Historical Antecedents
The awareness of man’s impact on the environment is not a new concept, nor a new scientific development. In 1868 George P. Marsh published The Earth as Modified by Human Action with the stated goal of addressing the character and, approximately, the extent of the changes produced by human action in
The physical conditions of the globe we inhabit____’’
He drew from Classical, Medieval, and historic sources to illustrate what would be described today as ‘quantified geospatial’ evidence and assessments of man’s impacts to the landscape. Marsh suggested major landscape and climate impacts based on records of nineteenth-century coastal drainage and land reclamation projects in coastal marsh and wetland areas (100 000-400 000 acres) in England, Holland, Hungary, and California. He also made the observation that the chronological analysis of official climate records, before and after draining, documented measurable fluctuations of between a tenth and a third of a degree, in temperature. What has changed, and what is illustrated by the following case studies of anthropogenic (man-made impacts), is the time-depth and geographic diversity of these impacts. The following cases illustrate the extent and magnitude of prehistoric alternations to the landscapes of Mexico, the Andes, and Lowland South America. They also illustrate the importance of modern high-resolution palaeoenvironmental sequences, new dating techniques, the importance of aerial photography and high-altitude remote sensing for the accurate measurement and documentation of these changes.
A wide body of archaeological and ethnobotani-cal evidence indicates that in the New World (and presumably elsewhere) much of the environment and landscape had been heavily altered and manipulated long before European settlement and impacts. In addition to evidence of large pre-Columbian populations and dense settlement patterns in concentrated areas of Mexico, the Andes, and the Lowlands of South America, the archaeological focus on landscape and wide-area studies are documenting massive earth-moving efforts, beyond those of mound and temple construction that altered topography and drainage patterns throughout wide regions of the Americas. As the following cases and recent compilations of long-term and wide-area multidisciplinary archaeological investigations document, these pre-contact, man-made alterations of the landscape were both broad in scope and ecologically significant.
In addition to the following specific examples, a number of general changes took place independently of localized cultural and environmental conditions. These general impacts included an increase in the number and range of domesticated plants, expansion in the distribution of vermin and savaging species that lived symbiotically as by-products of human activities, a reduction in nonessential animal and plant species, and a general reduction in former distribution and habitats of animals of prey. In addition to these general cross-cultural impacts, and without belaboring the point, archaeologists (especially those working in the Americas) have begun to compile repeated cases of significant regional impacts and alterations to the environment by indigenous peoples, long before European contact. Recent archaeological treatments have revealed examples of well-documented prehistoric man-made impacts to ancient habitats in Mexico, the Andes of Peru and Bolivia, and in the lowlands of the Amazon basin.
Middle America
Comparative studies by Charles Spencer between dry uplands of Mexico and the tropical savannas of Venezuela, have documented the construction of massive water-control systems that in many cases rival the productivity and environmental conservation capabilities of modern intensive agricultural systems. One example underscores the size and capacity of a huge prehistoric dam system in the Tehuaca Valley of Mexico. Built over several centuries, the 400-meter-long (c. 1200-foot-long) dam impounded a volume of 2.6 million cubic meters. This reserve of water was sufficient to irrigate land to support 1000 people, with an annual surplus. Although abandoned in AD 250, the author suggested that its topographic displacement surpassed those of modern efforts. Similarly, in Oaxaca, some 20 miles to the south, several hundred inhabitants built aqueducts and canals that efficiently irrigated the majority of the valley.
In contrast, contemporary water-control systems generally irrigate only parts of the same area for agriculture, and leave major sectors dry and unusable.
Finally, Spencer listed an extensive prehistoric system in the damp tropical plains of the Barinas region of Venezuela that drained and regulated fluctuating water levels throughout the year. Extensive networks of ditches and channels siphoned excess flood waters in the wet season and brought water to irrigate the same areas in the dry season. This seasonally adjustable, prehistoric water-control technology raised production to two crops per year, and appears to have supported populations some 20 times larger than todays.
Andean South America
The Andean regions of highland Peru and Bolivia also featured massive landscape alterations and impacts to the precontact environment. Recent work in the highlands of the Lake Titicaca Basin, such as that of Clark Erickson, have reevaluated the economic and settlement patterns of the Pre-Inca Tiahuanaco cultures living around the lake between c. AD 800 and 1200. These also underscored the extent of anthropic, or man-made, alterations to the environment, clearly also long before European contact. Based on surface survey and the ability to measure landscape alterations with air photos, Erickson calculated that the Lake Titicaca peoples had built over 500 000 ha (123 500 000 acres) of terracing on the surrounding foothills.
In the lower portions of the basin, extensive areas of perhaps as much as 256 ha (632 acres) had been transformed for intensive agriculture by the construction of sunken gardens or q’ochas. These plots provided static irrigation from groundwater for fields of potatoes, quinoa (Andean grain related to Amaranth), and feed for domesticated animals. Extensive canals irrigated fields and pastures in the dry seasons, apparently as early as 1800-2000 BC. Based on modern aerial imagery and remote sensing, it now appears that the entire landscape of the basin was managed and reconstructed - with little remaining to identify as natural or ‘pristine’.
Lowland South America
Perhaps the most striking new insights and divergences from old assumptions pertain to the prehistoric ecology and environmental history of the Amazon lowlands of South America. Twenty years of diligent multidisciplinary archaeological, ethnobotanical, and chrono-metric work by Anna Roosevelt is producing a body of new evidence that debunks nearly a century of misconceptions concerning man-landscape interactions in the Amazon basin. Long held assumptions are beginning to fall by the wayside in the face of this new, multidisciplinary evidence. These include (1) the notion that the Amazon was a pristine habitat, only recently impacted by modern deforestation; (2) the idea that the indigenous inhabitants lived in harmony with the lowland environment; and (3) the belief that early farmers could not subsist in the tropical rain forest.
Work at three large prehistoric settlement areas in the delta flood plain, near the Amazon’s outlet into the Atlantic, in the Tapajos confluence region of Monte Alegre, have revealed well-dated stratigraphic sequences, a host of well-preserved botanical and food plant remains. and clear evidence that these inhabitants were not living in small scattered settlements, but instead in large raised platform mounds above the flood plain. Roosevelt surmised that these centers covered core settlement areas of 4 km2, each with population levels of 10 000 people, and that they developed long before European contact. These early Monte Alegre inhabitants practiced shifting ‘slash and burn’ agriculture that resulted in cleared regions around their settlements. The dense populations and clearing practices also appear to have created what Dr. Roosevelt suggested were degraded landscapes of localized treeless savannas, distinguished only by dense secondary stands of palms or other single-type stands of trees. In addition to these patterns of localized forest clearing, Roosevelt also identified what appear to be raised fields distinguished by layers of dark fertilized soils from the waste and domestic by-products of the local residents. The new sequence of dated pollen cores, archaeological plant remains, and the isotopic analysis of human remains suggest that the appearance of the dry interior open savannahs was not a ‘natural’ event with ancient roots, but instead the relatively recent prehistoric by-products of ‘anthropogenic,’ or man-made, land clearing. What one sees today is not the result of only modern deforestation and land clearing, but also the ancient products of prehistoric agricultural practices and localized alterations to the landscape by peoples living in relatively large and dense centers of population. This thesis recently gained support from an innovative nonarchaeological source.
Recent work by a team of geochemists from the University of South Carolina has used deep-sea core samples from the Amazon discharge fan to argue that the savannahs were not ancient, but modern and that the Amazon basin had been covered by dense, high-canopy forests little changed for 70 000 years. The researchers used dated sediment samples to measure the relative ratios of carbon-13 to carbon-12, based on the fact that samples eroded from arid grasslands are significantly different from that of sediments from forested regions. The Amazon samples show consistently ‘high’ negative values indicative of runoff from forested areas versus open savannahs.
The new core evidence also counters a widely held theory, first promulgated by an ornithologist in 1969, that explained the biodiversity of the Amazonian bird populations as the result of being isolated by stands of primeval forrest, each separated by vast expanses of open interior savannah. Known as the Refuge (or Refugio) Hypothesis, this model presumed that the savannahs were ancient and served to create ‘refuges’ of isolated forest stands that fostered species distinctions within and between animal and bird populations. The theory was also adopted by some lowland archaeologists to explain settlement patterns and cultural differences among modern indigenous peoples today.
These new archaeological and deep-sea core data are the first concrete and testable evidence that refutes the popular Refuge Theory. They also suggest that clearing encountered by European colonists was, as Dr. Roosevelt suggests, the result of actions by prehistoric peoples, not natural forces.
Historic Old and New World Environmental Impacts
As Marsh argued over a century ago, historical archaeology and a focus on environmental indices (pollen, seeds) is providing comparable material evidence of environmental trauma in the medieval and colonial periods in the Americas and Europe as well. In England, the analysis of pollen and metal trace-element fractions from three cores taken from peat bogs in the Northern Pennines have provided new evidence of long-term environmental impacts from the regional mining industry. The identification of shifting tree and plant communities from dated pollen cores indicate that small short-term forest clearings had begun in the Neolithic and Bronze Ages. These early impacts were followed by substantial wide-scale clearing and deforestation in the subsequent Iron Age and Romano-British Periods. Landscape changes from local mining, however, were clearly evident by the Medieval Period. However, the measurement of lead and zinc levels in pollen core samples correlated with a permanent drop off of tree pollen, together with an increase in lead trace-element readings beginning in the eleventh century AD. It is noteworthy that a modern travel description on the Web treats the area as pristine, with idyllic terms as ‘‘one of England’s most special places - a peaceful, unspoilt
Landscape____’’ The archaeological evidence and the
Archical record instead point to a long history of environmental degradation.
Comparable indicators of man-made environmental trauma to the colonial United States environment have also been documented for later seventeenth-eighteenth and eighteenth-century sites as well. Excavations by the author along the original colonial shoreline at Pearl Street and Broadway in Lower Manhattan led to the discovery of well-preserved seventeenth-century remains of the first warehouse of the Dutch West India Company, as well as the house foundations and artifacts of some of its principal residents and officials from the 1650s. Well-preserved and tightly dated plant remains excavated from privies and cisterns were found buried and preserved 8-12 feet below the modern grade of Lower Manhattan. Instead of varieties suggestive of well-tended rear yard gardens, nurtured soils, and neatly kept yards, the earliest 1650s plants from the Dutch West India block showed little evidence of ornamentals. When the colonial seeds were compared to ornately illustrated contemporary sixteenth - and seventeenth-century European Herbals (e. g., Leonart’s Fuchs’ (German) The New Herbal of 1543, or Culpeper’s (English) The Complete Herbal of 1649), they proved to be both predominantly of European origin and used as ‘medicines, dyes, and industrial products’ (Figure 2).
Instead of indicating well-tended household gardens, the majority of the mid-seventeenth-century plants were adapted to acidic, heavily compacted, and disturbed soils, or waste ground similar to what one might find along heavily traveled dirt roads, open yards, or paths today. With the exception of the widely dispersed peach being present from the 1650s onward, the archaeological evidence for ethnobotanical indicators of potentially landscaped or intentionally planted specimens did not become evident until the first quarter of the eighteenth century. This unique archaeological evidence implies that Colonial Dutch New Amsterdam urban landscape had been traumatized and disturbed by the introduction of foreign, often genetically dominant, invasive ‘weeds’ as early as 1650 (purslane, bed-straw, Pigweed (amaranth), goosefoot/lambs quarter, copperleaf, carpetweed, carpetweed and indigenous berries, and squash and tobacco seeds).
It also suggests that archaeologists, historians, and ecologists must proceed with caution in accepting accounts by later, eighteenth - and nineteenth-century ‘naturalists’ of supposedly pristine environmental conditions in colonial America and elsewhere.
World History
