Abstract

Central Chile (28 ◦-35 ◦ S) is a biodiversity hotspot currently under extreme pressure from agriculture, mining activities and urban development. Future climate change scenarios will bring additional impacts to the region as the subtropics become drier. Here, we present an 11,000 yr BP rodent midden (feces, seeds, insects and bones gathered by rodents, encapsulated in a urine matrix) record from two central Chilean localities that affords a unique historical perspective for the region. Forty one AMS dated Abrocoma bennetti middens were collected at two different sites, a higher altitude rocky site with desert scrub that exhibited a relatively small degree of alteration (Cuesta El Espino, CEE ˜1200m) and a heavily altered site with ”espinal” vegetation (Cerro Blanco, CBL ˜600m). Our combined vegetation analyses (cuticles, pollen and plant macrofossils) show major changes in vegetation composition and community structure. The 11,000 yr BP midden from CEE reveals low taxa richness (mostly grasses) and a cold, steppe-like climate. Richness increased at ˜3500 yr BP including grasses and shrubs with a major turnover at ˜2500 yr BP. Middens from ˜600 cal yr BP to the present at CEE are relatively impoverished in comparison. Variations in taxa richness at CBL indicate aridity at ˜1150 yr BP followed by wetter conditions at ˜700 cal yr BP. Richness dropped by ˜400 cal yr BP, primarily due to a loss of shrub taxa. Modern CBL middens are comparatively more diverse and contain many introduced taxa, especially grasses. Overall, the contrasting trends in richness between these two site pointed to different selective pressures over the last 600 yrs. Decreased richness at CEE could be indicative of increased grazing and other human activities in the area whereas the introduction of Acacia caven and other species at CBL over the last 400 yrs could be due to increased cattle farming.