Using environmental DNA to inform biodiversity conservation in agricultural landscapes

The conversion of natural ecosystems to agriculture is a leading cause of habitat loss and threatens global biodiversity. For the past two centuries, the Midwestern United States (U.S.) has experienced agricultural intensification and expansion, resulting in losses of native tallgrass prairies, wetlands, and forests. To mitigate agricultural pressures, conservation practices have been widely implemented across the Midwest. As a result, forest cover in Midwestern states like Illinois has increased over the last several decades partially due to agricultural conservation practices like riparian buffers, which can improve water quality, alleviate nutrient transfer and reduce soil loss. While the benefits of riparian buffers to aquatic taxa are well-documented, benefits to terrestrial biodiversity are less understood. To monitor wildlife across taxa, a combination of conventional methods can be costly, time-consuming and invasive. Environmental DNA (eDNA), DNA collected and isolated from environmental samples, can provide a solution to this challenge. Further, rivers have proven to be conveyor belts of not only aquatic DNA but also terrestrial eDNA as well from upstream or adjacent riparian areas. Among many factors that can influence eDNA dynamics in a river, precipitation can either dilute eDNA due to increasing discharge or mobilize eDNA into rivers from adjacent riparian terrestrial ecosystems. For my first study, I sampled three rivers before and after precipitation events in the Vermilion River watershed of east-central Illinois to evaluate if terrestrial DNA exhibits a mobilization effect and if aquatic eDNA exhibits a dilution effect in response to rainfall. I found that rainfall had a positive, significant effect on terrestrial taxa richness and a negative, non-significant effect on aquatic taxa richness. This study not only advances eDNA applications for vertebrate community analysis but also informs future eDNA sampling efforts for detecting terrestrial and aquatic taxa from lotic environments. For my second study, I collected eDNA samples from streams across a forest cover gradient in central Illinois to quantify the terrestrial biodiversity co-benefit of riparian buffers, a proposed agricultural conservation practice for the Midwest, to terrestrial wildlife. I demonstrated that sites with complete (100%) riparian buffers can support three times the terrestrial vertebrate taxa richness compared to sites lacking buffers entirely, with highly forested sites harboring unique forest-associated communities. This study demonstrates the benefit of riparian buffers to terrestrial wildlife and validates eDNA as a rapid biomonitoring tool to assess biodiversity responses to agricultural conservation practices. Collectively, my thesis research seeks to support biodiversity conservation across agricultural landscapes.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Natural Res & Env Sciences

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Reves, Olivia P.

Contributors dc:contributor

• Larson, Eric R.
• Davis, Mark A
• Stickley, Samuel F.

• Agricultural Conservation
• Biodiversity
• Edna
• Environmental Dna
• Illinois
• Metabarcoding
• Riparian Buffers
• Stream Flow
• Vertebrates

Statement dc:rights

• Copyright 2025 Olivia Reves

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/130031

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F130031