savanna | ecological region - Encyclopedia Britannica

savanna, also spelled savannah, vegetation type that grows under hot, seasonally dry climatic conditions and is characterized by an open tree canopy (i.e., ... savanna TableofContents savanna IntroductionOriginEnvironmentBiotaFloraFaunaPopulationandcommunitydevelopmentandstructureBiologicalproductivity FastFacts Facts&RelatedContent Media Videos Images More MoreArticlesOnThisTopic AdditionalReading Contributors ArticleHistory Home Science Environment savanna ecologicalregion Actions Cite verifiedCite Whileeveryefforthasbeenmadetofollowcitationstylerules,theremaybesomediscrepancies. Pleaserefertotheappropriatestylemanualorothersourcesifyouhaveanyquestions. SelectCitationStyle MLA APA ChicagoManualofStyle CopyCitation Share Share Sharetosocialmedia Facebook Twitter URL https://www.britannica.com/science/savanna GiveFeedback ExternalWebsites Feedback Corrections?Updates?Omissions?Letusknowifyouhavesuggestionstoimprovethisarticle(requireslogin). 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ExternalWebsites BluePlanetBiomes-Savanna Alternatetitles:savannah By JeremyM.B.Smith • EditHistory TableofContents SerengetiPlain Seeallmedia RelatedTopics: shrubsavanna savannawoodland termitesavanna thornbushsavanna drysavanna ...(Showmore) Seeallrelatedcontent→ savanna,alsospelledsavannah,vegetationtypethatgrowsunderhot,seasonallydryclimaticconditionsandischaracterizedbyanopentreecanopy(i.e.,scatteredtrees)aboveacontinuoustallgrassunderstory(thevegetationlayerbetweentheforestcanopyandtheground).ThelargestareasofsavannaarefoundinAfrica,SouthAmerica,Australia,India,theMyanmar(Burma)–ThailandregioninAsia,andMadagascar.grasslandregions:savanna,prairie,andsteppePrincipalregionswheresignificantareasofnaturalsavanna,prairie,andsteppeoccur.EncyclopædiaBritannica,Inc. Origin SavannasaroseasrainfallprogressivelylessenedintheedgesofthetropicsduringtheCenozoicEra(66millionyearsagotothepresent)—inparticular,duringthepast25millionyears.Grasses,thedominantplantsofsavannas,appearedonlyabout50millionyearsago,althoughitispossiblethatsomesavanna-likevegetationlackinggrassesoccurredearlier.TheSouthAmericanfossilrecordprovidesevidenceofawell-developedvegetation,richingrassandthoughttobeequivalenttomodernsavanna,beingestablishedbytheearlyMioceneEpoch,about20millionyearsago. Climatesacrosstheworldbecamesteadilycoolerduringthatperiod.Loweroceansurfacetemperaturesreducedwaterevaporation,whichslowedthewholehydrologiccycle,withlesscloudformationandprecipitation.Thevegetationofmidlatituderegions,lyingbetweenthewetequatorialareasandthemoistcooltemperatezones,wasaffectedsubstantially. Themainregionsinwhichsavannasemergedinresponsetothatlong-termclimaticchange—tropicalAmerica,Africa,SouthAsia,andAustralia—werealreadyseparatedfromeachotherbyoceanbarriersbythattime.Plantmigrationacrossthosebarrierswasinhibited,andthedetailsoftheemergenceofsavannasoneachcontinentvaried.Ineachregiondifferentplantandanimalspeciesevolvedtooccupythenewseasonallydryhabitats. GetaBritannicaPremiumsubscriptionandgainaccesstoexclusivecontent. SubscribeNow Intemperateregions,savannasbecamemuchmorewidespread,attheexpenseofforests,duringthelong,cool,dryintervals—contemporaneouswiththeiceages,orglacialintervals,ofthePleistoceneEpoch(2.6millionto11,700yearsago).StudiesoffossilizedpolleninsedimentsfromsitesinSouthAmerica,Africa,andAustraliaprovidestrongsupportforthisview. NewfromBritannica Laughterthatcomesfromticklingiscalledgargalesis,andasidefromprimatestheonlyanimalknowntoexperienceitistherat. SeeAllGoodFacts Whenhumanbeings(Homosapiens)firstappeared,inAfrica,theyinitiallyoccupiedthesavanna.Later,astheybecamemoreadeptatmodifyingtheenvironmenttosuittheirneeds,theyspreadtoAsia,Australia,andtheAmericas.Theretheirimpactonthenatureanddevelopmentofsavannavegetationwassuperimposedonthenaturalpattern,addingtothevariationseenamongsavannatypes.Thesavannasoftheworldcurrentlyareundergoinganotherphaseofchangeasmodernexpansionofthehumanpopulationimpingesonthevegetationandfauna.