Humedales e Islas del Hum

Humedales e Islas del Hum is a 2,226.8-hectare national park located at the confluence of the Río Negro and Río San Salvador rivers where they meet the Río Uruguay in the Soriano department of western Uruguay. The protected area encompasses a chain of more than twenty river islands and surrounding wetlands that together form one of Uruguay's most ecologically and archaeologically significant landscapes. Designated as part of Uruguay's National System of Protected Areas in 2023, the park protects critical floodplain habitats, supports notable bird diversity, and preserves the highest concentration of pre-Columbian ceramic remains found along Uruguay's western coastal zone. Its incorporation brought ten new plant and animal species of conservation priority into the national protected area network.

The island and wetland habitats of Humedales e Islas del Hum support a rich assemblage of wildlife adapted to the dynamic floodplain environment of the Río Uruguay. The park is particularly recognized for its exceptional bird diversity, with the river islands and marshy margins providing nesting, roosting, and foraging habitat for waterbirds, raptors, and numerous passerine species. Wading birds such as herons and egrets frequent the shallow channels between islands, while kingfishers and cormorants hunt along the deeper waterways. The surrounding wetlands support populations of coypu, capybara, and marsh deer, all characteristic of Uruguay's riverine ecosystems. Reptiles including broad-snouted caimans and various freshwater turtle species inhabit the channels and backwaters, and the river systems support diverse fish communities including dorado, surubí, and sábalo that move through the archipelago's intricate waterway network.

The park's vegetation reflects the dynamic interface between terrestrial and aquatic environments characteristic of Río Uruguay floodplain islands. Dense gallery forests of native willow, ceibo, and timbó line the island shorelines, while the interior areas support herbaceous wetland communities of rushes, sedges, and aquatic grasses adapted to periodic flooding. Higher ground on some islands sustains patches of riparian woodland with species such as laurel, arrayán, and blanquillo, creating a layered canopy that provides habitat structure for forest-dwelling birds and mammals. The wetland margins feature floating and emergent aquatic vegetation including water hyacinth and camalote, which form extensive mats during high water periods. The park's inclusion in the national protected area system was notable for adding ten new species of conservation priority not previously represented, reflecting the botanical distinctiveness of this transitional riverine environment.

The islands and wetlands of Humedales e Islas del Hum are products of the ongoing sedimentary processes of the Río Uruguay and its tributaries, the Río Negro and Río San Salvador. The islands formed through the gradual accumulation of alluvial sediments deposited at this major river confluence, where changing flow dynamics create shifting sandbars, mud flats, and eventually stabilized landforms colonized by vegetation. The underlying geology consists of Quaternary fluvial deposits overlying older Cretaceous basalt formations that form the broader geological framework of western Uruguay. Seasonal flooding cycles continuously reshape the island margins and redistribute sediments, maintaining a dynamic geomorphological landscape where some islands grow while others erode. The confluence zone creates complex hydrological patterns with varying water depths, current velocities, and sediment loads that together produce the diverse mosaic of channels, backwaters, and marshes characteristic of the park.

The park experiences a humid subtropical climate typical of western Uruguay, with warm summers and mild winters and no pronounced dry season. Average annual temperatures hover around 17 to 18 degrees Celsius, with January highs reaching 32 degrees and June lows occasionally dropping to near freezing. Annual rainfall averages between 1,100 and 1,200 millimeters, distributed relatively evenly throughout the year though spring and autumn tend to receive slightly more precipitation. The Río Uruguay's water levels fluctuate substantially with rainfall patterns across its vast watershed, producing periodic floods that inundate the islands and surrounding wetlands, sometimes for extended periods. These flooding events are ecologically critical, replenishing soil nutrients, connecting isolated water bodies, and triggering breeding cycles for fish and amphibians. Strong winds from the south, known as pamperos, can sweep across the flat riverine landscape during winter months.

The islands at the confluence of the Río Negro and Río Uruguay have been sites of human habitation for thousands of years, as evidenced by the extraordinary concentration of archaeological material found throughout the archipelago. Pre-Columbian indigenous groups, likely including Charrúa and Guaraní peoples, established seasonal and semi-permanent settlements on the islands, leaving behind the densest accumulation of ceramic remains found along Uruguay's entire western coast. These archaeological deposits include pottery fragments, stone tools, and food refuse that document successive waves of indigenous occupation and cultural exchange along major river trade routes. The Guaraní migration into the region is documented through distinctive corrugated ceramic styles found in archaeological layers. Following European colonization in the sixteenth and seventeenth centuries, the islands served various purposes including cattle ranching, fishing camps, and timber extraction, though their remote riverine location preserved much of the archaeological record from disturbance.

The formal process to protect Humedales e Islas del Hum began in December 2011, when researchers from Uruguay's Faculty of Sciences submitted a proposal to the National Directorate of the Environment recommending the incorporation of these wetlands and islands into the national protected area system. The proposal emphasized the area's exceptional biodiversity values, archaeological significance, and scenic qualities. The islands, classified as fiscal lands, were transferred to the jurisdiction of the Ministry of Housing, Territorial Planning, and Environment as part of a broader initiative to place Uruguay's river islands under conservation management. After years of technical evaluation, public consultation, and administrative process, the area was formally incorporated into the National System of Protected Areas under the National Park category in 2023, making it one of Uruguay's newest protected areas. The designation represented a significant milestone in Uruguay's expanding conservation network along the Río Uruguay corridor.

As a newly designated and primarily island-based national park, Humedales e Islas del Hum is best explored by watercraft, navigating the channels and waterways that wind between its more than twenty islands. The scenic journey from the mainland through the archipelago reveals a constantly changing landscape of forested islands, open wetlands, sandy beaches, and quiet backwater channels teeming with birdlife. Birdwatching is among the primary attractions, with the diverse habitats supporting species assemblages that vary by season and water level. The archaeological sites scattered across the islands offer a window into millennia of indigenous occupation, though access and interpretation are still being developed. Sport fishing in the surrounding waters of the Río Uruguay and Río Negro confluence draws anglers seeking dorado and other prized freshwater species. The dramatic landscapes where three rivers converge provide exceptional opportunities for nature photography, particularly during golden hour when the forested islands are reflected in calm water.

Humedales e Islas del Hum is located in the Soriano department of western Uruguay, accessible from the departmental capital of Mercedes, which sits at the mouth of the Río Negro approximately 280 kilometers northwest of Montevideo. Mercedes serves as the primary base for visiting the park, offering accommodations, restaurants, and boat launch facilities along the riverfront. As one of Uruguay's most recently designated protected areas, the park's visitor infrastructure is still in early stages of development, and access to the islands requires private or chartered watercraft. Local boat operators and fishing guides in Mercedes can arrange excursions into the island archipelago. The nearest international airport is in Buenos Aires, Argentina, approximately 350 kilometers to the south, while domestic connections are available through Montevideo. Visitors should plan their trips considering seasonal water level variations, as extreme floods can restrict island access while very low water may limit navigation in shallow channels.

The designation of Humedales e Islas del Hum as a national park represents Uruguay's commitment to expanding its protected area coverage along the Río Uruguay corridor, a region of high biodiversity that has historically lacked formal conservation protection. The park's inclusion in the national system brought ten new species of conservation priority under formal protection, filling gaps in the country's biodiversity representation. Key conservation challenges include managing invasive plant species that threaten native vegetation communities, controlling illegal hunting and fishing, and mitigating the effects of upstream agricultural runoff on water quality in the wetland habitats. The dynamic nature of the floodplain ecosystem requires adaptive management approaches that account for natural flooding cycles while addressing human pressures. Collaboration between the Ministry of Environment, the Faculty of Sciences, and local communities in the Soriano department is essential for developing sustainable management plans that balance conservation objectives with traditional uses such as artisanal fishing. The park also serves as a focal point for archaeological research and cultural heritage preservation.