(122) Chihuahuan & Tehuacan Deserts - Mexico, United States [164,167,170] V This ecoregion has an exceptionall rich desert flora and fauna, globally outstanding for flora, with subregional endemism in some taxa and unusual floristic communities. The richest cactus communities in the world are found in the southern Chihuahua desert. Some of the worlds richest desert mammal and reptile faunas also occur here. The most diverse desert in the Neotropical and Neartic region, with globally outstanding levels of desert plant, reptile and mammal diversity.
MEDITERRANEAN SHRUBLANDS & WOODLANDS
(133) California Chaparral & Woodlands - United States, Mexico CE California coastal sage, or chaparral, is one of the most endangered ecosystems in North America. Development along the increasingly crowded seashore threatens to destroy this rare habitat, one of only five Mediterranean scrub ecoregions in the world, which collectively harbors 20% of the earth plant species. High endemism at species and genera levels, high beta diversity, the only Mediterranean shrubland in North America.
3 out of 35 Global 200 freshwater ecoregions = 8.57 %
(154) Colorado River Basin- United States - Mexico
[BSP FW ecoregions O and 2 based in WWF, 1999 map] The extreme conditions of the Colorado River - dropping two miles in elevation from its headwaters to the Sea of Cortez, with associated high flows as well as basins geographical isolation, have led to exceptional freshwater fauna adapted to fast-flowing water. Unusual warm temperate, large river fauna adapted to high flow regimes, several endemics.
LAKE & CLOSED BASIN FRESHWATER ECOSYSTEMS
(161) Chihuahuan Rivers and Springs - Mexico, United States
[BSP FW ecoregions 5, 6, 7, 8, 9, 11, 12, 13 and 14 based in WWF, 1999 map] The river basins in this ecoregion are remarkably different from each other, each containing unique species that evolved following geographical isolation. The fish and snails of Cuatro Ciénegas, for example, display an outstanding evolutionary phenomenon, in which endemic species can be restricted to just a few square meters. Other taxa have not diverged appreciably from ancestral forms and are important relict species. Diverse subtropical desert basin fauna with much local endemism, globally outstanding evolutionary radiations and adaptations of Cuatro Ciénegas biota.
(162) Mexican Highlands Lakes - Mexico
[BSP FW ecoregions 16, 17, 18, 19, 20, 23 and 27 based in WWF, 1999 map] These lakes are characterized by unusual swarms of freshwater fish species, as well as by unusual amphibian and invertebrate species. Neotropical lakes with unusual radiations of fish species.