Between Southern California’s popular beaches and much-traversed mountain trails lies an unsung natural landscape, teeming with its own special wildlife. As you head outdoors to celebrate Earth Day weekend — or to simply connect with nature and leave behind the anxieties of urban life — one option is our area’s often overlooked coastal wetlands. In Orange and Los Angeles counties, more than 90 percent of the estuaries, lagoons and other coastal waters that existed in the 19th century have been lost to roads, buildings and other development. But what remains provides a crucial habitat for resident animals and migrating birds, including several endangered species.