Prairie landscapes and broad spatio-temporal scales: Implication for managing short-term human systems

Todd A. Radenbaugh

Over the last 200 years in the northern Great Plains, land use has transformed the landscape from a grassland/wetland system (over 90% cover in 1880s) to an agroecosystem (presently croplands cover over 60%). Further, human social systems have reallocated energy, space, and resources away from native prairie systems; consequently, there has been a decline in abundance and distribution of prairie-associated species. Thus, in as little as 100 years society has become a major functional component of this ecosystem. What are the broad ecological implications of this? The answers may lie in the study of fossil diversity patterns. Broad-scale fossil evidence shows that large biophysical systems can remain stable or even reoccur for extended periods, resilient to many physical disturbances such as climatic or sea level change. However, when major biological innovations evolve the fossil record suggests that significant ecological change in interaction webs also occur. Thus, periods of ecological and evolutionary stasis are followed by punctuated intervals of structural change where regional species associations experience extinction, immigration, and rapid speciation. Thus, paleontological theory may provide a framework for modern studies of human sustainability and the current broad-scale ecosystem alteration. To explore this, regional resource use of breeding birds in the Mixed Grassland Ecoregion of Saskatchewan was examined for changes in ecosystem-level functions due to agriculture. Bird species that use prairie resources were in sharp decline; however, the regional species richness and diversity increased. This was due to introduced or immigrated bird species that utilize the ecological space and resources added by modern agricultural society. Thus, the broad-scale biotic interactions of this region may have been altered. This indicates that the region's natural selection forces are diversifying and evolutionary changes as seen in the fossil record may be occurring.