Long-term monitoring reveals widespread and severe declines of understory birds in a protected Neotropical forest.

Long-term studies on the population dynamics of tropical resident birds are few, and it remains poorly understood how their populations have fared in recent decades. Here, we analyzed a 44-y population study of a Neotropical understory bird assemblage from a protected forest reserve in central Panama to determine if and how populations have changed from 1977 to 2020. Using the number of birds captured in mist nets as an index of local abundance, we estimated trends over time for a diverse suite of 57 resident species that comprised a broad range of ecological and behavioral traits. Estimated abundances of 40 (∼70%) species declined over the sampling period, whereas only 2 increased. Furthermore, declines were severe: 35 of the 40 declining species exhibited large proportional losses in estimated abundance, amounting to ≥50% of their initial estimated abundances. Declines were largely independent of ecology (i.e., body mass, foraging guild, or initial abundance) or phylogenetic affiliation. These widespread, severe declines are particularly alarming, given that they occurred in a relatively large (∼22,000-ha) forested area in the absence of local fragmentation or recent land-use change. Our findings provide robust evidence of tropical bird declines in intact forests and bolster a large body of literature from temperate regions suggesting that bird populations may be declining at a global scale. Identifying the ecological mechanisms underlying these declines should be an urgent conservation priority.

Reducing livestock effects on public lands in the western United States as the climate changes: a reply to Svejcar et al.

Svejcar et al. (Environ Manage, 2014) offered several perspectives regarding Beschta et al. (Environ Manage 51:474-491, 2013)--a publication that addressed the interacting ecological effects of climate change and domestic, wild, and feral ungulates on public lands in the western United States (US)--by largely focusing on three livestock grazing issues: (1) legacy versus current day impacts; (2) grazing as a fire reduction tool; and (3) the complexity of grazing. Regarding these issues, we indicate that (1) legacy effects to western ecosystems were indeed significant and contemporary livestock use on public lands generally maintains or exacerbates many of those effects; (2) livestock grazing has been a major factor affecting fire frequency, fire severity, and ecosystem trajectories in the western US for over a century; and (3) the removal or reduction of grazing impacts in these altered ecosystems is the most effective means of initiating ecological recovery. Svejcar et al. (Environ Manage, 2014) offer no evidence that livestock use is consistent with the timely recovery of grazing-degraded uplands, riparian areas, or stream systems. We thus conclude that public-land ecosystems can best persist or cope with a changing climate by significantly reducing ungulate grazing and related impacts.

Adapting to climate change on Western public lands: addressing the ecological effects of domestic, wild, and feral ungulates.

Climate change affects public land ecosystems and services throughout the American West and these effects are projected to intensify. Even if greenhouse gas emissions are reduced, adaptation strategies for public lands are needed to reduce anthropogenic stressors of terrestrial and aquatic ecosystems and to help native species and ecosystems survive in an altered environment. Historical and contemporary livestock production-the most widespread and long-running commercial use of public lands-can alter vegetation, soils, hydrology, and wildlife species composition and abundances in ways that exacerbate the effects of climate change on these resources. Excess abundance of native ungulates (e.g., deer or elk) and feral horses and burros add to these impacts. Although many of these consequences have been studied for decades, the ongoing and impending effects of ungulates in a changing climate require new management strategies for limiting their threats to the long-term supply of ecosystem services on public lands. Removing or reducing livestock across large areas of public land would alleviate a widely recognized and long-term stressor and make these lands less susceptible to the effects of climate change. Where livestock use continues, or where significant densities of wild or feral ungulates occur, management should carefully document the ecological, social, and economic consequences (both costs and benefits) to better ensure management that minimizes ungulate impacts to plant and animal communities, soils, and water resources. Reestablishing apex predators in large, contiguous areas of public land may help mitigate any adverse ecological effects of wild ungulates.

Shifting priorities at the Department of Energy's bomb factories: protecting human and ecological health.

More than 50 years of research, development, manufacture, and testing of nuclear weapons at Department of Energy (DOE) sites has left a legacy of on-site contamination that often spreads to surrounding areas. Despite substantial cleanup budgets in the last decade, the DOE's top-to-bottom review team concluded that relatively little actual cleanup has been accomplished, although milestones have been met and work packages completed. Rather than solely use regulatory constraints to direct cleanup, many people have suggested that human and ecological health should guide long-term stewardship goals of DOE-managed sites. The main questions are how ecological and human health considerations should be applied in deciding the extent of cleanup that contaminated sites should receive and how near-term and longer run considerations of costs and benefits should be balanced as cleanup decisions are made. One effort to protect ecological integrity is the designation of the largest sites as National Environmental Research Parks (NERPs). Recently, the Competitive Enterprise Institute (CEI) suggested isolating and conserving DOE sites as a policy priority because of their rich ecological diversity. A more effective long-term stewardship approach for former nuclear weapons complex sites may emerge if the guiding principles are to (1) reduce risks to human and ecological health, (2) protect cultural traditions, and (3) lower short- and long-term cleanup and remediation costs. A "net benefits" perspective that takes both near- and longer-term costs and consequences into account can help illuminate the trade-offs between expensive cleanup in the near term and the need to assure long-term protection of human health, cultural values, and high levels of biodiversity and ecological integrity that currently exist at many DOE sites.

Biological Integrity: A Long-Neglected Aspect of Water Resource Management.

Water of sufficient quality and quantity is critical to all life. Increasing human population and growth of technology require human society to devote more and more attention to protection of adequate supplies of water. Although perception of biological degradation stimulated current state and federal legislation on the quality of water resources, that biological focus was lost in the search for easily measured physical and chemical surrogates. The "fishable and swimmable" goal of the Water Pollution Control Act of 1972 (PL 92-500) and its charge to "restore and maintain" biotic integrity illustrate that law's biological underpinning. Further, the need for operational definitions of terms like "biological integrity" and "unreasonable degradation" and for ecologically sound tools to measure divergence from societal goals have increased interest in biological monitoring. Assessment of water resource quality by sampling biological communities in the field (ambient biological monitoring) is a promising approach that requires expanded use of ecological expertise. One such approach, the Index of Biotic Integrity (IBI), provides a broadly based, multiparameter tool for the assessment of biotic integrity in running waters. IBI based on fish community attributes has now been applied widely in North America. The success of IBI has stimulated the development of similar approaches using other aquatic taxa. Expanded use of ecological expertise in ambient biological monitoring is essential to the protection of water resources. Ecologists have the expertise to contribute significantly to those programs.

Breeding Birds of Isolated Woodlots: Area and Habitat Relationships.

We investigated breeding bird communities of isolated woodlots (1.8-600 ha) in east-central Illinois during three summers (1979-1981) to compare the influence of area and habitat on community structure. Woodlots supported from 9 to 43 species and composition was relatively constant among years. Ecological generalists dominated small woodlots, while more specialized species increased in importance with area. Area accounted for most variation (86-98%) in total species number in each year and the species-area relationship did not change significantly among years. The amount of variance accounted for by area was greater than in previous studies. Neither habitat nor woodlot isolation explained significant additional variation in total species richness after area. Area accounted for most variation in number of species in different migratory and breeding habitat categories, except for short-distance migrants, which correlated most strongly with habitat. Variation in habitat was not related to woodlot area and habitat accounted for additional variation in bird species numbers in most cases. Abundances of one-third to one-half of species examined correlated with woodlot area, but a greater proportion (66-72%) were influenced more strongly by habitat variables. Results from Illinois support previous conclusions that species that breed in forest interior habitat and winter in the tropics are most likely to be adversely affected by a reduction in forest habitat. Results also show that bird communities in isolated tracts of forest are not random assemblages, but rather that species found in smaller woodlots are subsets of species found in larger forests.