Lagoa do Cajueiro

Parque Estadual Lagoa do Cajueiro is a protected area located in the municipality of Matias Cardoso in northern Minas Gerais, Brazil, centered on a permanent freshwater lagoon system embedded within a Caatinga-Cerrado transition landscape. ^[1] The park takes its name from the cashew tree lagoon—the Lagoa do Cajueiro, which is perennial and maintains approximately one meter of depth year-round, providing critical habitat for waterbirds, aquatic fauna, and plant communities. The lagoon and its surrounding vegetation are positioned along the middle course of the São Francisco River, with the marginal lagoons serving as breeding, shelter, and feeding areas for wildlife. Created in 1998 to protect this rare wetland in an otherwise semi-arid landscape, the park contributes to the conservation of seasonal wetland habitats disproportionately threatened by agricultural drainage across the Brazilian interior.

The permanent lagoon and its surrounding Caatinga-Cerrado margins support a diverse and productive wildlife community. Waterbirds are the flagship fauna, with large concentrations of jabiru storks, roseate spoonbills, limpkins, various herons, and migratory shorebirds using the lagoon, particularly during the wet season. ^[1] Larger animals documented in the park include tapirs, pumas, anacondas, yellow-throated caimans (Caiman latirostris), anteaters, and maned wolves. Capybara are abundant along lagoon margins. The surrounding Caatinga-Cerrado landscape hosts pampas deer and marsh deer adapted to seasonally flooded grasslands. Amphibian diversity peaks during the wet season when frogs exploit breeding pools throughout the lagoon margins.

The park encompasses two distinct biomes: Caatinga and Cerrado, with approximately 66% of the area in contact zones between steppe savanna (savana estépica) and seasonal forest, and 34% in deciduous seasonal forest. ^[1] Aquatic and semi-aquatic vegetation dominates the lagoon interior, with water hyacinths, emergent grasses, and floating macrophyte communities forming dense mats during the wet season. The lagoon margins support a fringe of riparian forest and campo limpo wetland vegetation adapted to seasonal inundation. Buriti palms are characteristic of the wetter areas adjacent to the lagoon, forming groves that serve as nesting sites for macaws and large herons. The surrounding upland vegetation transitions from gallery forest along permanent watercourses to cerrado sensu stricto and campo sujo on well-drained interfluves.

The park occupies a low-lying area on the Cerrado-Caatinga plateau associated with the São Francisco Craton. The lagoon occupies a shallow depression in the gently undulating lateritic surface, formed through geological processes involving differential subsidence or deflation of sandy substrates during drier Quaternary periods. Lacustrine sediments—fine clay and organic material—have accumulated in the lagoon floor over thousands of years, recording paleoclimatic fluctuations through pollen and microfossil sequences. Surrounding upland soils are deep oxisols typical of the Cerrado plateau, with high aluminum and low phosphorus concentrations. The geological configuration channels seasonal surface runoff from surrounding slopes into the lagoon.

The park experiences a tropical semi-arid climate with pronounced seasonal contrast, characteristic of the Caatinga-Cerrado transition zone of northern Minas Gerais. Annual rainfall of 1,000–1,300 millimeters falls mainly from October to April, when the lagoon supports peak waterbird populations. While surrounding vegetation becomes dramatically desiccated during the dry season, the Lagoa do Cajueiro itself is perennial—it never fully dries up, maintaining roughly one meter of depth year-round, which makes it an unusually stable refuge for aquatic fauna in the semi-arid region. Temperatures average 24–28°C with a modest winter cooling in June–July. The lagoon's biological productivity is influenced by interannual rainfall variability, which can expand or contract its extent significantly.

The northern Minas Gerais region surrounding the park has been settled since pre-colonial times by indigenous groups who exploited lacustrine resources including fish, waterfowl, and freshwater mussels. Cattle ranching penetrated the region from the 18th century, with fazendeiros establishing large landholdings across the Cerrado plateaus. The lagoon historically provided water for livestock, irrigation, and community fishing. Artisanal fishing communities developed around the lagoon margins, and the cashew tree that gives the lagoon its name was both an economic and cultural landmark for local settlements. Land conversion pressures intensified in the late 20th century with the expansion of soybean cultivation and eucalyptus plantations onto the surrounding Cerrado plateau.

Parque Estadual Lagoa do Cajueiro was established by Minas Gerais state Decree 39.954 on October 8, 1998, to protect the lagoon ecosystem and its surrounding Caatinga-Cerrado transition vegetation, recognizing the regional importance of wetland habitats for waterbird conservation and watershed function. ^[1] The park's establishment followed surveys that documented exceptional bird diversity using the lagoon, particularly concentrations of threatened waterbird species. Management by IEF-MG focuses on maintaining the lagoon's hydrological integrity, controlling encroachment at park boundaries, and managing visitor access to sensitive nesting areas. The park participates in regional waterbird monitoring networks that compile annual census data for São Francisco basin wetland species.

Birdwatching around the lagoon margins is the primary attraction, with waterbirds congregating in the shallow waters and adjacent riparian vegetation. Observation towers on the Lagoa do Cajueiro—the park has two—provide elevated vantage points for observing jabiru storks, herons, roseate spoonbills, and caimans. ^[1] Boat tours on the lagoon provide intimate access to the aquatic community and waterbird nesting colonies. Photography is a popular activity given the scenic quality of the lagoon framed by buriti palms. Guided natural history walks through adjacent Caatinga-Cerrado vegetation explain the ecological relationships between the wetland and surrounding upland habitats.

The park is accessible via state roads connecting to Matias Cardoso and neighboring municipalities in northern Minas Gerais, approximately 130 kilometers from Montes Claros. ^[1] The park is currently closed to general public visitation. Research facilities include a Research House, two observation towers, and a monitoring post on the lagoon. Researchers and authorized visitors may contact the IEF-MG regional office for information on access conditions. The optimal visiting season for authorized researchers is from November to March when waterbird concentrations are highest. Visitors should bring binoculars, insect repellent, and sun protection.

The lagoon's hydrological integrity is the primary conservation focus, requiring management of upstream land use to prevent excessive sedimentation and nutrient loading. Boundary encroachment by adjacent landowners for cattle grazing and fishing is monitored by park guards. Waterbird nesting colonies are protected from disturbance during the breeding season through seasonal management. Invasive aquatic plants, particularly water hyacinth, can reduce dissolved oxygen and outcompete native macrophyte communities, requiring active management. The park collaborates with state water resource agencies to monitor lagoon water quality and flow dynamics. Long-term climate monitoring tracks changes in rainfall patterns that directly influence the annual flood cycle underpinning the park's ecological character.