Preserving Baltimore's urban forest - baltimoresun.com:
Trees make a city more beautiful, and Baltimore is blessed with an abundance of them — some 2.7 million at last count. That leafy green canopy, which acts as the city's lungs and air conditioner by cooling and cleaning our air and water, doesn't always get the attention it deserves as a critical element of the urban infrastructure. Yet if Baltimore is to remain an attractive place to live and work, its urban forest must be constantly maintained and continually renewed.
Baltimore's tree canopy — a measure of the proportion of the city shaded by trees — has been declining in recent decades, largely due to commercial and residential development and the paving over of previously green spaces. The last time the U.S. Department of Agriculture's Forest Service measured the city's tree canopy, it found its coverage had declined from about 30.5 percent of the city in 2001 to just 28.5 percent in 2005.