A multi-proxy palaeoecological record of late-Holocene forest expansion in lowland Bolivia

Environmental impact of geometric earthwork construction in pre-Columbian Amazonia

“…This record of a savanna landscape changing to evergreen rainforest ∼2000 cal yr B.P. is consistent with paleoecological studies from other parts of southern Amazonia, which were dominated by savanna and seasonally dry tropical forest until ∼3000-2000 B.P., when humid evergreen rainforest began to expand southward (27)(28)(29). These records of expanding evergreen rainforest coincide with increasing lake levels at Lake Titicaca (38, 39) (an Andean site that receives most of its precipitation from lowland Amazonia), suggesting that rainforest expansion occurred as a result of increasing precipitation across southern Amazonia.…”

“…1A). Late Holocene climate-driven rainforest expansion has been documented in other parts of southern Amazonia (27)(28)(29), coinciding with rising lake levels in the tropical Andes (38,39), which demonstrates that the forest expansion at LO reflects a broad-scale vegetation response to increasing precipitation across the southern Amazon. However, the geographic scale of this biome shift in the context of large geometric earthwork construction has hitherto not been considered.…”

Hydrology and climatology at Laguna La Gaiba, lowland Bolivia: complex responses to climatic forcings over the last 25 000 years

“…Baker et al, 2001), although it may reflect differential sensitivity between tropical forest pollen and diatoms in response to drying. The strengthening of the SASM in the later Holocene has been widely reported as a response to insolation forcing, with southward expansion of the Amazon rainforest (Mayle et al 2000;Burbridge et al, 2004) and SDTF (Taylor et al, 2010) in more southerly locations and wetter conditions recorded by speleothems east and west of Amazonia (Wang et al, 2006;Mosblech et al, 2012). As Mosblech et al suggest this more uniform and predictable monsoon response to insolation may reflect the different boundary conditions of the Holocene compared with the full glacial period.…”

Review of past and recent fluvial dynamics in the Beni lowlands, NE Bolivia

“…In the SW Amazon Basin and the adjacent Andean uplands, this dry period was later widely corroborated by pollen and sedimentary evidence from lakes and attributed to a minimum in summer insolation at 10-15°S during the early to mid-Holocene Taylor et al 2010). In turn, an increase in insolation from the mid-Holocene on would have led to renewed and increased humidity, warmer summer temperatures and a strengthened South American Summer Monsoon (Taylor et al 2010). Thus, the transition to more humid conditions in the late Holocene may have caused increased discharge and/or sediment supply in the rivers, such as the Río Mamoré and the Río Beni, resulting in a reduction of the channel's capacity to accommodate the increased amount of water and sediments, and ultimately causing avulsions.…”

“…As for the Río Mamoré, Dumont (1996) has already stated that the first two Río Beni phases show much smaller traces than the subsequent ones, and has related them to a mid-Holocene dry period in the southern Beni basin during the period 7,000-5,000 14C yrs BP (Servant et al 1981). In the SW Amazon Basin and the adjacent Andean uplands, this dry period was later widely corroborated by pollen and sedimentary evidence from lakes and attributed to a minimum in summer insolation at 10-15°S during the early to mid-Holocene Taylor et al 2010). In turn, an increase in insolation from the mid-Holocene on would have led to renewed and increased humidity, warmer summer temperatures and a strengthened South American Summer Monsoon (Taylor et al 2010).…”