The largest areas of savanna are found in Africa, Australia, India, Madagascar, the Myanmar-Thailand region, and South America.
Sometimes midwestern savanna were described as "grassland with trees."
Alterations in savanna species composition brought about by grazing can alter ecosystem function, and are exacerbated by overgrazing and poor land management practices.
Prior to European settlement aboriginal land use practices, including fire, influenced vegetation and may have maintained and modified savanna flora.
Animals within savannas have adapted to surviving the seasonal variations in food supply.
The consumption of herbage by introduced grazers in savanna woodlands has led to a reduction in the amount of fuel available for burning and resulted in fewer and cooler fires.
A number of exotic plants species have been introduced to the savannas around the world.
Savannas are subject to regular fires and the ecosystem appears to be the result of human use of fire.
There exists the possibility that human induced climate change in the form of the greenhouse effect may result in an alteration of the structure and function of savannas.
Alternative subdivisions include woodland savanna, tree savanna, shrub savanna, and grass savanna.
The maquis shrub savannas of the Mediterranean region were likewise created and maintained by anthropogenic fire.
Aboriginal didgeridoo craftsmen spend considerable time in the challenging search for a tree that has been hollowed out—by termites—to just the right degree.
A number of techniques have been employed to clear or kill woody plants in savanna.
Many grassy landscapes and mixed communities of trees, shrubs, and grasses were described as savanna before the middle of the nineteenth century, when the concept of a tropical savanna climate became established.
Two factors common to all savanna environments are rainfall variations from year to year, and dry-season fires.
Grazing also promotes the spread of weeds in savannas by the removal or reduction of the plants which would normally compete with potential weeds and hinder establishment.
Different authors have defined the lower limits of savanna tree coverage as 5-10 percent and upper limits range from 25-80 percent of an area.
Some authors have suggested that savannas and grasslands may become even more susceptible to woody plant encroachment as a result of greenhouse induced climate change.
Savannas around the world are also dominated by tropical grasses which use the C4 type of photosynthesis.
Regardless of subcategory, all savannas can be defined as tropical or subtropical vegetation types with a continuous grass cover occasionally interrupted by trees and shrubs.
Substantial savanna areas have been cleared of woody vegetation and much of the area that remains today is vegetation that has been disturbed by either clearing or thinning at some point in the past.
Both birds and land mammals are usually seasonal migrants, occupying savannas during and immediately after the wet season, moving elsewhere as the dry season approaches.
Large areas of savanna have been cleared of trees, and this clearing is continuing today.
Savannas are an important ecosystem for the health and stability of the planet and places of profound beauty, adding to the human enjoyment and wonder of nature.
Pine barrens in scattered locations from New Jersey to coastal New England are remnants of these savannas.
A savanna or savannah is a tropical or subtropical woodland ecosystem characterized by the trees being sufficiently small or widely spaced so that the canopy does not close, above a continuous tall grass understory.
Some classification systems also recognize a grassland savanna from which trees are absent.
The divergence has sometimes caused areas such as extensive savannas north and south of the Congo and Amazon Rivers to be excluded from mapped savanna categories.