From Geophysical Fluid Dynamics to Terrestrial Ecosystems: The Convergent Science of Climate and Ecology

When the American Geophysical Union was founded in 1919 the term "ecosystem" was unknown, though "biosphere" had been introduced some years earlier. It was not until 1935 that Arthur Tansley first coined the expression, and it took many more years to articulate what an ecosystem is and how to study it. Today, the study of geophysics has expanded to a broad viewpoint that embraces the interconnections among planetary physics, chemistry, and biology and one in which terrestrial ecosystems are seen as a central component of the Earth system. The broadening of the geosciences to biogeosciences is especially evident in the study of Earth's climate, with a multidisciplinary perspective that includes terrestrial ecosystems, the plants, microbes, and other organisms that inhabit ecosystems, and the exchanges of energy and materials between ecosystems and the atmosphere. With the broadening of ecology to the macroscale and of atmospheric science to the Earth system, there is a convergence of science to observe and model ecosystems and atmosphere-ecosystem interactions in a changing planet. Although ecology and atmospheric science are distinctly different disciplines, they share an interwoven history and have many points of intersection. However, the ecosystem conceived of and modeled by atmospheric scientists is not necessarily the same as that of ecologists, and ecologists, themselves, differ in their conceptualization of ecosystems as a fundamental level of organization (a biogeochemical perspective) or as a collection of individual plants interacting among themselves and with the environment (a population perspective). This contribution discusses the ecosystem concept from various atmospheric and ecological perspectives. Spanning a range of topics including the climate influences of deforestation and afforestation; the spatial and temporal organization of plant communities; the physiological ecology of plants; the functioning of ecosystems and associated biogeochemical cycles; and a current focus on plant traits, optimality theory, and vegetation demography; the intertwined science of climate and ecology speaks to the importance of interdisciplinary study of planet Earth.