PARENT SESSION
Oral Session #2: Thermodynamics and Complexity. Presiding: T. Allen.
Monday, August 6, 2001. 8:00 AM to 11:45 AM. Madison Ballroom D.

Reconceptualizing biome: The hows and whys of extinction events.

BRANDNER, THOMAS¹, ALLEN, T. F.¹, ¹

ABSTRACT- Biomes represent stable vegetation patterns that are an emergent property of population dynamics of flora and fauna constrained by the external environment. In systems theoretical terms the relationship of dynamics held in check by external constraints can be characterized as an attractor. Biomes with robust attractors are stable over large spatio-temporal scales. However, these attractors can be destabilized by any change in the relationship between internal dynamics and external constraints, e.g., species loss or invasion, disruption of population dynamics, or changing climate. When old relationships break down, internal dynamics of the biota enter into feedback moving the entire system to a new configuration that eventually stabilizes against environmental constraints. Species with narrow environmental tolerances or broad territorial requirements will be most affected by such changes, and, therefore, most in danger of extinction. Considering biomes in this way can explain the Pleistocene extinctions, extinctions on islands after human colonization, and the current loss of species worldwide. Understanding how a stable biome can disintegrate following the disruption of its attractor explains how and why extinctions occur while overcoming the limitations of conventional mechanistic explanations. Current species displacements and invasions show that system dynamics are changing. Global climate change means that the stable context is in flux. A knowledge of biome attractors within a systems theoretical framework will enable us to respond appropriately when the changes come.

KEY WORDS: biome, extinction, attractor, global climate change