San Luis Hills

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There is an open scrubby meadow on top of Pinion Hills where we saw signs ofelk. From this vantage point, Blanca Peak, San Antonio Mountain and Ute Mountain -- sacred mountains of the First Peoples --mark the mid-distance. Solitude is found in being centered on the endless horizon.

Jean Smith, Denver

Wilderness Qualities
The San Luis Hills are a geologically unique landform of the southern San Luis Valley, rising over 1,000 feet above the valley floor. They are a remnant of the volcanic deposits that form the San Juan Mountains and underlay the depositional soils of the valley.

The area remained stable while the surrounding basin subsided along the faults of the Rio Grande Rift. The western fault forms the present day Rio Grande corridor and the area's eastern boundary. The San Luis Hills remain a physical anomaly within the San Luis Valley, still standing high after thousands of years of erosion have softened its features.

The area is dominated by rolling hills cut by twisting canyons, the longest of which is John James Canyon. Volcanic layers underlying the San Luis Hills may be seen in steep rock faces. Desert grasslands with sagebrush and prickly pear cactus characterize the area's slopes and mesas. Small stands of pinyon pine and juniper grow, mostly on the southern and eastern portions of the mesa top.

The unnamed summits provide a panorama of the river systems, landforms, and ecosystems of the valley. The Fairy Hills, Pinyon Hills, the Rio Grande, Sangre de Cristo Mountains, Great Sand Dunes, and the San Juan Mountains complete a sweeping 360
degree vista.

The San Luis Hills are ecologically unique and would provide scientific and ecological diversity to the National Wilderness Preservation System. The physical and climatic characteristics of the hills allow pinyon woodlands to reach beyond their typical elevation range of 4,000 to 9,000 feet. The pinyon-juniper woodland occurs on the highest slopes of the hills, at an elevation of 9,234 feet with some of the densest stands on the cooler east and north slopes. Since these pinyon-juniper woodlands are isolated from the montane forests of the surrounding mountains, climax stands occur where elsewhere they would gradually succeed to ponderosa pine and Douglas fir.

The San Luis Hills hold the only sizable representative of the fescue-mountain muhly prairie ecosystem that remains in a natural state in Colorado. They are also the only high desert biome dominated by desert shrub and grass species remaining under consideration for wilderness designation in the San Luis Valley. Its designation would add geographic diversity to the National Wilderness Preservation System.

Partly because of the uncommon vegetation communities and partly because of the presence of a rare plant species, Alete lithophila, BLM designated San Luis Hills as an Area of Critical Environmental Concern.

Wildlife species that inhabit the San Luis Hills include deer, antelope, various small mammal and rodent species, pinyon jays, and raptors. Water is a limiting factor for deer populations, as there are no perennial streams within the San Luis Hills, but the area nevertheless serves as critical winter range for 40-60 deer and is also home to approximately 150 pronghorn antelope. It is an important island of coniferous cover and winter range amid the agricultural lands of Conejos County.

The physical isolation and southern exposure of the San Luis Hills combine to provide ideal conditions for winter hiking and horseback riding. The diverse topography affords solitude, and scattered archeological sites, geologic features, and potential raptor sightings are of particular interest to visitors.

Resource Information
Although the San Luis Hills are located at the interface of two major geologic structures, a characteristic which has been known to produce localized ore deposits, investigations have provided no evidence of mineralization within the WSA, and there is thought to be
very limited potential for mineral exploration or development. No mining claims exist within either unit of the proposed wilderness.

Deep, unexplored sedimentary layers with potential for hydrocarbon resources underlie the San Luis Hills, but the existence of oil or gas deposits is considered improbable due to the lack of similar resources throughout the San Luis Valley. No mineral leases exist within the area. The San Luis Hills are covered by two grazing allotments. Forage production is considered marginal.

The pinyon-juniper woodlands have been harvested in the past for firewood and fence posts. However, the San Luis Hills are presently considered to contain no productive woodland.

San Luis Hills is a headwaters area. Several existing water rights for domestic and stock use are located just outside the wilderness boundary of the north unit in Section 10.

Boundary Issues
The proposed wilderness consists of two units. The south unit is BLM's San Luis Hills WSA plus additions of approximately 50 acres of BLM land and 640 acres of state land on the north side. The north unit includes the entire Flat Top Mesa and approximately one-half to one mile of surrounding lowlands on all sides. The southern boundary of Flat Top is defined by Highway 142 and the other boundaries are well-defined by dirt roads or private land.


san luis hills
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redcloud peak cwp Desert grasslands with sagebrush and prickly pear cactus characterize the slopes and mesas of the area. (Mark Pearson)


redcloud peak cwp
Flat Top Mesa in winter. (Mark Pearson)




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