"THE DEFORESTATION OF THE CITY
Concern is growing over the rate at which major cities are losing their trees. Conservationist body American Forests says tree cover is declining in many US urban areas, and the problem is worsening in many northern European areas. Based on satellite images, 'urban areas have 21% less tree canopy today than they did 10 years ago' and is drastically reducing the mitigation of the urban 'heat island' effect. 'In a city like Omaha, trees sheltering parking areas can reduce peak summer temperatures
by nine degrees...trees are useful for removing pollutants from the air and for absorbing carbon dioxide, giving off oxygen, and relieving human stress. If a metropolitan area has enough tree cover, it is less vulnerable to flooding and sewer overflows and less in need of expensive civil engineering projects...'
Tree die-off has become a pressing issue in northern climates, where ice-melting salt seeps into the soil and poisons curbside trees. And early tree death could intensify as global trade spreads diseases and insects from distant parts of the world."