Understanding how wetland species became rare or locally extinct using sedimentary DNA and stable isotopes - supporting future ecological restoration

Wetlands represent one of the most critical ecosystems globally for economic, social and ecological purposes, yet they are threatened due to anthropogenic activities causing wetland loss and degradation (Hu et al., 2017). Regarding climate change, wetlands affect global and local climates by absorbing carbon dioxide and emitting methane (Hu et al., 2017; Russi, 2013). Furthermore, freshwater wetlands cover 1% of the earth's surface yet provide habitats for >40% of the world's species, making it a large contributor to biodiversity (Mitra, S., Wassmann, R. and Vlek, P.L.G. (eds.), 2003). Wetlands also contribute to the hydrological cycle by replenishing groundwater, regulating water movement and purifying water (Millennium Ecosystem Assessment, 2005). For human health, wetlands provide traditional medicines of which 80% of the world's population rely on for primary health care, making them an absolute necessity for humans regarding their resources (Hu et al., 2017; Mitra, S., Wassmann, R. and Vlek, P.L.G. (eds.), 2003).

Environmental DNA and stable isotopes can explain species' feeding and diet habits, providing critical information about the types of prey consumed and their relative importance (Oliveira, 2018). Furthermore, it can aid in the interpretation of population dynamics and allow appropriate conservation actions when trophic resources are the limiting factor in their distribution and habitat use, survival and reproductive success (Martin, 1987; Molina and Erwin, 2006; Newton, 1998; Toral et al., 2012). Understanding past trophic levels within wetlands can aid in future management and restoration projects as it would provide insights into which species are native and their preferred environments. Furthermore, looking at the climate and trophic levels at certain historical stages could explain extinctions. In turn, this will ensure species are not introduced into areas where they could not survive due to inappropriate climatic conditions, competition, or anthropogenic pressures.

Over a third of the world's wetlands have disappeared since the 1970s, with 83% of freshwater species declining (Wildfowl and Wetlands Trust, 2022b). In 2018 the UK Government created a 25-year Environment Plan and specified restoring wetlands on a never-before-seen scale to reduce flood risk and provide valuable ecological habitats. Reintroduction guidelines require an understanding of which wetland species are genuinely native and why they disappeared. This project would aid those guidelines and provide a database of native species and possible reasons for their demise, allowing native wetlands to be created. Furthermore, it would create a method that can be applied to the worldwide restoration of wetlands and can potentially estimate rates and causes of the decline of previous species, preserving current wildlife.

This project aims to understand how modern technologies can reconstruct past ecosystems and solve ecological questions about wetlands. Furthermore, it endeavours to answer gaps in research with regards to using environmental DNA (eDNA) and stable isotopes to create models that can estimate rates and causes of decline in wetlands. Reaching these aims will provide enough information for organisations such as the Wildfowl and Wetlands Trust (WWT) to comply with the UK Government's guidelines to create wetlands.