title: Savanna woody encroachment is widespread across three continents.
abstract: Tropical savannas are a globally extensive biome prone to rapid vegetation change in response to changing environmental conditions. Via a meta-analysis, we quantified savanna woody vegetation change spanning the last century. We found a global trend of woody encroachment that was established prior the 1980s. However, there is critical regional variation in the magnitude of encroachment. Woody cover is increasing most rapidly in the remaining uncleared savannas of South America, most likely due to fire suppression and land fragmentation. In contrast, Australia has experienced low rates of encroachment. When accounting for land use, African savannas have a mean rate annual woody cover increase two and a half times that of Australian savannas. In Africa, encroachment occurs across multiple land uses and is accelerating over time. In Africa and Australia, rising atmospheric CO2, changing land management and rainfall are likely causes. We argue that the functional traits of each woody flora, specifically the N-fixing ability and architecture of woody plants, are critical to predicting encroachment over the next century and that African savannas are at high risk of widespread vegetation change.
authors.affiliation: Fynbos Node, South African Environmental Observation Network (SAEON), Cape Town, South Africa.|Department of Botany and Zoology, University of Stellenbosch, Private Bag X1, Matieland, Stellenbosch, 7602, South Africa.
authors.forename: Nicola
authors.initials: N
authors.lastname: Stevens
authors.affiliation: School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3FF, UK.
authors.forename: Caroline E R
authors.initials: CE
authors.lastname: Lehmann
authors.affiliation: Research Institute for the Environment and Livelihoods, Charles Darwin University, Darwin, NT, 0909, Australia.
authors.forename: Brett P
authors.initials: BP
authors.lastname: Murphy
authors.affiliation: Floresta Estadual de Assis, Instituto Florestal, Assis, SP, 19802-970, Brasil.
authors.forename: Giselda
authors.initials: G
authors.lastname: Durigan
mesh_terms: D000349:Africa; D001315:Australia; D003247:Conservation of Natural Resources; D017753:Ecosystem; D065948:Grassland; D013020:South America; D014197:Trees
keywords: 
  CO
  2
  ; N-fixation; allometry; deciduousness; fire suppression; forest expansion; land-use change; woody encroachment; woody vegetation change