SG: Collaborative Research: Effects of changing wildlife communities across climatic contexts on tick-borne disease in California

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Humans are concurrently changing the environment and wildlife communities. These two forms of global change have the potential to impact human, wildlife, and livestock exposure to infectious disease. Notably, these include vector-borne diseases which are carried and transmitted by blood-feeding invertebrates such as ticks, flies, and mosquitoes. Changes in environmental conditions may increase development rates of these vector species, or increase temperature-induced mortality. Similarly, removing or replacing large wildlife with livestock may alter food availability and reproductive ability for these vector species. Understanding the separate and combined impacts of these two forms of environmental change is thus of critical importance for both public health and wildlife conservation. This is particularly true for tick-borne diseases, like Lyme disease, where medical treatment can be problematic and costly. This study aims to understand how tick-borne disease risk will be impacted by environmental change and wildlife or livestock management to better prevent disease transmission. Notably this project will also support K-12 education by providing new scientific training to underserved 5th grade students in the Kids in Nature program. It will further support a Citizen Science mobile phone application on tick borne disease, which both engages the public in data collection and provides valuable information on tick abundance and risk of tick-borne disease. Many undergraduate and graduate students from underserved backgrounds will receive training in both field and lab components of this project. This project will mechanistically examine the effects of large wildlife loss coupled and the addition of livestock on tick abundance, tick-borne disease prevalence, and disease risk, under a range of climatic conditions. The study will use 1) a large-scale field exclosure experiment, replicated across a strong climate gradient serving as a proxy for regional environmental change predictions, and 2) a large-scale observational study across the same climate gradient and utilizing natural variation in wildlife/livestock densities. This project will be conducted in California, which is experiencing both warming and drying climates and strong declines in large wildlife with concomitant increases in livestock. In order to understand generality across systems, this study will investigate impacts on multiple tick species with variable life histories. Specifically, this project will evaluate the following hypotheses: 1) the effects of large wildlife removal on density of infected ticks will vary by tick species depending on the tick?s life history, 2) livestock and large wildlife will have very similar effects in this system, with effects proportionate to their biomass, 3) density of infected ticks will be lower in more arid environments and the effects of large herbivores on ticks will be stronger in more arid climates, and 4) both the magnitude and direction of the effect will vary based on tick life history strategyThis award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.