So where else should we look for climatic analogs to the ecosystems of the Western US? Head north, from Antarctica into the Pacific, staying close to the South American coast. To the east, the Andes rise out of Tierra del Fuego, building a very effective barrier to moisture for thousands of kilometers. Since the earth mirrors the atmospheric circulation on both sides of the equator, this means that the pattern of vegetation – from rainforest, to chapparal, to desert and then into the tropics in North America – repeats in reverse to the South. After the tropical belt comes the Atacama desert, then the Chilean Mattoral, and then the Valdivian rainforest, a twin to its North American counterpart in Cascadia.
Compounding the eerie similarity is the geology. Just as in Cascadia, a subduction zone lies off the coast of Chile, with the Nazca plate diving under the South American, periodically firing off massive earthquakes as it does. Jammed under the earth’s crust as they are, both plates send enormous plumes of melted rock to the surface where they express themselves as chains of spectacular volcanoes, one each for the Americas North and South.
Head to the lee side, and the drop out of the Andes takes you through the transition zone of dry forests and prairies. It’s no great surprise that Ponderosa pine, the iconic forest tree of the interior West, finds a home on degraded range in those borderlands. Travel further and you’re in the Patagonian steppe, indistinguishable to the untrained eye from the Great Basin.