Peeling back the Pavement - POLIS Water Sustainability Project

BOX 4: VALUING PROPERLY FUNCTIONING ECOSYSTEMS
“Stormwater” is strictly a human concept. Precipitation, on the other hand, is a dynamic
process of the natural world. The hydrological cycle connects the atmosphere, surface
water, soils, vegetation, and animals (including humans). The movement of water creates
a dynamic equilibrium as it flows from rain, to water stored on the leaves of plants and in
the soil, and then back to the atmosphere through evapotranspiration. The flow of water
through soil to groundwater and into streams and wetlands creates a baseflow for a watershed,
which provides moisture to plants and animals during dry periods.
Left to its own devices, the natural world is in a relatively comfortable state of equilibrium,
maintained by constant change, rebalancing, growth, and decay. The natural
water cycle in proper functioning condition supports ecologically productive wetlands,
streams, and lakes. These bodies of water provide us with a critically important water
supply as well as rich recreation, fish and wildlife, and cultural and historic values. They
also provide key economic inputs necessary for everything from crop and livestock
production to timber and energy production.
But, many contemporary patterns of human settlement, such as rapid increase of
impervious surfaces, fundamentally change these relationships. In urbanized areas,
streams and rivers frequently serve as conduits for pollution via urban stormwater
runoff. Large water infrastructure projects also strain the resilience of complex natural
systems by quickly moving large volumes of water within and even across watersheds.
These impacts compromise the quality of the ecological, social, and economic services
that watersheds provide.
In the future, we will need to better integrate the environment into urban areas and
mimic nature’s processes. As urban ecosystems, Canada’s cities must grow and decisions
must be made in ways that protect and promote — not erode — the proper
functioning condition of ecosystems. To do this, society needs to be prepared to make
difficult trade-offs. As a starting point, we need to learn how to better value ecosystems
and incorporate “full cost accounting” into all of our activities. We also need to plan on
a much broader watershed scale and work with the water cycle, not against it.
Sources on page 65.
Photo: R.J. Frith
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