Una

Una Biological Reserve (Reserva Biológica de Una) is a federal strictly protected conservation unit covering approximately 11,400 hectares in the southern coastal zone of Bahia state, Brazil. Administered by ICMBio, the reserve is situated in the southern Bahia Atlantic Forest, one of the most species-rich regions in the entire Atlantic Forest biome. Una is internationally recognised as the primary stronghold for the golden-headed lion tamarin (Leontopithecus chrysomelas), a small primate endemic to southern Bahia that is classified as Endangered on the IUCN Red List. The reserve's combination of size, coastal forest integrity, and role as habitat for charismatic and critically threatened species places it among the most important Atlantic Forest conservation units in Brazil.

Una Biological Reserve is most celebrated for its population of golden-headed lion tamarins (Leontopithecus chrysomelas), estimated at fewer than 6,000 individuals in the wild globally, with the reserve and its surrounding forests constituting the species' core range. The reserve also supports the eastern black-and-white colobus analogue, the northern muriqui (Brachyteles hypoxanthus), and populations of brown howler monkeys (Alouatta guariba). The oncilla (Leopardus tigrinus) and ocelot (Leopardus pardalis) are resident small felids. The avifauna exceeds 400 species, including spectacular endemics such as the banded cotinga (Cotinga maculata), the white-winged cotinga (Xipholena atropurpurea), and the hook-billed hermit hummingbird (Ramphodon naevius). Amphibian diversity is extraordinary, with numerous species new to science having been described from Una's forests.

Una Biological Reserve is situated within the southern Bahia Atlantic Forest, regarded by botanists as one of the richest areas of plant diversity on Earth. The reserve's dominant vegetation is evergreen dense humid forest with a complex multi-storeyed structure, achieving canopy heights of 25 to 35 metres with emergent trees reaching 40 metres. Characteristic tree genera include Eschweilera, Lecythis, Pouteria, and various Meliaceae species. The understorey is extraordinarily diverse, with thousands of species of herbs, ferns, orchids, bromeliads, and aroids competing for limited light. The reserve contains portions of the Una River watershed, where gallery forests maintain high species richness. Botanical surveys have documented over 1,000 plant species within the reserve, including many endemics restricted to the southern Bahia lowlands.

Una Biological Reserve lies on the coastal lowlands of southern Bahia, underlain by Tertiary sedimentary formations including sandstones and clays of the Barreiras Formation, deposited in fluvial and coastal environments along the ancient South American margin. The reserve's terrain is gently undulating to flat, reflecting the sedimentary origin of the substrate. The Precambrian basement rocks of the São Francisco Craton underlie the region at depth and are exposed in some river valley sections. The coast near Una is characterised by marine terraces and beach-ridge systems that record Holocene sea-level changes. Soils are predominantly yellow and red-yellow oxisols typical of the coastal sedimentary formation, with moderate fertility under forest cover but susceptible to degradation when cleared. The Una River watershed drains from the interior highlands towards the Atlantic coast through the reserve.

Southern Bahia's coastal zone experiences a perhumid tropical climate with no distinct dry season, receiving between 1,800 and 2,500 mm of annual rainfall. Unlike most of north-eastern Brazil, the southern Bahia coast is not affected by the severe droughts that characterise the interior semi-arid zone, owing to its position on the Atlantic coast receiving consistent trade wind moisture. Monthly temperatures range from 22°C to 28°C with minimal seasonal variation. The consistent warmth and moisture creates ideal conditions for the dense evergreen forest that characterises the southern Bahia Atlantic Forest sub-type. Occasional cold fronts penetrating from southern Brazil bring temporary temperature drops and heavy rainfall during the austral winter, but prolonged cold events are rare. The reserve's intact canopy maintains forest interior humidity well above ambient levels.

The southern Bahia coastal zone was inhabited by Tupi and Pataxó indigenous peoples prior to Portuguese colonisation in the 16th century. The region's forests were exploited from the earliest colonial period for brazilwood (Paubrasilia echinata), used for red dye and exported to Europe in vast quantities. Plantation agriculture, particularly cocoa (Theobroma cacao) cultivation using the cabruca agroforestry system, became the dominant land use from the 18th century onwards. The cabruca system, which cultivates cocoa under modified native forest canopy, inadvertently preserved substantial tree cover across much of southern Bahia, creating a mosaic of protected reserves and shaded cocoa plantations that together form a partially forested landscape. The Una municipality's economy historically centred on cocoa, though the arrival of witches' broom disease (Moniliophthora perniciosa) in the late 1980s severely impacted production.

Una Biological Reserve was established in 1980 by the Brazilian federal government to protect a critical remnant of the southern Bahia Atlantic Forest and, specifically, to secure habitat for the golden-headed lion tamarin following surveys that identified the reserve area as the species' most important remaining stronghold. The reserve's creation was supported by international conservation organisations, particularly the IUCN and WWF, which recognised the tamarin's extreme endemism and vulnerability. ICMBio has managed the reserve in partnership with national and international NGOs, with the Projeto Mico-Leão-da-Cara-Dourada (Golden-headed Lion Tamarin Project) conducting long-term population monitoring. The Instituto de Estudos Socioambientais do Sul da Bahia (IESB) and other regional organisations have supported conservation work in the reserve's buffer zones and surrounding cabruca landscapes.

Una Biological Reserve prohibits general public visitation as a Biological Reserve under SNUC. Authorised scientific researchers study the reserve's ecosystems with particular focus on golden-headed lion tamarin population dynamics, Atlantic Forest plant inventories, and herpetological surveys. The surrounding Una municipality and adjacent conservation units, including the Una Wildlife Refuge (Refúgio de Vida Silvestre de Una), offer legitimate ecotourism opportunities for wildlife watching. Guided tours in the buffer zone and surrounding cabruca plantations provide opportunities to observe tamarins, birds, and other forest wildlife. The Una Wildlife Refuge, established as a complementary unit allowing controlled visitation, is the preferred destination for ecotourists seeking an encounter with the southern Bahia Atlantic Forest ecosystem.

Una Biological Reserve has no visitor facilities or public access. Scientific access requires ICMBio's SISBIO research authorisation. The reserve is located near the town of Una on the BA-001 coastal road in southern Bahia. Una town provides basic services including accommodation and food. Ilhéus, a larger city with an airport, lies approximately 50 kilometres north and provides more comprehensive travel infrastructure. The region is accessible by bus from Salvador (approximately 420 kilometres north) or Ilhéus. International visitors typically arrive via Salvador or fly directly to Ilhéus from São Paulo. The coastal road BA-001 connecting Ilhéus to Una passes through significant portions of remaining Atlantic Forest landscape, offering in-transit views of the regional ecology.

Una Biological Reserve is a cornerstone of conservation efforts for the southern Bahia Atlantic Forest, one of two recognised sub-centres of endemism within the broader Atlantic Forest biome. The reserve's long-term conservation faces challenges including illegal logging and hunting in adjacent areas, conversion of cabruca agroforestry to pasture following the cocoa witches' broom disease crisis, and increasing pressure from tourism infrastructure development along the southern Bahia coast. ICMBio coordinates with the Projeto Mico-Leão-da-Cara-Dourada to maintain tamarin population monitoring, genetic analysis, and reintroduction programmes. The golden-headed lion tamarin is a focal species for global lion tamarin conservation, with breeding programmes at international zoological institutions supporting ex-situ conservation. International funding from organisations including the Global Environment Facility (GEF) has supported habitat restoration and community engagement in the reserve's buffer zones.