The Consequences of Harvesting on Regeneration of a Non-timber Wax Producing Species (Euphorbia antisyphilitica Zucc.) of the Chihuahuan Desert

Abstract

The Consequences of Harvesting on Regeneration of a Non-timber Wax Producing Species ( Euphorbia antisyphilitica Zucc.) of the Chihuahuan Desert. For two centuries large quantities of non-timber candelilla (Euphorbia antisyphilitica Zucc., Euphorbiaceae) have been harvested from wild populations in northern Mexico. The wax that candelilla produces is used for various purposes by many different types of industries. Although extraction is regulated by the government, lack of ecological information has led to concern for overexploitation and population decreases. In the arid region of Cuatrocienegas, Coahuila, Mexico, we measured growth and reproduction in candelilla populations with variable harvest rates. Interviews were used to determine how harvest criteria and volume relate to plant performance and to learn about current extraction policies. We found the average annual harvest to be high (8,273.02 ± 2,076.09 kg/per person/per year) but the population size to be consistent (9,278 to 73,250 individuals/ha). Initial number of stems and height per plant at first census, time elapsed since last harvest, as well as seasonal changes affected individual plant performance. Relative growth rate (TR) was higher but also more variable among small plants relative to larger plants, making them more vulnerable to harvest effects. TR and fecundity rates are negatively affected when less than two years elapsed between harvests. Nowadays, although fewer local people work in candelilla extraction, those from the lowest socioeconomic brackets depend on it most. The incorporation of the ecological information obtained here into Mexican law will ensure better management of this NTFP resource. Also, improving the techniques of wax extraction and promoting fair trade to increase the price paid to producers could reduce the negative impacts on plant performance and ensure sustainable use of natural populations.