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Trees And The Future Of Cities

April 16, 2019 By EarthWise Leave a Comment

The shade of a single tree is a welcome source of relief on a hot summer day. But even a relatively small patch of woods can have a profound cooling effect. A new study at the University of Wisconsin-Madison looks at the role trees play in keeping towns and cities cool.

According to the study, the right amount of tree cover can lower daytime temperatures in the summer by as much as 10 degrees. The effects are noticeable from neighborhood to neighborhood and even on a block-by-block basis.

Cities are well-known to be hot spots due to the urban heat islanding effect. Using trees to keep temperatures more comfortable in cities can make a big difference for the people who live and work there.

The man-made structures of cities – roads, sidewalks, and buildings – absorb heat from the sun during the day and slowly release it at night. Trees, on the other hand, not only shade those structures from the sun, but they also transpire -or release water in the air through their leaves – which helps to cool things down.

According to the study, to get maximum cooling benefits, tree canopies must exceed forty percent, meaning that city blocks need to be nearly halfway covered by tree branches and leaves. To get the biggest bang for the buck, cities should start planting more trees in areas that are already near the forty percent threshold. But

trees can’t just be in parks. They need to be in places where people are active.

If we want the places where we live to be more comfortable and resilient in a warming world, we need to plant more trees.

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Study suggests trees are crucial to the future of our cities

Photo, posted May 26, 2012, courtesy of Mislav Marohnic via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Australian Plastic Bag Ban

December 31, 2018 By EarthWise Leave a Comment

Last summer, the two largest supermarket chains in Australia – Coles and Woolworth’s – decided to stop offering single-use disposable plastic bags to customers. The initial public reaction was decidedly negative. However, within just three months after the radical change, the country’s National Retail Association reported an 80% drop in the consumption of plastic bags nationwide.

In that three-month period, it is estimated that 1.5 billion bags have been prevented from use. Some retailers are reporting reduction rates as high as 90% in the use of the bags. The move by the big supermarkets has paved the way for smaller businesses to follow suit. The smaller businesses typically can’t afford to risk the wrath of their customers with a major change like this. Customers have to learn to bring their own bags or buy reusable bags at the store.

In much of Australia, the phase-out of plastic bags has been legislated, but the state of New South Wales, home to Sydney, the country’s largest city, has not enacted such legislation. So, supermarkets themselves are doing the work of getting rid of the bags.

The change has not been without hiccups. For the first couple of months after the plastic bag ban was put in place, Woolworth’s saw poor sales in its stores. However, customers eventually got used to the new way of doing things and sales levels returned.

Disposable plastic bags often find their way into the oceans where they break down into microparticles. Studies have shown that these plastic bits are ingested by a wide variety of marine life. For example, a UK study found that 100% of sea turtles in the Pacific and Atlantic oceans as well as the Mediterranean Sea had plastic in their digestive systems.

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