An ecological trap for parasites and its impacts on human disease risk, nutrition, and income

This project focuses on the measurement of the wide variety of products and services, including benefits to human health that natural ecosystems provide and on which humans depend. For savanna ecosystems worldwide, an important ecosystem service is the production of forage for consumption by domestic livestock. While this form of resource extraction often is thought to conflict with the conservation of wildlife, recent evidence suggests that livestock and wildlife may sometimes improve forage quality for one another. In addition, recent research suggests there may be an additional benefit to the integration of livestock and wildlife in savanna ecosystems: control of ticks and tick-borne pathogens that affect wildlife, livestock, and human health. In the Laikipia District of Kenya, preliminary evidence suggests that the presence of cattle treated with acaricides (tick-specific pesticides) greatly reduces the abundance of ticks in the environment. For both livestock ranches and wildlife conservancies, this finding offers a potential management tool with important implications for the control of parasite populations that may threaten economic benefits from both wildlife ecotourism and livestock production. Ticks and tick-borne pathogens are only one of many factors that influence human well-being in savanna ecosystems, however. Despite great interest in the sustainable management of ecosystems, many of the services most critical to rural well-being, such as those that contribute to agriculture and livestock production, are missing from existing measurements of ecosystem services. In order to understand how diverse biological and social phenomena interact to determine human well-being within savanna ecosystems, this interdisciplinary research project will use an integrated approach drawing from expertise in the ecology of infectious diseases and modeling of ecosystem services to better understand the interactions between all of the ecosystems services generated by savanna ecosystems that influence human health and well-being. The researchers will experimentally manipulate the distribution of an ecological trap (acaricide-treated cattle) to rigorously assess the consequences of management strategies for tick abundance and forage quality. They will evaluate tick abundance and forage quality on ranches with a suite of replicated approaches to cattle and wildlife management, and they will develop simple production function models of this coupled natural-human system that capture forage-livestock-wildlife interactions, contributions of wildlife to tourism visitation and income, contributions of livestock to income and human nutrition, and wildlife-livestock-tick interactions that determine tick-borne disease risk. They also will employ production function models through scenario analysis to explore the consequences for wildlife and human well-being of different management strategies across the Laikipia District.

This project will integrate social and ecological approaches to advance understanding of systems in which the health of humans and nature are strongly interconnected. This project will experiment with a novel approach to parasite control that may yield numerous unintended benefits, and it will be among the first projects to attempt to assess the value of multiple different ecosystems services within a common ecosystem. The project will provide diverse educational opportunities for both U.S. and African students and scientists. The project holds promise for yielding significant benefits for society by characterizing the elements of potential win-win scenarios between natural and human components of an ecosystem, with positive ramifications for livestock husbandry, wildlife conservation, livestock and wildlife health, and human income, nutrition, and well-being. Project findings will have utility in other regions with similar socioecological contexts, possibly providing a new model for the sustainable management of coupled natural-human systems. This project is supported by the NSF Dynamics of Coupled Natural and Human Systems (CNH) Program.