a. Polynesia: The great stone statues of Easter Island are familiar to most of us, but we know very little about this society, which collapsed sometime after 1500 A.D. Deforestation of the island, which had been covered with palms and other trees, was complete by this time and all forest species had become extinct. The island is now barren and treeless. Deforestation led to soil erosion, and, therefore, poor agricultural capacity, and the lack of trees also meant that no boats could be built for fishing. In other regions of Polynesia, forest destruction degraded land so that it became unproductive. This has occurred in New Zealand, Hawaii, the Cook and Society Islands, and elsewhere (Diamond, 1986).

b. Mexico: Mexico is famous for the ruins of its splendid civilizations, but is less well known as the point of origin of agriculture in the New World. Pollen of presumably cultivated maize (Zea) has been found in lowland tropical areas (later the home of the Olmec civilization) and is associated with clearings (indicated by charcoal deposits and grass pollens). Such pollens have been dated to 5100 B.C. Pollen from about 5000 B.C. appears to be from domesticated plants. Other species, such as manioc, sunflowers, and cotton, were apparently domesticated at a later time (Pope, et al., 2001). New World agriculture may have begun within its tropical forests.

For many years, people have burned forests to provide land for agriculture. This makes them more open and alters their species composition to favor species tolerant of fire or species which are able to reproduce quickly under the conditions existing after burning. Because of human activities, grasslands and cultivated fields replaced forests in many areas. Agricultural methods varied over the centuries. Sometimes forests were stripped, probably by slash-and-burn agriculture; at other times practices were more benign (agroforestry, terracing and raised-field methods). During the tenure of the Maya, there were several episodes of rapid population decline, at least partially attributable to deforestation. Around 800 A.D. the classical Mayan civilization collapsed, and population levels decreased substantially. Around 1250, the population again began to increase, and agriculture and the demand for fuel wood and housing intensified. At the same time, soil erosion increased as the inevitable consequence of deforestation, particularly on hillsides. Erosion reached enormous levels (as much as 85 tons of soil per acre annually). By the time the Spanish arrived, the Mayan civilization had already been weakened, at least partially because of environmental factors, and fell easily to the conquistadors (Abrams, 1996; Stevens, 1993).

c. South America: Some anthropologists believe that the flooded forest (varzea) regions of the Amazon basin were the sites of relatively large societies of indigenous peoples. Recently the remains of what might have been transportation canals, agricultural fields, mounds and other constructions have been found in the Beni region (now savanna) of Bolivia, and in Colombian savannas bordering the Caribbean, as well as smaller areas in Ecuador, Peru, Guyana, Surinam, Venezuela, and Central America (Mann, 2000; Bray, 2000). This has led some people to believe that there were dense populations and elaborate cultures in these regions hundreds of years ago, but that they were abandoned between 300 and 600 years ago. Thus, the interspersion of savanna and tropical forest now present would have been at least in part anthropogenic. The existence in the upper Xingu River region of southwestern Brazil of a quite sophisticated and extensive network of villages linked by roads has been much touted (Heckenberger, et al., 2003, 2008; Heckenberger, 2009). The remains of walled towns and roads, the presence of “terra preta” (earth enriched by the charring of surface vegetation), concentrated patches of useful plants, remains of fish ponds, and mysterious earthworks (C. Mann, 2008) give evidence of a considerable population in the Amazon during the centuries prior to the arrival of Europeans. If true, then these urban entities were able to surmount the poor soils and difficult conditions of the forest to supply themselves with sufficient food and trade items, and in doing so, transform the composition of the forest and improved its productivity. The argument is that only after humans had made the area favorable for forests – by mulching, enriching the soil, planting edible crops, depositing wastes – could the current forest environment have arisen. If this hypothesis were validated, it could have important consequences for our future treatment of the Amazon basin. It has led to the argument that there is no necessary incompatibility between human use and biodiversity in the tropics, even that human actions have increased biodiversity. Others believe that the fragile ecology of the region and its nutrient-poor, acidic soils could not have supported extensive agriculture or large populations, and that the heavy rains and flooding which occur in this area could account for many of the “artefacts,” such as large mounds (for example, Meggars, 2003). The contemporary cultures of indigenous peoples, according to this view, represent the best accommodation to the environmental limits of Amazonia. For overviews of this topic, see Stokstad, 2003; Pearce, 2007; Willis, et al., 2004)

d. Central America: At La Selva in Costa Rica, remnants of prehistoric maize cultivation have been found – archeological structures, ceramics and lithic objects, which date from approximately 1000 B.C. – 500 A.D. Charcoal, which indicates burning, has also been found in the soils of this forest, and swamp sediments contain maize pollen associated with charcoal which is approximately 700 years old. In Panama, five to-seven thousand-year-old starch grains of manioc, yams, maize and arrowroot have been found on milling stones (Piperno, et al., 2000). Maize pollen grains dating from the ninth to perhaps the seventeenth century have been located near La Selva, and fluctuations in pollen levels there may indicate human vegetation disturbances. Maize pollen deposits are underlain by charcoal deposits which may indicate agricultural burning prior to maize cultivation (Kennedy and Horn, 2008).

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