|dc.description.abstract||The resilience and adaptation of past societies to climate change remain
unclear, especially in the tropical cloud-forests of the Andes and the aseasonal
forests of lowland western Amazonia. Long thought to have been too humid for
significant human settlement, a new image of cloud-forests is emerging in which
they supported human settlements for millennia. Anthropogenic disturbance, such
as forest clearance, fire activity, and land-use has been suggested to have
intensified during times of drier climates. Even so, the mid-elevational Andes and
western Amazonia probably supported smaller pre-Columbian populations than
settings with a distinct dry season. Uncertainties persist, however, regarding the
spatial and temporal extent of pre-Columbian occupation in western Amazonia.
Prior paleoecological studies have reported human disturbance in this region as
temporally discontinuous, with localized disturbance strongly influenced by
distance from rivers, lakes, or seasonal flood-plain/savanna settings. The trajectory of Amazonian population growth is often portrayed to be exponential in the late
Holocene, leading to the expectation that peak occupation and disturbance were
interrupted by European colonization. Some recent studies from Amazonia point to
peaks of land clearance occurring in the period 1150–950 cal. yr BP rather than
around 450 cal. yr BP, perhaps complicating the simple narrative of steady
population growth prior to collapse after European contact.
Here, I derive paleoecological data from a mid-elevation lake, Lake
Condores, in the Peruvian cloud-forest and from two lakes in lowland Amazonia,
. I use high-resolution pollen, phytolith, charcoal,
sediment chemistry, and diatom data to provide detailed reconstructions of past
land-use and connections to climate. By investigating the anthropogenic impacts of
these settings over the past 2100–2500 years, I ask the key questions: Were times
of drier climate characterized by more severe human disturbance? Did human
manipulation of the lake basins peak at the time of European arrival?
Lake Condores, Peru, was characterized by forest clearance, burning, and
maize cultivation from the onset of the record ca. 2085 cal. yr BP until ca. 850 cal.
yr BP, where increased times of land-use were associated with profound droughts.
Forest regrowth and reduced maize cultivation reshaped the valley after 850 cal. yr
BP, shortly preceding the start of burial activity in adjacent cliff tombs about 700
cal. yr BP amid a long-term shift to wetter conditions. In Ecuador, Lake Ayauchi
provided a 2460-year long history of continuous maize cultivation until 550 cal. yr
BP where fire was actively used as a tool for land clearance and forest suppression. Lake Kumpaka
, Ecuador, was the least impacted of the three sites and provided a
2460-year history of discontinuous maize cultivation. Sparse evidence of fire usage
suggested a preference for slash-and-mulch rather than slash-and-burn to clear
forest. At Kumpaka
, maize cultivation ceased ca. 750 cal. yr BP, long before
European contact. Increased land-use at Ayauchi
periods of drier conditions whereas wetter periods were characterized by
abandonment or reduced land-use.
Neither of the three sites showed indications of a steady population growth
interrupted by European arrival; rather, land-use appeared to peak before 650 cal.
yr BP. Old-growth forest elements remained abundant (>40%), as intensified
periods of land-use and forest clearance alternated with times of less intense landuse or abandonment. Overall, I find evidence of people exploiting these wet
western Amazonian settings, opportunistically expanding into previously forested
areas during dry events, but abandoning marginal areas or changing land-use as
conditions became too wet. These data support both the importance of the
environment in shaping human actions, and also the capacity for humans to
prioritize their actions and adapt to new conditions.||en_US