Carrying Capacity: Concept and Critique

Sources:

Caughley, G. and J. H. Lawton. 1981. Plant-herbivore systems. Ch. 7 in Theoretical Ecology (R. M. May, Editor). Blackwell Sci. Publ.

McCullough, D. R. 1992. Concepts of large herbivore population dynamics. Pages 967-984 in Wildlife 2001:Populations (Edited by D. R. McCullough and R. H. Berrett). Elsevier Applied Science.

Miller, K. V. and J. M. Wentworth. 2000. Carrying capacity. Ch. 7 in Ecology and Management of Large Mammals in North America (S. Demaris and P. R. Krausman, Eds.), Prentice Hall.

Ricklefs, R. and G. L. Miller. 2000. Ecology. W. H. Freeman and Co.

Key Points:

• The concept of carrying capacity has many meanings/definitions• Many important management decisions are based on concepts of carrying capacity• A critical perspective on the concept, its verbal and mathematical definitions, and its

applications are key to intelligent management and policy

Pierre-Francois Verhulst 1804-1849

Raymond Pearl 1879-1940

From Miller and Wentworth 2000

Originally modified from McCullough 1992

What is Carrying Capacity?

Problems with Definitions

• KCC: does provide an understandable benchmark. •Faulted on two issues:

• population may never reach KCC because of resourcesthat are limiting other than food resources

• KCC has high temporal variance so average value mean may not be useful

• HOWEVER, that other limiting factors exist does not mean that environmental limits do not exist.“…relevant to distinguish between limits of the support capacity of the land,the mortality imposed by human or natural predation…, or that combination….. that determines the numbers of a population” (McCullough 1992)

K-Carrying Capacity

• Does CC need to be constant? Isn’t the VAR(CC) important to understand and thusprovide guidance in using measures of CC in management?

I-Carrying Capacity ????

Carrying Capacity as an Equilibrium

Originally modified from Caughley 1979

Originally modified from McCullough 1979

Application of Carrying Capacity with Environmental Variation

Carrying Capacity as a Useful Concept In Ecology and Natural Resource Management???

Discussion led by Kaia and Todd:

Papers include Dhondt 1988 and McCleod 1997