Julia Lenhardt Dissertation Defense
Title: Evaluating Impact: Ecosystem Services for Monitoring Sustainable Land Management
Abstract: This dissertation investigates the use of broadscale ecosystem service modeling for monitoring sustainable land management efforts on working lands. The focus is primarily on California farmland but also explores the potential of similar analyses in the data-scarce region of the Congo Basin. Chapter 1 reviews fifty-two agricultural incentive programs in California, assessing their prioritized ecosystem services and comparing them to the impacts of the top funded federal conservation practices. The findings reveal some overlap in goals and outcomes, but several ecosystem services require additional attention in the allocation of resources through federal incentives.
Chapter 2 further explores the influence of farming practices on environmental benefits in California from 2010 to 2020 using land cover change analysis and ecosystem service modeling. This chapter analyzes the trade-offs between soil erosion control, soil carbon storage, and food production across five agricultural regions in California. The results indicate that these trade-offs vary by regional context, with significant land use changes, particularly in almond production, leading to diverse impacts statewide. While overall soil organic carbon storage and erosion control increased, the study suggests that sustainable land management practices are unlikely to be the cause of such changes, and incentive programs may need to be regionally tailored for optimal outcomes.
Chapter 3 develops a novel index combining landscape-scale spatial entropy with annual crop rotation to examine the spatiotemporal patterns and drivers of agricultural diversity in California from 2010 to 2020. This research finds that the most diverse farmlands are in the state's most productive areas, driven by high-value crops and extensive irrigation infrastructure. It also reveals positive correlations between agricultural diversity and agrochemical inputs and higher temperatures, but a negative correlation with most native species biodiversity. Federal conservation incentive programs showed no significant impact on agricultural diversity, emphasizing the need to re-evaluate these programs to genuinely enhance biodiversity and reduce reliance on irrigation and agrochemicals.
Finally, Chapter 4 addresses the critical role of accurate land use and land cover (LULC) data in ecosystem service modeling, particularly in data-scarce regions like the Congo Basin. This chapter evaluates the influence of eight global LULC datasets on erosion control modeling, revealing substantial discrepancies and overall accuracies below 60%. The study projects a 16.52% increase in soil erosion by 2030 due to LULC changes, intensified by predicted increases in precipitation. This highlights the urgent need for robust, high-resolution LULC maps and international partnerships to reduce uncertainty in conservation planning for tropical forest ecosystems. Collectively, this dissertation underscores the complex interplay between land use and ecosystem services, advocating for regionally specific, data-driven, and adaptively managed conservation strategies to achieve genuine sustainability and resilience.