Utilising aquatic environmental DNA to address global biodiversity targets

Achieving global biodiversity goals requires assessing, attributing and reversing the ongoing, unprecedented biodiversity decline in aquatic ecosystems, and relies on adequate data to inform policy and action. Analysis of environmental DNA (eDNA) has become established as a novel and powerful approach to assess the state and functioning of aquatic ecosystems, and although increasingly implemented by stakeholders its potential is not yet fully tapped. 
In this talk, we review the current state of aquatic eDNA research, focusing in particular on the policy relevance of eDNA and its utility in contributing towards the Global Biodiversity Framework. We first summarize key technological developments in eDNA science to measure organismal diversity and its potential for spatial and temporal upscaling to become a key reference for local to global biodiversity action. We particularly discuss methodological advances in the context of metabarcoding, reference library and species assignment, and the direct calculation of biodiversity and ecosystem state indices. We exemplify the power of the approach with examples on whole-river assessments of biodiversity in Switzerland and Thailand, respectively, particularly demonstrating the method's effectiveness in highly biodiverse, yet understudied regions globally. We also discuss how the focus should be on novel opportunities and not solely on retrofitting biodiversity estimates. Then, we outline the next steps needed to effectively implement eDNA for decision-making and reaching biodiversity targets. We specifically demonstrate the power of linking eDNA with remote sensing analyses to get an integrated understanding of biodiversity across the land-water interface. 
Using eDNA to support biodiversity assessment will also benefit the understanding of understudied ecosystems and allow the direct calculation of ecological indices and implementation of FAIR and inclusive data curation. Important next steps for eDNA require proper method standardization and commonly agreed quality standards, populating reference databases, and overcoming methodological constraints in retrofitting novel eDNA-based approaches to existing biodiversity monitoring approaches.