Northwest Forest Plan, the first 15 years (1994-2008) : status and trend of nesting habitat for the marbled murrelet

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The primary objectives of the effectiveness monitoring plan for the marbled murrelet (Brachyramphus marmoratus) include mapping baseline nesting habitat (at the start of the Northwest Forest Plan [...

The primary objectives of the effectiveness monitoring plan for the marbled murrelet (Brachyramphus marmoratus) include mapping baseline nesting habitat (at the start of the Northwest Forest Plan [the Plan]) and estimating changes in that habitat over time. Using vegetation data derived from satellite imagery, we modeled habitat suitability by using a maximum entropy model. We used Maxent software to compute habitat suitability scores from vegetation and physiographic attributes based on comparisons of conditions at 342 sites that were occupied by marbled murrelets (equal numbers of confirmed nest sites and likely nest sites) and average conditions over all forested lands in which the murrelets occurred. We estimated 3.8 million acres of higher suitability nesting habitat over all lands in the murrelet's range in Washington, Oregon, and California at the start of the Plan (1994/96). Most (89 percent) baseline habitat on federally administered lands occurred within reserved-land allocations. A substantial amount (36 percent) of baseline habitat occurred on nonfederal lands. Over all lands, we observed a net loss of about 7 percent of higher suitability potential nesting habitat from the baseline period to 2006/07. If we focus on losses and ignore gains, we estimate a loss of about 13 percent of the higher suitability habitat present at baseline, over this same period. Fire has been the major cause of loss of nesting habitat on federal lands since the Plan was implemented; timber harvest is the primary cause of loss on nonfederal lands. We also found that murrelet population size is strongly and positively correlated with amount of nesting habitat, suggesting that conservation of remaining nesting habitat and restoration of currently unsuitable habitat is key to murrelet recovery.

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