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

HARVESTS

River populations of mahogany were logged along the Rio Envira in west Acre, Brazil during the 1930s and again in the 1980s.
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River populations of mahogany were logged along the Rio Envira in west Acre, Brazil during the 1930s and again in the 1980s.

The earliest commercial extraction of mahogany from natural forests by colonial Spain and England targeted populations growing along the banks of rivers in Mexico and Central America (see History > Exploitation). Trees were felled directly into water, or were rolled or dragged short distances to river edges, and floated downstream to coastal shipyards. The vagaries of weather and water made mahogany logging a risky business during the pre-mechanized era. Logs gathered at river’s edge sometimes could not be moved during low-rainfall years when water levels did not rise sufficiently for floating downstream; or they might be scattered and lost during flood years. Back when whole logs were transported by ship to Spain or England for milling, further losses often occurred moving log-rafts from shore where rivers flowed into the sea to ships anchored one to several kilometers offshore due to shallow water.

The Rio Envira runs shallow during the dry season, but fills during the rainy season, allowing logs to be floated downstream.
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The Rio Envira runs shallow during the dry season, but fills during the rainy season, allowing logs to be floated downstream.

Gradual depletion of the most accessible riverine mahogany populations forced the development of new technologies for industrial logging. Ox teams and mules were hauling logs in Mexico and British Honduras (now Belize) by 1805, extending loggers’ reach 8 or more kilometers into primary forests. Next came narrow-gauge railroad tracks and crawler-type tractors for moving logs, expanding the available resource to 60 or more kilometers from the nearest river. Heavy machinery – trucks, tractors, skidders – transformed mahogany logging after World War II, essentially eliminating transport as a constraint on extraction.

This technological progression was repeated in South America beginning in the early 1900s in the Peruvian Amazon. There, and by the 1930s in the western Brazilian state of Acre, riverine populations were exploited first, followed by trees growing further from flowing water, hauled by men or livestock and eventually by heavy machines as transportation infrastructure penetrated increasingly remote Amazonian forests beginning in the 1960s. Well into the 1970s mahogany was being axe-felled and hauled overland to the nearest river by men using palancas (pole levers), palancónes (massive pole levers), and molinetes (pulley systems) in Peru. See White (1978) for descriptions of how crews of four to eight men could move 9-ton logs across hilly and uneven terrain using poles and fixed levers. Meanwhile across southern Amazonian states in Brazil – Rondônia, Mato Grosso and Pará – the construction of TransAmazonian highways in the 1960s and 1970s opened vast new areas for mechanized logging targeting mahogany in non-riverine terra firme forests.

Wagon train of mahogany logs hauled by tractor during dry season. From Lamb 1966.
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Wagon train of mahogany logs hauled by tractor during dry season. From Lamb 1966.

Mahogany’s occurrence in seasonal forests forces a predictable rhythm on annual harvest cycles, regardless of geographic location or available technology.

New commercial supplies are located during the rainy season by mateiros (woodsmen) who fan out into new forest areas, marking harvestable mahogany trees and cutting trails for fellers who follow with axes or, nowadays, chainsaws. Though mahogany typically occurs at low densities in primary forests, it tends to aggregate predictably into stands or groves, and its crown shimmers distinctively in the slightest breeze, making it easy to spot from the ground. Mateiros in southeast Pará say that the largest buttress often points to the next tree. In the early 1920s loggers began locating new commercial stands in Mexico using small planes to fly low over forest canopies, spotting mahogany’s large irregular crown emerging from the forest overstory. In Mexico and Central America mahogany often turns crimson red before losing its leaves during the dry season, a characteristic that plane spotters exploited in advance of the next year’s harvest (this color change has not been observed in South America). In southeast Pará, spotters in small planes located the richest groves which in turn were explored by mateiros on the ground. For a time, small plane spotters skimming the forest canopy for mahogany trees held the most dangerous job in the business.

Mahogany logging with tractor and arch in Bolivia. From Lamb 1966.
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Mahogany logging with tractor and arch in Bolivia. From Lamb 1966.

The tropical rainy season with its consequent slippery ground and mud places severe restrictions on moving heavy logs, whether by men, livestock, or machines. In mechanized mahogany logging operations as many trees as possible are felled during the late rainy season so that logs are ready for transport to the nearest river or sawmill during the dry season. Axe felling often required construction of pole scaffolding to lift fellers above tall buttresses; chainsaws slice through buttresses with ease. Before mechanized tractors and skidders were available for hauling, logs had to be rounded for rolling or dragging by livestock, especially swollen butt (base) logs and curving stems. For this reason, non-mechanized technology constrained tree size and stem quality that could be harvested, forcing loggers to leave many mahogany trees standing in the forest. Mechanized logging equipment allows nearly all trees to be felled and hauled, eliminating nearly all adult and sub-adult trees in a given area and severely constraining population recovery. The rainy season’s return shuts down overland transport, bringing each year’s logging season to an end.

By the late 1980s in Brazil, mahogany’s extraordinary value made it possible for loggers to cut access roads into previously inaccessible primary forests to distances more than 500 km from the nearest sawmill. Mahogany logging represented the first wave of highly selective ‘conventional’ logging which proceeded largely unplanned and unregulated across vast stretches of Amazonia, introducing rudimentary transportation infrastructure that would be used by ranchers, small-holder agriculturists, and a second wave of loggers returning to mahogany-depleted forests to extract timber species of lesser value. Extended to secondary species occurring at higher densities than mahogany, conventional logging practices severely degrade forest structure, drying out the forest understory and increasing the risk of dry season fires which further degrade forest structure in a predictable, vicious cycle.

Large mahogany stump logged in the late 1980s near the banks of the Rio Envira, Acre, Brazil.
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Large mahogany stump logged in the late 1980s near the banks of the Rio Envira, Acre, Brazil.
Mahogany stump logged in the early 1990s near Juruena, Mato Grosso, Brazil.
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Mahogany stump logged in the early 1990s near Juruena, Mato Grosso, Brazil.
Mahogany stump logged in the early 1990s at Marajoara, southeast Pará, Brazil.
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Mahogany stump logged in the early 1990s at Marajoara, southeast Pará, Brazil.

Advances in tropical forest management in recent decades have concentrated on reducing damages associated with unplanned conventional logging. Current state-of-the-art forest management practices in Brazil are embodied in reduced-impact logging systems, or RIL. RIL reduces damage to residual stands through improved felling and extraction techniques, and improves harvest efficiency through planned operations based on detailed spatial knowledge of commercial trees. Since 2003, when new federal regulations came into effect in Brazil in response to the 2002 CITES Appendix II listing, any forest management plan that includes mahogany must be implemented using RIL as its base operational system.

SELECTED SOURCES

Cochrane MA & Schulze MD (1999) Fire as a recurrent event in tropical forests of the Eastern Amazon: effects on forest structure, biomass, and species composition. Biotropica 31: 2-16.

Grogan J, Barreto P & Veríssimo A (2002) Mogno na Amazônia Brasileira: Ecologia e Perspectivas de Manejo (Mahogany in the Brazilian Amazon: Ecology and Perspectives on Management). IMAZON, Belém, PA, Brazil. 58 pp.

Grogan J, Jennings SB, Landis RM, Schulze M, Baima AMV, Lopes JCA, Norghauer JM, Oliveira LR, Pantoja F, Pinto D, Silva JNM, Vidal E & Zimmerman BL (2008) What loggers leave behind: impacts on big-leaf mahogany (Swietenia macrophylla) commercial populations and potential for post-logging recovery in the Brazilian Amazon. Forest Ecology and Management 255: 269-281 (http://www.treesearch.fs.fed.us/pubs/29979).

Gullison RE, Panfil SN, Strouse JJ & Hubbell SP (1996) Ecology and management of mahogany (Swietenia macrophylla King) in the Chimanes Forest, Beni, Bolivia. Botanical Journal of the Linnean Society 122: 9-34.

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

Schmink M & Wood C (1992) Contested Frontiers in Amazonia. Columbia University Press, New York, NY, USA. 385 pp.

Snook LK (1998) Sustaining harvests of mahogany (Swietenia macrophylla King) from Mexico's Yucatan forests: past, present and future. In: Primack B, Bray DB & Galletti H (Eds.), Timber, Tourists and Temples: Conservation and Development in the Maya Forests of Belize, Guatemala and Mexico, pp. 61-80. Island Press, 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.

White S (1978) Cedar and mahogany logging in eastern Peru. The Geographical Review 68: 394-416.

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