Scrub Biomes

In climates that are too dry for forest but wetter than desert, one can either have scrub or grassland. Whether scrub or grassland vegetation actually occurs in a particular place depends on a range of factors including soil type, the time of year when rain occurs, fire frequency and the abundance of grazing mammals. It also depends partly on what species of plants happen to have evolved locally; whether they are mostly grasses or mostly bushes. Also, if the soils are thin, infertile and rocky, scrub is more likely than grassland.

Many places around the world that would naturally be forested have been reduced to scrub by human influence, through frequent burning and goat-grazing (see below). Around the Mediterranean, a natural scrub vegetation known as garrigue has expanded greatly in area over the past several thousand years due to these influences. If burning is prevented and goats are kept out, this vegetation often reverts to forest over several decades.

Some scrub areas of the world are strikingly rich in species of plants. For example, there is the very species-rich fynbos vegetation of the Cape region of South Africa, which has some 600 species of heathers (the genus Erica) plus thousands of other types of plants packed into an area only a couple of hundred kilometers across.

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