The Imprinting Foundation



April 17, 2002

R.M. Dixon

Exotic invasive species are often cited as endangering natives second only to habitat loss. However the cause-and-effect relationship between habitat loss and invasion by exotics is often overlooked or underemphasized. Without habitat loss, exotics are seldom capable of invading, let alone endangering species. This is certainly true of southern Arizona where habitat has been lost for a number of endangered species because of the invasion of two mammals-Europeans and their cattle. Cattle have nearly eradicated the native perennial grasses that were uniquely capable of holding the rainwater resources in place to nourish native plant communities, recharge upland aquifers and feed springs and streams for flourishing riparian habitats. Exotic grasses were introduced to provide forage for the exotic cattle while providing some of the hydrologic functions of the native grasses. Native grasses are no longer adapted because of habitat loss and the inability to cope with the grazing by large herbivores with whom they had not coevolved. Thus what we need in southern Arizona is restoration of habitat not eradication of exotic grasses by destructive means. In fact, the exotics can even be helpful in the ecological restoration of habitat and the protection of endangered species. Land imprinting uses weeds to advance the causes of ecological restoration and sustainable agriculture.

Photo: Imprinter mulched exotic tumbleweed in Avra Valley ,
AZ aids revegetation of abandoned croplands.

The Imprinting Foundation
1616 E. Lind Road
Tucson, AZ 85719

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