A savanna or savannah is a mixed woodland grassland ecosystem
characterised by the trees being sufficiently widely spaced so that
the canopy does not close. The open canopy allows sufficient light to
reach the ground to support an unbroken herbaceous layer consisting
primarily of grasses.
Savannas maintain an open canopy despite a high tree density. It is
often believed that savannas feature widely spaced, scattered trees.
However, in many savannas, tree densities are higher and trees are
more regularly spaced than in forests. The South American
savanna types cerrado sensu stricto and cerrado dense typically have
densities of trees similar to or higher than that found in South
American tropical forests, with savanna ranging from
800–3300 trees per hectare (trees/ha) and adjacent forests with
800–2000 trees/ha. Similarly Guinean savanna has
129 trees/ha, compared to 103 for riparian forest, while
Eastern Australian sclerophyll forests have average tree densities of
approximately 100 per hectare, comparable to savannas in the same
Savannas are also characterised by seasonal water availability, with
the majority of rainfall confined to one season; they are associated
with several types of biomes, and are frequently in a transitional
zone between forest and desert or grassland.
approximately 20% of the Earth's land area.
3.1 Changes in fire management
3.2 Grazing and browsing animals
3.3 Tree clearing
3.4 Exotic plant species
3.5 Climate change
5 See also
7 External links
The word originally entered English in 1555 as the Latin
Zauana, equivalent in the orthography of the times to zavana (see
history of V). Peter Martyr reported it as the local name for the
plain around Comagre, the court of the cacique Carlos in present-day
Panama. The accounts are inexact, but this is usually placed in
present-day Madugandí or at points on the nearby
Guna Yala coast
opposite Ustupo or on Point Mosquitos. These areas are now
either given over to modern cropland or jungle.
Tarangire National Park
Tarangire National Park in Tanzania, East Africa
Many grassy landscapes and mixed communities of trees, shrubs, and
grasses were described as savanna before the middle of the 19th
century, when the concept of a tropical savanna climate became
Köppen climate classification
Köppen climate classification system was strongly
influenced by effects of temperature and precipitation upon tree
growth, and his oversimplified assumptions resulted in a tropical
savanna classification concept which resulted in it being considered
as a "climatic climax" formation. The common usage meaning to describe
vegetation now conflicts with a simplified yet widespread climatic
concept meaning. 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.
"Barrens" has been used almost interchangeably with savanna in
different parts of North America. Sometimes midwestern savanna were
described as "grassland with trees". Different authors have defined
the lower limits of savanna tree coverage as 5–10% and upper limits
range as 25–80% of an area.
Two factors common to all savanna environments are rainfall variations
from year to year, and dry season wildfires. In the
Americas, e.g. in Belize, Central America, savanna vegetation is
South America and to the Caribbean.
Over many large tropical areas, the dominant biome (forest, savanna or
grassland) can not be predicted only by the climate, as historical
events plays also a key role, for example, fire activity. In some
areas, indeed, it is possible the occurrence of multiple stable
Changes in fire management
Savannas are subject to regular wildfires and the ecosystem appears to
be the result of human use of fire. For example, Native Americans
Pre-Columbian savannas of North America
Pre-Columbian savannas of North America by periodically
burning where fire-resistant plants were the dominant species.
Pine barrens in scattered locations from
New Jersey to coastal New
England are remnants of these savannas. Aboriginal burning appears to
have been responsible for the widespread occurrence of savanna in
Australia and New Guinea, and savannas in
India are a
result of human fire use. The maquis shrub savannas of the
Mediterranean region were likewise created and maintained by
Prescribed burn; Wisconsin bur oak savanna
These fires are usually confined to the herbaceous layer and do little
long term damage to mature trees. However, these fires either kill or
suppress tree seedlings, thus preventing the establishment of a
continuous tree canopy which would prevent further grass growth. Prior
to European settlement aboriginal land use practices, including fire,
influenced vegetation and may have maintained and modified savanna
flora. It has been suggested by many authors that
aboriginal burning created a structurally more open savanna landscape.
Aboriginal burning certainly created a habitat mosaic that probably
increased biodiversity and changed the structure of woodlands and
geographic range of numerous woodland species. It has been
suggested by many authors that with the removal or alteration
of traditional burning regimes many savannas are being replaced by
forest and shrub thickets with little herbaceous layer.
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. The introduction of exotic
pasture legumes has also led to a reduction in the need to burn to
produce a flush of green growth because legumes retain high nutrient
levels throughout the year, and because fires can have a negative
impact on legume populations which causes a reluctance to burn.
Grazing and browsing animals
Oak savanna, United States
The closed forest types such as broadleaf forests and rainforests are
usually not grazed owing to the closed structure precluding grass
growth, and hence offering little opportunity for grazing. In
contrast the open structure of savannas allows the growth of a
herbaceous layer and are commonly used for grazing domestic
livestock. As a result, much of the world's savannas have
undergone change as a result of grazing by sheep, goats and cattle,
ranging from changes in pasture composition to woody weed
The removal of grass by grazing affects the woody plant component of
woodland systems in two major ways. Grasses compete with woody plants
for water in the topsoil and removal by grazing reduces this
competitive effect, potentially boosting tree growth. In addition
to this effect, the removal of fuel reduces both the intensity and the
frequency of fires which may control woody plant species. Grazing
animals can have a more direct effect on woody plants by the browsing
of palatable woody species. There is evidence that unpalatable woody
plants have increased under grazing in savannas. 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. In addition to this, cattle and horses are
implicated in the spread of the seeds of weed species such as Prickly
Acacia (Acacia nilotica) and Stylo (
Alterations in savanna species composition brought about by grazing
can alter ecosystem function, and are exacerbated by overgrazing and
poor land management practices.
Introduced grazing animals can also affect soil condition through
physical compaction and break-up of the soil caused by the hooves of
animals and through the erosion effects caused by the removal of
protective plant cover. Such effects are most likely to occur on land
subjected to repeated and heavy grazing. The effects of
overstocking are often worst on soils of low fertility and in low
rainfall areas below 500 mm, as most soil nutrients in these
areas tend to be concentrated in the surface so any movement of soils
can lead to severe degradation. Alteration in soil structure and
nutrient levels affects the establishment, growth and survival of
plant species and in turn can lead to a change in woodland structure
Large areas of Australian and South American savannas have been
cleared of trees, and this clearing is continuing today. For example,
until recently 480,000 ha of savanna were cleared annually in
Australia alone primarily to improve pasture production.
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.
Clearing is carried out by the grazing industry in an attempt to
increase the quality and quantity of feed available for stock and to
improve the management of livestock. The removal of trees from savanna
land removes the competition for water from the grasses present, and
can lead to a two to fourfold increase in pasture production, as well
as improving the quality of the feed available. Since stock
carrying capacity is strongly correlated with herbage yield, there can
be major financial benefits from the removal of trees, such as
assisting with grazing management: regions of dense tree and shrub
cover harbors predators, leading to increased stock losses, for
example, while woody plant cover hinders mustering in both sheep
and cattle areas.
A number of techniques have been employed to clear or kill woody
plants in savannas. Early pastoralists used felling and girdling, the
removal of a ring of bark and sapwood, as a means of clearing
land. In the 1950s arboricides suitable for stem injection were
developed. War-surplus heavy machinery was made available, and these
were used for either pushing timber, or for pulling using a chain and
ball strung between two machines. These two new methods of timber
control, along with the introduction and widespread adoption of
several new pasture grasses and legumes promoted a resurgence in tree
clearing. The 1980s also saw the release of soil-applied arboricides,
notably tebuthiuron, that could be utilised without cutting and
injecting each individual tree.
In many ways "artificial" clearing, particularly pulling, mimics the
effects of fire and, in savannas adapted to regeneration after fire as
most Queensland savannas are, there is a similar response to that
after fire. Tree clearing in many savanna communities, although
causing a dramatic reduction in basal area and canopy cover, often
leaves a high percentage of woody plants alive either as seedlings too
small to be affected or as plants capable of re-sprouting from
lignotubers and broken stumps. A population of woody plants equal to
half or more of the original number often remains following pulling of
eucalypt communities, even if all the trees over 5 metres are uprooted
Exotic plant species
Acacia savanna, Taita Hills Wildlife Sanctuary, Kenya.
A number of exotic plants species have been introduced to the savannas
around the world. Amongst the woody plant species are serious
environmental weeds such as Prickly Acacia (Acacia nilotica),
Rubbervine (Cryptostegia grandiflora), Mesquite (
Lantana camara and L. montevidensis) and Prickly Pear
Opuntia spp.) A range of herbaceous species have also been introduced
to these woodlands, either deliberately or accidentally including
Rhodes grass and other Chloris species, Buffel grass (Cenchrus
ciliaris), Giant rat's tail grass (Sporobolus pyramidalis) parthenium
Parthenium hysterophorus) and stylos (
Stylosanthes spp.) and other
legumes. These introductions have the potential to significantly alter
the structure and composition of savannas worldwide, and have already
done so in many areas through a number of processes including altering
the fire regime, increasing grazing pressure, competing with native
vegetation and occupying previously vacant ecological niches.
Other plant species include: white sage, spotted cactus, cotton seed,
Human induced climate change resulting from the greenhouse effect may
result in an alteration of the structure and function of savannas.
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. However, a recent case described
a savanna increasing its range at the expense of forest in response to
climate variation, and potential exists for similar rapid, dramatic
shifts in vegetation distribution as a result of global climate
change, particularly at ecotones such as savannas so often
Mediterranean savanna in
Alentejo region, Portugal
Savanna ecoregions are of several different types:
Tropical and subtropical savannas are classified with tropical and
subtropical grasslands and shrublands as the tropical and subtropical
grasslands, savannas, and shrublands biome. The savannas of Africa,
including the Serengeti, famous for its wildlife, are typical of this
type. The Brazilian savanna (Cerrado) is also included in this
category, known for its exotic and varied flora.
Temperate savannas are mid-latitude savannas with wetter summers and
drier winters. They are classified with temperate savannas and
shrublands as the temperate grasslands, savannas, and shrublands
biome, that for example cover much of the
Great Plains of the United
States. (See areas such as the Central forest-grasslands transition).
Mediterranean savannas are mid-latitude savannas in Mediterranean
climate regions, with mild, rainy winters and hot, dry summers, part
Mediterranean forests, woodlands, and scrub
Mediterranean forests, woodlands, and scrub biome. The oak tree
savannas of California, part of the
California chaparral and woodlands
ecoregion, fall into this category.
Flooded savannas are savannas that are flooded seasonally or
year-round. They are classified with flooded savannas as the flooded
grasslands and savannas biome, which occurs mostly in the tropics and
Montane savannas are mid- to high-altitude savannas, located in a few
spots around the world's high mountain regions, part of the montane
grasslands and shrublands biome. The Bogotá savanna, located at an
average altitude of 2,550 metres (8,370 ft) on the Altiplano
Cundiboyacense, Eastern Ranges of the Andes, is an example of a
montane savanna. The savannas of the Angolan Scarp savanna and
woodlands ecoregion are a lower altitude example, up to 1,000 metres
^ Anderson, Roger A., Fralish, James S. and Baskin, Jerry M.
editors.1999. Savannas, Barrens, and Rock Outcrop Plant Communities of
North America. Cambridge University Press.
^ McPherson, G. R. (1997). Ecology and management of North American
Savannas. Tucson, AZ: University of Arizona Press.
^ a b Werner, Patricia A.; B. H. Walker; P. A Stott (1991).
"Introduction". In Patricia A. Werner.
Savanna Ecology and Management:
Australian Perspectives and Intercontinental Comparisons. Oxford:
Blackwell Publishing. ISBN 978-0-632-03199-3.
^ Alexandro Solórzano, Jeanine Maria Felfili 2008”Comparative
analysis of the international terminaoolgy for cerrado” IX Symposio
Cerrado 13 a 17 de outubro de 2008 Parlamundi Barsilia, DF
^ a b Manoel Cláudio da Silva Jánior, Christopher William Fagg,
Maria Cristina Felfili, Paulo Ernane Nogueira, Alba Valéria Rezende,
and Jeanine Maria Felfili 2006 “Chapter 4.
Phytogeography of Cerrado
Sensu Stricto and Land System Zoning in Central Brazil” in
“Neotropical Savannas and Seasonally Dry Forests: Plant Diversity,
Biogeography, and Conservation” R. Toby Pennington, James A. Ratter
(eds) 2006 CRC Press
^ a b Abdullahi Jibrin 2013 “A Study of Variation in Physiognomic
Characteristics of Guinea
Savanna Vegetation” Environment and
Natural Resources Research 3:2
^ a b Erika L. Geiger, Sybil G. Gotsch, Gabriel Damasco, M. Haridasan,
Augusto C. Franco & William A. Hoffmann 2011 “Distinct roles of
savanna and forest tree species in regeneration under fire suppression
in a Brazilian savanna” Journal of
Vegetation Science 22
^ a b Scholz, Fabian G.; Bucci, Sandra J.; Goldstein, Guillermo;
Meinzer, Frederick C.; Franco, Augusto C.; Salazar, Ana. 2008
“Plant- and stand-level variation in biophysical and physiological
traits along tree density gradients in the Cerrado”, Brazilian
Journal of Plant Physiology
^ Tait, L 2010, Structure and dynamics of grazed woodlands in
North-eastern Australia, Master of Applied Science Thesis, Central
Queensland University, Faculty of Science, Engineering and Health,
Oxford English Dictionary, 3rd ed. "savannah", n.
Press (Oxford), 2012.
^ a b D'Anghiera, Peter Martyr. De Orbe Novo Decades. Cum Ejusdem
Legatione Babylonica. [The Decades of the New World. With the
Babylonian Legation.] Arnao Guillén de Brocar (Alcala), 1516 (in
Richard Eden as The decades of the newe worlde or west
India conteynyng the nauigations and conquestes of the Spanyardes with
the particular description of the moste ryche and large landes and
Ilands lately founde in the west Ocean perteynyng to the inheritaunce
of the kinges of Spayne, Book III, §3. William Powell (London), 1555.
^ Richard Eden: "The palace of this Comogrus, is ſituate at the foote
of a ſtiepe hyll well cultured. Hauynge towarde the ſouthe a playne
of twelue leages in breadth and veary frutefull. This playne, they
^ Eden (1555), Book III, §6.
^ The account of Peter Martyr itself differs in places, variously
placing Comagre 25 leagues west of and accessible by ship from
Dariena or 70 leagues (roughly 290 kilometers or 180 miles) west
Dariena and beside a river flowing into the southern ocean.
^ Bancroft, Hubert H. (1882). "History of Central America.
1501–1530". San Francisco: A.L. Bancroft & Co.
^ Bancroft (1882), p. 362.
^ Bancroft (1882), p. 347.
Land Cover Classification]" from
Earth Observatory. The Image
Composite Explorer. Exercise 4:
Vegetation Vital Signs. Accessed 1
^ David R. Harris, ed. (1980). Human Ecology in
London: Academic Press. pp. 3,5–9,12,271–278,297–298.
^ Roger C. Anderson; James S. Fralish; Jerry M. Baskin, eds. (1999).
Savannas, Barrens, and Rock Outcrop Plant Communities of North
America. Cambridge University Press. pp. 2–3.
^ David L. Lentz, ed. (2000). Imperfect balance: landscape
transformations in the Precolumbian Americas. New York City: Columbia
University Press. pp. 73–74. ISBN 0-231-11157-6.
^ Moncrieff, G. R., Scheiter, S., Langan, L., Trabucco, A., Higgins,
S. I. (2016). The future distribution of the savannah biome:
model-based and biogeographic contingency, Philos. T. R. Soc. B, 371,
2015.0311, 2016. link.
^ Staver, A.C., Archibald, S., Levin, S.A. (2011). The global extent
and determinants of savanna and forest as alternative biome states.
Science 334, 230–232. link.
^ "Use of Fire by Native Americans". The Southern
Assessment Summary Report. Southern Research Station, USDA Forest
Service. Retrieved 2008-07-21.
^ a b c Flannery, Timothy Fridtjof (1994). The Future Eaters: An
Ecological History of the Australasian Lands and People. Frenchs
Forest, New South Wales: Reed New Holland.
^ Saha, S. (2003). "Patterns in woody species diversity, richness and
partitioning of diversity in forest communities of tropical deciduous
forest biomes". Ecography. 26 (1): 80–86.
^ Pyne, Stephen J. (1997). Vestal Fire: An Environmental History, Told
through Fire, of Europe and Europe's Encounter with the World.
Seattle: University of Washington Press.
^ a b c d e Wilson, B., S. Boulter, et al. (2000). Queensland's
Vegetation Management in Queensland. S. L. Boulter,
B. A. Wilson, J. Westrupet eds. Brisbane, Department of Natural
Resources ISBN 0-7345-1701-7.
^ a b Lunt, I. D.; N. Jones (2006). "Effects of European colonisation
on indigenous ecosystems: post-settlement changes in tree stand
structures in Eucalyptus–Callitris woodlands in central New South
Wales, Australia". Journal of Biogeography. 33 (6): 1102–1115.
^ Archer S, (1994.) "Woody plant encroachment into southwestern
grasslands and savannas: Rates, patterns and proximate causes." pp.
13–68 in Vavra, Laycock and Pieper (eds.) Ecological Implications of
Livestock Herbivory in the West. Society For Range Management, Denver
^ a b Pressland, A. J., J. R. Mills, et al. (1988). Landscape
degradation in native pasture. Native pastures in Queensland their
resources and management. W. H. Burrows, J. C. Scanlan and M. T.
Rutherford. Queensland, Queensland Government Press
^ Dyer, R., A. Craig, et al. (1997). Fire in northern pastoral lands.
Fire in the management of northern Australian pastoral lands. T. C.
Grice and S. M. Slatter. St. Lucia, Australia,
Australia ISBN 0-9590948-9-X.
^ Lodge, G. M. and R. D. B. Whalley (1984).
Management of Australia’s Rangelands. G. N. Harrington and A. D.
Wilson. Melbourne, CSIRO Publishing.
^ Mott, J. J., Groves, R.H. (1994). Natural and derived grasslands.
Australian Vegetation. R. H. Groves. Cambridge, Cambridge University
^ Winter, W. H. (1991). "Australia's northern savannas: a time for
change in management philosophy". In Patricia A. Werner. Savanna
Ecology and Management: Australian Perspectives and Intercontinental
Comparisons. Oxford: Blackwell Publishing. pp. 181–186.
^ Burrows, W. H., J. C. Scanlan, et al. (1988). Plant ecological
relations in open forests, woodlands and shrublands. Native pastures
in Queensland their resources and management. W. H. Burrows, J. C.
Scanlan and M. T. Rutherford eds. Brisbane, Department of Primary
Industries ISBN 0-7242-2443-2.
^ Smith, G., A. Franks, et al. (2000). Impacts of domestic grazing
within remnant vegetation. Native
Vegetation Management in Queensland.
S. L. Boulter, B. A. Wilson, J. Westrupet al. Brisbane, Department of
Natural Resources ISBN 0-7345-1701-7.
^ Florence, R. G. (1996). Ecology and silviculture of eucalypt
CSIRO Publishing ISBN 0-643-10252-3.
^ Foran, B. D. (1984). Central arid woodlands. Management of
Australia’s Rangelands. G. N. Harrington and A. D. Wilson.
CSIRO Publishing ISBN 0-643-03615-6.
^ Scanlan, J. and C. Chilcott (2000). Management and production
Vegetation Management in Queensland. S. L. Boulter, B.
A. Wilson, J. Westrupet al. Brisbane, Department of Natural Resources.
^ Harrington, G. N., M. H. Friedel, et al. (1984).
and management. Management of Australia's Rangelands. G. N. Harrington
and A. D. Wilson. Melbourne,
CSIRO Publishing ISBN 0-643-03615-6.
^ Harrington, G. N., D. M. D. Mills, et al. (1984). Semi-arid
woodlands. Management of Australia's Rangelands. G. N. Harrington and
A. D. Wilson. Melbourne,
CSIRO Publishing ISBN 0-643-03615-6.
^ Harrington, G. N., D. M. D. Mills, et al. (1984). Management of
Rangeland Ecosystems. Management of Australia's Rangelands. G. N.
Harrington and A. D. Wilson. Melbourne, CSIRO Publishing
^ Partridge, I. (1999). Managing grazing in northern Australia.
Brisbane, Department of Primary Industries ISBN 0-7345-0035-1.
^ a b Scanlan, J. C. (1988). Managing tree and shrub populations.
Native pastures in Queensland their resources and management. W. H.
Burrows, J. C. Scanlan and M. T. Rutherford. Queensland, Queensland
Government Press ISBN 0-7242-2443-2.
^ Tothill, J. C. and C. Gillies (1992). The pasture lands of northern
Grassland Society of Australia
^ Archer, S. (1991). "Development and stability of grass/woody mosaics
in a subtropical savanna parkland, Texas, USA". In Patricia A. Werner.
Savanna Ecology and Management: Australian Perspectives and
Intercontinental Comparisons. Oxford: Blackwell Publishing.
pp. 109–118. ISBN 978-0-632-03199-3.
^ Allen, C. D. & D. D. Breshears (1998). "Drought-induced shift of
a forest–woodland ecotone: Rapid landscape response to climate
variation". Proceedings of the National Academy of Sciences. 95 (25):
14839–14842. doi:10.1073/pnas.95.25.14839. PMC 24536 .
^ Calvachi Zambrano, Byron (2002). "La biodiversidad bogotana" (PDF).
Revista La Tadeo (in Spanish). Universidad Jorge Tadeo Lozano. 67:
89–98. Retrieved 2017-03-04.
^ Pérez Preciado, Alfonso (2000). La estructura ecológica principal
de la Sabana de Bogotá (PDF) (in Spanish). Sociedad Geográfica de
Colombia. pp. 1–37. Retrieved 2017-03-04.
^ Angolan Scarp savanna and woodlands
Wikimedia Commons has media related to Savanna.
"Savanna". Encyclopædia Britannica (11th ed.). 1911.
"Savannas". New International Encyclopedia. 1905.
Montane grasslands and shrublands
Broadleaf and mixed forests
Grasslands, savannas, and shrublands
Moist broadleaf forests
Dry broadleaf forests
Grasslands, savannas, and shrublands
Mediterranean forests, woodlands, and scrub
Deserts and xeric shrublands
Flooded grasslands and savannas
Temperate Northern Pacific
Tropical Eastern Pacific
List of ecoregions
Global 200 ecoregions
Ecological land classification
Forests, woodlands, arboretum
Shrublands, scrubs, thickets, fruticetum
Dwarf-shrubland, subshrublands, dwarf-scrubs, suffruticetum
Herbaceous communities, grasslands, steppes, prairies, herbetum
Scarcely vegetated areas, desert vegetation
Pluvial, rainy, ombrophilous
Loss of leaves
Sclerophyll, stiff leaves
Orthophyll, hyptiophyll leaves