Ecosystem

The term ecosystem (or ecological system) refers to communities of organisms and their environment. Ecosystems can vary greatly in size. Small ecosystems occur in tidal pools, in a back yard compost pile, or in the rumen of an individual cow. Larger ecosystems can include a lake or forest. Landscape-scale ecosystems comprise still-larger regions. Ultimately, all of Earth’s life and its physical environment represents an ecosystem known as the biosphere.

With so much variation in what constitutes an ecosystem, it is useful to define the barrier of the system that is being studied. Depending on the specific interests of an ecologist, an ecosystem might be delineated as the shoreline vegetation around a lake, or perhaps the entire waterbody, or maybe the lake plus all the land that drains into the lake (a watershed).

Ecosystems take various forms of energy and simple inorganic materials, and create relatively focused combinations of these, occurring as the total amount of biological material (the biomass) of plants, animals, and microorganisms. Solar electromagnetic energy, captured by the chlorophyll of green plants, is a common energy source of many ecosystems. The most important of the simple inorganic materials are carbon dioxide, water, and ions or small molecules containing nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and some other nutrients.

Virtually all ecosystems (and life itself) rely on inputs of solar energy to drive the physiological processes by which biomass is synthesized from simple molecules. To carry out their various functions, ecosystems also need access to nutrients. Unlike energy, which can only flow through an ecosystem, nutrients can be utilized repeatedly. Through biogeochemical

cycles, nutrients are recycled from dead biomass back into living organisms.

One of the greatest challenges facing humans and their civilization is understanding the fundamentals of ecosystem organization—how they function and how they are structured. This knowledge is absolutely necessary if humans are to design systems that allow a sustainable utilization of the products and services of ecosystems.

An example of a disastrous influence of humans on an ecosystem is the collapse of the cod fishery on the Grand Banks. This expanse of the Atlantic Ocean off the Eastern Coast of Maine and Atlantic Canada was once home to seemingly unlimited numbers of cod. However, over centuries destructive fishing practices and overfishing decimated the cod stock to the point where the species became nearly extinct. As of 2006, the cod stock has not recovered.

Bill Freedman