The contribution of federal and nonfederal habitat to persistence of the northern spotted owl on the Olympic Peninsula, Washington: report of the reanalysis team.

Abstract

We analyzed likely patterns of distribution and persistence of northern spotted owls (Strix occidentalis caurina) on the Olympic Peninsula. Analysis focused on the effects of Federal habitat under provisions of the Northwest Forest Plan; additional benefits to the owl population of different levels of habitat retention on non-Federal lands; effects of establishing a habitat connection between the Olympic Peninsula and other parts of the owl's range; the likely rate of habitat regrowth in the National Forest and its effect on the owl population; and the likely effect of a worst-case fire. We used a spatially explicit population model for northern spotted owls for the analysis and also reviewed current information on demographics and likely owl population numbers on the Olympic Peninsula. We concluded that it is likely, but not assured, that a stable population of northern spotted owls would be maintained in portions of the Olympic National Forest and the Olympic National Park in the absence of any non-Federal contribution of habitat, and that the retention of non-Federal habitat would make a biologically significant contribution to the maintenance of the population. Finally, we concluded that a habitat connection across southwestern Washington, based on the design proposed by the Northern Spotted Owl Recovery Team, would have little effect on the status of the owl population on the peninsula if that population was stable or nearly stable.

How Big and How Close? Habitat Patch Size and Spacing to Conserve a Threatened Species

“…6); LNVM likewise suggested, albeit only qualitatively, that preserving connectivity outweighs benefits from increasing size of habitat clusters. Also, based on modeling work by Holthausen et al [1995] and Raphael et al [1998], Noon and McKelvey (1996:157) subsequently recommended that “more recent modeling suggests that carrying capacities of perhaps 30–40 pairs per HCA [habitat cluster] are needed.”…”

Optimization of Habitat Placement: A Case Study of the Northern Spotted Owl in the Olympic Peninsula

“…Following completion of the NFP (FEMAT 1993) as part of the analyses in support of a Final Environmental Impact Statement, Raphael et al (1994) used a spatially explicit simulation model (''OWL,'' McKelvey et al 1992) to evaluate how owl populations might respond to land allocations under the NFP compared to under two alternative plans. In a subsequent analysis this simulation model was used to compare alternative scenarios for management of owl habitat on the nonfederal land in the Olympic Peninsula (Holthausen et al 1995). The latest alternative being considered by the U.S.…”

“…This alternative, hereafter referred to as ''the plan,'' will be analyzed in this paper. Following Holthausen et al (1995), we will divide the Olympic Peninsula into hexagonal 1500-ha cells, the size of which represents a core area or territory for an owl pair. This yields a model with 1681 cells (41 ϫ 41), with the carrying capacity set at zero for any cell that does not currently contain any habitat.…”

“…To bracket the likely actual population behavior of the owl, we include two ''rule sets'' from Holthausen et al (1995): rule set ''B,'' which is relatively pessimistic, and rule set ''D,'' which is relatively optimistic (relative to projected rates of population change). These rule sets contain parameter estimates for adult and juvenile survival rates and fecundity in relation to amount of habitat in each cell.…”

Forest Structure Within Barred Owl (Strix varia) Home Ranges in the Eastern Cascade Range, Washington

“…The specific importance of the role of non-Federal lands will vary by individual physiographic province and conditions within each province. Holthausen et al (1995), Raphael et al (1995), Michaels (1996) and Hof and Raphael (1997) We remain poorly informed concerning habitat trends on non-Federal lands. A recent report (American Resource Council, 2004) illustrates the difficulty in obtaining data that could relate to habitat change on private lands.…”