Herds of large herbivorous animals, as shown in the latest works on the subject, can evolve as a leading geosystemic factor even at a regional level. Such developments have been studied in Eastern Europe's woodlands for European bisons, and their action in districts where these animals, first grown in captivity, were set free into a natural environment. The habitation areas of such royal beasts take in sundry geosystems—from warm interfluvial plains to riverside glades and ponds. Cavorting, the bisons damage big trees and undergrowth which they put away as food. As a consequence, large forest glades appear in the thicket connected by wide pathways to watering-places and feed sites. Communities of meadow plant species spring up here and there, this accompanied by intensive weathering processes in some places.

Such zoogenic grassy glades that owe their existence to hoofed herbivores vary in size from 0.1 to 3-5 hectares (0.25 to 7.5-12.5 acres, respectively); they include spotty biogeocenoses with individual bison "stalls" in what we call "rolling grounds"—places in which the plant and surface soil cover is injured worst of all. The animals migrate elsewhere when their fodder runs out (when all vegetation is gone in practical terms), leaving bare patches of trampled ground. Step by step the process of rehabilitating succession sets in with the invasion of pioneer plant species.

In pre-agricultural times herds of hoofed animals exerted an essentially different effect on the forest zone: interfluvial valleys were the homeland of shady forests crisscrossed by the many trails connecting zoogenic glades of bisons, aurochs (extinct wild oxen of Europe), tarpan horses and other ungulates. Most of the landscapes were under plant communities with all conditions on hand for renewal of sun trees and bushes. The disappearance and/or contraction of the population of large gregarious ungulates ushered in changes in many of the forestland ecosystems and ongoing processes there.

The impact of such animals on the landscape structure differs with region. In forestlands gaps in tree vegetation and profuse growth of grasses provide conditions for the sustainable development of the light-requiring plants and animals. In steppelands high-productivity pastures come into being: grazing there, hoofed animals fertilize the soil with their manure. And in tundra plains herds of northern deer may work changes in the type of tundra—lichens are supplanted by grasses, shrubs and other plants.

But the conclusion that large gregarious herbivores are a formative landscape factor on the regional level should be viewed as a hypothesis only—still debatable, albeit based on cogent arguments and copious factual evidence collected in wildlife preserves and national parks, particularly, in Africa. One such park, Serengeti, is populated by 1.5 to 2 mln ungulates and around three thousand elephants, one of the few places on earth where such animals are found at large. Their impact on natural landscapes is alike in many respects. The elephants, assigned to the "keymost species" of the African savannahs, stand out. Each year they destroy and damage as much as 30 percent of trees at Serengeti, forming a specific "elephantine landscape".

The above-cited examples do not cover all zoogenic landscape complexes in their diversity. We might as well mention biocenoses associated with wild boar "diggings", or termite (white ant) colonies in savannahs - you can read more about termite signs right now. In most cases such activities result in the transformation of lithogenic beds and give rise to peculiar microrelief features. The physical condition and the chemical composition of soil is changed, and so are the microclimate and water regime; the plant cover and the associated flora are modified as well. Some zoogenic landscape complexes (insular bird colonies, those of termites and marmots) may be as old as zonal geosystems. But other landscapes are short-lived—for instance, wild boar ravages. In some instances we come to deal with larger geosystems—bird colonies occupying all of an island, or large herds of plant-eating animals.

Zoogenic complexes are rated as rare or unique as part of larger landscapes. Their relative area within sustainable natural complexes is fairly steady percentagewise (if below 10 percent). But a 10 to 15 percent increase is indicative of a geosystemic imbalance (population explosion of lemmings, expansion of termite colonies, higher density of wild boar population). But all returns "according to its circuits" with the easing of the zoogenic pressure.

This has been in the natural scheme of things for thousands and thousands of years...