In December 1999 Vice President Gore released figures indicating the loss of farmland to development. This problem is not just concentrated near large urban centers, but also in mid-sized cities. You can read the press release of the Vice President's briefing or see highlights of the actual report on the USDA's Natural Resources Conservation Service site. Urban sprawl destroys over 100,000 acres of wetlands annually. Some of America's most important ecosystems such as the Chesapeake Bay and the Everglades are now threatened by urban sprawl.
Urban development is the biggest threat to endangered plants also.
The news isn't all bad. Sprawl can be managed. Cooperation among state and local governments, planning commissions, developers, environmentalists, and concerned citizens can bring about changes in land use and development. Most were approved. Some states have land trusts, while others are actually purchasing parks.