Climate warming will continue alongside human modification of the landscape. Therefore, studying systems modified by land use may highlight factors that mitigate or exacerbate predicted biological responses to ongoing climate warming. Using historical museum specimen records and recent field surveys, I examine temporal patterns in the ecological dynamics of the small mammal fauna on five mountain ranges in central Utah over time intervals of 27-53 years during the past century. This landscape was heavily modified by livestock grazing early in the twentieth century and since then has witnessed a steady decline in grazing intensity. In general, at regional and landscape scales, species preferring mesic habitats increased in percent abundance, rank abundance, and rank occurrence over time. This result is opposite that predicted from regional climate trends and probably represents the recovery of forest conditions following a release over time from earlier periods of severe overgrazing. Decreased grazing intensity may thus mitigate the predicted biological effects of climatically driven environmental change for small mammals. This work also illustrates that abundance data gleaned from natural history collections can be an appropriate tool for assessing temporal changes in composition, especially when comparisons are drawn using time- and space-averaged data sets.
