MANAGING AND SUSTAINING MANAGING AND SUSTAINING GRASSLANDSGRASSLANDS

December 19, 2011December 19, 2011

What are grasslands?What are grasslands?

Grassland biomes are…• dominant vegetation are grasses rather than trees or shrubs• also known as prairie, savanna, or steppe• located mostly in the interior of continents.• too moist for desertification – receive 15-40 inches of annual

rainfall• prevented from succeeding to forest by seasonal drought,

herbivore grazing, and fire• include pasture – usually enclosed, managed grasslands

planted with domesticated species

Grassland biomes are places where the dominant Grassland biomes are places where the dominant vegetation are grasses rather than trees or shrubs.vegetation are grasses rather than trees or shrubs.

Grassland biomes include prairie,

Savanna

Steppe

Grasslands are located mostly in the interior of continents.

Grassland biomesGrassland biomes

Grasslands are too moist for desertification. They generally receive 15-40 inches of seasonal annual rainfall.

Grasslands are prevented from succeeding to forest by seasonal drought, herbivore grazing, and fire.

Grasslands include pasture – usually Grasslands include pasture – usually enclosed, managed grasslands planted with enclosed, managed grasslands planted with domesticated species.domesticated species.

And also rangelands like this shortgrass And also rangelands like this shortgrass prairie in Montana. prairie in Montana.

Ecological Importance of Ecological Importance of GrasslandsGrasslands

Soil formationErosion controlStorage of atmospheric carbonGene pools for crossbreeding grain cropsNutrient cyclingBiodiversityHabitat Food

The moniker of amber waves of grain is no exaggeration.

According to Landscape Native, a Canadian “grassroots” organization, tallgrass prairies (TGPs) are extremely important for sequestering carbon from the air in their extensive root systems. Globally, the above and below ground storage of carbon in temperate grasslands is estimated at 335 billion tons, 97% of which is contained in the soil. This represents the amount of carbon released by 240 billion cars in one year(Amthor et al., 1998; U.S. Climate Technology Cooperation, 2007) TGPs are also great for biodiversity as they attract many insects, birds, and many other animals. 

Photo source: http://landscapenative.com/landscape_your_school

An aerial view shows the J. Clark Salyer National Wildlife Refuge, ND. Wedged amid grain fields, it remains one of the most productive breeding grounds for migratory waterfowl in the United States.

Wisp grass seedpods sway in the wind in Wisp grass seedpods sway in the wind in South Dakota's Badlands National Park. South Dakota's Badlands National Park. Fifty-six different grass species are found Fifty-six different grass species are found in Badlands.in Badlands.

Economic Importance of Economic Importance of GrasslandsGrasslands

Mostly used for agricultural purposes:• domestic crops• rangelands and pasture for livestock grazing

Lately, grasslands have become a source of biofuels such as this switchgrass plantation.

Threats to GrasslandsThreats to Grasslands

• Poor agricultural practices can strip rich grassland soils of nutrients.• Continued global warming could turn marginal grasslands into

deserts as rainfall patterns change.• Land once incompatible with row-crop agriculture, but which

provided a living to ranching families and habitat for prairie wildlife, is being converted to row crops.

• Development of urban areas is increasingly cutting into grassland habitat.

• Drought-hardy, cold-resistant, and herbicide-tolerant varieties of soybeans, wheat, and corn allow crops to expand into native grassland.

• Where only one crop is grown, pests and disease can spread easily, creating the need for potentially toxic pesticides.

The Konza Prairie, in the Flint Hills south of Manhattan, Kansas is the last remaining untouched tallgrass prairie in the United States.

Another Threat -- OvergrazingAnother Threat -- Overgrazing

• OvergrazingOvergrazing (left) occurs when too many animals graze for too long and exceed carrying capacity of a grassland area.

Figure 10-21Figure 10-21

Managing GrasslandsManaging Grasslands

Moderate grazing Moderate grazing levels are healthy• Remove mature vegetation• Stimulate plant growth• Encourages diversity

OvergrazingOvergrazing• Reduces vegetative cover• Increases erosion• Compacts soil• Makes area prone to invasion by undesirable species

UndergrazingUndergrazing – absence of grazing for > 5years

Overgrazed slope in East Timor

Sustainable Grassland Sustainable Grassland ManagementManagement

Control the number of grazing animals• Rotational grazing• Provide multiple strategic accesses to water• Supplemental feeding locations

Suppress invader plant species• Herbicide spraying• Mechanical removal• Controlled burning• Controlled, short-term trampling

Replanting and restoration with native seeds

Rotational Grazing System, Washington County, VA

A Case for Rotational GrazingA Case for Rotational Grazing

Sustainable Grassland Sustainable Grassland ManagementManagement

Example of restored area along the San Pedro River in Arizona after 10 years of banning grazing and off-road vehicles.

Figure 10-22Figure 10-22

Other SolutionsOther Solutions

• Continue education efforts on how to protect the soil and prevent soil erosion.

• Protect and restore wetlands, which are an important part of grassland ecology.

• Rotate agricultural crops to prevent the sapping of nutrients.

• Plant trees as windbreaks.• Conduct dry season burning to obtain fresh growth

and to restore calcium to the soil that builds up in the dry grasses.

Case Study: Grazing, Land Management, and Case Study: Grazing, Land Management, and Urban Development in the American WestUrban Development in the American West

• Four government agencies – the Bureau of Land Management (BLM), U.S. Forest Service, U.S. Fish & Wildlife Service and the National Park Service --administer over 383 million acres of public lands (17% of the total area of the United States).– Grazing allowed on 256 million of these acres (11%)

• As cattle ranching is supplanted by agribusiness, ranchers are selling their land to developers for housing developments, condos, and small “ranchettes.”

• Ranchers, ecologists, and environmentalists are joining together to preserve the grasslands on cattle ranches.– Paying ranchers conservation easements (barring future owners from

development).– Pressuring government to zone the land to prevent development of ecologically

sensitive areas.

What is the best strategy for preserving western U.S. grasslands?

Further Reading

• Splendor of the Grass: The Prairie’s Grip by Verlyn Klinkenborg

Work Cited:Unless otherwise cited photographs are from:Miller Jr., G.T. Living in the Environment, 15th ed. Brooks-Cole,

Thomson Learning, 2007.National Geographic Society