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A one-stop location for information on big-leaf mahogany (Swietenia macrophylla, Meliaceae)

NATURAL RANGE

Three Neotropical or New World mahoganies make up the genus Swietenia in the plant family called Meliaceae. Swietenia mahagoni (L.) Jacquin is the West Indian or Caribbean or little-leaf mahogany, originally found from the southern tip of Florida through the Florida Keys, the Bahamas, Cuba, Jamaica, Haiti, and the Dominican Republic. (The terms ‘(L.) Jacquin’ tell us who named the species: L is for Linnaeus with a later revision by Jacquin.) Swietenia humilis Zuccarini is the Pacific Coast mahogany whose range stretches from Mexico to Panama in Central America. The third species, Swietenia macrophylla King, is the big-leaf (‘macro’ = big, ‘phylla’ = leaf) mahogany described in these pages. Originally thought to be the same as the West Indian species, in 1886 Sir George King renamed the Swietenia with the big leaves that was being harvested from British Honduras (Belize) and elsewhere along the Atlantic coast of Mexico and Central America.

Historic distribution of mahogany from Mexico to southeastern Amazonian according to Lamb (1966). From Martinez et al. 2008.
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Historic distribution of mahogany from Mexico to southeastern Amazonian according to Lamb (1966). From Martinez et al. 2008.

Mahogany’s natural range stretches from Mexico at 23º N of the equator down the Central American Atlantic coastal strip into South America, continuing in a broad southeasterly arc from Venezuela through Amazonian regions to points as far south as 18º S in Bolivia. Countries where mahogany naturally occurs include Mexico, Belize, Guatemala, Honduras, Nicaragua, Costa Rica, Panama, Venezuela, Colombia, Ecuador, Peru, Brazil, and Bolivia. Its distribution generally corresponds to forests classified as ‘tropical dry’ with 1000–2000 mm annual precipitation. Mahogany also grows in humid and subtropical zones, at elevations ranging from sea level in Central America up to 1400 m in the Andean foothills of Ecuador, Peru, and Bolivia, in a wide variety of soil types and soil conditions.

FB Lamb’s 1966 estimate of mahogany’s historic range in South America was based on anecdotal reports and his wide travels during the first half of the 20th Century rather than on structured inventories. In a study by Martinez et al. (2008, see sources below) and later published by Grogan et al. (2010), expert respondents revised Lamb’s estimate for South America downward by 19% to 278 million hectares, roughly equivalent to the total land area of Colombia, Ecuador, and Peru combined. Reductions were most pronounced in Venezuela, Bolivia, and Brazil, where Lamb’s range overlapped extensive areas of savanna, cerrado, and scrub woodland that are unsuitable for mahogany. Brazil alone accounts for 57% of the revised historic range in South America, most of this occurring along the seasonally dry southern rim of closed Amazon forests. Nearly 7% of mahogany’s revised historic range in South America is under legal protection, and an additional 15% lies within legally recognized Indigenous Lands.

Revised historic distribution of mahogany in South America based on expert surveys. From Martinez et al. 2008.
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Revised historic distribution of mahogany in South America based on expert surveys. From Martinez et al. 2008.

In Brazil, mahogany originally occurred in natural forests covering an estimated 159 million hectares along the southern and southeastern rim of legal Amazonia, an area equivalent to mahogany’s historic range in all other South and Central American countries combined, including Mexico. Known in Brazil as mogno (except in Acre where the common name is aguano), mahogany’s range extended as far north and east as the Transamazon Highway (BR-230) at Altamira and the Tocantins River valley east of Marabá. From these limits mahogany occurred in a broad southwesterly swath across the states of northwest Tocantins, south Pará, north Mato Grosso, southeast Amazonas, and most of Rondônia and Acre.

Just as forest types grade continuously in structure and composition across Brazil’s southern Amazon, mahogany occupied a wide range of habitats at highly variable densities. Before industrial logging, high-density populations occasionally exceeding one tree per hectare at landscape scales occurred along perennial rivers and seasonal streams in the southeastern corner of the state of Pará. Mahogany is reputed to have occurred at similar densities in parts of the mid-western state of Rondônia, but those populations were logged before they could be rigorously inventoried. Moving west and north from these high-density zones, population densities declined to near zero at the geographical limits of mahogany’s range in Brazil. Western populations in Acre and Amazonas occur at low densities compared to southeastern populations, on the order of 1 tree in 5 to 20 hectares, in both terra firme and riverine forests.

In Bolivia, mahogany’s historic range covered an estimated 30 million hectares of tropical and subtropical wet and seasonally dry forests in the Departments of El Beni, Cochabamba, La Paz, Pando, and Santa Cruz. Known in Bolivia as mara, mahogany occurred at highest densities along the margins of perennial rivers draining the Andean foothills. Mahogany occurs or occurred at lower densities in terra firme (‘high ground’) forests, often associated with seasonal streams as in Brazil. Though expert respondents reported isolated regions where mahogany populations may persist at high densities (1–10 per hectare), most surviving populations are expected to occur at densities well under one commercial tree per hectare.

Mahogany’s historic range in Peru covered an estimated 55 million hectares across most of the country’s eastern Amazon region. Known in Peru as caoba, mahogany was found along riverbanks and in terra firme lowlands including mixed bamboo forests, as well as in terraced foothills at the base of the Andes mountains. Little is known about abundance patterns of riverine populations that had largely vanished by the early 1970s, but United States import volumes from 1908–1960 reported by Lamb suggest that these populations occurred at relatively low densities. Based on the densities of surviving populations and trade statistics, it is probable that terra firme populations seldom exceeded one commercial tree per hectare at landscape scales.

Mahogany’s historic range in Ecuador covered approximately 7 million hectares of Amazonian forests east of the Andes mountains. Mahogany most commonly occurred on alluvial terraces in nutrient-rich, deep, well-drained soils adjacent to major rivers draining the Napo, Pastaza, and Sucumbíos Provinces, and within tributary watersheds in Andean foothills up to 500 m elevation. Possibly due to the relative aseasonality of Ecuador’s Amazon region, natural populations occurred at low or very low densities (fewer than 0.1/ha). One indication of this is the fact that no forest inventory in the Amazon region during the period 1942–1980 registered mahogany’s presence; it was not until 1985 that mahogany was first recorded in Ecuador. Mahogany’s frequent association with rich alluvial soils means that gradual conversion of riverine forests to agriculture by Amerindian communities during the past century has likely reduced natural range and population densities through habitat loss.

Historic distribution of mahogany in Mexico and Central America. From Calvo et al. 2000.
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Historic distribution of mahogany in Mexico and Central America. From Calvo et al. 2000.

In Colombia, mahogany’s historic range covered an estimated 18 million hectares and included three or more disjunct regions corresponding roughly with seasonally dry lowland or piedmont (upland) forests flanking the lower slopes of Andean and northern mountain ranges. These include: 1) the Pacific-side, northwest Darién region adjacent to Panama (Chocó Department), extending to the lower dry zones of the Mulatos and San Juan River watersheds; 2) the northern Caribbean-side lowland plains and foothills of the Cordillera Oriental that continues into Venezuela, extending south into mountain valleys drained by the Cauca and Magdalena Rivers; and 3) seasonal foothill forests flanking the eastern Andean slopes above the Amazonian lowlands draining towards Brazil. Commercial logging has also been reported from the southwestern corner of Colombia in the Puré and Purite River watersheds. No information is available regarding abundance patterns, but Colombia’s minor historic role as a mahogany exporter indicates that natural population densities were, on average, low to very low.

In Venezuela, mahogany’s historic range was split by coastal mountains that connect with the Andean Cordillera in the southwest. Mahogany occurred north of these mountains in the region surrounding the Maracaibo Lake depression, and on the south side in the plains region stretching across the western states of Barinas, Portuguesa, and Cojedes. The revised natural range in Venezuela covers an estimated 9 million hectares. According to experts, mahogany was most abundant in rich alluvial soils in lowland riparian forests, but was also widely distributed in semi-evergreen upland forests and in foothill gallery forests up to 900 m above sea level. Though inventory data are scarce, what sources are available indicate that mahogany occurred, on average, at densities well below one commercial tree per hectare.

In Mexico and Central America, mahogany’s natural range is estimated to have covered 42 million hectares or 17% of this region from the Yucatan Peninsula to Panama. See the Calvo et al. (2000) reference for an update to Lamb’s 1966 treatment of mahogany in Mesoamerica.

SELECTED SOURCES

Calvo JC, Bolaños R, Watson V & Jiménez H (2000) Diagnóstico de la caoba (Swietenia macrophylla King) en Mesoamérica: Visión general (Evaluation of Mahogany in Mesoamerica: General Overview). Tropical Science Center / PROARCA / CAPAS, San José, Costa Rica.

Grogan J, Barreto P & Veríssimo A (2002) Mahogany in the Brazilian Amazon: Ecology and Perspectives on Management. IMAZON, Belém, PA, Brazil. 58 pp. Available in Portuguese & English at www.imazon.org.br.

Grogan J, Blundell AG, Landis RM, Youatt A, Gullison RE, Martinez M, Kometter RF, Lentini M & Rice RE (2010) Over-harvesting driven by consumer demand leads to population decline: big-leaf mahogany in South America. Conservation Letters 3: 12-20.

Kometter RF, Martinez M, Blundell AG, Gullison RE, Steininger MK & Rice RE (2004) Impacts of unsustainable mahogany logging in Bolivia and Peru. Ecology and Society 9: http://www.ecologyandsociety.org/vol9/iss1/art12.

Lamb FB (1966) Mahogany of Tropical America: Its Ecology and Management. University of Michigan Press, Ann Arbor, MI, USA.

Martinez M, Blundell AG, Gullison RE & Grogan J (Eds.) (2008) Historic range and current status of big-leaf mahogany (Swietenia macrophylla) in South America. Report for the Center for Applied Biodiversity Science–Conservation International, Washington, DC, USA.

Veríssimo A, Barreto P, Tarifa R & Uhl C (1995) Extraction of a high-value natural resource in Amazonia: the case of mahogany. Forest Ecology and Management 72: 39-60.

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