Humans Altering The Natural Vegetation Shifting Biomes

In some areas the natural vegetation has been almost totally removed such as where there are now ploughed fields or cityscapes. But, in many other places, the effect of human actions has been more subtle. Often the result of anthropogenic influence seems to be a "downgrading" of the vegetation to something that might be found in a rather drier or colder climate.

For example, a meadow in the English countryside can only exist under human influence; the forest that once covered the land has been removed, and kept from returning by artificially high densities of grazing animals that bite off any tree seedlings. A meadow is in many respects an imitation of a dry Ukrainian or Turkish grassland, which is where many of its characteristic wild flowers (plus the rabbits and sheep that eat the plants) ultimately came from.

In the summer-dry Mediterranean climate zones of the world, the original forest cover has often been completely removed by a combination of agriculture, burning and grazing. Both pollen and historical evidence shows that the vegetation in even the barrcncst parts of Greece, Spain and Cypress were once fairly lush forest, usually dominated by deciduous broadleavcd trees. After thousands of years of intensive assault from humans and their goats, soil erosion has left thin, droughty soils. The lack of water-holding capacity in the soils favors tough, prickly vegetation known as garrigue or maquis that would once have been more typical of drier climates in North Africa and the Near East. As we shall see in Chapter 6. the lack of trees may also be due to a regional drying of climate, that was itself partly caused by the loss of forest.

Continue reading here: Predicting Where Vegetation Types Will Occur

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