A simple population viability analysis of the Critically Endangered Euphorbia clivicola R.A. Dyer under four management scenarios Original Research Article

This paper describes a population viability analysis (PVA) for Euphorbia clivicola R.A. Dyer, a threatened succulent confined to only two known populations in the Northern Province of South Africa, one of which is protected in a nature reserve. The PVA explicitly compared the relative effectiveness of four management scenarios in bringing about the recovery of the protected population that had shown a 91% decline over the decade during which the population was monitored. Demographic monitoring data as well as autecological data collected in 1996 were used to determine the temporal variation in observed demographic and reproductive parameters. The model parameters were allowed to vary randomly over the observed ranges in order to incorporate stochasticity of the environmental factors fire, herbivory and rainfall. If future management practices remain unchanged, the model predicted that there is an 88% probability of the protected population becoming extinct within the next 20 years. The population should recover under a management scenario involving a fire frequency of every 3 years, the exclusion of herbivores and augmentation. The model has since been validated with data collected in 1999. Such analyses are useful for adaptive management purposes.