Defenders of Wildlife is a 501(c)(3) non-profit conservation organization based in the United States. It works to protect all native animals and plants throughout North America in their natural communities.
Ecological and evolutionary characteristics need to be combined with the taxonomic identity of species to comprehensively characterize biodiversity, and to determine the relative importance of ecological and evolutionary mechanisms in shaping spatial patterns. We examined the elevational patterns of multiple dimensions of biodiversity in two suborders of passerines (oscines and suboscines), which differ in their biogeographic history, to gain insights into the complex interplay between ecological context and historical biogeography in shaping Andean bird assemblages. Specifically, we quantified and contrasted elevational gradients of species richness, phylogenetic dispersion, and functional dispersion of passerines, suboscines, and oscines along the extensive elevational gradient of Manu Biosphere Reserve in the Peruvian Andes. Furthermore, we determined if the empirical gradients of phylogenetic and functional dispersion were indicative of non-random mechanisms dominating community assembly. For all passerines and suboscines, species richness decreased in a saturating manner, phylogenetic dispersion declined linearly, and functional dispersion was stochastic with respect to elevation. For oscines, species richness and phylogenetic dispersion decreased linearly, and functional dispersion decreased in a saturating fashion. These differences in elevational gradients of oscines and suboscines likely result from a combination of adaptations arising from radiations that occurred elsewhere and an in-situ radiation in the Andes. Combined, our results suggest that biogeographic history, evolutionary contingencies, and potentially, climatic niche conservatism within each suborder might have contributed to the elevational biodiversity gradients at Manu. Our findings highlight the importance of explicitly considering historical biogeography across phylogenetic scales when examining whole-assemblage biodiversity gradients.
Pi & ntilde;on-juniper woodlands are one of the largest ecosystems in the United States and harbormany pi & ntilde;on-juniper-associated bird species. It is a common practice to reduce tree cover and density of these woodlands for various objectives, including increasing livestock forage and reducing wildfire hazard. Understanding the different pathways of how pi & ntilde;on-juniper thinning affects bird species of conservation concern is important for both woodland management and avian conservation and thus warrants investigation. In this study, we aimed to understand the pathways of the effects of pi & ntilde;on-juniper woodland thinning on bird species groups of high, moderate, and low conservation concern, as well as seven priority bird species. During the month of May from 2021 to 2023, we collected count data with distance sampling and removal sampling information from 46 1km & times; 1 km plots (23 treated <= 10 years previously and 23 controls). We then used these data to estimate abundance of bird species across the gradients of pi & ntilde;on-juniper thinning and eight environmental factors such as canopy cover. By using a path analysis based on N-mixture modeling, we were able to decompose the effects of pi & ntilde;on-juniper thinning on avian abundance that can be explained by the environmental factors considered or by other unmeasured factors. Our results revealed multiple pathways of the effects of pi & ntilde;on-juniper thinning on bird groups and species. Overall, pi & ntilde;on-juniper thinning had negative effects on the species group of high and moderate conservation concerns, mainly through reduced tree density and canopy cover. Pi & ntilde;on-juniper thinning also had negative effects on five priority species: Pinyon Jay (Gymnorhinus cyanocephalus), Woodhouse's Scrub-Jay (Aphelocoma woodhouseii), Juniper Titmouse (Baeolophus ridgwayi), Virginia's Warbler (Leiothlypis virginiae), Black-throated Gray Warbler (Setophaga nigrescens), and a positive effect on one priority species (Gray Vireo, Vireo vicinior), with this total effect being explained by environmental factors considered or unmeasured factors, depending on the species. Our results showed that the pathways of the effects of pi & ntilde;on-juniper thinning on avian biodiversity were complicated and multifaceted, and indicated that a reevaluation of thinning in pi & ntilde;on-juniper woodlands might be needed.
We synthesized reported threats to US imperiled species to identify which of the five predominant drivers of biodiversity loss-climate change, invasive species, land and sea use change, pollution, and overexploitation-negatively influence species persistence across taxa. Using threats identified at listing under the Endangered Species Act (ESA), International Union for Conservation of Nature (IUCN) assessments, and novel climate sensitivity assessments, we document which drivers affect the 2766 imperiled species analyzed. Our results are the first in which climate change has been identified as the leading threat to species listed under the ESA. We found that updated climate sensitivity assessments are essential for understanding the breadth of this threat. We also show that the majority of US imperiled species experience multiple threats, with some groups such as cnidarians, bivalves, and amphibians facing a higher total number than average. As climate change rapidly accelerates, we emphasize the need for up-to-date assessments and highlight existing data gaps.
Development can pose a substantial threat to imperiled species listed under the US Endangered Species Act (ESA), particularly as two‐thirds of these species rely on private lands. Habitat Conservation Plans (HCPs) outlined in Section 10(a)(1)(B) of the ESA have emerged as crucial instruments for harmonizing conservation and development needs. Yet, despite being established for over 30 years, the HCP program's impact remains inadequately understood. Consequently, we evaluated 629 HCPs—covering 38 states and territories, and 748 species—to assess the program's transparency, organization, and impact by examining three key factors: (1) the presence of required documents, (2) the adequacy of monitoring, and (3) the consistency of conservation measures. A lack of required documents made it difficult to quantitatively assess the overall impact of the program, including the adequacy of monitoring. Conservation measures outlined in the plans were also often inconsistent. Our findings indicate that enhancements are needed to modernize data management, increase transparency, strengthen oversight to improve the monitoring and evaluation of both individual HCPs and the program overall, and establish or update species conservation standards. These changes could significantly improve program functionality, streamline development and implementation processes, and offer greater opportunities to gauge success in the program.
The National Wildlife Refuge System (NWRS) presents an opportunity for climate‐change refugia conservation through the expansion of the U.S. protected areas network. Dedicated to conserving and restoring fish, wildlife, and plants and their habitats, the U.S. Fish and Wildlife Service (USFWS) uses best available science to assess three main criteria in the evaluation and prioritization of proposed new refuges and refuge expansions: species listed under the U.S. Endangered Species Act, migratory birds, and waterfowl. We used spatial datasets to explore the current and potential capacity for national wildlife refuges to serve as climate‐change refugia and enable the persistence of these three priority groups of species. We developed a refugia metric for each of the three species groups, analyzing values for lands and waters managed by the agency, approved for acquisition, and within 25 km of managed boundaries. We found that, as a whole, the NWRS had significantly greater refugia value than, on average, for the contiguous United States, with variability by USFWS region and refugia metric. While, on average, acquiring approved interests in lands and waters did not significantly increase the refugial value of the NWRS, it did not lower its elevated value, suggesting that current interests could also make a relatively strong contribution. Importantly, there was high variability among refuge units with regard to the refugial value of approved acquisition areas and refuge‐adjacent areas, providing expansion options that resulted in improvements for all refugia metrics and regions. We discuss the implications of these findings for expansion as well as additional considerations for next steps and application.
