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outcrossing species); or demographic factors, such as extirpation of isolated colonies following a stochastic event without the possibility of re- establishment due to lack of nearby colonies. In the future it may be desirable to try to re- connect fragmented populations by reintroducing these rare species to protected sites such as restored former agricultural lands where the conditions are appropriate. Fragmentation of land ownership between public and private parties can lead to conflicts when actions taken on private lands (such as application of pesticides) may have adverse impacts on adjacent protected habitats. Loss of important ecological processes - Certain environmental parameters, for example, seasonal temperature and precipitation patterns, are still reasonably intact in Willamette Valley prairies, despite the legacy of habitat loss over the last 150 years. But a number of important ecological processes, such as fire and flooding, to which Willamette Valley prairies were subject for thousands of years, have been greatly diminished or eliminated from the landscape. The examples mentioned here have been the subject of some field research (Pendergrass, 1995; Finley 1994), and further research and monitoring, over a period of many years, will be vital to better identify and understand the important ecological processes occurring within Willamette Valley prairies. Loss of keystone animal species and important ecological services- In many ecosystems, certain keystone species provide important ecological services of habitat structure that numerous other plant and animal species, including rare species, rely upon. Examples include birds or mammals that excavate cavities in trees or excavate burrows in the ground; insects that pollinate the flowers of native plants, and animals that disperse seeds of native plants. At present we know very little about ecological interactions at this level that may be important in west Eugene and in similar habitats elsewhere in the Willamette Valley. Implications of invasive non - native species - One predominant feature of remnant Willamette Valley habitats is the abundance of non - native species, both plant and animal, which have the capability to disrupt native communities and diminish populations of rare native prairie species. Typically, even when resources exist to address non - native species problems, they are reactive rather than pro- active, and the focus on specific sites or ownerships without examining trends occurring over larger areas. For example, it may be difficult and expensive to eliminate an invasive non - native species when a large population exists on adjacent lands under other ownership. Working across ownerships, both public and private, may be the best way to address specific invasive species, especially when infestations are relatively recent and still fairly small. Invasive non - native species removal will be much more cost efficient if isolated patches (foci) can be eliminated while they are still relatively small. 17