A method for setting the size of plant conservation target areas

Realistic time frames in which management decisions are made often preclude the completion of the detailed analyses necessary for conservation plannin g. Under these circumstances, efficient alternatives may assist in approxim ating the results of more thorough studies that require extensive resources and time. We outline a set of concepts and formulas that may be used in li eu of detailed population viability analyses and habitat modeling exercises to estimate the protected areas required to provide desirable conservation outcomes for a suite of threatened plant species. We used expert judgment of parameters and assessment of a population size that results in a specifi ed quasiextinction risk based on simple dynamic models The area required to support a population of this size is adjusted to take into account determi nistic and stochastic human influences, including small-scale disturbance d eterministic trends such as habitat loss, and changes in population density through processes such as predation and competition. We set targets for di fferent disturbance regimes and geographic regions. We applied our methods to Banksia cuneata, Boronia keysii, and Parsonsia dorrigoensis, resulting i n target areas for conservation of 1102, 733, and 1084 ha, respectively. Th ese results provide guidance on target areas and priorities for conservatio n strategies.