Assessing Presence, Decline, and Extinction for the Conservation of Difficult-to-Observe Species

Abstract

Knowledge of decline and extinction is variable for different species in different circumstances but remains important in deciding upon, and managing, conservation interventions. Where a species is present in a very small population, there can still be an opportunity for recovery up to sustainable levels as experienced by many conservation interventions. Misdiagnosis of extinction, survival, recovery, or decline will have major consequences on successful conservation management of species. Four concepts should inform balanced conservation decision-making, including the Precautionary Principle, Romeo’s Error, the phenomenon of Lazarus Species, and the Thylacine Effect. Cryptic or otherwise rarely encountered species may be either highly visible and rare on one hand or more common but elusive. The factors which influence the difficulty in making observations are variable and have a combined effect under different circumstances. Emerging methods and technologies and indirect measures of presence offer ways of surmounting the challenge presented by difficult-to-observe species. Local people have a role in providing knowledge on species presence and in some instances provide manpower to support data collection. Several methods of measurement are discussed including analytical methods for assessing survival, decline, or recovery. With cryptic or rare species, patchy presence data can still inform an understanding of extinction and recovery patterns, and examples from a variety of taxa illustrate those approaches. Several examples are presented of better analysis of declines and extinction to improve strategic decision-making and the design of conservation interventions. Professional attention needs to be applied to uncertain information on species, including presence, recovery, decline, and possible extinction, to utilise and improve available knowledge to support relevant conservation action.