Today, only about 5,000 chinampas, all affixed to the lake bottom, still exist in their original form, surrounded by canals and used for agriculture. The rest have become solid ground and urbanized. In the center of Xochimilco, there are about 200 chinampas, covering an area of 1,800 hectares. However, one reason the number has decreased is that smaller chinampas have been combined to create larger ones. While there are still those who maintain chinampas traditionally, and use them for agriculture, the chinampa culture is fading in the borough, with many being urbanized or turned into soccer fields and sites for housing and businesses. The deterioration of many of these chinampas can be seen as their edges erode into the dark, polluted water of the canals. The most deteriorated chinampas are located in the communities of Santa María Nativitas, Santa Cruz Acalpixca, San Gregoria Atlapulco, and Ejido de Xochimilco. Together, these have a total of thirty eight illegal settlements. To repair a number of chinampas, the borough, along with federal authorities, has reinforced of shoreline, of the that exist in the lake area. This involves the planting of juniper trees and the sinking of tezontle pylons into the lakebed.