LATE-HOLOCENE ENVIRONMENTAL CHANGE OF THE MONTE VISTA NATIONAL WILDLIFE REFUGE, SOUTHERN COLORADO, USA

This study focuses on Late-Holocene environmental change on the Monte Vista National Wildlife Refuge (MVNWR) in the semi-arid San Luis Valley (SLV) of Southwest Colorado. The SLV is a high-elevation (2,300 m) region surrounded by 14,250 m peaks of the Sangre de Cristo Mountains to the east and the San Juan Mountains to the west. The paleowetlands reside on the distal edge of a bajada of coalescing alluvial fans at the foot of the San Juan Mountains and are fed by groundwater and the first-order Spring Creek. Multi-proxy evidence including pollen analysis, radiocarbon dating, soil and peat descriptions, isotopic analyses, and paleontological data on bones of mammoths, extinct bison, and dire wolves provide a rich record of environmental change, landscape change, and hydrological variability over the past 33,000 years. This project focuses on the past 550 years and a set of recently identified near-surface peat deposits that represent higher water tables than today. The MVNWR has been in a legal dispute; agriculturalists claim that the wetlands are here because of seepage from a the Monte Vista Canal (MVC) that was dug for agricultural purposes in 1892. This idea has been used to justify removal of water rights from the MVNWR. Our data suggest otherwise; three radiocarbon ages on paleowetland peat deposits of 512, 492, and 435 BP suggest that the wetlands were present before the MVC was dug in 1892. These data, therefore, are highly important in protecting valuable wetland ecosystems that support multitudes of species, one of which being the flagship Sandhill Cranes. Another interesting aspect of these dates is that our pollen analyses highlight the environment of these wetlands just before colonization. They also represent important data for the MVNWR to argue that the wetlands dried up because of increased groundwater use in the past few hundred years. By examining historical variations in water availability, policymakers and water resource managers can gain insights into the natural range of hydrological conditions in the region, aiding in the development of more sustainable and effective water management strategies in a time of changing climates.