Want to cool off – plant trees

If there is one sure and easy way for all of us can help reduce global warming, naturally cool our homes, combat the heat island effect of cities, and temper the searing mid-summer heat, it is to plant trees. Not only do trees provide cooling relief on hot summer days, but they also reduce the effects of global warming by consuming carbon and replacing it with oxygen.

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Just two weeks ago while I was visiting Chicago, temperatures were in the upper 80s with humidity — but while walking under a lovely canopy of street trees in Evanston and Hyde Park, I never needed to wear my hat and never felt uncomfortably warm.

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In fact, allowing trees native to the local ecosystem to grow has been shown as a way to combat and even reverse desertification in Burkina Faso, Africa.

SOURCE: burkinafaso_map_2007-worldfactbook

Below is a 2009 report by Mark Hertsgaard for Public Radio International’s “The World” He also documents the success of these efforts in his terrific 2011 book entitled Hot, Living Through the Next Fifty Years on Earth.

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“The paved road heading north from Burkina Faso’s capital ends in the hot, dusty town of Ouahigouya. Most locals here are farmers, scratching out a living in the savannah that stretches to the horizon on all sides. I’d come here hoping to get a glimpse of how Africa might feed itself under a hotter, more volatile climate. Africa already has the highest proportion of malnourished people on earth. And scientists say climate change will hit this continent hard.

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I hadn’t meant to do any radio reporting here, but I met a local radio producer and hired him to record some interviews. I felt the story I was finding shouldn’t wait for the book.

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The sound he recorded isn’t great, I’m afraid. His equipment was quite basic. Or maybe it was the ferocious heat. Across the border in Mali, it was 114 degrees in Timboctou, making it the hottest city in the world that day.

But the air felt noticeably cooler at the farm of Yacouba Sawadogo.

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Sawadogo wears a brown cotton gown beneath his gray beard. He can’t read or write. But he’s pioneering a simple yet ingenious response to the rising temperatures and withering droughts plaguing his homeland.

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Amidst his fields of millet and sorghum, Sawadogo is also growing trees. And the trees, he says, work wonders. The temperature here is very different than in town, Sawadogo says. The forest acts like a pump. The air comes in hot. The shade cools it. So when the air leaves, it’s cooler.

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That shade provides relief from the brutal heat. The trees’ roots also help the earth retain rainfall and their fallen leaves boost soil fertility, so crop yields have gone up. Branches provide vital firewood.

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Sawadogo, I should emphasize, is not planting these trees, like Nobel Prize winner Wangari Matthai has been promoting in Kenya. Sawadogo is growing them. Planting trees is too expensive, and most of them die anyway. But young trees sprout naturally every year. What farmers are doing is nurturing those sprouts, often by digging a shallow pit that concentrates scarce rainfall onto the roots.

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The trees have helped my family get through good years and bad, Sawadogo says. And he says he’s shared this information with many others. He’s used his motorbike to visit about 100 villages. Others have visited his farm to learn from him.

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Mixing trees and cropland is an ancient practice in West Africa, but it fell out of favor when colonial and corrupt African governments seized trees for their own purposes. Recent reforms have reduced such thefts. Now the mixing of trees and cropland is again spreading from farmer to farmer across vast areas of Burkina Faso, Mali and neighboring Niger.

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Chris Reij, a Dutch geographer who’s been working in the region for thirty years, says farmers in Niger alone have grown an estimated 200 million trees.

“This is probably the largest environmental transformation in the Sahel, if not in Africa. There are fifteen to twenty times more trees than there were in 1975, which is completely opposite of what most people tend to believe.”

Reij says this form of agro-forestry requires little outside funding… and that makes it a more sustainable response to climate change than most western aid programs.

“In the end, what will happen in Africa depends on what farmers will be able to achieve, and they should be the owners of the process, and not outsiders.”

The quiet greening of the western Sahel shows that Africans are not surrendering in the face of mounting climate change. But all forms of adaptation have their limits. If the outside world does not do its part—by dramatically reducing greenhouse gas emissions—even the most resilient African farmers will find it hard to manage. Meanwhile Yacuba Sawadogo is putting his faith in trees.

Trees are like lungs, he says. If we do not protect them and increase their numbers, the earth will fall apart.

While planting (or growing) trees is not the only answer to problems associated with global warming and climate change, they certainly are an important part  of a comprehensive solution or adaptation strategy. As planners, we should be looking for all opportunities to advocate and incorporate additional shade trees and ancillary landscaping into our plan design and review efforts.

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If there is one thing I have learned from the heat wave of 2011, there is not enough shade provided in parking lots or major streets in my community, even though it is one of the most wooded in the metropolitan area.

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Here is a list of the top ten reasons we need trees as prepared by the U.S. Department of Agriculture’s Forest Service and listed by Scenic America on its website:

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Top 10 Reasons We Need Trees

Source: USDA Forest Service

1. Trees help purify the air we breathe by absorbing pollutants.

2. Trees increase property values and improve the tax base in communities.

3. Trees improve neighborhood appeal, attracting business, shoppers, and homeowners.

4. Trees cool our cities and towns by reducing heat generated by buildings and paved surfaces.

5. Tree shade, properly placed, can save an average household up to $250 annually in energy costs.

6. Trees reduce the amount of pollutants in sewer systems, saving communities millions of dollars in water treatment costs.

7. Trees soften harsh building lines and large expanses of pavement, making urban environments much more pleasant.

8. Trees provide habitat for birds and other wildlife, maintaining a balance with nature even in urban areas.

9. Trees reduce the amount of water-borne pollutants that reach streams and rivers.

10. Trees reduce levels of domestic violence and foster safer, more sociable neighborhood environments.

Numerous organizations around the world support tree planting and replanting efforts. Prior to making a donation to any of them, it is suggested that you research the organization beforehand. Below are some weblinks:

• American Forests:  established in 1875  and known for its Global ReLeaf program.
• Keep America Beautiful
• National Arbor Day Foundation:  which also sponsors the Tree City USA program and the National Tree Trust.
• Scenic America
• The Woodland Trust: Britain’s largest tree conservation organization.
• Tree Aid
• United Nations Environment Programme: Billion Tree Campaign