Definition of Ecology

Our definition of ecology is:

The scientific study of the processes influencing the distribution and abundance of organisms, the interactions among organisms, and the interactions between organisms and the transformation and flux of energy and matter.

Our definition is unique in that it emphasizes several things:

  • A starting focus on organisms, aggregations of organisms, or systems incorporating organisms or their by-products
  • The bounding of ecology by both the biological and physical sciences
  • The breadth of subject matters within ecology
  • The joint consideration of both biotic and abiotic aspects of nature
  • Depending on the ecological specialty, the focus can be on different proportions of biotic or abiotic aspects of nature 
  • The relationships between organisms and the physical world can be bidirectional, although different specialties may emphasize the effect of the organisms (and systems containing them) on the physical world, or the effect of the physical world on the organisms
  • The boundary between the abiotic and the biotic aspects of ecology is blurry
  • The disciplinary focus is on "processes", "interactions" and "relations" rather than on the physical entities per se


Ecology was originally defined in the mid-19th century, when biology was a vastly different discipline than it is today. The original definition is from Ernst Haeckel, who defined ecology as the study of the relationship of organisms with their environment. In the intervening century and a half, other definitions of ecology have been proposed to reflect growth of the discipline, to found new specialties, or to mark out disciplinary territory.

There are three pervasive definitions of ecology. The first definition stems from the Haeckelian form -- the study of the relationship between organisms and environment. The second definition, which is perhaps the most commonly repeated, considers ecology to be the study of the distribution and abundance of organisms (Andrewartha and Birch 1954). The third definition focuses ecology on the study of ecosystems (Odum 1971).

The three kinds of definitions each have their limits and advantages. The hallmark of ecology is its encompassing and synthetic view of nature, not a fragmented view. Our definition of ecology is a blend of the second and third definitions. This new overarching definition attempts to bridge the spectrum of ecological approaches, with the goal of promoting synthesis and integration.

Cary Institute of Ecosystem Studies | Millbrook, New York 12545 | Tel (845) 677-5343

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