The desert bordering the Gulf of California, extending from the crest of the peninsula to the shores of the Gulf – and to the Gulf islands as well, is mostly a rain-shadow desert. Air flowing across the peninsula descends after passing the crest and this subsidence prevents the formation of low clouds that are common west of the peninsula’s divide. The greater annual sunlight and warmer temperatures result in much greater aridity and a desert that looks different from the central desert of Baja California.
The Central Gulf Desert map also includes portion of the eastern side of the Gulf of California in Sonora and also Sinaloa – as far south as to the coastal hills around Topolobampo (this latter area is not shown on the map). As we will note elsewhere, despite the best intentions of biogeographers, there are few hard boundaries between these different floristic regions and it is often hard or impossible to define the boundaries between them. They are products of human efforts to simplify the interpretation of the natural world.
One of the odd aspects of the Central Gulf Desert is that it includes coastal vegetation than can be part of many different floristic regions. In particular, mangrove swamps dominated by two mangrove species (Red Mangrove (Rhizophora mangle) and Black Mangrove (Avicennia germinans) occur here and in many other floristic realms in the Americas. Their occurrence is essentially independent of the local climate – except they cannot take much frost or coastlines with strong wave action. The wave action criteria is a consequence of the mangroves requiring silty mudflats for their propagation – especially the Red Mangrove that drops its long seeds that eventually anchor into the soft mud.
The fauna of the Central Gulf Desert can also be considered a bit strange. In addition to the usual birds of dry deserts, probably the most obvious birds of this region are actually shorebirds and sea birds. As the road meanders close to the shore in many places wading birds, shore birds and pelagic birds like Frigatebirds, Pelicans and Boobies can be seen. For tourists from higher latitudes probably the most novel birds are the Frigatebirds that never stray far from the ocean and often soar high overhead. Ospreys are common, as are pelicans and some gull species. In the vicinity of mangroves and where seasonal streams enter the gulf one finds Reddish and Little Blue Egrets and Great Blue Herons and Black Crowned Night Herons. None of these birds are however endemic to the peninsula and have wide distributions.