Mexico is blessed with an amazing biological heritage. It has been identified as one of 17 megadiversity countries in the world, owing largely to a high degree of endemism. It has one of the highest species counts of vascular plants and amphibians; it hosts 12% of the world’s mammal species and over 1000 bird species. And these riches are not limited to the country’s tropical southern regions: more species of reptiles are said to occur in Mexico than in any other country, thanks largely to the diversity of arid habitats found in northern Mexico; the Baja California peninsula has the highest known density of scorpion species in the world; the state of San Luis Potosí has the highest known concentration of cactus species. Facts like these are presented in this welcome volume and serve as the backdrop for further discussions regarding the conservation of these threatened resources.