View Electronic Edition

Biogeographical Provinces

Is there any reason' to produce a new classification for a natural world that has already been classified and reclassified by numbers of ecologists and geographers? Why draw lines on a map and say that the areas enclosed are to be called biogeographic provinces? Do these have any meaning in reality? To answer these questions I'll start by saying that I was drawn into the mapping game by the demands of conservation,   in the lUCN (International Union for Conservation of Nature and Natural Resources) headquarters in Morges, Switzerland, we wanted to know the extent to which the various communities of wildlife were being protected by existing national parks, reserves, or other protected areas.  From this we could determine those areas most badly in need of conservation and establish some priorities for action.

Examination of existing systems of classification revealed inadequacies.  Plant ecologists had developed many systems based on taxonomic relationships of plants, or upon the appearance or ecological characteristics of vegetation. These did not, however, take animals into account, and we were concerned with protecting the greatest array of animal and plant species.

In North America, early in this century, the plant ecologist Frederick Clements joined with the animal ecologist Victor Shelford to produce the biome system of classification.''   Biomes are easily recognized, they are the obvious subdivisions of the world's biota — the desert, grassland, coniferous forest, tropical rain forest, and such. They are characterized by one prevailing dominant form of "climax" vegetation, meaning that which will develop if nature is allowed to take her course over a few centuries, without human interference. The prevailing climate shapes the climax vegetation along with the soils and associated animal life.
The biome system of classification has now been widely accepted and has been the basis of many international research programmes, but for conservation purposes it does not go far enough.  For temperate and arctic North America, Clements and Shelford did a reasonably thorough job of subdividing biomes into associations and smaller units of classification. These could have been the basis for a conservation-oriented system. But the challenge was not picked up on other continents, and there only the larger units are recognized.

!t began to appear inevitable to us in lUCN that if we wanted a global system that would take into account not only vegetation, but also plant and animal species distribution, we would have to do more work, starting from whatever system seemed the most promising. This then became a task for lUCN's Commission on Ecology, with the job of preparing drafts and sketch maps largely falling into my hands. After several preliminary publications, the principal work was passed over to a biogeographer. Professor Miklos Udvardy, of Sacramento State University.  He has produced the maps which form the basis for what is presented here.2

The scheme of classification that we developed was not really new.  In the 1940s the bio tic provinces of North America were mapped by Lee R. Dice of the University of Michigan.3   Like other American schemes, however, this one was not adopted in other countries.  Nevertheless it seemed a good basis on which to work, taking into account as it did the distribution of both plant and animal species. The lUCN task was to extend the biotic province system to the entire world, and this was done in a preliminary way, recognizing that our knowledge of many areas was inadequate.  Udvardy, however, pointed out that the term, biotic province, had become through usage, almost synonymous with faunal province, and plants had been forgotten.  He proposed the new term biogeographic province, which has yet to be corrupted.

It can be said that biogeographic provinces are simply subdivisions of biomes, based on animal and plant distribution. To a degree that is true, but we have freed ourselves from the question of what is, or is not, the true climax vegetation which is involved in the Clements-Shelford system.   Essentially biotic provinces are areas that differ considerably, either in their animal or plant species, or in the character of their vegetation, from one another. To illustrate the concept, I will use the example of California, since it is the area I know best. The state includes all or part of 5 biotic provinces:  Oregonian, Sierra-Cascade, Great Basin, Sonoran and Californian (a sixth that I had added, the Channel Islands, has been dropped by Udvardy).'4

The Oregonian province belongs to the Northwest and extends up to Canada.   It is a region of tall, massive coastal forests, rain drenched in winter' often fog bound in summer.  A greater mass of' vegetation per square mile grows here than in any other area of the world.  California has its own unique subdivision of this province, in the redwood region of which it shares only a small corner with Oregon.

The second extends along the high mountains of the Pacific Coast from the Fraser River in British Columbia south through the volcanic Cascades and then down the Si erra Nevada to the Tehachapi Mountains. Although the Sierra and Cascade sections differ strongly geologically, their v-egetation and animal life do not separate out sufficiently to warrant different provincial status.  Their vegetation is arranged in the life zones characteristic of western mountains, with a broad band of ponderosa pine near the lower edges of the province and a fringe of timberline forest at the upper limits of tree growth.

The third province belongs to the intermountain region, from the Sierras to the Rockies — the Basin and Range province of physiographers.  California includes only a small area, in the Lassen-Modoc region of the northeast, and the Inyo-Mono section east of the highest Sierra. This is a country characterized by sagebrush, juniper and pinyon pine.

The fourth province is desert and has its affinities with Arizona, New Mexico and Sonora.  California's Mojave and Colorado deserts have many differences from their counterparts across the Colorado River, but not enough to be called separate provinces.

All of the rest of the state is in the Californian province, which has a fauna and flora characteristic of California and, in most respects, of nowhere else. This is the region of chaparral, broadleaved evergreen forest and woodland, of open oak savannas and prairies that are summer dry, and winter green.

I have analyzed the differences in mammalian species distribution between the provinces, admittedly using fairly crude methods. The greatest similarity is between the Oregonian and Sierra-Cascade provinces, which had approximately 68 per cent of their mammal species or subspecies in common. This was not enough difference to warrant provincial separation on the basis of mammals alone.  Much greater differences show up, however, in bird faunas and in vegetation.   By contrast the Great Basin province shares only around 36 per cent of its mammal species or subspecies with the Sonoran, and 38 per cent with the Californian province. The Californian province has less than 50 per cent of its mammal species or subspecies shared with any other province.

If we can agree at this point that biotic provinces are indeec^different, then we can agree that to protect a particular array of plants or animals we should establish at least one reserve or other protected area in each province.   Looking around the world, however, we find that whereas there are many national parks in some provinces, those of the African savanna, for example, there are none or scarcely any in others — the desert and semi-arid provinces of the Old World, or in various tropical rain forest provinces.   If there is to be a choice it makes more sense to establish a national park in the Sahara, in a place where desert wildlife survives, than to establish another park in the East African savanna.

However, the usefulness of the province concept can be extended beyond the practice of plant and animal species conservation. They represent areas within which ecologicalconditions are relatively uniform, with certain natural potentials and limitations.  During human history societies and cultures developed within certain provinces and adapted to their potentials and limitations. A sense of identity or place develops where an individual grows up within a particular province and learns to recognize its flora and fauna, to respond to its climatic regime, to become familiar with its limits.   Many serious land use blunders could have been avoided if people had not tried to transplant land-use practices developed within one biotic province to the differing ecological conditions of another.

In the United States we are cursed with state and county boundaries drawn with straight edges bypeople who did not know the land. Would it not make more sense to re-orient them toward ecological realities? World-wide the existing national boundaries are for the most part absurd, particularly in those Third World regions where former colonial powers decided where the lines should be drawn.   If people were allowed to sort themselves out rationally some new array of ethno-biotic entities would take the place of the existing nation states.

I don't think we have gone far enough yet in our thinking about biogeographic provinces to start reorganizing the political world.  People have been living on the planet for too long for their influence to be ignored.  The distribution of human groups
which have developed a sense of self-identity is at least as important as the distribution of plant species. One cannot put the English and Irish in the same country just because they share a biotic province, However, if we are to find a way out of the mess in
which global industrial culture has placed us, the biogeographic map could be pointing in a useful direction.


1.    Clements, F. and V. Shelford.   1939.  Bio-ecology. John Wiley, New York.
2.    Udvardy, M.D.F., 1975.  A classification of the hiogeographical provinces of the world.  lUCN Occasional Paper No. 18, lUCN, Morges, Switzerland.
3.    Dice, L.R., 1943.   The biotic provinces of North A?nerica. Univ. of Michigan Press, Ann Arbor.
4.    Dasmann, R.F., 1973.  A system for defining and classifying natural regions for purposes of conservation. lUCN Occasional Paper No. 7, lUCN, Morges, Switzerland.