Urban protected areas are an important resource to people and wildlife, providing many ecosystem services. During the initial phase of the COVID-19 pandemic lockdown during March-June 2020, there was a major increase in the number of hikers and bicyclists in urban protected areas, including the Webster Woods in Newton, Massachusetts (USA), an 82.5-ha protected area. The Webster Woods is one of the largest protected areas near the center of Boston and is widely used in conservation textbooks as an example of the effects of habitat fragmentation on the amount of undisturbed habitat. Prior to the pandemic, the Webster Woods had been extensively fragmented by paved roads, dirt roads, and trails, with little interior habitat remaining. During the first four months of the pandemic, hikers and bicyclists made 4.9 km of new social (or informal) trails, an increase of 36%. This recent fragmentation represents a dramatic increase in the level of human impact on the area, reducing the amount of interior habitat from 3.2 to 2.1 ha. Levels of human activity returned to pre-pandemic levels in autumn 2020 and city officials have started closing access to some of the new trails, allowing vegetation to regrow. It is possible that similar increases in social trails and associated fragmentation have occurred in other protected areas (especially those in urban areas) around the world due to the pandemic, and these disturbances should be evaluated for their effects on plant and animal populations.