Vulpicida viridis was described as Cetraria viridis by Abraham Halsey in the first checklist of lichens of New York City in 1823. Although it was originally called Cetraria viridis, it has been continuously recognized as a very distinctive species for the two centuries since its description. It is one of six species in the genus Vulpicida and belongs to the family Parmeliaceae (Thell et al 2002). While molecular studies of Vulpicida have led to changes in species delimitation for other taxa, V. viridis has consistently been recovered as monophyletic and distinct (Mark et al 2023). Vulpicida canadensis of western North America and V. juniperina of Europe are morphologically similar species from other regions that have occasionally led to misidentified records of V. viridis from outside of its range. Many of these records were examined and corrected as part of this assessment.

The range of Vulpicida viridis spans the temperate regions of the eastern United States, especially the Coastal Plain and mountains regions of the Appalachians and Ozarks, with a disjunction in the Great Lakes region (Brodo et al. 2001). It occurs as far north as southern Canada and as far south as Louisiana and Mississippi but is mostly concentrated in the Southeastern region of the United States.

Detailed demographic data and quantitative estimates of the numbers of individuals are lacking for this species across its range. Nonetheless, population size and range of Vulpicida viridis is suspected to have decreased since the year 1990. From 1924–2024 the area of occurrence (AOO) was 952 km2. From 1990 – 2024 AOO had decreased to 392 km2.  Population decreased as well by 49%. While there are more than 10 locations where V. viridis occurs, the population is strongly fragmented due to its restriction to old growth forest habitat and reliance on mature Atlantic white cedar (Chamaecyparis)  and hardwood trees. Both the suitable habitat and substrate trees were historically widespread but subjected to significant declines and impacts from anthropogenic land-use change and habitat loss prior to 1900 (Barnes et al 2024). These trends have continued during the last one hundred years and are continuing, with both declines and further fragmentation of mature forest stands and shifts away from late successional states and taxa to mid-successional forest types with corresponding changes in local environmental conditions (Thompson et al 2013, Heilman et al 2002, Turner et al 2003). AOO is inferred to be declining and continues to decline due to old-growth forest decline, particularly Atlantic white cedar forests in the northeastern US (Howard 2024, Olson et al 2023) and oak forest fragmentation in the Ozarks (DellaSala et al 2022, Wang et al 2007).

Vulpicida viridis is a bark-dwelling species of temperate regions, where it occurs in mixed hardwood and conifer forested habitats. It has been reported most frequently from Atlantic white cedar swamps of the Coastal Plain in eastern North America (Brodo et al 2001) but records from inland temperate regions are mostly from low and middle elevation mixed hardwood and conifer forests in humid habitats, such as along waterways. Across its range the species is most often found on canopy or subcanopy tree branches and is likely a canopy specialist that requires both high light and high humidity (Tripp and Lendemer 2020).

Loss of habitat due to residential and commercial development, logging, and other factors contributing to fragmentation and decline of suitable forest stands are the primary threats to Vulpicida viridis. Atlantic White Cedar swamps used to be a significant landscape in what is now New Jersey and New York. However, beginning in the 1800s these cedar swamps were drained for small-holder farming agricultural use of their soils and cedar wood was an important resource, leading to intentional large-scale harvest and loss of mature trees (Howard 2024). By the 1970s, Atlantic White Cedar swamps were greatly reduced in this region and the keystone species of this ecosystem is considered to be in widespread decline across its range (Karlin 2024). This species favors specific tree species and bog conditions, and its range has decreased due to loss of Atlantic White Cedar forests in the Northeast and Mid-Atlantic region of the eastern United States. Its inland range in the Ozarks and Appalachian Mountains has also been significantly impacted by widespread fragmentation and declines and extent of mature forests for more than a century, which continues to present day, and is projected to continue in the future. Oak species, the primary substrate for the species in its inland range, have undergone and are undergoing large-scale die-back and declines due to increased drought conditions, invasive insects (Lymantria dispar dispar, gypsy moth) and expansion of native boring insects (Red oak borer, Enaphalodes rufulus)

Kentucky’s Lichen Inventory and Monitoring Program tracks lichens that qualify within the state as needing conservation and Vulpicida viridis is tracked as part of this program (Rodgers et al 2022). Habitat conservation is needed in areas with known populations of V. viridis, such as protection against logging in mature forests, and preventing further fragmentation by development and roads.

More research is needed on population trends and habitat trends, as well as increasing recovery, restoration strategies, and habitat.

Vulpicida viridis is collected for scientific study and does not have any other known uses.