I GARDEN
LAVA ROCK GARDENS MAINTAIN MEXICO’S NATURAL LANDSCAPE By: Jimena Martignoni The Ecological Preserve of Saint Angel Lava Rock (REPSA, or Reserva Ecológica del Pedregal de San Angel) is a designated area within the National Autonomous University of Mexico (UNAM) which protects the ecosystem of the “Pedregal”. The Pegregal, which is the colloquial name of this natural environment, is the 80km2-territory situated south of Mexico City which was covered by lava from the Xitle Volcano approximately 1670 years ago. Today, the conserved fragments of the pedregal extend over only 29.5km2, something like 36% of the original area. Part of the remaining lava field is located within the UNAM campus, which covers a total area of 719 hectares representing the largest and more important university in Mexico; for this reason and with the object of protecting this original and cultural landscape from the rapid urbanization of Mexico City, in 1983, the university’s authorities decided to create the preserve with an initial area of 124.5 hectares. In 2005, after several delimitations, REPSA was finally defined as an area of 237 hectares. The lava spewed from the volcano extended from 3,100 meters above sea level until 2,270; along this altitudinal gradient different plant communities were developed over time: Conifer woods (3,000 to 2,850), Oak (Quercus desertícola) woods (2,850 to 2,350) and the xerophile brushwood (2,350 to 2,100). The latter is the ecosystem that can be found in the UNAM campus, becoming the last relict of this arid landscape within the most populous city in Latin America. More than 300 drought-tolerant species grow in the Saint Angel Pedregal -senecios, echeverrias and cacti being
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