According to the U.S. Forest Service, approximately 59 percent of Pennsylvania's total land mass consists of forested areas. This is the equivalent of over 17 million acres. Nearly 16 million acres of this are a part of the state's commercial timber industry. The predominant tree species in Pennsylvania are deciduous, such as oak and hickory trees. Some of Pennsylvania's large forested areas include Allegheny National Forest, Sproul State Forest and Delaware State Forest. Pennsylvania forests are also home to a wide variety of wildlife species, including black bears, bobcats, bald eagles and Canadian geese.
Since none of Pennsylvania's borders come into contact with saltwater, all of Pennsylvania's water falls under the freshwater category. The largest body of water near Pennsylvania is Lake Erie, which touches the northwestern corner of the state. Pennsylvania's largest inland body of water is Pymatuning Reservoir in western Pennsylvania. This man-made lake is over 17,000 acres in size. The Keystone State also possesses a large network of rivers, including the Delaware River -- which serves as the state's eastern border -- Allegheny River and Monongahela River.
Approximately 26 percent of Pennsylvania's total land mass is made up of grasslands. Some of the only true grasslands -- meaning a minimal amount of trees and flat terrain -- are in western Pennsylvania. According to Pennsylvania Envirothon, a state-sponsored educational program for high schoolers, the primary reason for grasslands in Pennsylvania is man-made interference, such as agricultural development and mining. Pennsylvania's grasslands provide a habitat for birds -- including grasshopper sparrows and meadowlarks -- and flowers. Some of the state's grasslands flowers are black-eyed Susans and goldenrods.
Urban ecosystems are areas constructed by human beings, including cities, towns and villages. An urban ecosystem's relationship with other ecosystems hinges on the amount of energy and resources consumed within the confines of the urban ecosystem. Pennsylvania is one of the most populous states in the United States. According the 2010 U.S. Census Bureau, the Keystone State has approximately 12.6 million residents; the majority of Pennsylvania's residents live in an urban ecosystem. The largest city in Pennsylvania is Philadelphia at over 1.5 million. This city has several programs, including Philadelphia Green and Green City Strategy, to revitalize Philadelphia's neighborhoods and make them more environmentally friendly.