Paso Centurión y Sierra de Ríos

Paso Centurión y Sierra de Ríos is a Protected Landscape situated in the department of Cerro Largo in northeastern Uruguay, near the border with Brazil. This protected area encompasses a rugged landscape of hills, rocky outcrops, gallery forests, and grasslands that contrasts markedly with the more typical rolling plains of Uruguay. The protected area is recognized for its exceptional biodiversity, harboring species characteristic of both the Atlantic Forest and Cerrado biomes that extend southward from Brazil. It forms part of Uruguay's National Protected Areas System and is considered one of the country's most important sites for wildlife conservation, particularly for large mammals that have become rare elsewhere in Uruguay. The area around Paso Centurión has been identified as a priority conservation zone given its role as a biological corridor connecting Uruguayan ecosystems with the more extensive protected area networks of southern Brazil.

Paso Centurión y Sierra de Ríos is renowned as one of Uruguay's most wildlife-rich protected areas. The site supports populations of several large mammal species that are endangered or functionally extinct elsewhere in the country. Giant anteaters have been documented here, representing one of the few viable populations in Uruguay. Pumas are present, as are maned wolves, pampas deer, and South American tapirs. Smaller mammals include crab-eating foxes, coatis, and various rodent species. The area is particularly important for birds, with species of the Atlantic Forest, Cerrado, and Pampas grasslands all represented. Harpy eagles have been recorded in the region, alongside many raptors and forest birds. Reptiles including caimans in riparian habitats and various snake species inhabit the protected landscape.

The vegetation of Paso Centurión y Sierra de Ríos reflects its transitional position between major South American biomes. Gallery forests along watercourses contain tree species characteristic of the Atlantic Forest, including species of Ficus, Myrtaceae, and various subtropical trees. Rocky outcrops support distinctive rupestral vegetation adapted to thin soils and exposed conditions. The surrounding landscape consists largely of native grasslands typical of the Uruguayan Pampas, with the protected area preserving some of the best-remaining examples of this habitat in the department of Cerro Largo. Cerrado-influenced vegetation appears on the rocky hills, adding to the botanical diversity of the site. This mosaic of habitat types across a relatively compact area creates exceptional ecological richness, supporting species from multiple South American biomes within a single protected landscape.

The Sierra de Ríos forms part of the ancient crystalline basement of the Río de la Plata craton, among the oldest geological formations in South America. The rocky outcrops and hills characteristic of this protected landscape are composed primarily of Precambrian granites, gneisses, and quartzites that have been exposed through millions of years of erosion of overlying sedimentary layers. These ancient crystalline rocks give the landscape its distinctive rugged character, with inselbergs and rocky ridges rising above the surrounding plains. The geological history of the region spans more than two billion years, with metamorphic rocks recording ancient mountain-building events that shaped the deep structure of South America. The varied lithology across the protected area creates diverse soil conditions that support the high plant species diversity observed in botanical surveys.

Paso Centurión y Sierra de Ríos experiences a humid subtropical climate typical of northeastern Uruguay, with warm summers and mild winters. Annual rainfall is distributed relatively evenly throughout the year, averaging between 1,200 and 1,500 millimeters, with slight seasonal variation. Summer temperatures can exceed 35 degrees Celsius, while winter frosts occasionally occur, particularly in topographic depressions. The proximity to the Brazilian border means the area receives slightly higher rainfall than southern Uruguay, supporting the more diverse forest ecosystems within the protected landscape. Thunderstorms are common during summer months, with occasional hailstorms. Wind patterns are variable, with warm northerly winds alternating with cold southerly fronts known locally as surazos during winter. This climatic variability contributes to the ecological diversity of the protected landscape.

The Cerro Largo region has been inhabited since prehistoric times, with indigenous peoples including the Charrúa and Minuán nations occupying the territory before European colonization. These seminomadic hunter-gatherers utilized the diverse resources of the rocky hills and grasslands for millennia. Spanish colonization of Uruguay began in the eighteenth century, with the establishment of cattle estancias transforming the landscape. The area around Paso Centurión served as a crossing point on the route between Uruguay and Brazil, with the paso being a ford across a river used by travelers and cattle drovers. Settlement of the Cerro Largo region accelerated during the nineteenth century following Uruguayan independence, with large estancias dominating the rural economy. The persistence of extensive grazing systems in the region inadvertently helped preserve native grassland habitats, though at the cost of reducing forest cover.

Paso Centurión y Sierra de Ríos was incorporated into Uruguay's National Protected Areas System following the passage of the Framework Law on Protected Areas in 2000, which established the legal basis for the country's modern conservation network. The site was recognized for its outstanding biodiversity values and its role in harboring species that were disappearing from the broader Uruguayan landscape. Its designation as a Protected Landscape reflects both the ecological importance of the area and the presence of traditional land uses, particularly cattle ranching on private estancias that form part of the protected landscape. Management has involved working with private landowners to develop practices compatible with conservation goals, recognizing that most of the protected area consists of privately owned land managed under stewardship agreements with the Uruguayan Ministry of Environment.

The primary attraction of Paso Centurión y Sierra de Ríos is wildlife observation in an intact subtropical landscape. The area offers some of the best opportunities in Uruguay for encountering large mammals such as giant anteaters, tapirs, and potentially pumas. Birdwatching is exceptional, with forest and grassland species both accessible. The rocky hills and cerros provide panoramic views over the surrounding landscape and into Brazil, and the geological features of the Precambrian outcrops are of interest to those interested in natural history. The Paso Centurión crossing point on the local waterway retains historical significance as a colonial-era river ford. Visitors exploring the area can also observe traditional estancia culture, with cattle ranching remaining the dominant land use in the surrounding region. Access is via rural roads from the city of Melo, the departmental capital of Cerro Largo.

Visitor infrastructure at Paso Centurión y Sierra de Ríos is modest, reflecting its character as a working rural landscape with conservation overlay. The nearest significant urban center is Melo, approximately 100 kilometers away, which provides accommodation, fuel, and supplies. The protected area is accessed via unpaved rural roads that may become difficult during wet periods, and a four-wheel-drive vehicle is recommended. There are no formal visitor centers within the protected area, though the National Protected Areas System administration maintains information about the site. Guided tours can be arranged through local operators and conservation organizations working in the region. Visitors should be prepared for basic conditions and carry adequate provisions. The remote location and limited facilities are part of the appeal for wildlife enthusiasts seeking authentic encounters with Uruguay's most remarkable natural landscapes.

Conservation at Paso Centurión y Sierra de Ríos faces the challenge of protecting biodiversity on a landscape dominated by private landholdings and traditional cattle ranching. The Uruguayan protected areas authority works with landowners through stewardship agreements that provide incentives for conservation-compatible management. Monitoring of large mammal populations, particularly giant anteaters and tapirs, provides data for adaptive management. Illegal hunting has historically been a threat to wildlife in the region, and ranger patrols work to reduce poaching pressure. The protected landscape model attempts to reconcile conservation objectives with the economic realities of rural communities dependent on livestock production. Connectivity with protected areas in southern Brazil is recognized as essential for the long-term viability of large mammal populations, and transboundary conservation initiatives have been developed to address this landscape-scale challenge.