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Woody encroachment is a widespread phenomenon affecting grasslands and savannas worldwide. While its effects vary widely depending on local conditions, encroachment often can have adverse effects on an ecosystem. Several causes have been proposed in the literature, such as grazing of domestic livestock, fire suppression, climate change, and increasing atmospheric CO2 levels; however, the widespread removal of a native grazer, and keystone species, the prairie dog (Cynomys spp.), is one potential cause that has received little attention in North America. Prairie dogs physically alter their environment by burrowing, foraging, and maintaining short vegetation on their colonies, which provides habitat and shelter for other species, creates macropores for water percolation, turns over soil, provides young nutritious plant shoots for grazers, creates fire breaks in grasslands, and potentially suppresses woody plant growth. Despite their many services, prairie dogs have been considered pests range wide, and many eradication programs, some state and federally sponsored, were carried out beginning in the early 1900s. Because of these eradication programs, the black-tailed prairie dog (Cynomys ludovicianus; hereafter BTPD) was extirpated from Arizona by 1960, but has recently been reestablished to Las Cienegas National Conservation Area in southeastern Arizona. Our study aimed to determine if/how these recently reestablished prairie dogs were influencing the grassland ecosystem. We measured soil nutrient content on colonies and at nearby control sites, installed exclosures around woody plants, and conducted artificial sapling experiments on and around BTPD colonies. We found that prairie dog burrows contained higher concentrations of several nutrients than control sites, and that prairie dogs were having a significant effect on woody plants on their colonies. Our findings suggest that the reestablishment of this highly persecuted, yet ecologically critical species could simultaneously function as a management tool for degraded rangelands across the North American West.