Linking culture, ecology and policy: the invasion of Russian-olive (Elaeagnus angustifolia l.) on the Crow Indian Reservation, south-central Montana, USA
2013 Spring. ; Includes bibliographical references. ; Native plant diversity in riparian systems is currently threatened by the invasive Russian olive (Elaeagnus angustifolia L.) replacing woody riparian species, including plains cottonwood (Populus deltoides Marsh), used for centuries by the Apsáalooke or Crow Tribe of south-central Montana. The Dawes Act of 1887, also known as the Allotment Act, created a land tenure system that restricted ownership rights and forced an unfamiliar agro-economy on the Crow people. Land cessations, illegal land sales and/or leases over the last century resulted in a mosaic of private non-Indian land ownership parcels interspersed within Crow tribal and individual allotment lands. Crow Tribe and individual land allotments are held in trust by the federal government and managed by the federal trust agent, U.S Department of Interior-Bureau of Indian Affairs (BIA). Elaeagnus angustifolia was intentionally planted in the early 20th century along the floodplains of the Little Bighorn and Bighorn Rivers to support a largely non-Indian owned agro-economy. Mapped presence points of E. angustifolia trees within land use type and land ownership status were used as an indirect measure of policy induced invasion. Stem density of E. angustifolia (stem/km2) varied significantly by land use type (13 predictor variables) (p 1.0) suggesting that near-term climate changes may influence the spread of E. angustifolia, particularly downstream from diversion dams used for irrigation purposes. Personal interviews of Crow Elders overwhelmingly agreed (~80%) that sub-adult cottonwood trees were the most difficult to find now compared to 25 years ago. Maximum distances to travel to obtain sub-adult size classes used exclusively in ceremony increased in present-day by 30 km compared to recent history. Plot data comparing near and far from ceremonial and Crow Fair campground sites indicated that cottonwood stem heights (from 7.32 m plots where n=10) were significantly shorter near ceremony sites ( 2.4 km away; p 55 years) had higher knowledge than younger age groups. Taken in total, I conclude that E. angustifolia is displacing culturally important native biota harvested by the Crow people, and has heavily invaded private or fee-patent lands. Density of this species in allotted lands, however, is not managed by the Crow, as approximately two thirds are leased to non-Indians for farming or ranching operations. Lack of access and management oversight by the Crow Tribe for all lands within the reservation boundaries resulted in drastic changes in vegetation from the once dominant plains cottonwood to an almost mono-culture of E. angustifolia. Growth of this thorny shrub severely restricts the ability to harvest important woody species used in the expression of Crow culture through ceremony. Traditional Crow knowledge related to harvesting practices of culturally important native biota may be in the initial stages of erosion. Future land policy should reflect the ability of the Crow Tribe to manage invasive species within reservation boundaries, regardless of ownership class. To preserve traditional knowledge of native biota, E. angustifolia removal projects coupled with re-vegetation of culturally important species closer to Crow communities will allow access by Elders, and hence preserve their rich cultural knowledge for generations to come.