“Greening” Urban Waters

In May 2007, the world reached a tipping point. We entered the “Urban Millennium,” which marked the first time more of the world’s population lived in urban areas than in rural ones. The United Nations Environmental Program (UNEP) estimates the next milestone—two-thirds—will occur in 2050 when 68.7% of Earth’s population is expected to reside in urban areas. This is a significant increase from the 50.5% living in urban areas in 2010 and represents an additional 3 billion urban dwellers by 2050. The United States adheres to the projected increase as well: the 82.3 % of U.S. urban dwellers in 2010 is expected to rise to 90.4 % by 2050 (Minne et al., 2011). All regions of the world—illustrated in the UN image below—follow this projection.

World Urbanization

Image credit: United Nations, Department of Economic and Social Affairs, Population Division: World Urbanization Prospects, the 2011 Revision. New York, 2012.

Coupled with population growth projections (note the familiar “hockey stick graph” below, and its similarity to the hockey stick graph associated with increasing carbon emissions), the shift towards urban centers suggests dramatic changes for both human society and our relationship with natural environments.

World Population Growth

Image credit: United Nations, Department of Economic and Social Affairs, Population Division (2011): World Population Prospects: The 2010 Revision. New York.

As we become increasingly urban (check out a neat animated graphic here), we are simultaneously scrambling to figure out how on earth we are going to make the transition smoothly—to make it sustainably. Of course, “sustainability” is a weighted term carrying many different definitions. For demonstration purposes, I will use the term in its simplest form: from the Latin sustinere (tenere, to hold; sus, up), sustainability is the ability to sustain, or put another way, the capacity to endure.

With this definition of sustainability in mind, the question now becomes: with a rapidly growing global population urbanizing against the backdrop of an unpredictable climate, in what capacity and by what means will earth continue to endure?

The root causes of our current situation will not be solved by an all-encompassing solution—we are not David facing Goliath. Nor will we be able to change everything we need to all at once—our current path was not blazed overnight. But we can use our lessons as a basis for innovation and the search for a new path. I will continually revisit this idea throughout my posts, but focus on one particularly impactful movement now: “greening” urban areas.

If we want to reach the most people and realize the highest value for resources used, it makes sense to go to where people are congregating at high densities—the “most bang for our buck,” as they say. With two-thirds of the world’s population in cities by 2050, efforts to make urban areas more sustainable will reach a lot of people (potentially around 6.4 billion urban residents by 2050) in a relatively small area.

Discover Storm Water

Much of the effort to green cities focuses on improving storm water management (Project WET Foundation has a KIDs book on the subject). Runoff is a serious concern when precipitation is improperly managed and allowed to flow over impermeable surfaces (think streets, sidewalks, and rooftops) and into storm drains. Storm water threatens flooding and public safety, poses risk to drinking water sources and community investment, and carries city pollution to storm drains that channel into rivers, streams, and oceans. The Philadelphia Water Department is an enthralling example of the available tools for better manage storm water.

Philadelphia is currently experimenting with a large toolbox. The city is using natural features—trees, grass, shrubs, perennials, and the like— to divert storm water and prevent it from becoming runoff. These tools take the form of green roofs, rain barrels, stormwater tree trenches, rain gardens, porous paving, stormwater bumpouts, stormwater planters, infiltration/storage trenches, stormwater wetlands, and stormwater basins. These tools employ basic mechanisms often taught to seventh graders: plants aid in the evaporation, infiltration, evapotranspiration, and filtration of storm water. Storm water management infrastructure built around self-perpetuating operations found in nature is one example of innovation working towards a more sustainable future.

Green Stormwater Infrastructure Tools

Image credit: Philadelphia Water Department (2012): Green Stormwater Infrastructure

Philadelphia is just one among many cities exploring new strategies for sustainability. Adelaide, AU, launched 5000+ in 2011 to collect and enable ideas from design professionals, businesses, non-profit organizations, government agencies, and academia for the redesign, renewal, and reactivation of the city. The German city of Freiburg is known as one of the world’s most sustainable cities for its progressive actions with energy saving and climate protection, solar energy, environmental education, environmental protection, waste management, forestry, and urban parks. Our Canadian neighbors in Vancouver generate93 % of their energy from renewable sources and have invested heavily in walking, cycling, and transit infrastructure—efforts rewarded with the smallest per capita carbon footprint of any North American city. Vancouver also adopted an ambitious Greenest City 2020 Action Plan to stay on the front lines of urban sustainability. Reykjavik, IS, tops many green city lists. Iceland’s capitol runs entirely on renewable energy—including hydroelectric and geothermal—it’s transit system uses hydrogen buses, and green spaces and cycling/walking paths are integrated and easily accessible throughout the city. Lists of urban areas taking steps towards sustainability are numerous and attest to the global challenge of sustainability (check out these: 10 Amazing Green Cities, Top 5 Greenest Cities in the World, and 10 World’s Greenest Cities).

Last week I discussed why we ought to care to conserve water. Today I echo that call: over 150 million people living in cities experience recurrent water shortage (less than 100 L/person/day of clean surface and groundwater within their urban area). This number will rise to nearly 1 billion people by 2050. An additional 100 million urban dwellers will live with water shortages resulting from a changing climate (McDonald et al., 2011).

Recognizing we will begin to experience these consequences within our lifetimes is imperative. However, while urban centers everywhere may be particularly vulnerable to tragic futures, they also offer an incredible source of hope and inspiration. We can make changes with far-reaching impacts—water conservation is a fantastic example. I would one day like to see Top Green Cities of the World lists a thing of the past, as being green becomes an expectation rather than an exception.


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