ABSTRACT
Changes in land-use practices have been a central element of human adaptation to Holocene climate change. Many practices that result in the short-term stabilization of socio-natural systems, however, have longer-term, unanticipated consequences that present cascading challenges for human subsistence strategies and opportunities for subsequent adaptations. Investigating complex sequences of interaction between climate change and human land-use in the past-rather than short-term causes and effects-is therefore essential for understanding processes of adaptation and change, but this approach has been stymied by a lack of suitably-scaled paleoecological data. Through a high-resolution paleoecological analysis, we provide a 7000-year history of changing climate and land management around Lake Acopia in the Andes of southern Peru. We identify evidence of the onset of pastoralism, maize cultivation, and possibly cultivation of quinoa and potatoes to form a complex agrarian landscape by c. 4300 years ago. Cumulative interactive climate-cultivation effects resulting in erosion ended abruptly c. 2300 years ago. After this time, reduced sedimentation rates are attributed to the construction and use of agricultural terraces within the catchment of the lake. These results provide new insights into the role of humans in the manufacture of Andean landscapes and the incremental, adaptive processes through which land-use practices take shape.
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.
