Dimensions of sustainability: The use of vara blanca as a natural resource in the tropical deciduous forest of Sonora, Mexico

Abstract

Croton fantzianus Seymour (Euphorbiaceae), is a structurally important tree in the tropical deciduous forest of the Municipality of Alamos in southern Sonora. It has become important as a non-timber forest product within the last thirty-five years, harvested for stakes (vara blanca ) for the agricultural fields in Sonora, Sinaloa and Baja California. A study was carried out on ecology of the species, macroeconomics and household economics to determine sustainability of current patterns of use. During a study on the ecology of the tree the species was identified from specimens collected and found to be a disjunct population known previously from Nicaragua. It was determined that vegetative and reproductive phenologies are driven by water availability with responses along a water gradient varying among study sites. Rapid development of silver mining precipitated woodcutting for timber and fuel at unprecedented rates in the late 17th century. The original tropical deciduous forest was transformed to secondary forest by this extraction. Closure of the mines in the early 20th century began economic isolation of the Municipality that persists today. The economy of Alamos is depressed in response to national and state economy, people are under- or un-employed. Many cut vara blanca. Economic strategies in the Municipality include exploitation of non-timber forest products, the most important is vara blanca. There are three levels of organization for vara extraction: cutters, middlemen truckers, and large truckers. Income generated by each level is significantly larger than the daily minimum wage. Financial records indicate that nine of eleven respondents rely on the resource for all or part of their incomes. A study of the population ecology of the species indicates it is the most important component of the forest community at all study sites. Population structure and composition are variable and may be related to prior harvest history. Loss of reproductive capacity was recorded on a recently harvested area. The tree may be a successional species and does well in disturbed areas. Government records and informant interviews indicate intensification of extraction has depleted the population. It is questionable if extraction at recent rates can be sustained.