Greening urban environments

The world's urban population is rising, so that by the end of the century half of humanity may live in cities. Urban populations are rising so fast in lower-income countries that it can lead to extreme environmental degradation, and dirty and unsanitary living conditions. Many such cities, as well as cities all over the world, lack effective environmental or "green" action programs, such as maintaining pollution and litter minimal environments and providing green areas. Parks, for instance, may provide leisure, recreational, and air improvement services, and link urbanites with nature. Communities may need to green their urban environments.