EVIDENCE THAT LOCAL LAND-USE PRACTICES INFLUENCE REGIONAL CLIMATE, VEGETATION, AND STREAM-FLOW PATTERNS IN ADJACENT NATURAL AREAS

We present evidence that land use practices in the plains of Colorado influence regional climate and vegetation in adjacent natural areas in the Rocky Mountains in predictable ways. Mesoscale climate model simu lations using the Colorado State University Regional Atmospheric Model ling System (RAMS) projected that modifications to natural vegetation in the plains, primarily due to agriculture and urbanization, could pr oduce lower summer temperatures in the mountains. We corroborate the R AMS simulations with three independent sets of data: (i) climate recor ds from 16 weather stations, which showed significant trends of decrea sing July temperatures in recent decades; (ii) the distribution of see dlings of five dominant conifer species in Rocky Mountain National Par k, Colorado, which suggested that cooler, wetter conditions occurred o ver roughly the same time period; and (iii) increased stream flow, nor malized for changes in precipitation, during the summer months in four river basins, which also indicates cooler summer temperatures and low er transpiration at landscape scales. Combined, the mesoscale atmosphe ric/land-surface model, short-term trends in regional temperatures, fo rest distribution changes, and hydrology data indicate that the effect s of land use practices on regional climate may overshadow larger-scal e temperature changes commonly associated with observed increases in C O2 and other greenhouse gases.