A conservation assesment of endangered tropical tree species, Guiaicum sanctum and G. coulteri, in Mexico

In this thesis, I propose a general framework to generate robust information on the distribution, abundance and conservation status of threatened species. I used ecological niche modelling techniques to estimate the historic distribution of Guaiacum sanctum and G. coulteri. These models were then combined with land use maps to estimate habitat loss associated with the conservation of forest to agriculture-pasture and human settlements during the period 1976-2000, and to compute the amount and distribution of suitable habitat contained within existing protected areas. The results showed that by 2000 the distributions of G. sanctum and G. coulteri had been reduced to 72% and 59% of their historic distributions, respectively. If habitat loss continues to occur at the same rate as during the period 1976-2000, the amount of habitat available for G. sanctum and G. coulteri will decline to 51-70% and 48-56% of the historic ranges, respectively, by 2020. To explore options for sustainable management of G. sactum I compared the demography and dynamics of populations on plots in recently logged forest and in a protected area, and parameterized a transition matrix model to simulate harvesting regimes. I found that G. sanctum populations had their highest mortality rates in the seedling and juvenile size classes and that mortality rates were very low in the adult size classes. Although the estimated population growth rate (λ) at the exploited site (Ejido Pich Forest Reserve) was lower than that in the protected area (Calakmul Biosphere Reserve), both populations were growing in size (λ = 1.088 and 1.033, respectively). This analysis supported the conclusion that harvesting did not have a major impact on the Guaiacum sanctum population growth rate at the stand level. My research suggests that the current management regime implemented at Ejido Pich Forest Reserve would not threaten the existence of the species if extended across similar forests in Campeche. Land use change is the most important factor threatening the conservation of G. sanctum. I conclude that avoidance of changes to land use should underpin the conservation strategy for this species, combined with a promotion of sustainable forest management in the area.EThOS - Electronic Theses Online ServiceGBUnited Kingdo