Two histories of environmental change and human disturbance in eastern lowland Amazonia

Two long palaeoecological records (pollen, diatoms, C-14, chemistry and charcoal) provide a detailed record of Holocene environmental conditions in the lowlands of the lower Amazon. Changes in the composition of the terra firme forest are evident but a forest cover is maintained throughout. Fluctuations in lake level and changes in seasonality are tracked in both sedimentary sequences. Rising early-Holocene sea levels and the consequent rise of local water tables probably caused the flooding of one of the sites. A stepped increase in precipitation is suggested with increases evident at 8800 yr BP, 7400 BP and between 6100 and 5800 yr BP. Increased storminess is suggested between similar to 7400 yr BP and similar to 6100 yr BP. Human disturbance is manifested in the palaeoecological records at one study site as early as 5500 yr BP (c. 6500 years ago), and an intensification, or onset, of agriculture is evident at c. 3350 yr BP. The terminating phase of the long record of disturbance is a period of forest regrowth that may correlate to the depopulation of Amazonia following European contact.