Changes in Site Occupancy of Marsh‐Breeding Frogs Are Associated With Surrounding Land Cover: Implications for Conservation Planning

Conservation of frogs and toads (Anura, hereafter frogs) is challenging, especially in highly‐developed landscapes. To help ensure the growth and persistence of populations, we quantified how initial occupancy and subsequent local extinction or colonization of eight marsh‐breeding frog species, or groups of species, were influenced by the composition of, and concurrent changes in, surrounding land cover within 200–6400 m. We used data from the Great Lakes Marsh Monitoring Program delivered by Birds Canada at 377 sites across four time periods (2000–2001, 2005–2006, 2010–2011, 2015–2016) throughout southern Ontario, Canada, and land cover data from the Southern Ontario Land Resource Information System (SOLRIS). Occupancy of four species was positively associated with surrounding wetland and forest land cover, as shown by higher initial occupancy or colonization, or lower local extinction where surrounding wetland or forest land cover was higher. Occupancy of four species was negatively associated with surrounding urban land cover, as shown by lower initial occupancy or higher local extinction where surrounding urban land cover was higher. Occupancy was positively related to surrounding agricultural land cover in three species, as shown by higher initial occupancy or lower local extinction, and was lower in Great Lakes coastal wetlands compared to inland wetlands in three species, as shown by lower initial occupancy or colonization, or higher local extinction. Most of the positive associations with surrounding wetland or forest land cover (63%), and the negative associations with surrounding urban land cover (60%), were within 3.2 and 6.4 km. These findings suggest that protecting and/or increasing wetland and forest land cover connected by safe movement pathways and limiting urban expansion should occur within at least 3 km of the wetland edge, and ideally within 6 km, to be effective for frog conservation in southern Ontario and other highly‐developed landscapes.