Home » Climate Change Impacts to Grasslands
Climate change impacts to grasslands and prairie bioregions include increased seasonal, annual, minimum, and maximum temperature and changing precipitation patterns. Because these ecosystems are relatively dry with a strong seasonal climate, they are sensitive to climatic changes and vulnerable to shifts in climatic regime. For example, model simulations show that regional drought in the Prairie Pothole Region may result in loss of valuable habitat for breeding waterfowl, from an area that historically has produced 50-80% of the continent’s ducks. Dryer and hotter conditions may also lead to the encroachment of new species, and a greater risk of wildfire.
Increasing temperatures, reduced rainfall, and drought are already being observed in some regions, and the arid Southwest in particular is projected to become even drier in this century. In wetter areas forests are likely to encroach on existing savannas, while in increasingly arid areas deserts projected to expand in extent and move upward in elevation, causing “desertification” of arid grassland ecosystems.
Drought is a major driver of impacts to grassland and prairie ecosystems, and is likely to lead to increased wildfires and loss of wetland habitats – such as prairie potholes that are critical habitat for migratory bird species – as well as species migration and habitat shifts. Vegetation shifts from C3 to C4 grassland communities and phenological shifts will impact ecosystems and species, and changes in species composition and plant productivity may also impact the human communities that rely on agricultural production in these regions. NASA satellite imagery indicates predictable changes in plant productivity are already occurring worldwide.
Slight changes in temperature and precipitation can substantially alter the composition, distribution, and abundance of species in arid lands, and the products and services they provide. For example, observed and projected decreases in the frequency of freezing temperatures, lengthening of the frost-free season, and increased minimum temperatures can alter plant species ranges and shift the geographic and elevational boundaries of many arid lands. The extent of these changes will also depend on changes in precipitation and fire. Increased drought frequency could also cause major changes in vegetation cover. Losses of vegetative cover coupled with increases in precipitation intensity and climate-induced reductions in soil aggregate stability will dramatically increase potential erosion rates. Transport of eroded sediment to streams coupled with changes in the timing and magnitude of minimum and maximum flows can affect water quality, riparian vegetation, and aquatic fauna. Land trusts and conservation agencies are already observing these changes and are working to identify risks, reduce vulnerabilities, and manage grassland systems for shifting conditions.
"C3" and "C4" refer to different biochemical reactions that occur during photosynthesis - C3 plants produce three carbon atoms and C4 produce four. C4 plants include typically low-latitude crops such as maize, sugar-cane, millet, and many pasture and forage grasses. C3 plants include mid-latitude food staples such as wheat, rice, and soybean.
In the central plains of the United States grasslands are typically dominated by a few highly productive C4 grass species as well as numerous C3 forb species, which must compete with the dominant grasses for multiple potentially limiting resources, including nitrogen, water, and light. In general C4 plants uptake water and store carbon more efficiently than C3 plants, however, both of these plant types play important roles in the ecological makeup of current grasslands and prairies. In an environment of increasingly warm temperatures, periodic drought, and low nitrogen availability, C4 dominance over the C3 species may occur, with potentially dramatic impacts to habitat and species within these sensitive systems.