During the early years of the 20th century, as biologists strove to discover the processes governing plant succession, it was argued that a fundamental understanding would emerge not only by considering the suite of dynamic interactions among organisms but by expanding the conceptualization to include the influence of non-living factors contributed by climatic and soil complexes. This broader, integrative framework was described as an ecosystem (Tansley 1935). Nearly a century later, the ecosystem concept is recognized as an essential framework for assessing the long-run sustainability of natural capital within the United States (Anon. 2008) and around the world (Millennium Ecosystem Assessment 2005).