(gentle music) - [Narrator] The science of measuring ecosystem diversity is still pretty young, but scientific knowledge at the ecosystem level is now recognized as a critical part of understanding total biodiversity on Earth. Defining ecosystems is hard, but we do know a distinct ecosystem when we see one. We usually describe an ecosystem in terms of a habitat and a climatic descriptor, such as tropical rainforest or arid grassland, but it's important to note that there's diversity of habitats and ecological processes within each ecosystem type. You can have similar-looking ecosystems that have very different makeups. The name of an ecosystem doesn't automatically imply that all the species in that ecosystem are the same everywhere in the world. High diversity among types of ecosystems means that there will also be a high diversity of species themselves. Each species is specialized to a type of ecosystem in a particular place. Most people are familiar with ecosystems in terms of where they are, that is, in terms of ecosystem distributions. A tropical reef in the Philippines will still be a coral reef but, in terms of species composition, could be very, very different from a reef in the Caribbean. Organisms making up a Philippine reef might be similar to and do the same jobs as those in a Caribbean reef, but they will be different species, sometimes very distantly related species at that. In other words, the ecosystem functions performed by these different reef organisms will be the same in spite of how different the lists of species from each reef might be. And, in turn, the ecosystem functions will be similar, but the species will be different in the Great Barrier Reef off Australia or reefs off Madagascar or wherever things that we would label a tropical coral reef might occur. To me, that's the essence of ecosystem diversity, distinct types of ecosystems, such as tropical reef or tropical rainforest, combined with the diversity of the species within a specific type of ecosystem. Recognizing this means that we can ask what makes a South American tropical rainforest different from one in Africa? It's always important to keep ecosystem diversity in mind in any management or conservation strategy. We can maximize protection of species numbers in a given type of ecosystem by protecting the most biodiverse example of that ecosystem in the world. For coral reefs, that would be the ones in the Philippines, for example. But what about all the others? What effect will there be on the stability of all Earth's ecosystems if we focus on only one example of a particular ecosystem? Is it enough to preserve a single ecosystem as a kind of museum of diversity for that type of ecosystem? I think most scientists would agree with me that the only successful strategy is to try to maximize the protection of as many ecosystems and all their unique biodiversity as possible. And there's another factor to consider when we're talking about biodiversity at the ecosystem level, the interactions between the different types of ecosystems. The interconnectedness of these systems is not best served by labeling this or that ecosystem as if it were some kind of distinct entity that can be put in a giant, imaginary box and guarded. There are complex webs of interactions among the species that make each type of ecosystem unique. But just as there are complex webs of species interactions within ecosystems, there are webs of interactions among ecosystems themselves. And what will we lose if we don't attempt to protect those interactions as well?
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