The Greenbelt, a wide belt of open land around the cities and towns of the San Francisco Bay Area, includes about 3.75 million of the Bay Area's 4.5 million acres. The Bay Area Greenbelt is one of the largest areas of open land in any U.S. urban area. Open land is land that has few buildings and lots of natural areas. The Greenbelt's open land includes parks, forests, beaches, and more than 8,500 farms. What are the advantages of the Greenbelt? The Greenbelt has many advantages for people in the Bay Area, which include: l walking and biking areas close to the cities and towns; l places for wild plants and animals; l cleaner air and water; l income from farms. Is the Greenbelt in danger? Five hundred seventy thousand acres of the Greenbelt are in danger. There are builders who want to build suburbs on them. If those acres become suburbs, many things will change: l the urban and suburban area will almost double; l many farms will disappear; l traffic will become worse; l the air will become dirtier. What is Greenbelt Alliance  ? Greenbelt Alliance, an organization that saves land in the San Francisco Bay Area, works alone and with other groups to save the Greenbelt in four ways: 1.Try to persuade people to build new buildings on land that is already urban, not on open land. 2.Make sure that the city and town governments are all making plans to save the Greenbelt. 3.Help Bay Area towns and cities to buy pieces of open land to make into natural areas. 4.Teach people in the Bay Area why the Greenbelt is important and what they can do to help save it. The Greenbelt is in danger because   _  .
traffic is getting worse some plans to build suburbs on it the suburban area has doubled pollution is becoming serious