WC129 MarApr2023 - Flipbook - Page 16
H2OPINION
Walter Jehne, a soil microbiologist
from Australia who has been tirelessly
spreading his message around the world,
believes that if we don’t start to care for
our soils, ecosystems, and the hydrological cycle that they support, then our
civilization will be cactus. While water
sustains living organisms, soil is the
foundation. Jehne describes soil as “the
crucible of life.” Hundreds of millions
of years ago, land on Earth was only
rock. Microbes spread from the ocean, broke down the rock, began forming soil, and eventually plants emerged. The soil stored
life-giving water for the plants and slowly ecosystems emerged to
green the barren terrestrial surface.
Imagine a thriving old-growth rainforest on Vancouver Island,
verdant and dripping with moisture. After the rains, the tree
canopy catches water and slows its downward descent. Once on
the ground, a deep soil sponge absorbs the rainwater and stores it
for longer periods of time. Water slowly makes its way down into
underground aquifers far beneath the surface for even longerterm storage. This system adapts seamlessly to seasonal fluctuations, with the water table rising during the rainy season and
lowering during periods of drought as it supplies the vegetation
above.
The roots of trees, shrubs, and other groundcover draw water
from the soil sponge and plants release some of this moisture
into the atmosphere through transpiration. During hot, sunny
weather, evaporation can also occur; but even on the hottest
days, the forest floor temperatures rarely exceed 20°C, whereas
soil exposed to direct sunlight could reach 50-to-60°C. Plants
and soil form a system that regulates the flow of water into the
ground as well as the flow of water back into the atmosphere—
an ecological system that has evolved over millions of years.
When an old growth forest is clearcut, the soil can no longer
benefit from this relationship and will quickly degrade as it is
baked by the sun and eroded by rainfall.
In B.C., around 200,000 hectares of forest is harvested every
year. Since the turn of the millennia, we’ve lost over four million
hectares of mostly primary forest and the tree farms that replaced
them are just beginning to mature. It can take 60 years or more
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WATER C AN ADA • M ARCH/APRIL 2023
to establish a tall stand of trees, and the young seedlings in a tree
plantation don’t have the root systems or biomass to provide the
shade, transpiration, and healthy soil sponge required to adequately regulate the hydrological cycle, resulting in a landscape
that is far less able to absorb rainfall. Instead, the water runs off,
causing swollen streams and flooding at lower elevations. The
runoff washes away soil and fills creeks with muddy water, swelling rivers and ultimately flushes into the ocean, instead of slowly
percolating into underground aquifers.
Is it any wonder then that the atmospheric river of 2021 caused
massive flooding and erosion across the heavily logged regions
of B.C.? Without the ecosystems that regulate water flow, there
is no capacity to handle rainfall on that scale. This outcome is
completely aligned with Jehne’s warnings about destabilizing the
hydrological cycle by compromising the soil sponge.
Last fall’s severe drought conditions shouldn’t have been a
surprise. Climate science has warned us that drought is one of
the many consequences of deforestation. Replacing the protective tree canopy of old growth forests with an exposed surface
of clear cuts and immature tree farms also contributes to the
warming and drying effect. Greenhouse gases trap the heat, but
greater heat reflecting from the surface of the planet amplifies
the amount of heat being trapped.
As the atmosphere warms, it actually retains more water that
would otherwise be on the surface. Jehne explains that a forest
helps draw that moisture back down to earth. For condensation
and rain to occur, the water vapour in the atmosphere must
attach to a solid in order to form water droplets. These solids
include dust, pollen, or hydroscopic bacteria released by plants.
Jehne asserts that hydroscopic bacteria released by trees and other
WAT E R C A N A D A . N E T
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” The regeneration of agricultural soil and restoration of forests
damaged by wildfires and logging has to be an emergency-scale effort.”
