Texas blind salamander (Typhlomolge rathbuni), Comal Springs riffle beetle (Heterelmis comalensis), Comal Springs dryopid beetle (Stygoparnus comalensis), and Peck's cave amphipod (Stygobromus pecki) are listed as endangered. Another species, the Blanco blind salamander, is unlisted because it is unknown whether the species is extant or extinct. Land use Land use through the region atop the Edwards aquifer varies between rangeland, agricultural and residential/urban. The northern portion is primarily rangelands and contains most of the streams feeding the recharge zone. Until the late 1990s much of the land area that recharged the aquifer was undeveloped rangeland, but since that time it has undergone a significant increase in development. From 1996 to 1998 residential land use increased 9 percent in the Edwards aquifer recharge zone; even so, 72 percent remains undeveloped. The region atop the Edwards aquifer continues to increase in population today. In 2012 the US Census Bureau noted four counties located within the Edwards Region; Kendal, Comal, Hays and Travis were among the fastest growing in the nation, all with growth rates between 25 and 50 percent. An estimated 4.6 percent of the recharge zone is now covered with impervious surfaces which decrease aquifer recharge and can negatively affect water quality. Almost all of agricultural lands and a large portion of San Antonio overlie the confined portion of the aquifer (Barker 1996). In an effort to preserve undeveloped land the city of San Antonio passed the Edwards Aquifer Protection Plan in 2000 (renewed in 2005, 2010 and 2015). The plan allows the city to purchase conservation easements for land in Bexar, Medina and Uvalde counties. The landowners retain and upon agreement the landowners cannot divide or develop the land and are paid 40-45% of market value for the easement. The plan has over 130,000 acres enrolled. Demographics More than 1.7 million people rely on water from the Edwards Aquifer for municipal, industrial and daily use. One of the major cities on the aquifer is San Antonio, America's 7th largest city, with a population of over 1 million. San Antonio is heavily dependent on the Edwards Aquifer for their municipal, industrial and daily use. Another major city on the aquifer is Austin. More than 50,000 people in the city of Austin (6% of Austin's population) rely on the Barton Springs segment of the Edwards Aquifer. Between 1990 and 2015, the population increased by two thirds, at this rate, the population of