Fields of Research and Scholarship

What is ecosystem science?

Bill Currie

Ecosystem science is an interdisciplinary field that combines elements of biological, physical, and environmental sciences. A focus is to understand the structure and function of environmental systems from an integrated perspective. This perspective is applied to terrestrial systems, such as forests, to aquatic systems, such as lakes or estuaries, and to linked terrestrial-aquatic systems such as wetlands and watersheds. It makes use of basic sciences such as physics, chemistry, and biology, as well as applied environmental sciences such as soil science, hydrology, geology, limnology, and geographic information science (GIS).

What does it mean to study environmental systems from an integrated perspective? Is a forest ecosystem scientist interested in understanding how fungi in soil use enzymes to obtain nitrogen? Yes. Is she interested in understanding how photosynthesis in a tree depends on the amounts and forms of nitrogen in foliage? Yes. An ecosystem scientist needs to understand these examples of what we call fine-scale processes and how they vary among species, soils, climates and biomes. But what distinguishes the field is that we are more interested in how these types of fine-scale processes might be linked, through nonlinear interactions and feedbacks, in a real, functioning system in the environment (as opposed to how they might operate in hypothetical isolation). We are interested in how the sum total of such fine-scale processes in an ecosystem give rise to nutrient cycling as an emergent phenomenon. And, to push the example futher, we seek to understand what causes the system-level nutrient cycling to vary among ecological communities, among climates and biomes, and along environmental gradients.

The diagram (above right) represents the idea that nutrients (in grey) have inflows and outflows to and from an ecosystem, and they also cycle within the system. In contrast, energy (in pink) can only flow through the system in one direction. According to the laws of thermodynamics, energy cannot cycle because it is degraded as it flows through the system and it is this flow that drives all of the life processes of the organisms in the system as well as all of the ecosystem-level functions such as nutrient cycling. This diagram was published by E.P. Odum in the early 1970s and stands as an excellent illustration of these key organizing principles in ecosystem science.

The flow, storage, and balance of carbon are also a key part of the purview of ecosystem science. Carbon is different from nutrient elements such as nitrogen, phosphorus, calcium, and others, because carbon does not cycle in an ecosystem. Ecosystems are highly open in their fluxes of carbon. Carbon enters and leaves at high rates, closely connected to the flows of energy through the system.

Ecosystem science historically derived from a marraige of, on the one hand, a view of plants, soils, and animals as integrated biological communities, and on the other hand, a view from thermodynamics and general systems theory of energy and matter flows and transformations. In the past few decades, ecosystem science has broadened even further to include aspects of global change and human activities as being central to its scholalry purview.

What is biogeochemistry?

Bill Currie

The term biogeochemistry originated in an effort to capture the view that when we study the geochemical fluxes, storage, or transformations of certain elements like carbon, nitrogen, and others over large spatial scales (up to the globe) and long time scales, we see that many key regulating processes are biological, hence biogeochemistry. In use, the term has come to mean any fine-scale or integrated set of processes in the environment in which elements change from organic to inorganic form or vice versa. For example, the oxidation and mineralization of carbon from an organic form such as cellulose to the inorganic form CO2, or the uptake of inorganic nitrogen by bacteria in the environment and its transformation to organic amino acids, are examples of the purview of biogeochemistry.

Biogeochemistry is a central part of ecosystem science because it deals with the processes that give rise to the cycling of nutrients and the inflows and outflows of carbon in an ecosystem.

What is sustainability science?

Bill Currie

In February of 2007, the US National Academy of Sciences, one of the premier scientific bodies in the US, declared in an editorial in its journal, the Proceedings of the National Academy of Sciences (PNAS), that sustainability science was a new field of science and would now have its own section in PNAS (Clark 2007). In the same month, the American Association for the Advancement of Science (AAAS), publisher of Science, held its annual national meeting with the theme "Science and Technology for Sustainable Well-Being."

So what is sustainability science? As Clark (2007) pointed out, this field is characterized by the questions it poses and the new type of applied understanding it seeks to create. The focus is on:

"...the complex dynamics that arise from interactions between human and environmental systems. Central questions include the following. How can those dynamic interactions be better incorporated into emerging models and conceptualizations that integrate the Earth system, social development, and sustainability? How are long-term trends in environment and development reshaping nature–society interactions? What factors determine the limits of resilience and sources of vulnerability for such interactive systems? What systems of incentive structures can most effectively improve social capacity to guide interactions between nature and society toward more sustainable trajectories? How can science and technology be more effectively harnessed to address sustainability goals?"

Note the emphasis, in the quote above, on the need to achieve a better understanding of the nature of coupled human-environment, or human-natural systems. In 2007 the US National Science Foundation, the premier funding agency for non-human-health, non-defense, scientific research, began a new funding program titled "Coupled Natural Human Systems."

In my view, it is a natural progression in the development of ecosystem science that it should become a cornerstone of this new field of sustainability science. It is hard to imagine a scientific study of human-environment system complexity, resilience, and vulnerabilty that would not build upon the organizing principles developed over the last half century in the scientific study of ecosystems.

Clark, W. C. 2007. Sustainability Science: A room of its own. Proceedings of the National Academy of Sciences 104:1737-1738.