Anthropogenic disturbance and land alteration driven by urbanization and agriculture produce high local extinction rates and are a primary cause of decreasing biological diversity. Classic theories predict how disturbance can both maintain and reduce diversity because disturbance alters the environments to which species are currently adapted. Although rare species and habitat specialists may be at a greater risk due to localized disturbances that fragment and alter their niches, we have a limited understanding of how habitat type and functional groups influence local extinctions. Examination of a large sample of species can reveal the traits that influence the distribution of taxa across habitats and inform their vulnerability to local extinction. We use historical data from Kalamazoo County, MI, to investigate habitat-specific patterns of diversity decline, correlate disturbance with species loss, and examine what functional groups may be most at risk. A model testing the role of niche breadth, rarity (the number of Michigan counties a species is found in), disturbance (determined as whether a site is near a railway or road), genus, and several species-specific factors on the current status of local species was developed to investigate the role of disturbance and habitat in local extinction rates.
Certain habitats, namely prairies and wooded wetlands, have experienced high rates of extinction, and this habitat variation is important for the persistence of regionally rare species (habitat c2=55.74, p<0.0001; rarity c2=59.31, p<0.0001; community*rarity c2=6.31, p=0.09). Disturbance affects community extinction differently depending on habitat characteristics, and is especially harmful to locally rare species (habitat*disturbance*rarity interaction, c2=9.54, p<0.0001). This result suggests that management needs to focus on spatially differentiated patterns of diversity loss. Extinction also varies by genus (c2=330.69, p<0.0001), suggesting that evolutionary history and traits may influences responses to human disturbance. To investigate this, we examined extinction rates for several functional groups, and found that native species, forbs, and species with limited niches or at the edge of their native range are more vulnerable to local extinction. This nonrandom distribution of extinction reflects the idea that certain species attributes are beneficial or detrimental in the face of anthropogenic change and land use. Understanding spatial and taxonomic patterns of local extinctions will aid in identification of the species and habitats that are most in need of conservation attention.