By Dennis Ojima, Colorado State University

The potential impact of climate changes in the Central Great Plains region (i.e., the Colorado, Kansas, Nebraska and Wyoming area) is anticipated to affect winter snowfall and snow-melt, growing season rainfall amounts and intensities, minimum winter temperatures, and average summer temperatures. The combined effect of these changes in weather patterns and average seasonal climate will affect numerous sectors critical to the economic, social, and ecological welfare of this region. In response to the call for regional assessments of these impacts, an assessment strategy has been developed which provides greater stakeholder involvement as well as scientific input.

The social and economic characteristics of the Great Plains have changed dramatically over the past 50 years. People have made changes in the manner in which they manage their lands; farm and ranch sizes are becoming larger; populations have become more concentrated in community centers or cities; and farm income is no longer the sole source of rural income for most families in the Great Plains. In addition, the population age structure is changing, and there are growing concerns regarding recruitment of new farmers and ranchers to continue the land productivity of the region. These changes in social and economic features of the Great Plains will determine the long-term sustainability of this critical agricultural region as climate changes.

The diverse water needs of the region compound the difficulty of managing water use among the various sectors. Water availability must be determined before development plans in this region are initiated. Therefore, the assessment needs to involve members of the water use and supply sectors to better understand the competing water needs among the agricultural sectors, urban and industrial uses, and natural ecosystems. Current understanding of the water needs of aquatic ecosystems under both current and projected conditions is incomplete. Water apportionment decision-making between aquatic ecosystems and human needs must be more clearly understood and evaluated. These issues need to include how best to address agricultural demands and overall water management. And changes in land use and climate will also affect water quality. For example, we need to know how to best manage livestock wastes during extreme precipitation events.

Projections by some of the general circulation models indicate that both annual average temperatures and total annual precipitation will increase over the region. However, the seasonal patterns are not uniform. For example, one model projects a 4°C increase is projected for the winter period at the end of the next century for the Colorado-Wyoming area. This warming, coupled with about a 50% increase in winter precipitation, would greatly modify the amount and timing of snow-melt from the Rocky Mountains. During the summer, minimum temperatures are projected to increase while maximum temperatures would be less affected. The change in minimum temperatures may affect plant communities by increasing the amount of cool season plant species. The hydrological cycle may also be affected, resulting in more intensive storm activity. Whether or not the plant community will be able to accommodate these changes in growing season climate or hydrological patterns is a matter of concern among stakeholders who depend on these weather patterns for their livelihood.

Changes in plant communities may also result from shifting weather patterns. The diverse plant communities and ecosystems that populate the Great Plains are sensitive to changes in habitat and climate patterns. Many of the species which have adapted to thrive in the Great Plains have adapted to the variable rainfall patterns and the warm moist summers. The agricultural and livestock industries have also adapted to these climate regimes. Changing climate patterns will cause changes in habitat extent and species mixtures for crops and livestock activities. As climate changes, the expansion of weeds and pests may occur. Our understanding of what effects the exotic species have on habitats and how climate change will affect susceptibility of different habitats to invasion needs to be included in the assessment activity.

Agricultural and rangeland ecosystems play an important role in soil conservation and land management. The agricultural management have produced beneficial systems incorporating the use of grass/legume mixtures in dryland crop rotation, different cropping systems to improve soil carbon levels and reductions of trace gas emissions, improved water management, and integrated farming analysis to evaluate changes in farm management and conservation of natural resources. These efforts need to be extended relative to changes in climate in different regions of the Great Plains.

Assessment of rangeland ecosystem relationships to livestock dynamics and invasive species relative to rangeland condition needs to be carried out. The issue of the role that the diversity of both plant and animal components of rangeland ecosystems play in maintaining good rangeland condition needs to be evaluated. Studies of climate change and carbon dioxide changes on the vegetation and animal dynamics need to be evaluated relative to the ecosystem level response to these changes. Evaluation of various management strategies for coping with climate change including alteration of changes in frequency and intensity of grazing is needed to develop strategies that promote sustainable rangeland use.

The Great Plains Assessment team is now striving to promote understanding of the relative importance of the possible effects of changes in greenhouse gas concentrations, temperature, and precipitation in the region. The team is preparing climate analyses, environmental evaluations of impacts, and a survey of coping strategies to better understand the potential opportunities and stresses this region may undergo. A stakeholder meeting will be held March 21-24, 1999 in Colorado to take stock of the range of climate change impacts on critical sectors of the region.

For more information, contact:

Dennis Ojima, Natural Resources Ecology Laboratory, Colorado State University; Fort Collins, CO 80523; phone: (970) 491-1976; fax: (970) 491-1965; email: dennis@nrel.colostate.edu