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The alternative is to think and make measurements in terms of the volume. I think that fish in ponds or lakes should be expressed in terms of biomass per 1000 cubic meters, not in terms of surface area. Birds do not live on areas (but perhaps meadow larks and a few exclusive ground dwellers may be an exception). They live within a volume. Tree canopy dwellers have their volumes where they spend 80 % or more of their time. Others live between the ground and 4 meters. Birds on the same mapped area occupy different layers. Each layer has a volume. Birds seem to compete for or maintain territorial volumes. Rodents living in an area from which firewood has been removed do not live within the same volume. The thichkess has been reduced (in addition ot other changes). The thickness of the volume explains the difference between the animal density in otherwise similar looking and well-measured area. Differences in results of species-area curve analyses, I hypothesize, are largely differences in the thickness of the vegetation on islands. Of course vegetative thickness is influenced by other dominant factors such as elevation but as a simplification, Thus, some future analyses might be not for species-area but for species-volume curves.

The relevant spatial system for wild animals and their management is a volume, a "chunk" as if cut from dough by a cookie cutter, approximating a hexagon when seen from the top, undulating as clouds along the top, having topographic roughness along the bottom surface.

So What?

A volume estimate might help in analyzing and explaining differences in the fauna of areas. If the volume will increase due to management, perhaps knowledge of the relation between animals and their life volume will help predict the future populations. Computer help makes the cost of a few extra measurements insignificant. Thinking volume is likely to be fun because it will be challenging and may provide insights. It will help gain statistical control over field variations, and it will help in comprehending the places for management, the many-layered volume from below the land surface to the air high above the vegetation canopy.

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Last revision January 17, 2000.