Abstract
Although the Neotropics are recognized as a region rich in biological diversity, the origin, evolution, and maintenance of this phenomenon continues to be debated. Historical ecologists and landscape archaeologists point out that the Neotropics have a long, complex human history that may have been a key factor in the creation, shaping, and management of present day biodiversity. The construction of monumental earthworks referred to as ring ditches of the Bolivian Amazon and surrounding regions in late prehistory had considerable impact on the fauna, flora, soils, and topography of forest islands. Patterned landscape features, historical documents, energetics, and historical ecology are used to understand the transformation of forest islands into anthropogenic built environments.
Highlights
In a recent article, Leigh and colleagues ask, “Why do some tropical forests have so many species of trees?” [1]
Despite early historical accounts by eyewitnesses describing still flourishing complex societies in numerous locations throughout the Amazon and adjacent Neotropics [22,23,24], the indigenous societies ravaged by conquest, epidemics, exploitation, wars, and colonial policies encountered by later historians, ethnographers, archaeologists, and travelers were interpreted as representative of their ancestors
Forest islands are common features of the Bolivian Amazon formed by a combination of geomorphological processes and anthropogenic activities including earthmoving, settlement, and agriculture [38,39]
Summary
Leigh and colleagues ask, “Why do some tropical forests have so many species of trees?” [1]. Increased activity of specialized pests and pathogens in less seasonal climates appears to be a primary cause of the latitudinal gradient in tree diversity” [3] In reaching their conclusions, the authors ignore the long and complex human history of tropical forest environments extending back into the late Pleistocene. In contrast to niche opportunity provided by nature proposed by Leigh and colleagues, historical ecologists favor human agency and intentionality, since human activities in the Amazon can promote the rapid distribution and success of isolated rare species in the competitive tree environment of a typical Amazonian forest. The proposed functions of ring ditches include defense, settlements, elite residences, land and resource markers, animal traps, cemeteries, water management features, and/or public ceremonial spaces [18] These structures, often called “geoglyphs” because of their symmetry and complex geometric designs, are monumental in scale.
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