Científicos: propósitos para la práctica divulgativa

The climate over the past 3,000 years of the Late Holocene is better understood. The Late Holocene experienced a period of drought that occurred from ca. 2000 B.P. to 700 B.P. (Stine 1990, Larson, no date) known in Europe and much of North American as the Medieval Climatic Anomaly (MCA). The highest C14 content of marine shell occurred between 1900 B.P. to 1200 B.P. Ingram (1998) shows that the age of the West Berkeley (San Francisco Bay area) mound top is coeval with the long drought, coastal upwelling and low river inflow into San Francisco Bay. This period of the Holocene experienced significant climatic shifts, that may coincide with cultural shifts seen in the archaeological record (Jones and Schwitalla 2008). The MCA is characterized by a period of extreme drought. According to York this period has received a

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large amount of archaeological attention ―due to the apparent severity of the droughts and to its apparent coincidence with important cultural changes (York 2006:7). Raab and Larson (1997) indicate that the severe drought led to hiatuses in occupation of the coastal region of Southern California and may have led to increasing cultural complexity that is seen in the archaeological record.

Based on tree ring and pollen dating developed by Larson and Michaelson (1989) the period from 1450 B.P. to 950 B.P. displays a high degree of precipitation variability. Precipitation generally declines from 1450 B.P. to 1200 B.P. resulting in extreme drought conditions between 1200 B.P. to 1180 B.P. The drought was followed by 200 years (circa 1150 B.P. to AD 950) of the highest precipitation amounts for the entire 1,000 year period.

The Little Ice Age dating from 700 B.P. to 200 B.P. was the end of the prolonged period of drought resulting from the Medieval Climatic Anomaly. Feng and Epstein (1994) indicate rapid cooling at 350 B.P. with temperatures as cold as any during the entire Holocene. Michaelson and Haston (1998) indicate that tree ring data from the Pseudotsuga macrocarpa shows more frequent wet winters from 550 B.P. to 450. Although the Little Ice Age resulted in minimal changes to the vegetation (Minnich 2007) there was a worldwide significant and rapid change in the climate. Coupled with lower temperatures there was an increase in precipitation. ―For the late prehistoric and early historic occupants of the lower Santa Margarita River, this likely meant more frequent floods than are seen today‖ (York 2006:8). The increased flooding can be extrapolated to have occurred throughout the rivers of the region.

2.7.3 Natural Resources

Coastal southern California is one of the most biologically diverse regions in the continental United States INRMP 2007). The diversity of habitat types within the region is reflected in the rich diversity of natural resources on Camp Pendleton. Based on the climate information it seems that there was little change in the climate and vegetation from the late Middle Holocene through

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to the Late Holocene when the modern coastal vegetation emerged (Byrd 2003)., Of course, this does not account for the rising sea stands which would make what was Middle Holocene inland, the Late Holocene coast line. There are currently four major ecosystems on the Base: estuary, beach, riparian, and uplands (Camp Pendleton Integrated Natural Resources Management Plan [INRMP] 2007). These includes the Santa Margarita River Estuary and the coastal lagoons located at Cocklebur, French, Aliso, Las Flores, San Onofre, and San Mateo Creeks.

The coastal habitats can be significant to understanding the various physical landscapes and their relationship to archaeological remains. They provide a knowledge base to provide a point of comparison between what is seen today and what was present in the past. Archaeologists often during CRM surveys and site excavations do not look at a prehistoric landscape in terms of what would have been present when the archaeological site was occupied. This is driven by the types of projects as well as the perspective of the researcher. Linear projects such as power lines are usually narrow corridors that go from point A to point B and the project proponent wants only a document that provides compliance with laws, not necessarily a research undertaking. One such project was a powerline project on Camp Pendleton that came from off- base. One site was recorded in the corridor, but no attempt was made to place the site into a regional landscape (Cleland 2003). Another project on Camp Pendleton was the National Register evaluation of a prehistoric site in the Santa Margarita river Basin. The evaluation of significance focused on site specific questions and did not look at the site as to how it fits into the regional landscape (Collett 2001).

The estuary and beach habitats include the intertidal zone which is inundated on a regular basis by the ocean; the strand or beach, subject to wave action and deposition; foredunes subject to sand deposition, high winds, salt deposition; back dunes, stable or moving; and coastal bluffs/cliff faces toward the ocean subject to exposure by high winds and high salt deposition (Camp Pendleton INRMP 2007). The estuary and beach habitats would have been

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the site of shellfish collection by prehistoric people. The dunes habitat would often have been used for residential locations.

There are 3,966 hectares of floodplain on Camp Pendleton: of this amount riparian habitats cover about 3,318 hectares. The varieties of habitats in riparian ecosystems include riparian scrublands, riparian woodlands, fresh water marsh and open water/gravel. San Diego County upland areas are generally moisture deprived, so riparian vegetation can be easily discerned visually, from the surrounding more xeric vegetation. Riparian vegetation is dominated by winter-deciduous trees – willows, cottonwoods, alders, and sycamores in contrast to oak woodlands and coastal sage scrub (Camp Pendleton INRMP 2007). Riparian habitats provided significant resources for wood construction material, medicinal and food plants as well as habitat for various animal species. However, based on early Spanish records discussed in subsequent sections, it is likely that many of the large riparian areas on Camp Pendleton are an artifact of modern land management practices. The records point to prehistoric grasslands in areas such as Las Flores Creek (Bolton 1926); where today the vegetation is very dense riparian habitat.

Upland ecosystems on Camp Pendleton are made up of shrublands, vernal pools, grasslands and oak woodlands. San Diego County‘s weather is characterized by hot, dry summers and cool, rainy winter reminiscent of land around the Mediterranean Sea, central Chile, the Cape region of South Africa, and the coastal regions of southeast and southwest.