El Niño Southern Oscillation (ENSO) is a periodic disruption of coupled oceanic-atmospheric conditions in the tropical Pacific, which changes global precipitation regimes. One area strongly affected by positive (el Niño) phases is the Pacific Coast of South America. The specific effects of ENSO on Andean ecological communities have received little attention, however. We examine vegetation gross primary productivity (GPP) on Peru's north coast arid-lands during a recent (2016–2017) el Niño, using a time series of Sentinel 2 imagery. By comparing GPP time-series in three agricultural subregions and three endemic desert vegetation communities, we demonstrate that levels of primary productivity in desert regions during ENSO-positive phases meet or exceed thresholds of adjacent agricultural lands. These results, the first that quantify and spatialize changing GPP between ENSO-neutral and ENSO-positive phases for South American arid-land biomes, both outline the scale and distribution of the el Niño effects on terrestrial ecosystems and highlight the resulting opportunities for human inhabitants. The dramatic changes to endemic vegetation on the normally hyperarid coastal desert of Peru revealed by reconstructed GPP suggest that periodic el Niño precipitation plays a critical role in arid land ecodynamics by enhancing establishment, green growth, and seedbank development. These findings improve our understanding of ENSO's net effects and highlight the roles of abrupt climate events in the arid land ecology of NW South America.

South American arid lands present unique constellations of climatic risk to their human inhabitants, due to volatile events that can create markedly different hydroclimate conditions over interannual–centennial scales. However, a main driver of such volatility – the El Niño/Southern Oscillation (ENSO) – occurs with semiregular periodicity. Paleoclimatic and archeological evidence indicate not only that the strength and periodicity of ENSO patterns have changed over the late-Holocene, but their impacts were likely recognized, adapted to, and perhaps capitalized upon by agriculturalists employing adaptive risk strategies. We examine relationships over the last 1.3 kyr between ENSO periodicity, ecological transitions, and archeological settlement in Peru’s Chicama Valley through a coupled paleohydroclimate and agroecology model. We reconstruct periods when ENSO-like conditions dominated past hydroclimates and present a quantitative, spatially-explicit analysis of ecological productivity during modern ENSO-positive hydroclimate conditions. We show that archeological settlement patterns are sensitive to these transformations and reflect efforts to capitalize on expanded agroecological niches. Such expanded niches potentially offset the adverse impacts and risks associated with abrupt ENSO climate events. These results suggest archeological communities were aware of ENSO risk and managed productive strategies accordingly, highlighting the importance of a risk calculus that considers the net ecological effects of climate events.

Severe aridity during the mid-Holocene, ca. 8.0–4.0 kyr BP, led to extreme ecological stress in the tropical Andes. Here, we report paleolimnological and archeological data from Lake Suches in southern Peru (70° 24’ 12” W, 16° 55’ 35” S) spanning 13.6–4.4 kyr BP. Integrated paleoclimate and archeological data reveal that moisture was locally available and the basin served as an ecological refugium throughout the mid-Holocene. Mid-Holocene aridity was established no later than 7.2 kyr BP, with maximum aridity ca. 5.5–4.8 kyr BP. However, water levels in Lake Suches were sustained throughout peak middle-Holocene aridity, even as other systems desiccated. Isotopic enrichment of water in Lake Suches (δ 18 O lake ) and extensive wetlands (δ 18 O bofedal ) surrounding the lake indicate prolonged residence time. These reservoirs, combined with elevation-linked hydrographic factors, mitigated mid-Holocene net decreases in atmospheric moisture. Archeological data from Suches indicate successive population increases beginning ca. 11.0–9.8 kyr BP as drier but more stable early Holocene conditions were established regionally. Population maxima in Suches during the mid-Holocene/mid-Archaic period ca. 9.0–7.0 kyr BP coincide with peak aridity in the Titicaca and Atacama systems, as well as documented archeological hiatuses in these regions. Population decreases coincide with peak aridity recorded in Lake Suches ca. 6.0–5.0 kyr BP, but the basin was never fully abandoned. Evidence for refugial microenvironments is key to understanding the persistence of human populations and other endemic Andean flora and fauna during the highly adverse climates of the middle-Holocene. We outline several mechanisms which likely explain the formation of refugia linked to bofedales and hydrographic characteristics of Suches. Understanding refugial dynamics will be key to understanding the effects of past climatic change, as well as addressing current warming and decreased precipitation trends in the tropical Andes.

Mobility and migration are critical processes that influence cultural and socio-economic development, and have lasting effects on demographic and ecological arrangements. However, these are ephemeral behaviors which are difficult to reconstruct archaeologically. Here, we employ geospatial approaches to reconstruct mobility corridors likely used by Tiwanaku migrants during the Andean Middle Horizon, ca. AD 500–1000. Prehispanic mobility relied on caravans of Andean camelids. We reconstruct probable mobility corridors while comparing cost- and permeability-based modeling approaches. We further use remote sensing to examine how modern ecological dynamics relate to modeled mobility corridors. Imagery from the Landsat family of multispectral satellites is used to document the response of green vegetation to seasonal and interannual moisture variability. We find that there is a statistically significant increase in the amount of perennially-green vegetation land cover along the corridor linking Tiwanaku with its principal colonial enclaves on the Pacific coast. Such perennially-green vegetation provides a critical resource for prehispanic caravans. The data indicate a relationship between high volumes of migration and enhanced vegetation. We explore whether Tiwanaku migration routes were established in part on the basis of this resource, or if modern land cover reflects an anthropogenic legacy.

Archaeological land use results in the modification of natural environments according to cultural templates and strategies. Deeply entrenched environmental legacies can result from such “niche construction,” influencing subsequent cultures and continuing to resonate in modern ecological function. These changes can be better understood through archaeological remote sensing.

We describe diachronic evidence of moisture reduction and its consequences for coastal irrigation, agriculture, and settlement at Quebrada Tacahuay, a large drainage south of the Osmore River in far southern Peru. These observations are the first for a drainage of this size and for one with occupation spanning over 12,000 years for southern Peru. Following several millennia of occupation by coastal foragers, farming populations settled the lower elevations of the drainage. Our analysis indicates that agricultural production was well developed in the fourteenth century prior to a previously documented, catastrophic El Niño Southern Oscillation (ENSO) flood that took place sometime during the early-fourteenth century. Later in the fifteenth century the Inca conquest of the region and establishment of a coastal tambo and village was accompanied by agricultural expansion and the creation of new terraces. Subsequent Spanish colonization took place during the Little Ice Age and a period of increased coastal moisture. The historic and modern contraction of a large olive grove document the ongoing reduction in the coastal aquifer.

Aymara herders in the highland regions of southern Peru and Bolivia express highly ambivalent attitudes towards archaeological patrimony. In this post-colonial setting, they follow strong avoidance behaviours towards archaeological sites directly associated with gentiles - the mummified remains of prehistoric, pagan individuals. Conversely, certain archaeological features are incorporated into modern discourses. This selective embracing of archaeological landscapes inscribes socially relevant features within contemporary identities, while repudiating others. Aymara use perceived spatial and temporal distance, reinforced with linguistic and mytho-historic constructs, to map social difference onto archaeological landscapes. Perceived distance separates Aymara from undesirable gentiles, whose threatening characteristics are embedded in historic experience. They relegate these dangerous social others to the past and envelop them in notions of remoteness. Simultaneously, Aymara use perceived proximity with favourable sites to draw inclusive social and geographic boundaries around their communities and to establish strategic priority for themselves, often in the context of conflicts. These divergent responses are highly sensitive to economic aspirations, political environments and resource-rights disputes, indicating that instrumental motivations factor significantly in Aymara attitudes towards archaeological heritage. Such opposing interactions underscore the contingency of attitudes towards the archaeological past. Both, however, can be understood as part of a coherent worldview that uses space, time and distance to construct social landscapes.

Multispectral remote sensing is increasingly common in archaeology, but is largely oriented towards site-detection applications. A high-resolution approach using ASTER data to map environmental and geological resources in the vicinity of Cerro Baúl is outlined here. Spectral mapping evaluates several band ratio and relative band depth image transforms that target diagnostic reflectance/absorption features of earth materials. Available geological resources had a high degree of spatial heterogeneity, which conditioned household strategies for obtaining raw materials. However, some variability cannot be explained by the geological environment alone. Using Minimum Convex Polygons and Kernel Density home-territory estimates, I outline the spatial organization of resource networks that differed from household to household. Differences in household resource networks suggest that socio-economic factors conditioned the use of materials, including locally-available ones. These results demonstrate the utility of multispectral remote sensing to construct palaeoecological models on a scale congruent with archaeological questions.

This paper provides data and analysis from an intensive settlement survey in the southwestern Titicaca Basin. This research was designed to assess the nature of Tiwanaku (AD 600–1100) long-distance trade. The survey area was placed between the prehistoric urban capital of Tiwanaku and its primary colony in Moquegua, a valley located on the Pacific watershed approximately 325km away. The survey was specifically placed in an area where GIS analysis indicated a least-cost transit route between Tiwanaku and Moquegua. Field adjustments to the survey area were made based upon informant data about the historic location of caravan routes. The results of the survey indicate that there is a light but virtually continuous string of Tiwanaku occupation along the trails and roads in the area sampled between Tiwanaku and Moquegua. However, in contrast to the later Inca (AD 1450–1532) period pattern, Tiwanaku did not maintain way stations or build any kind of formal road system. The data indicate that Tiwanaku had indeed relied upon camelid caravans utilizing the least-cost pathways, but it did so in a more decentralized and informal way than the later Inca state.

A geophysical survey at the pyramid complex of Senwosret III at Dahshur sought to determine the suitability of magnetometry and electromagnetic induction (EMI, or conductivity) for mapping the area where several ancient boat-burials were found in the 1 890s. At least one boat reported at the time of excavation remains unaccounted for. Tests demonstrated that magnetometry does detect subsurface structures of stone, fired brick, and unfired brick under current site conditions. Data indicated areas of geological activity as well as unexcavated archaeological remains, though no definitive traces of boat burials. No excavation was undertaken but another survey season is planned.

In this paper we explore the use of high-platform remotely sensed data from Landsat ETM, SPOT IV HRV, Radarsat and ASTER satellites in combination with sedimentological data from previous geological coring research to understand the alluvial history of the Ambracian Gulf, Greece. Using sensor response to variable compositions and textures of discrete deposits, we are able to reconstruct the spatial extent of sedimentary lithosomes. Geological cores allow us to relate these deposits diachronically with absolute radiometric determinations, stratigraphical correlations and periods of coastal formation predicted by geomorphological research. Copyright © 2006 John Wiley & Sons, Ltd.

Long before they devised a written calendar, the Maya articulated their seasons by means of an "orientation calendar" that consisted of visual alignments involving their architecture. One specialized set of buildings, Group E at Uaxactun, Guatemala, in the Peten lowlands, has been regarded as the prototype of such a calendar. We present new data based on precise measurements made in the field at 12 Group E complexes and obtained for a number of additional sites from reliable maps where on-site astronomical fixes were acquired. Statistical analysis of the resulting 99 alignments supports the hypothesis that, at least at some stage of development, certain of these specialized complexes did indeed function astronomically. The earliest version of the orientation calendar seems to have developed in the Peten; it was focused on the solstices. A later orientation calendar seems to have functioned principally during the season leading up to the onset of rain and crop planting. It consisted of a division of the dry season into 20-day months prior to the first annual passage of the sun across the zenith (approximately May 10 in the Christian calendar). We argue that this later orientation calendar was derived from Teotihuacan during the Early Classic period (A.D. 278-593).