The guanaco fulfills several functions in the ecosystem, namely, regulating the growth of vegetation, being part of the diet of the main carnivore in these environments, such as the puma, as well as serving as carrion for condors, culpeo foxes (Lycalopex culpaeus), and other smaller species. 

These animals belong to the only stable population in the high mountain range of the Metropolitan Region, and reproduces in the area. The guanaco is the largest wild herbivore in Chile and is classified as vulnerable for the northern and central macro-zone of Chile by the Ministry of the Environment. This camelid can be considered as a “key” species that sustains the camelid - puma - condor triad (herbivore - predator - scavenger) present in the Andean-Patagonian axis and by protecting the guanaco, species that coexist with are in turn protected. 

This space encompasses the complex dynamics of plants, animals, and microorganism communities in their living environment, which interact as a functional unit. 

The Cruz de Piedra Sub-Andean scrub ecosystem is located between 1,500 and 1,750 meters above sea level, covering approximately 260 hectares (642.474 acres). Vegetation includes an arborescent scrub dominated by Kageneckia angustifolia (frangel), Guindilia trinervis and Colliguaja integerrima, and other important specia, such as Haplopappus illinitus, Baccharis rhomboidalis spp. truncata and Schinus montanus. 

Among the flora, the frangel (K. angustifolia) is a dioecious species endemic to Chile, classified as “Near Threatened” and grows in ravines and hillsides between the provinces of Limarí (Coquimbo Region) and Talca (Maule Region). The population at Cruz de Piedra is better preserves as compared to others in the Metropolitan Region. The fauna in this ecosystem is dominated by the chiricoca bird (Ochetorhynchus melanurus), a species endemic to Chile.

This ecosystem is located between 1,750 and 2,700 masl, and covers approximately 15,200 hectares (37,065.807acres) of the Santuario Cruz de Piedra.

It is widely heterogeneous, considering all the plant, animal, and microorganism communities in its living environment. Between 1,750 and 2,200 masl, a thicket of grasses and low shrubs about 0.5 m tall dominate the landscape, with an approximate coverage of 40%. The dominant species are Chuquiraga oppositifolia, Ephedra chilensis, Tetraglochin alata and Azorella prolifera. On the other hand, above 2,200 meters, a dense thicket of 1-2 m in height can be found, composed mainly of Adesmia pinifolia and Adesmia obovata.

The flora of this ecosystem includes different species of the genus Adesmia, at least two of which have a restricted distribution. It includes the tuco tuco mendocino (Ctenomys mendocinus), a new species for Chile as it is an extension of the species coming from Argentina, the cordilleran parakeet (Psilopsiagon aurifrons), with a stable population and the largest in the region, and high Andean reptiles, less studied and probably sharing the area with endemic and vulnerable species from other valleys in the Cajón del Maipo.

This conservation target covers approximately 2,401 hectares (5,933 acres) is highly fragile to disturbances that could reduce water flow.

As part of the basin's water system, the vegas (flood meadows) play a key ecological role in regulating water runoff, while providing the habitat for specialized flora and fauna species. The vegetation in this ecosystem is not specific to the area is widely spread in the Andes, growing on slopes with water outcrops, ravine bottoms and gullies, interrupting the distribution of the steppes and zonal scrublands.

Vegetation includes grasslands densely covered by Juncaceae and Cyperaceae. Along the watercourses, a dense cover of marsh and aquatic species develops. Wetland birds such as the cordilleran plover (Phegornis mitchellii) classified as Near Threatened and the piuquén (Chloephaga melanoptera) classified as Endangered live in this area. There are also several amphibians, such as the toad Alsodes tumultuosus and the mountain toad (Alsodes montanus), both classified as Endangered.

This conservation target includes all the rivers, estuaries, lagoons, glaciers, and headwaters of the Maipo River basin found within the Sanctuary’s territory. The Maipo River basin begins on the slopes of the Maipo volcano at 5,523 meters asl and runs for 250 kilometers until it flows into the Pacific Ocean, covering an area of slightly more than 15,000 km². The water network covers approximately 112 linear km in four rivers (Claro, Blanco, Barroso and Maipo) and four streams (Extravío, Catedral, El Circo and Escalones). In addition, there are 281 glaciers, covering an area of about 62.12 km², with a water equivalent of 1.41 km³ according to the Public Inventory of Glaciers (DGA, 2022). 

This physical conservation object includes the geological structures and geo-sites present in the Sanctuary. Among these, the following can be highlighted:

• Mass removals: Processes characteristic of the area such as detrital flows, alluvium, landslides, block falls, among others.

• Tectonic deformation: Geoforms that reflect the complex structural evolution of Central Chile, where folds and faults are found, one of the main ones being the Diablo fault.

• Intrusive and sedimentary rocks: There are different deposits, the most significant ones being: 
  Colimapu Formation: earth sediments including lutites and red sandstones, interspersed with mixed in limestone and gypsum lenses.
  Apron Formation: made up of volcanic tuffs and breccias with interspersed lavas and clastic sediments.
  Farellones Formation: composed of lavas, tuffs and ignimbrites with breccia intercalations.
  Río Damas Formation: composed of reddish-gray clastic sediments and dark reddish-gray and greenish-gray andesitic vulcanite.

• Volcanism: In the Apron and Farellones formations, lithologies of extrusive igneous origin predominate, both of Cenozoic age (40 to 5 Ma). Volcanic features include lava flows, tuffs, ignimbrites, ash deposits, and domes, among others

• Hot springs and mineral waters: Thermal springs and outcrops are common in the area, mostly sodium chloride of cogenetic origin; also, calcium sulfate waters are present in this area, providing for recreational and tourism potential, associated with the geothermal activity provided by the volcanoes.

The Sanctuary “is a reservoir of the past, a time capsule of human occupation in the central mountain range of Chile, whose vestiges remain in a good state of conservation”.
Source: Patricio Bustamante, Researcher of sites under study, Cruz de Piedra, 2014.

The author reports a variety of open-air sites, overhangs and pyramid structures that point to settlements from the Archaic III (3950 BC approximately) to the Late Pottery Period. Likewise, researchers have determined that these four settlements housed hunter-gatherers and seasonal residential camps.

For the Early Pottery Period, seven open-air settlements of hunter-gatherers were recorded, largely continuers of the Archaic tradition, but the style of their ceramic vessels belongs to the Late Archaic Period.

The Maipo Pass played a leading role in a large territory between the Aconcagua and Cachapoal rivers during over most of the prehistoric time, as it facilitated the transfer of goods and associated social interaction. In addition, it has been found that this space is much more complex than a simple place of transit between mountain slopes, since it encouraged more prolonged settlements by some groups.

Fossil charophytes can be found in the Colimapu formation and evidence of carbonaceous remains and fossil flora in the Abanico formation has been detected. In addition, a large number of sedimentary structures are recognized in the Río Damas formation, such as vertebrate ichnites, graded stratification, mud cracks and raindrop traces, among others. Likewise, four of the 40 geosites identified to be part of the Cajón del Maipo Geopark are found in the Cruz de Piedra Sanctuary, as follows:

• Termas Puente de Tierra Hot Springs
  

• Basaltic Columns

• Los Monjes mass removal

• Maipo Volcano Eruptive Center - Diamante Caldera

This conservation target includes the relationship between humans and mountains, including ways of life, work, customs, beliefs, toponymies, stories, tales and myths, among others, the following:

• Passages and expedition routes: from the Archaic III (3950 BC approx.) to the Late Pottery or Inca Period, there is evidence of human use and passage through Cruz de Piedra. Likewise, it has been recorded that in 1883 the first ascent was made by the German geologist Paul Güssfeldt, together with the Chilean muleteer Francisco Zamorano, as part of his exploration trips covering the mountain range.
  

• Custody of sovereignty: The Carabineros border station at Cruz de Piedra is located at 3,200 meters above sea level and its main mission is to safeguard sovereignty in this border area of the mountain range, visit the four milestones located in the sector and carry out patrols on horseback. It was established in 2011.
  

• Mountain sports activities: since the construction of the gas pipeline road south of the volcano, the Sanctuary is the passage for mountaineers to climb the Maipo volcano on the southwest face. Currently, the Foundation has an entrance protocol to authorize the passage.
  

• Since the beginning of the century, generations of transhumant muleteers have used the Sanctuary as summering grounds for their animals in the wetlands and pastures of the territory. The Foundation is currently working with them so that they move from traditional to restorative livestock breeding in order to make this tradition and cattle feeding compatible with the conservation of biodiversity.