The development of a protocol for declaring alien species absent from South Africa

Abstract

Invasive alien species are a major driver of ecological threat globally. Effective conservation efforts can be hindered by inaccurate lists of alien species. This study addresses the challenge of inaccurate alien species lists, specifically focusing on the issue of disputed record regarding the presence or absence of certain species in a given region. These disputed records contribute to uncertainties in conservation and management efforts, as species may be erroneously regulated or overlooked based on conflicting data and interpretations. To address this, the study develops a protocol for systematically assessing the presence or absence of alien species. It introduces a robust protocol for declaring the absence of alien species, addressing concerns raised regarding the need for clear evidence in absence declarations. Emphasising evidence-based lists as foundational for strategic conservation efforts, the protocol, rooted in literature reviews and argument maps, classifies species based on their historical likelihood of being present and the probability of them being no longer present given they were once present. The study's methodology, encompassing identification certainty, evidence quality, temporal evidence accumulation, population loss likelihood, search effort, and ongoing introductions, enhances our understanding of species persistence. Applied to Chilean black urchin [Tetrapygus niger (Molina, 1782)], the protocol demonstrates its worth as a valuable tool, integrating detailed species information, assessment data, rationale behind the absence/presence assessment and a probability scoring system to provide clear justification for the conclusions drawn. Based on this, I suggest the removal of T. niger from regulatory lists in South Africa. This demonstrates the protocol's simplicity, flexibility, and applicability, particularly in situations where data is limited. To test the usability and efficacy of the protocol, it was applied to two additional case study species with disputed presence data in South Africa, Calluna vulgaris and Euphorbia esula. Based on the proposed probability scoring guide, C. vulgaris resulted in a medium probability of absence necessitating further investigation, while E. esula was pronounced likely to be absent. Validation through field observations for C. vulgaris and E. esula confirms the protocol's efficacy as C. vulgaris was found and E. esula was not. Continuous monitoring is thus crucial, especially for cases with a medium probability score, indicating ongoing uncertainty. The results emphasise the protocol's usefulness but also acknowledges inherent limitations and context-specific dependencies. The study emphasises the importance of recent, verified field observations for accurate list and highlights the significance of robust data collection for effective conservation management. The implications also underscore the importance of methodological rigor in search efforts and survey methodologies. The adaptation of the approach to address mobile species is anticipated, and the development of databases capturing search efforts is recommended. This protocol holds potential in enhancing the precision, transparency, and uniformity of alien species presence/absence determinations. However, it should be viewed as a targeted tool tailored for specific contexts, such as ecosystems with limited data availability or disputed species records, rather than a universal solution to the challenges related to alien species management and conservation