How long it takes for plastic bag to decompose ?

For everyday consumers, plastic shopping bag are cheap and easy to use, but ugly to look at when they stuck on tall trees or being littered to the street. I still remember a local news (of late 80's) profiling a young business star; he was on the news because the big profits earned from the plastic bag plant he owned. There is a social revolt going on lately to stop people using traditional plastic shopping bag due to enviromental concerns. Some want to make it "as fashionable to carry plastic as it is to wear fur", others simply baned them.
The most common type of plastic shopping bag is made of polyethylene, a man-made polymer that microorganisms don't recognize as food. In another word, they are not biodegradable like newspaper and banana peel
However, plastic bag do photodegrade. When exposed to ultraviolet radiation from sunlight, polyethylene's polymer chains become brittle and start to crack, and plastic bags will eventually fragment into microscopic granules. As of yet, however, scientists aren't sure how many centuries it takes for the sun to work its magic due to many variables. That's why certain news sources cite a 500-year estimate while others prefer a more conservative 1,000-year lifespan. It feels like these figures are just another way of saying "a really, really long time."
For me, the quickest way to solve the problem is to develop plastic bags sensitive to photodegradation and biodegradation. Consumer are willing to spend a bit more money on these new bags, instead of stop using them.

Our urban deforestation

Trees are struggling to survive in U.S. cities, according a TIME report.

Tree cover across the country has fallen substantially in recent decades, victims of cities expansion, pollution, and slow replanting due to tight municipal budgets. In the past few decades, San Diego has lost 25% of its peak tree cover, while Washington, D.C., has lost 50%, the cover in cities in Michigan, North Carolina and Florida has fallen to about 27% of what it once was; Chicago and Philadelphia are just 16%.

Just in case you are not familiar with the 'tree-city ecology', here is the refresher: tree leaves filter out particulate pollution. The crown of a large tree also intercepts rain water that might otherwise clog cities’ aging drainage systems. In some cases, a tree can ensure that 1,500 gallons of water a year will evaporate before it hits the ground. Finally, tree shade stops asphalt from reflecting the sun’s heat and creating so-called heat islands. As an example, according to the National Aeronautics and Space Administration, Atlanta’s temperature is now five to eight degrees higher than the surrounding countryside following decades of development that bulldozed wooded areas.

Hug a tree, please.