Parque Nacional Laguna Negra: A Detailed Atlas of Coastal Wetlands and Native Grasslands

The history of Parque Nacional Laguna Negra is closely tied to the land history of the Potrerillo de Santa Teresa property. Before becoming part of the Uruguayan state, the field belonged to the Banco República. In 1939, Law 9889 of 9 November formalized the donation of the property from the bank to the State, creating the basis for what would later become an ecologically managed reserve.

In 1991, Law 16226 placed this reserve under the provisions of article 458 of Law 16170, giving the Ministry of Housing, Territorial Planning, and Environment the task of studying, defining, regulating, and managing the area as a site of protection and ecological reserve. Although this represented a significant step toward formal conservation, the precise boundaries and management plan were still to be defined, and the land continued to be managed in a coordinated fashion by PROBIDES and DINAMA in subsequent decades.

The decisive institutional moment came on 20 February 2025, when Decree 43/025 approved the selection and delimitation of the Laguna Negra natural protected area and incorporated it into the National System of Protected Areas under the category of National Park. This decree transformed a long-running conservation effort into a fully designated national park, integrating Laguna Negra's water body, the Potrerillo de Santa Teresa biological station, and the northern portion of Santa Teresa National Park lying north of Route 9.

The landscape of Parque Nacional Laguna Negra is defined by a sharp mosaic of environments packed into a relatively small territory. Within the Potrerillo de Santa Teresa area, coastal wetland is the dominant element, occupying roughly 465 hectares, or about 64 percent of the property. This wetland is filled with dense pajonales of cortadera and espadaña, interrupted by patches of grama, sarandí colorado, ceibo, curupí, duraznillo, and junco, giving the basin a lush, almost impenetrable appearance in many stretches.

Native grassland covers about 215 hectares, roughly 30 percent of the area. Grasses dominate, with local patches of spiny shrubs such as espina de la cruz, paja estrelladora, and caraguatá. On higher ground, the butiá palm stands out as a characteristic feature of the savanna-like appearance, while in lower and seasonally flooded areas, one finds species adapted to wet conditions such as cola de zorro and grama. The terrain shifts here from relatively dry knolls to periodically soaked lowlands, producing a textured and visually varied open landscape.

Indigenous monte forest occupies around 35 hectares, or about 5 percent of the property, and is made up of small trees such as chal-chal, arrayán, coronilla, canelón, and tala trepador, accompanied by shrubs like envira. Although limited in extent, these wooded patches provide important shade, structural variety, and habitat continuity with adjacent protected areas. Finally, a sandy Atlantic shoreline of less than one percent of the property closes the mosaic, where sarandí colorado and maritime grasses colonize the dunes and migratory shorebirds forage along the water's edge.

Ecologically, Parque Nacional Laguna Negra functions as a layered system of cooperating habitats. The wetland is the hydrological heart of the area, holding and slowly releasing water through the dense root mats of cortadera and espadaña, and providing the moisture that sustains the grassland and forest communities downstream in the landscape gradient. The interplay between saturated soil and drier upland creates conditions for both wetland specialists and savanna species to coexist.

Native grassland and monte indígena act as transitional habitats between the wetland and the coast. In the grasslands, periodic flooding and drier spells produce different microhabitats, while the small monte remnants harbor shade-loving birds, climbing plants, and tree species that would otherwise be scarce in this open coastal environment. The presence of species such as butiá palm, arrayán, coronilla, and canelón links the park's flora to the broader phytogeography of eastern Uruguay, where coastal forest fragments are increasingly important refuges for native ligneous species.

The shoreline completes the ecological picture by introducing a dynamic, wind- and wave-driven edge with vegetation adapted to salt spray and shifting sands, such as sarandí colorado. Together, these habitats create a gradient that supports a wide spectrum of feeding, breeding, and shelter opportunities for both resident and migratory fauna.

The fauna of Parque Nacional Laguna Negra reflects the diversity of its habitats. The wetland environment hosts aquatic and semi-aquatic mammals such as nutrias, carpinchos, and lobitos de río, along with water-associated birds like ipecá, pico de plata, piojito gris, and the locally named dragón.

The grassland habitats support open-country species typical of the Uruguayan countryside, including zorrillo, apereá, ñandú, the small lechucita común, and the distinctive lagarto overo. In the monte indígena, larger mammals such as guazú virá, gato montés, and mano pelada find cover, while the bird community includes species such as the cardinal azul, zorzal, and sabiá, as well as reptiles like the culebra verde esmeralda.

The Atlantic shoreline is the most dynamic wildlife arena, attracting migratory shorebirds such as chorlos and gaviotines, along with espátulas rosadas, garzas blancas, cigüeñas, and several species of wild ducks. The combination of resident mammals, breeding birds, and seasonal migrants gives the park a full annual wildlife cycle.

From a conservation perspective, Parque Nacional Laguna Negra is significant because it anchors a formally protected corridor in the eastern wetlands of Uruguay, where coastal lagoons, grasslands, and fragments of native forest are under growing pressure from land use change. By bringing the Laguna Negra basin and the Potrerillo de Santa Teresa reserve into the National System of Protected Areas, the park ensures long-term legal protection for habitats that had previously been conserved mainly through coordinated interagency management rather than formal designation.

The site also strengthens the ecological relationship between Laguna Negra and the older Parque Nacional Santa Teresa to its south. The northern portion of Santa Teresa is now part of the same protected landscape, helping to maintain habitat continuity for terrestrial species and to safeguard the dune systems and forest patches that connect the two reserves. The shared ownership between the Ministry of Environment and the Ministry of Defense adds a distinctive institutional dimension, embedding the park within both environmental and national defense land stewardship frameworks.

The longstanding conservation role of PROBIDES, focused on the eastern wetlands' biodiversity and sustainable development, and the regulatory involvement of DINAMA mean that the park inherits an established scientific and management tradition. The two interpretation trails, El Tarumán and El Ceibo, further serve a conservation-education function, allowing visitors to engage directly with native forest and the broader mosaic of grassland, wetland, and coastal habitats.

Parque Nacional Laguna Negra carries a meaningful but understated cultural-historical layer through its archaeological heritage. Within the Potrerillo de Santa Teresa property, two cerritos de indios are preserved. Excavations at these earthworks recovered a human burial and a dog burial, along with ceramics from more superficial layers, confirming the funerary role of these structures for indigenous populations that once inhabited the area.

The archaeological record also reveals information about the historical environment of the lagoon basin. Remains of now locally extinct fauna such as large cérvidos and possibly pumas have been recovered, alongside bones of species that still inhabit the park, including small rodents, nutrias, comadrejas, birds, and guazú-bira. This stratigraphy illustrates a long-term human presence in the landscape and documents ecological change that reaches back well beyond modern conservation efforts. The preservation of these cerritos within the new national park gives the site an enduring cultural and paleoecological value alongside its natural significance.

Parque Nacional Laguna Negra stands out for the unusually compressed diversity of its habitats, which combine coastal wetland, native grassland, monte indígena, and an Atlantic shoreline within the boundaries of a single national park. The wetland basin of Potrerillo de Santa Teresa, the open grassland butiá palm savannas, the arrayán and coronilla monte remnants, and the migratory bird-rich coast each contribute a distinct visual and ecological identity.

Equally important is the park's institutional profile as a node in Uruguay's expanding National System of Protected Areas, with formal linkages to the older Santa Teresa reserve and a deep cooperative management history through PROBIDES and DINAMA. The presence of cerritos de indios and the long-documented archaeological record add a cultural dimension that complements the park's natural appeal.

Because Parque Nacional Laguna Negra encompasses coastal wetland, native grassland, monte forest, and an Atlantic shoreline, the character of a visit varies meaningfully across the seasons. The warmer months tend to bring more active birdlife and richer wetland vegetation, while migratory shorebird use of the coast is notable throughout much of the year.

Visiting in cooler months can make the open grasslands and trails more comfortable for walking, while also offering clearer views across the lagoon and surrounding habitats. For those primarily interested in migratory shorebirds and waterfowl, periods when coastal and wetland habitats are fully active offer the strongest wildlife interest. The interpretation trails El Tarumán and El Ceibo provide year-round access to representative examples of the park's native forest and mosaic of ecosystems.