A simple population viability analysis of the Critically Endangered Euphorbia clivicola RA Dyer under four management scenarios

This paper describes a population viability analysis (PVA) for Euphorbia cl ivicola R.A. Dyer, a threatened succulent confined to only two known popula tions in the Northern Province of South Africa, one of which is protected i n a nature reserve. The PVA explicitly compared the relative effectiveness of four management scenarios in bringing about the recovery of the protecte d population that had shown a 91% decline over the decade during which the population was monitored. Demographic monitoring data as well as autecologi cal data collected in 1996 were used to determine the temporal variation in observed demographic and reproductive parameters. The model parameters wer e allowed to vary randomly over the observed ranges in order to incorporate stochasticity of the environmental factors fire, herbivory and rainfall. I f future management practices remain unchanged, the model predicted that th ere is an 88% probability of the protected population becoming extinct with in the next 20 years. The population should recover under a management scen ario involving a fire frequency of every 3 years, the exclusion of herbivor es and augmentation. The model has since been validated with data collected in 1999. Such analyses are useful for adaptive management purposes. (C) 20 00 Elsevier Science Ltd. All rights reserved.