The main threat for Coryphantha spp. is the fast growth of the population of Mexico and the consequent activities such as construction of settlements and roads, expansion of areas used by agriculture, intensified use of natural resources, deforestation and clearing by fire. Fortunately, most species are only marginally affected by these changes, thanks to their wide distribution and their remote and unfruitful habitats.
However, some Coryphantha species are extremely and acutely endangered. The most endangered species is C. vogtherriana, of which one single location remains which is extremely threatened by erosion due to deforestation and overpasturing. There are only a few hundred adult plants left and seedlings are never observed.
All those species which need plain, deep soils are heavily threatened by the extension of agriculture. This is true mainly for C. pyc-nacantha, C. hintoniorum and C. maiz-
tablasensis, but also to a somewhat lesser degree, for C. elephantidens and C. ottonis. Today, C. pycnacantha can only be found in pitiful remnants of habitats between the fields and the roads or near railroad banks.
Certain species suffer from a permanent loss of individuals by the "clearing" of pastures either by burning off the dry vegetation or by intentional removal of the plants, because they are regarded as a source of injury to cattle, as observed for C. elephanti-dens and C. ottonis.
Again and again, some habitats are completely destroyed unintentionally or through ignorance. This happened to the only known location of C. maiz-tablasensis outside the lagoon of Las Tablas near Matehuala, which was almost completely destroyed by the construction of the new highway. At the location of C. sulcata near Monclova COAH, which is right in the centre of a fast-growing industrial zone with continuous construction, there was one single plant left when we last visited (2001).
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