On the challenges of cactus (Cactaceae) conservation in Southern Brazil and Central Argentina

The main challenges to conserving native Cactaceae in Southern Brazil and Central Argentina (Pampas) are summarized. To date, Rio Grande do Sul (Southern Brazil) holds 65 cactus species, 17 of them (26.15%) being endemic to the State and 56 (87.7%) threatened according to the IUCN criteria. In comparison, the Central Argentinian mountains hold around 35 species, 13 (38%) of them being endemic to the region, but they are mostly non-threatened. Indeed, many of these Brazilian and Argentinian species are not represented in Conservation Units. Basic taxonomy can be problematic since few genera have been studied on a phylogenetic/phylogeographic background and several species have been described by amateur botanists. The main threats to native cacti are poaching, habitat loss, silviculture (Pinus and Eucalyptus), wildfires, and invasion by exotic plants and animals, especially pines and boars. Some measurements are suggested to deter poachers: the coordinates of wild populations of threatened cactus species may be kept under secrecy, and unnecessary postings on social webs and other databases should be avoided. Few native cacti have been studied regarding their natural pollination, breeding systems, and other basic aspects of their biology and ecology. Such knowledge is relevant for the conservation and proper management of species, especially if they are threatened. For preservation, propagation, and -hopefully- reintroduction purposes, The Porto Alegre Botanical Garden already holds ca. 80% of the native cactus species, but no similar projects are held in central Argentina. Germination experiments are gradually being undertaken, but long-term seed viability studies are also necessary. Some measurements are suggested and we believe these suggestions could be replicated in areas with analog problems.