Environmental Factors

OVERVIEW:
Aztec Ruins National Monument encompasses 320 acres in northwestern New Mexico and straddles the boundary of the City of Aztec. The monument was established in 1923 for its significant physical remains of Ancestral Puebloan culture and was designated a World Heritage Site in 1987 because of its status as a Chacoan outlier.

Ancestral Puebloans related to those from the Chaco region farther south built an extensive community at this site beginning in the late 1000s A.D. Over the course of two centuries, the people built several multi-story structures called "great houses," small residential pueblos, tri-wall kivas, great kivas, road segments, middens, and earthworks. The West Ruin, the remains of the largest structure that they built and which has since been partially excavated, had at least 450 interconnected rooms built around an open plaza. Several rooms contain the original wood used to build the roof. After living in the area about 200 years, the people left at about 1300 A.D.

General Setting and Resources:
Aztec Ruins is found in the Animas Valley south of the La Plata Mountains of southwestern Colorado. The Animas River forms the eastern border of the monument.

NATURAL RESOURCES:
Biotic communities at Aztec Ruins belong to the Colorado Plateau Semi-Desert Province (Bailey et al. 1994).

Vegetation and Flora:
Located along the Animas River, the borders of Aztec Ruins encompass 11 vegetation types including riparian, pinon-juniper woodlands, and grasslands. Nearly 300 plant species have been documented at the monument. Many of the plant species are indicative of the Sonoran Floristic province such as big sagebrush (Artemisia tridentata), fourwing saltbush (Atriplex canescens), rabbitbrush (Chrysothamnus spp.), and pinon pine (Pinus edulis).

Fauna:
Aztec Ruins supports at least 70 bird species, and one is a State of New Mexico species of concern. There are 28 documented mammal species, including seven species of bats. Two bat species are federally listed as species of concern. There are three amphibian species and ten reptile species.

Water:
Few natural water resources exist at Aztec Ruins. The primary water is the perennial Animas River that runs for 1.7km (1.1 miles) along the monument's east boundary.

Air:
Aztec Ruins is listed as a Class 2 park under the Clean Air Act.

Geologic and Paleontological:
The Aztec Ruins area is underlain by sandstone of the Nacimiento Formation, which is typically overlain by a thin sandy to sandy loam residuum and gravels and cobbles deposited by Pleistocene melt waters.

Significant Resources:
High Biotic Diversity. A unique characteristic of Aztec Ruins is the diversity of habitats and associated flora and fauna within a small area.

MANAGEMENT ISSUES:

Noxious and Exotic Species:
An important management issue is the presence of noxious and exotic plant species that threaten the grassland and riparian habitats. Among the noxious weeds are bull thistle (Cirsium vulgare), whitetop (Cardaria draba), and Russian knapweed (Acroptilon repens L.). Among the more prevalent exotic weeds are cheatgrass (Bromus tectorum), Russian olive (Elaeagnus angustifolia) and saltcedar (Tamarisk spp.). Park roads, trails, landscaped areas, work sites, and an irrigation ditch are functioning as paths for and sources of exotic plant species. Feral animals including dogs, cats and domestic rabbits are found at the monument and are surviving by depredating native species.

Adjacent Land Management:
Urban and mineral development at the borders of the monument have the potential to impact natural resources. A mobile home park and a housing development border the monument on the south. Scattered developments in other directions include natural gas and oil wells and associated pipelines, and the potential for additional housing development. As the City of Aztec expands, housing and other development may eventually surround the monument.

Conflicting Cultural and Natural Resource Management:
Some plant and animal species adversely impact the cultural resources, resulting in conflicting needs for management of the natural and cultural resources. For example, the roots of grasses and other plants growing on or near the ruin walls break down the integrity of the wall structure. Rodents such as rock squirrels can destabilize ruin walls by creating tunnels through original cultural deposits.

Additional Concerns:
Other management issues in the monument include:
1.) Three active gas wells and the potential for additional gas wells that may impact cultural and natural resources.
2.) Water management
3.) Potential poaching
4.) Natural or human-caused fires.



LITERATURE CITED:
Bailey, R.G., Avers, P.E., King, T., McNab, W.H., eds. 1994. Ecoregions and subregions of
the United States (map). Washington, DC: USDA Forest Service. 1:7,500,000. With
supplementary table of map unit descriptions, compiled and edited by W.H. McNab and
R.G. Bailey.