Woody Invasion in the Great Plains Diminishes Water Resources

New research details impacts to water from encroaching eastern redcedar and other conifers on landscapes in the Great Plains.

A new study from University of Nebraska-Lincoln ecologist and Working Lands for Wildlife partner, Dirac Twidwell, synthesized decades of research on the growing impact of invading conifers.

The Great Plains cover one-fifth of America and provide critical farming and agricultural lands, while hosting numerous grassland-dependent species, like the lesser prairie-chicken. Comprised predominantly of grasslands, the Great Plains depended on regular low-severity fire, which removed woody plants and maintained native grass cover. As historic fire regimes have been altered through fire suppression and land conversion, woody plants like eastern redcedar, Ashe juniper, and mesquite have moved into rangelands at an alarming and increasing rate.

This vegetation conversion is a national issue given how it affects the economies of several states that play key roles in agricultural production and wildlife habitat.

Simple transitions in vegetation can have far-reaching impacts. This study shows how trees taking over rangelands can affect working lands, wildlife and water in complex ways — even impacting our well-being in metro areas. – Dirac Twidwell, study author.

Key Findings from the study:

• Lesser prairie-chickens won’t nest in grasslands with more than one tree-per-acre and stop using grasslands altogether when tree density reaches three trees-per-acre. (Read a prior Science to Solutions about this here.)
• Encroaching woody species are rapidly taking over native prairie in the Great Plains, which causes unfortunate ecologic, economic, and hydrologic consequences.
• These impacts include: forage loss, increased risk of fire, decreased habitat quality for wildlife, and diminished water resources.
• Model simulations suggest that complete conversion of rangelands to redcedar woodlands in the central Great Plains would reduce streamflows by 20-40 percent.

Fortunately, through a variety of Working Lands for Wildlife and Lesser Prairie-Chicken Initiative projects, producers and land managers are removing encroaching conifers. In fact, through Working Lands for Wildlife, the NRCS has worked with producers to remove encroaching conifers on 110,000 acres of rangeland in the Great Plains.