All cacti are included in Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES), which "lists species that are not necessarily now threatened with extinction but that may become so unless trade is closely controlled." Control is exercised by making international trade in most specimens of cacti illegal unless permits have been issued, at least for exports. Some exceptions are allowed, e.g., for "naturalized or artificially propagated plants". Some cacti, such as all Ariocarpus and Discocactus species, are included in the more restrictive Appendix I, used for the "most endangered" species. These may only be moved between countries for non-commercial purposes, and only then when accompanied by both export and import permits.
The three main threats to cacti in the wild are development, grazing and over-collection. Development takes many forms. The construction of a dam near Zimapan, Mexico, caused the destruction of a large part of the natural habitat of Echinocactus grusonii. Urban development and highways have destroyed cactus habitats in parts of Mexico, New Mexico and Arizona, including the Sonoran Desert. The conversion of land to agriculture has affected populations of Ariocarpus kotschoubeyanus in Mexico, where dry plains were plowed for maize cultivation, and of Copiapoa and Eulychnia in Chile, where valley slopes were planted with vines. Grazing, in many areas by introduced animals, such as goats, has caused serious damage to populations of cacti (as well as other plants); two examples cited by Anderson are the Galápagos Islands generally and the effect on Browningia candelaris in Peru. Over-collection of cacti for sale has greatly affected some species. For example, the type locality of Pelecyphora strobiliformis near Miquihuana, Mexico, was virtually denuded of plants, which were dug up for sale in Europe. Illegal collecting of cacti from the wild continues to pose a threat.
Conservation of cacti can be in situ or ex situ. In situ conservation involves preserving habits through enforcement of legal protection and the creation of specially protected areas such as national parks and reserves. Examples of such protected areas in the United States include Big Bend National Park, Texas; Joshua Tree National Park, California; and Saguaro National Park, Arizona. Latin American examples include Parque Nacional del Pinacate, Sonora, Mexico and Pan de Azúcar National Park, Chile. Ex situ conservation aims to preserve plants and seeds outside their natural habitats, often with the intention of later reintroduction. Botanical gardens play an important role in ex situ conservation; for example, seeds of cacti and other succulents are kept in long-term storage at the Desert Botanical Garden, Arizona.
