Assessing the resilience of ecosystem functions in Mediterranean wetlands

Abstract

Research has shown the importance of considering functional diversity when constructing planetary safety boundaries for biodiversity. This is becoming a highly debated topic within the scientific community and it is increasingly getting attention in the policy arena. Within this framework, functional traits would possibly be a good measure of the change in biosphere integrity or – in other words – biodiversity loss. Although several attempts have been made at local scale for measuring a boundary based on functional traits, establishing indicators to estimate the resilience of ecosystem functioning at broader scales is a challenging endeavour. Data availability restricts our ability to operationalize many of these indices in certain biomes. As an example, data on how wetland ecosystems have been changing in the Mediterranean area, and the consequences in terms of biodiversity, functions, and ecosystem services, are patchy or meagre at best; hence, we count on few metrics on their current status and trends at regional or international scales. In this study, we aim to determine the resilience of ecological functioning of Mediterranean wetlands by focusing on the Camargue delta, one of Europe’s most biodiversity rich wetland in the Mediterranean basin. We assess changes in species richness and abundance from the 1970s to present time. To obtain data over a sufficiently long time period on species presence/absence and abundance, we organised a series of iterative consultation of experts to collect data for several taxonomic groups, i.e. birds, mammals, reptiles, amphibians, vascular plants, fish and two invertebrate groups (Odonata and Orthoptera). Using information on approximately 2000 species gathered over a five-month extensive collection period, we present the first attempt to compute a functional-type-based index for the Camargue. We also reflect on how our computations can be improved to better capture the reality of Mediterranean wetland ecosystems. The development of this type of indices can be of paramount importance for measuring progress towards the Aichi Targets and in the context of the post-2020 Strategic Agenda of the Convention on Biological Diversity. Determining the key components of biodiversity which are crucial for humanity, for instance through the estimation of the resilience of ecosystem functions, is necessary for studying, reporting, and managing biodiversity change at a global level.