About the only thing people agree on about the Sacramento-San Joaquin Delta the subject of countless white papers, editorials, and political debates is that it’s in a heap of trouble. But this 1,000-square-mile patchwork of islands, sloughs, wetlands, and farmlands is also a rich and complex if highly altered ecosystem at the core of the San Francisco Estuary. Here we take a look behind today’s news to understand what the Delta once was, how it has been changed, and what it might become . . . with a lot of help from its friends.