Imagine a sleek contraption for your backyard so powerful it has the cooling effect of 10 air conditioners, quietly filters dust, allergens, and pollutants, runs for free on solar power, and its only byproduct is oxygen.

Dream no longer. This elegant machine is a healthy, mature tree.

Using energy from sunlight, a tree can soak up almost 400 litres of water from the ground each day, and cool the surrounding air through transpiration. Trees absorb airborne contaminants and breathe out clean oxygen. They're such efficient air filters that Columbia University researchers estimate that for every 343 trees added to a square kilometre asthma rates in young people drop by about 25 per cent.

What else can these handy natural contraptions do for us? The U.S. Forest Service says trees near buildings reduce air-conditioning needs by a third and, because they break the wind, save up to half the energy used for heating. According to the University of Washington's Center for Urban Horticulture, mature tree canopies reduce the air temperature of urban areas between five and 10 degrees Celsius.

Imagine replacing these ecological services with human-built substitutes. While we can handle cooling a building, creating city-sized air conditioning that could reduce the temperature of an urban area by 10 degrees is an engineering feat that would require massive amounts of energy.

The sophisticated services that nature provides are not only misunderstood and underappreciated; they tend to be ignored in modern economics and urban planning. When a forest or wetland is converted to another use, municipal decision-makers focus on infrastructure costs, property values, and future contributions to the tax roll.

We continue to deplete natural resources and degrade nature in and around urban areas, failing to recognize the contribution of ecosystem services -- like clean air, fresh water, and cooling -- to the economy and health of communities. As The Economics of Ecosystems and Biodiversity initiative notes, this ecological damage is the "perfect crime", a theft barely noticed. We wouldn't let a bank get away with losing our life savings. We shouldn't let decision-makers off the hook when they allow our natural wealth to be squandered.

Encouragingly, a growing chorus of economists and policy-makers has begun advocating for a smarter way of accounting for the true value of nature - something called natural capital economics.

Most people understand the concept of financial capital. We pay for things we find valuable. Natural capital extends that perspective to ecological goods and services. It would be expensive to develop and build facilities to replace the things nature does. So we calculate the dollar value we would have to pay if we had to provide them ourselves.

How much is our natural capital worth? According to the David Suzuki Foundation's research, the 7,000-square-kilometre Ontario Greenbelt provides at least $2.6 billion in non-market benefits each year. British Columbia's Lower Mainland region is estimated to be worth at least $5.4 billion annually. Global studies have estimated the total value of the world's ecosystem goods and services to be on par with the value of the entire global economy. In short, our natural capital is a source of staggering wealth.

Why do we continue to fritter away these amazing assets, despite their immense value? Unfortunately most people don't have a clear picture of what stocks of natural capital exist in their communities, let alone the true cost of converting natural areas for industrial, commercial, or residential development.

That's why the David Suzuki Foundation and Google Earth Outreach are launching an online map that will allow residents and decision-makers to zoom in to their community and calculate the economic value of natural capital assets. The interactive Putting Natural Capital on the Map application allows users to select a parcel of land and find out what types of natural ecosystems it contains and what economic benefits it provides.

While economists, ecologists, and decision-makers grapple with how to estimate an appropriate economic value for nature's benefits, I am hopeful that the field will spur communities to consider the true value of their natural riches. In the meantime, I encourage you to beat the heat and keep your community cool by investing in your own bit of natural capital -- a tree for your yard or park.

Dr. David Suzuki is a scientist, broadcaster, author, and co-founder of the David Suzuki Foundation. Written with contributions from David Suzuki Foundation Communications Specialist Jode Roberts. Learn more at www.davidsuzuki.org

For more insights from David Suzuki, please read Everything Under the Sun (Greystone Books/David Suzuki Foundation), by David Suzuki and Ian Hanington, now available in bookstores and online.

This Blogger's Books from

The Japan We Never Knew: A Voyage of Discovery
by David Suzuki, Keibo Oiwa

David Suzuki: The Autobiography
by David Suzuki