in the driveway for forty
hours. Small engines contribute twenty percent of urban smog.
What
you will find is that your landscape design is influenced by the
available technology. The suburban estates with massive concrete
driveways and acres of turf would not have been built if the only way
to clean them was with a broom and push mower. The availability of leaf
blowers has lead to the design that requires them.
The concrete
driveway itself has massive impacts, both on global air quality and on
local water quality. The manufacture of concrete is one of the largest
sources of atmospheric carbon dioxide. Concrete is made by grinding
limestone, a rock that was formed when atmospheric carbon dioxide was
sequestered in water to form a sedimentary rock, during the
carboniferous era that we are hoping, but not acting, to avoid
repeating. The ground limestone is processed in a kiln at high enough
temperatures to drive off the carbon dioxide and leave the mineral in
an oxidized form, the cement pre-mix, that forms a polymer when
hydrated. That is to say, just add water and it temporarily forms a
malleable goo that hardens to a rock like form: concrete. This has been
done since ancient times, the Romans built massive public works
projects with concrete.
So the manufacture of concrete requires
massive energy inputs to drive carbon dioxide from a rock form into the
atmosphere. The energy required increases global fossil fuel
consumption.
What can you do about all this? Well, most of the
time home buyers do not have the choices available to influence the
construction industry with demand for "built green" homes and land. But
maybe just once in your life you will have the opportunity to build a
custom home on an undeveloped lot. At that point, if you know the
impacts of different construction choices, you may choose to follow the
"built green" movement and to require your contractors to treat the
land changes with the same concern for quality and the environment that
you require for the structure of your house.
And, as more and
more people do this, these estates will eventually enter the market and
be rewarded by an informed, concerned buyer.
The changes in land
use that result in vast impermeable surfaces have impacts most acutely
on water quality, as the land looses the capacity to purify water and
contaminates it instead. The flow rate also loses the capacity for
deep, porous soils to absorb large quantities of water without becoming
saturated during the downpours and then release it slowly to the
streams. But for now, let's look at the carbon cycle on that land over
the long term. In the primordial forests of the Puget Sound region the
trees were of all ages: young, mid-life, old, standing deadwood, and
fallen decaying logs. This creates a wide variety of habitats in three
dimensions. Over time, the quantity of carbon taken from the air to
form wood is many thousands of tons per acre (I'm guessing here, but I
think it is a good guess). As the dead trees decay the humus remains in
the soil, with about half of the dead vegetative detritus decomposing
back to carbon dioxide each year.
As the old growth forests were
cut, fire was used to clear the branches and stumps. Then, a uniformly
young forest took it's place. Much less dead wood returned to the soil.
A second logging occurred, and then land clearing with bulldozers to
form a smooth, level compacted building pad from property line to
property line throughout the suburban development. Shopping malls are
built. This is what some people call "progress."
What is lost in the process is soil tilth, water quality, air quality, and quality of life. Sounds nice doesn't it?
So
what can you do differently? Learn about the difference between
compacted fill dirt and soil tilth. Visit national parks to see what is
being lost. Seek out land that has the ability to sustain life. And
then restore life to the land.
We can help you do that.
August 21, 2004
Michael J Swassing
(206) 841-5954
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