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Little question exists that the main bodies of North American prairie (i.e., the tall‐grass, mixed, and shortgrass) are among the most endangered resources on the continent. The purpose of this paper is to provide a past and present biological baseline by which to understand North American prairies and to provide a platform for future conservation. Events both immediate to the end of the Pleistocene and historic suggest that the present grassland conditions are different from those within which most of the grassland organisms evolved. Our analysis suggests that few grassland landscapes remain adequate in area and distribution to sustain diversity sufficient to include biota and ecological drivers native to the landscape. A robust and history‐based scenario to conserve Great Plains grasslands is to 1) identify areas large enough to sustain an ecological system with all its biodiversity, 2) reverse significant losses in area of native grasslands, 3) ensure that restoration matches the grassland previously existing at that site, 4) refocus the profession of range management, and 5) establish a more meaningful agency design for grassland and natural resource management.

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Conservation of riparian vegetation in westernNorth America ha~ in parg emphasized providing habitats for a locally diverse avifaunat Site diversity, especially reia. tire to the number of species preseng is generally high within riparian avifaunas. Between-habitat diversity changes across a watersheag with riparian species assemblages differ. ing most from upland assemblages at the highest and lowest elevation~ This pattern can be attributed to enhanced avian movements within the riparian vegetatiorL The corridors for bird movements, in turn, facilitate faunal mixing on a broader scal~ influencing regional diversity within land-scape~ Riparian ecosystems are viewed as connectors of forests across fragmented landscape~ In western setting& however, they are highly lineartzed forests transecting watersheds between upland associations of high elevations and very different associations at lower elevation£ Regionally, riparian vegetation represents linear islands that are internally both flortstically and faunistically dynamic rather than mere bridges of homogeneous vegetation in landscape network~ The significance of riparian vegetation as habitat for western birds has been defined primartly at the local level Conservation activities fatmring site dimity are short.sightea[ however, and could have severe consequences for unique elements of riparian avifauna~ Conservation actions must evaluate how local activities alter potential dispersal opportunities for ecological-generalist versus riparian-obligate specie~ Maintaining the character and integrity of riparian avifaunas requires planning from regional and continental perspective~ Perspectivas de escala sobre la diversidad de ayes en ecosistemas riberefios del oeste Resumen: La conservaci6n de ia vegetaci6n riberefm en el oeste de Am&rica del Norte ha enfatizado en parte la provi-si6n de hdbitats para una avifauna localmente diversct La diversidad de sitiog en especial relativos al nt~mero de especies presente~ es generalmente alta en avifaunas rtbereBa~ La dtversidad entre hd.bitats cambtag a lo largo* de una cuenc~ con eusambles ae especies ri~ diflriendo rods de los ensambles de tierras altas en las elevaciones menores y mayore~ Este patr6n puede set atrihuido al realce de los movimientos de las aves dentro de la vegetaci6n ribere~ Los corredores para el movimiento de ave~ a su vez, facilitan la mezcla fauntstica a una escala mas ampit¢ tnfluenciando la diversidad regional dentro de los paisaje.z Los eco-sisterm~ ribere~os son vistos como conectores de forestas a lo largo de paisaJes fragmentado~ En ambtentes del oest¢ sin embargo, estos son forestas altamente ltnearizadas que atraviezan cuencas entre asociaciones de tterras altas de gran elevaci6n y asociaciones muy diferentes en elevaciones menore~ Regionalment~ la vegetaci6n riberegua repmenta islas tineares que son internamente dindmtcas tanto floristtca como fauntsticament~ no siendo meros puentes de ve-getaci6n homogd, nea en redes de paisajex El significado de la vegetact6n ribem~ como hdbitats para aves del...

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