Optimism for the Future Use of Environmental DNA (eDNA) to Study Global Climate Change

Abstract

Countries are differentially vulnerable to the effects of global climate change, and it is important for us to understand the impacts of climate change more completely by examining the impacts across different regions, including in the Global South. To better understand the effects of climate change, we could use methodologies like environmental DNA (eDNA), or DNA that is released by organisms into their surrounding environment. eDNA has successfully been used to detect rare, cryptic, imperiled, and invasive species (e.g., Taberlet et al. 2012). Because of the success of eDNA to detect species, it has been used in applied conservation management, with the hope that it could be used in the future to estimate species abundance and population genetics (e.g., Adams et al. 2019). Despite the rapid advancement of eDNA methods and research, limited studies have used eDNA to examine the effect of climate change on aquatic ecosystems. Due to the noted strengths of eDNA, it would likely be a cost-effective method to assess the impacts of climate change by detecting changes in community compositions, and across a broad geographic region by considering changes in species distributions. However, most eDNA research has been published in the Global North, while countries most vulnerable to the effects of climate change are generally in the Global South (Table 1). We examined this pattern in use of eDNA to study the impact of climate change. We reviewed the scientific literature to summarize how eDNA has been used to study climate change and to assess whether there were geographic disparities between where eDNA research has been conducted and which countries are most vulnerable to climate change. We conducted a Web of Science literature search using the following topic keywords: environmental DNA, eDNA, and climate change on 16 November 2022. We scanned the 93 initial articles produced from this search for relevance and retained 12 that used eDNA to study the impacts of climate change (Table 2; Supporting Information). Many of the initial articles discussed the potential of eDNA to study the impacts of climate change but did not directly study these effects and were excluded from our summary. To date, most of the research has been conducted in freshwater ecosystems (7/12) compared to marine (5/12). These studies focused on a variety of taxa, coupling eDNA with habitat suitability modeling, and examining community and network changes. Research has also been predominantly located in the Global North (11/12), compared to the Global South (1/12). These current disparities may be attributed to the fact that the first eDNA studies published came from the Global North and thus, scientists, communities, and laboratories have had more time to establish their methodologies. But, as the field begins to transition from the development of assays and proof-of-concept methodological papers, the geographic range of eDNA research will hopefully expand to provide more information about the impacts of global climate change in the Global South. Given the laboratory space and equipment necessary to extract and preserve eDNA (e.g., clean room), the cost of processing samples may be prohibitive to some researchers, especially if sampling is conducted over large regions (or inaccessible regions) and/or there is repeated sampling/long-term monitoring. Additionally, the cost of eDNA sampling may prohibit some researchers from being able to conduct genetic work or limit long-term frozen storage of DNA samples. For example, the cost for a single-species eDNA (i.e., qPCR) sample had been estimated at roughly US$56 per sample and the cost of community analysis (i.e., metabarcoding) at ~US$60, not including travel or assay optimization costs (see Harper et al. 2018). The cost of laboratory supplies increased since the start of the COVID-19 pandemic and associated supply-chain issues, overall increasing the current cost to conduct eDNA research compared to this estimate. As highlighted elsewhere in this collection, the cost of publication in an Open Access journal, such as Environmental DNA (~US$2500) or Scientific Reports (~US$2248+), can add an additional financial challenge. Despite rising costs, using an eDNA approach is generally considered to be more cost-efficient than conventional sampling and can often increase species detection, especially when species are rare (Fediajevaite et al. 2021). We believe that eDNA may provide a unique ability to examine the impact of climate change on aquatic communities, especially in areas most susceptible to climate change and where this type of approach may be lacking (i.e., the Global South). Based on the strengths of eDNA, we believe it could be a powerful and complementary methodology in the following ways: (1) detecting changes in species movement, behavior, and reproduction, (2) examining changes in species interactions and community networks, such as mismatches or niche shifts, (3) archiving and repurposing of eDNA samples, so archived samples could be reanalyzed for new species or coupled with ancient DNA samples from the same site to examine past and current trends, and (4) coupling eDNA results with other co-occurring techniques such as field surveys, camera traps, bioacoustics, and predictive modeling (e.g., climate envelope modeling). Additionally, the use of current and future Open-Access databases (e.g., ANEMONE DB*) would allow anyone to access, use, and analyze eDNA data. Rapid climatic changes and the associated biodiversity crisis is undoubtedly one of the greatest challenges that we face, and “eco-anxiety” can leave one feeling helpless, especially for scientists working in the field of conservation. We are optimistic that current and future initiatives will fund more global collaborations and in particular support work in regions which currently have less access to eDNA such as the Global South. For example, the eDNA collaborative (https://www.ednacollab.org) awards grant money, hosts visiting scholars, and provides eDNA research and protocols, all specifically targeted to make eDNA more accessible. The United Nations Educational, Scientific and Cultural Organization recently announced a two-year investment into examining how climate change is impacting marine ecosystems (https://www.unesco.org/en/articles/unesco-launches-global-edna-project-study-vulnerability-species-climate-change-marine-world-heritage). Continued assistance from community scientists and integration of school programs that can assist with eDNA sampling could help folks feel more motivated to understand the ongoing issues and future climate change impacts on their local ecosystems. The field of eDNA is still young and rapidly developing, with new researchers constantly contributing to the development of better technologies, methodologies, and applications of using eDNA for global ecological conservation. Appendix S1. Supporting Information Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.