title: Human disturbance amplifies Amazonian El Niño-Southern Oscillation signal.
abstract: The long-term interaction between human activity and climate is subject to increasing scrutiny. Humans homogenize landscapes through deforestation, agriculture, and burning and thereby might reduce the capacity of landscapes to provide archives of climate change. Alternatively, land-use change might overwhelm natural buffering and amplify latent climate signals, rendering them detectable. Here we examine a sub-annually resolved sedimentary record from Lake Sauce in the western Amazonian lowlands that spans 6900 years. Finely-laminated sediments were deposited from ca. 5000 years ago until the present, and human activity in the watershed was revealed through the presence of charcoal and maize agriculture. The laminations, analyzed for color content and bandwidth, showed distinctive changes that were coupled to more frequent occurrence of fossil maize pollen. As agricultural activity intensified ca. 2200 cal. BP, the 2- to 8-year periodicity characteristic of El Niño-Southern Oscillation became evident in the record. These agricultural activities appeared to have amplified an existing, but subtle climatic signal that was previously absorbed by natural vegetation. When agricultural activity slowed, or land use around Lake Sauce changed at ca. 800 cal. BP, the signal of El Niño-Southern Oscillation (ENSO) activity became erratic.
authors.affiliation: Department of Biological Sciences, Florida Institute of Technology, Melbourne, FL, 32901, USA.
authors.forename: Mark B
authors.identifier: 0000-0001-6894-8613
authors.initials: MB
authors.lastname: Bush
authors.affiliation: Instituto de Geología, Universidad Nacional Autónoma de México, Coyoacán, Mexico City, 04510, Mexico.
authors.forename: Alexander
authors.initials: A
authors.lastname: Correa-Metrio
authors.affiliation: Department of Biological Sciences, Florida Institute of Technology, Melbourne, FL, 32901, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: van Woesik
authors.affiliation: Department of Biological Sciences, Florida Institute of Technology, Melbourne, FL, 32901, USA.
authors.forename: Courtney R
authors.initials: CR
authors.lastname: Shadik
authors.affiliation: Palaeoecology & Landscape Ecology, Institute for Biodiversity and Ecosystem Dynamics, University of Amsterdam, Science Park 904, 1098 XH, Amsterdam, The Netherlands.
authors.forename: Crystal N H
authors.initials: CNH
authors.lastname: McMichael
mesh_terms: D000383:Agriculture; D001938:Brazil; D057231:Climate Change; D017753:Ecosystem; D059000:El Nino-Southern Oscillation; D005580:Fossils; D019015:Geologic Sediments; D006801:Humans; D010944:Plants
keywords: Amazonia; El Niño-Southern Oscillation; erosion; fire; human disturbance; maize cultivation; sediment analysis