The Habitat series focuses on oceans and forests as essential and threatened. All habitats are important, but these two are habitats that we use and understand somewhat. Of all the many species of animals, plants and microorganisms that depend upon these habitats, birds and fish are species that we are somewhat familiar with, so here they are representative of the larger ecosystems. We now know that that many more species communicate than we ever dreamed possible in the past. Trees communicate chemically via their roots and fungi as well as through the air. And species are connected between habitats also, and in surprising ways, including, for example, fish proteins found in large quantities in trees along riverbanks far inland upstream. The series emphasises the biological linkages by taking them a bit further visually: fish are found in the trees, and birds are everywhere.