The Pedregal de San Angel Ecological Reserve (REPSA) is a protected area within the Ciudad Universitaria. The area is noted for biodiversity, geomorphology, and as simply a striking and beautiful landscape. The university makes extensive use of the reserve as the subject of studies by many schools, and for hosting both the Botanic Garden and the University Cultural Center.
The area’s bedrock is primarily basalt which lends importance to the area as it filters water into area aquifers, maintains humidity and air quality, and contributes to buffering temperature changes. Plantlife is characterized as xerophytic scrubland. The entire reserve is 237.33 hectares.
The area ecosystem began in 280 CE with the eruption of the Xitle volcano. The peak is about 8 kilometers south, but the eruption covered some 80 square kms in lava. This gave rise to the entire broad area today called Pedregal but which remained mostly undeveloped until the 20th century.
By 1983, much of the pedregal was in danger of being lost and the reserve area was designated by the UNAM. In 2005, the size was considerably extended and it’s remained at its current size since then.
The Pedregal de San Ángel Ecological Reserveis home to some 377 species of flowering plants. There are 67 species of ferns and mosses and 30 different kinds of lichens. The reserve also 30 different mammals, among them 13 kinds of rodents and 12 species of bats. More unusual are cacomixtles, opossums, rabbits, and gray fox. 20 species of reptiles include three species of lizard and six species of snake, plus one very prominent species of rattlesnake. There are also three species of amphibians including one type of salamander and two frogs.
The area is especially important to the 138 bird species. 64 of these will spend only part of each year here and will stop at the Cerro Zacatépetl, the Bosque de Tlalpan on their way to the Cumbres del Ajusco and other points to the south.