Using expert-elicitation to deliver biodiversity monitoring priorities on a Mediterranean island

generating scientific data, is often seen as an attractive option by policy-makers to fill knowl- edge gaps in biodiversity datasets [25]. Citizen science can provide broad geographic coverage of species’ occurrences [26, 27] and has been used to monitor trends in the distributions [28, 29] and abundances of species [30–32]. Biodiversity-based citizen science typically follows two methods of data collection: structured biodiversity recording, i.e. recording that follows some sort of protocol or design, and unstructured recording, which refers to the ad hoc collection of records [28]. The provision of early warnings of the arrival of new IAS is one area in which this has been successful [33–35]. Even in regions without long-standing traditions of amateur contributions to natural history, important discoveries have been made in this way. For exam- ple, a new marine alien species to Cyprus was discovered by recreational divers in 2019, and was identified through photographs posted in the online data repository of the iSea project “Is it Alien to you? Share it!!!” [36]. Despite all of this biodiversity monitoring activity, i.e. the existence of open databases, new technology, and the diversification of mechanisms for collecting monitoring data, knowledge gaps still exist [37, 38]. Where existing data and models cannot answer questions needed to inform management and policy, expert-elicitation, i.e. using the knowledge and experience of experts, can be used to address these gaps [39]. Expert-elicitation methods, such as the Delphi

technique and similar approaches [40, 41], have been used to address many questions in con- servation science [42], including the prioritisation of knowledge needs for enabling implemen- tation of “nature-based solutions” in the Mediterranean [43], and the prioritisation of needs for biodiversity monitoring in the UK [44]. Prioritising biodiversity monitoring requirements or “needs” for data contributors (whether amateur or professional), and end users of data (e.g. governments), can prove a useful mechanism for mediating between potentially competing priorities between such groups [44], and can help to focus spending where resources are limited. We use expert-elicitation approaches to collaboratively prioritise the biodiversity monitor- ing needs of a range of stakeholders, with expertise and/or experience in biodiversity monitor- ing, on a Mediterranean island (Cyprus). This was undertaken in order to increase understanding of the relative importance of different biodiversity monitoring needs, and to provide a hierarchical checklist on which to base future policy development, resource alloca- tion, and general biodiversity conservation decision-making. Biodiversity and monitoring on Cyprus The island of Cyprus is the third largest island in the Mediterranean [45] and very rich in bio- diversity in relation to its size [46]. Cyprus is home to a variety of landscapes, species and habi- tats of European importance, and has high cross-taxon levels of endemism [47–50]. Plants in particular have one of the highest levels of endemism in the European Union [51, 52].

The Government of the Republic of Cyprus and Sovereign Base Area Administration fund the monitoring of protected species and habitats. However, to date, as throughout the world, the biodiversity recording effort on Cyprus has been uneven, with many geographical areas and taxonomic groups poorly represented on biodiversity data platforms, particularly at finer spatial scales. Whilst structured biodiversity monitoring does exist on the island, this is gener- ally aimed at generating temporal trends in population counts, and is largely restricted to birds; although we also note the monitoring of the endemic mouflon going back over two decades. BirdLife Cyprus has been publishing annual reports of unstructured bird records since 1970, as well as monthly checklists based on reports by birdwatchers. Their longest run- ning structured monitoring scheme is the monthly water bird survey (starting 2005). The Cyprus Dragonfly Study Group and the Cyprus Butterfly Group have also recently begun to PLOS ONE Expert-elicitation to prioritise biodiversity monitoring PLOS ONE | https://doi.org/10.1371/journal.pone.0256777 March 24, 2022 3 / 20