Bot1320 Chapter 9 Long-Range Forecast
  1. As prairies continue to decline; so do organisms such as birds and bison.
    • Loss of grassland and other habitats may lead to decline of birds such as this Yellow-headed Blackbird not adapted to human disturbance.

    • Over-hunting almost brought the American Bison to extinction: by 1884 only 1,000 bison remained in North America.

      Private ranchers and non-governmental organizations (NGO) such as the Bronx Zoo and the American Bison Society has restored and preserved some herds.

      Today more than 200,000 bison exist in the U.S., though most are raised for meat consumption and have been cross-bred with domestic cattle.

      About 40-50,000 of the bison are on ranches owned by Ted Turner, who sells its meat in his Montana Grill restaurants.

  2. Prairies face numerous threats of loss and degradation.
    • habitat loss and fragmentation
      • Fragmentation of ecosystems can result in decreased biodiversity of the remnant patches.

        As the area of a habitat decrease, it species diversity also decreases.

        Ecologists Robert MacArthur and E. O. Wilson have proposed an Island Biogeography model for the relationship between fragment size and species diversity.

      • Large populations tend to have more genetic diversity.

        A small population often exhibits inbreeding, resulting in reduced genetic variation.


      • As woodlands become fragmented, edge-adapted species such as the Brown-headed Cowbird benefits at the expense of songbirds that require large, intact forests for nesting.

      • Species-area curve.

        In general, a larger geographic area has more species, as shown in this graph of North American breeding birds, plotted on a logarithmic scale.

        A 0.2-hectare plot in Pennsylvania has 3 species, while the whole U. S. and Canada, with 1.9 billion hectare, can support 625 species.

      • Island biogeography
        The equilibrium number of species on an island is a balance between the immigration of new species and the extinction of extant species. On larger islands, Immigration rates are higher and extinction rates lower, resulting in richer diversity of species. Review:

      • Ecologists Robert MacArthur and E. O. Wilson found that on the Galapagos Islands, plant species diversity increased with island size, supporting the island biogeography model.
    • energy development
      • Many types of human activity can kill birds.

        Cause Bird deaths per year (U.S.)
        Feral and domestic cats Hundreds of millions
        Power lines 130 million -- 174 million
        Windows 100 million -- 1 billion
        Pesticides 70 million
        Automobiles 60 million -- 80 million
        Lighted towers 40 million -- 50 million
        Wind turbines 10,000 -- 40,000

    • invasive plants

    • Introduced plants such as White Sweet Clover (Melilotus alba) may become invasive, establishing themselves in disturbed areas and crowding out native species.

      Many of these weeds were introduced from the Old World.

      • Garlic Mustard (Alliaria petiolata)
      • Common Buckthorn (Rhamnus cathartica)
      • White Mulberry (Morus alba)

      Some New World natives such as Gray Dogwood (Cornus racemosa) may become invasive in disturbed remnants.

  3. Opportunities for conservation still exist.
    • Significant tracts of grasslands still remain on the Great Plains; only 1% has been set aside as parks or conservation reserves.

      The Commission for Environmental Cooperation and the Nature Conservancy identified 18 intact grasslands with high biodiversity that should be given priority in conservation.

      Future conservation efforts will need cooperation between government programs, commercial interests, NGO initiatives, as well as effort from private citizens.

    • preserve relic prairies
      • Pristine prairies may still be found along railroad rights-of-way (as in the Brooks/Lease Prairie in Iowa) and in pioneer cemeteries (such as Warren Township Cemetery Prairie).

        These small parcels may contain relic prairies that have never been plowed or grazed, allowing a glimpse into what the original prairies may have looked like.

        Seeds from these relics can be good sources for restoring nearby prairies.

    • connect fragments
      • Remnant habitat fragments may be connected to form larger patches.

        • Corridors

        • Stepping stones

      • A movement corridor connects fragments of quality habitat.

        The corridor itself may not be a good natural area, but facilitates movements of individuals between habitat patches.

        This bridge in Banff National Park, Canada, helps animals cross a road.

        Note a corridor may also help spread disease and undesirable species.

      • When a continuous movement corridor is not possible, stepping stones may be used to connect habitat fragments.

        These small isolated patches may serve as resting areas, feeding waystations, or breeding refuges for organisms able to cross the gaps.

        Care should be taken to minimize gaps between the "steps": a large gap that prevents a target species from crossing becomes a "critical gap" that should be filled.

    • mitigation banking
      • Many wetlands have been drained for human development.

        One strategy for conserving wetlands is mitigation banking: a developer who removes an existing wetland (often already fragmented and degraded) can offset that loss by investing in a restored wetland elsewhere.

        Often restoration of a wetland (or even a prairie) begins with removal of existing drainage tiles.

    • establish conservation easements
      • • Private landowners may elect to set their land aside in a conservation easement.

        The land restricted from commercial development in return for payment from a government agency or conservation group.

        An example is the McDonald Farm managed by the Conservation Foundation in Naperville.

    • promote ecotourism

    • Ecotourism may provide economic incentives for local citizens to preserve habitat for wildlife.

      For example, Kearney, Nebraska bills itself as the "Sandhill Crane Capital of the World"; preserving the area's wetlands (as well as cornfields).