A unit of Lasting Forests Sustained forests; sustained profits evolving since March 30, 1999

Many definitions of carrying capacity have been given and used Edwards and Fowle reviewed some as of 1955 and Barber listed others in 1974. It is complex and the phrase should be used only in a superficial way with the public. Because of multiple definitions, it is unlikely that it will clarify discussions among professionals. In some groups a common definition might be agreed upon to expedite work. It might be:

I

There are two types, species or life-group specific and composite species.

II

Life-group-specific carrying capacity is the mean quality biomass of animals of a life group (under the influence of social and behavioral constraints) for which a particular area, having objectives(e.g., quality, units, etc.) specified by users of the population, will supply all energetic and physiological requirements over a long but specified period.

Composite species work requires only minor changes in the definition.

The concept is one of land expressed in animal units. Animals of different size consuming different amounts of food can influence the number on an area. Time must be specified. Actual carrying capacity changes among years. There are social limits to the animals on an area; foraging capacity may not be reached. Capacity can be changed by managers; it is not innate, but has an upper limit that few have considered or explored, and never in the wild with public funding.

As in ranching, in a year with abundant forage (due to water, nutrients, etc.) it is unwise to have too few animals to consume the available forage. When a poor forage year occurs and the rancher has many animals in preparation for a "good" year, the range may be damaged. The manager is in a strategic battle: how many animals should be present now to produce the population that will consume the forage that will occur in the next growing season producing an unknown amount of forage.

Note that animals can excede the capacity, a problem with the term when viewed as analogous to a pail or bucket but not to a load on a truck.

Last revision January 17, 2000.