Effective conservation of old-growth ecosystems, along with their unique biodiversity and climate benefits, requires coordinated actions from the scale of individual trees to broad regions. The US government is currently developing a conservation strategy for old-growth forest on federal lands, and similar efforts are occurring globally as nations implement the Kunming-Montreal Global Biodiversity Framework. An effective strategy must include elements at three spatiotemporal scales: immediate restrictions on harvest of old-growth and mature forests and old trees, standards to ensure management activities do not degrade old growth at the stand scale, and longer-term planning for old-growth restoration and recruitment across landscapes. Lessons from previous US forest policy, especially the Northwest Forest Plan, can inform efforts to strengthen each of these three components in the US old-growth conservation strategy. Ecosystem-based standards are needed to ensure protection of sufficient mature forest so that recruitment into the old-growth stage shifts ecosystems closer to historic proportions of old growth. In addition to clarifying existing goals related to ecological integrity, comprehensive old-growth policy must incorporate specific goals for recovering at-risk species based on empirical relationships across scales of biodiversity between forest habitat and species viability that are relevant across varied ecological contexts. Reversing extinction debt and ensuring long-term adaptation potential requires designation of large landscapes anchored by remaining old-growth stands, surrounded by areas managed for restoration of ecological integrity, native biodiversity, and ecosystem services including climate change mitigation.
Results from the pretreatment habitat factor analysis using the nine local-scale forest structure variables measured at four study sites in Arizona and New Mexico.
Effective wildlife conservation strategies require an understanding of how fluctuating environmental conditions affect sensitive life stages. As part of a long-term study, we examined post-fledging and post-independence survival of 89 radio-marked juvenile Northern Goshawks (Accipiter gentilis) produced from 48 nests in northern Arizona, USA, during 1998–2001. Information-theoretic methods were used to examine within- and among-year variation in survival relative to environmental (prey abundance, weather), territory (hatching date, brood size), and individual (gender, body mass) sources of variation. The results support age- and cohort-specific differences in survival that were best explained by behaviors occurring at distinct stages of juvenile development, annual changes in the density of primary bird and mammal prey species, and gender-related differences in body mass. Survival between fledging and independence increased linearly with age and varied among annual cohorts of radio-marked juveniles from 0.81 (95% ci = 0.60–0.93) to 1.00 (95% ci = 0.95–1.00) in association with annual differences in prey density; the slope coefficient for the additive effect of prey density on survival was 1.12 (95% ci = 0.06– 2.19). Survival declined to 0.71 (95% ci = 0.60–0.93) shortly after juveniles initiated dispersal (weeks 8–12 post-fledging) and moved to more open habitats at lower elevations. Survival was not closely associated with weather or territory-level parameters. A comparison of the predictions of environmental-, territory-, and individual-based models of survival demonstrated that food availability was the primary factor limiting juvenile survival. This finding indicates that forest management prescriptions designed to support abundant prey populations while providing forest structural conditions that allow goshawks to access their prey within breeding areas should benefit juvenile survival.
The Prairie Pothole Region (PPR) of the north-central U.S. and south-central Canada contains millions of small prairie wetlands that provide critical habitat to many migrating and breeding waterbirds. Due to their small size and the relatively dry climate of the region, these wetlands are considered at high risk for negative climate change effects as temperatures increase. To estimate the potential impacts of climate change on breeding waterbirds, we predicted current and future distributions of species common in the PPR using species distribution models (SDMs). We created regional-scale SDMs for the U.S. PPR using Breeding Bird Survey occurrence records for 1971–2011 and wetland, upland, and climate variables. For each species, we predicted current distribution based on climate records for 1981–2000 and projected future distributions to climate scenarios for 2040–2049. Species were projected to, on average, lose almost half their current habitat (-46%). However, individual species projections varied widely, from +8% (Upland Sandpiper) to -100% (Wilson's Snipe). Variable importance ranks indicated that land cover (wetland and upland) variables were generally more important than climate variables in predicting species distributions. However, climate variables were relatively more important during a drought period. Projected distributions of species responses to climate change contracted within current areas of distribution rather than shifting. Given the large variation in species-level impacts, we suggest that climate change mitigation efforts focus on species projected to be the most vulnerable by enacting targeted wetland management, easement acquisition, and restoration efforts.
We tested three predictions of a hypothesis that states Northern Spotted Owls (Strix occidentalis caurina) select habitat according to the distribution of their primary prey. Our predictions were that Northern Spotted Owls should (1) select larger (> 100 g) species among the assemblage of available prey, (2) select habitats according to the distribution of large prey, and (3) the owl's reproductive success should be influenced by the availability of large prey. We also evaluated the potential energetic value of several prey species. We found that Northern Spotted Owls (n = 11 pairs and 1 single male) in northwestern California differentially selected the dusky-footed woodrat (Neotoma fuscipes), a moderately large sigmodontine rodent (x¯ mass = 232 g). When foraging, owls selected late seral forest edge sites where dusky-footed woodrats were more abundant. Although the relationship between site selection, prey abundance, and the owl's breeding success was not statistically significant, the average abundance of dusky-footed woodrats at sites foraged by breeding owls (x¯ = 11.4 woodrats 100-trap-nights-1) was greater than at sites foraged by nonbreeding owls (x¯ = 4.7 woodrats 100-trap-nights-1). We estimated that a male Spotted Owl would require 150,015 to 336,232 kJ over a 153-day period while helping to produce one young, and concluded that the selection of woodrats provided a potential energetic benefit over the use of other prey. These findings provide a partial explanation for the owl's affinity for late seral forests.
Sex ratio, and the extent to which it varies over time, is an important factor in the demography, management, and conservation of wildlife populations. Greater sage‐grouse Centrocercus urophasianus populations in western North America are monitored using counts of males at leks in spring. Population estimates derived from lek‐count data typically assume a constant, female‐biased sex ratio, yet few rigorous, empirically derived estimates of sex ratio are available to test that assumption. We estimated pre‐breeding sex ratio of greater sage‐grouse in a peripheral, geographically isolated population in northwestern Colorado during two consecutive winters using closed‐population, robust‐design, multi‐state, genetic mark–recapture models in program MARK. Sex ratio varied markedly between years, with estimates of 3.29 (95% CI: 2.36–4.59) females per male in winter 2012–2013 and 1.54 (95% CI: 1.22–1.95) females per male in winter 2013–2014. Rather than assuming a constant sex ratio, biologists should consider the potential for large annual variation in sex ratio of greater sage‐grouse populations when estimating population size or trend from male lek‐count data.
Abstract In December 1997, Secretary of Agriculture Dan Glickman convened an interdisciplinary committee of 13 scientists to provide scientific and technical advice on the Forest Service's land and resource management planning process. The committee was asked to recommend how best to accomplish resource planning within the existing environmental laws and statutory mission of the Forest Service; to provide technical advice on planning and provide material for the agency to consider in revising planning regulations; to recommend improvements in coordination with other federal agencies, state and local government agencies, and tribal governments; and to suggest a new planning framework that could last a generation. The committee took field trips and met in cities and towns around the country to hear from Forest Service employees, representatives of tribes, state and local governments, related federal natural resource agencies, and members of the public. Drawing on many of the approaches and improvements to planning it observed, the committee has made its recommendations.
