Search USGS⌕ Search

SEARCH · Search USGS

Results for “Biodiversity”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38Linked to original sources
USGS2025

Reframing fish passage prioritization for human nutrition outcomes

Water control infrastructure forms barriers that fragment river habitats, reducing aquatic biodiversity and the ecosystem services it provides. Irrigation infrastructure, for example, although implemented to support food production, highlights problematic trade-offs against wild food systems like inland fisheries which are a critical food resource for tens of millions of people, particularly in tropical countries. To reduce fragmentation at a broad range of barriers, fish passage technology is sometimes implemented to support migrating fish, aided by frameworks designed to prioritize barriers for remediation. This study critically evaluated 93 fish passage barrier prioritization frameworks globally to explore how they could strategically guide fish passage investments in tropical contexts and identify criteria relevant to delivering on nutrition security outcomes. Results showed prioritization frameworks were ill-equipped to support the broader human development goals that may drive fish passage investments in tropical countries, such as supporting human nutrition under United Nations Sustainable Development Goal (SDG) 2: Zero Hunger. Tropical contexts were underrepresented despite substantial recent fish passage investment, whereas temperate and conservation focused frameworks, particularly from North America, dominated. These findings prompt reflection on the inherent biases in fish passage barrier prioritization frameworks and criteria. Improving understanding of and collaboration with local partners to integrate SDG 2 into future prioritization frameworks could improve fish passage infrastructure and help support better nutrition and food production for communities.

Environmental Management↗
USGS2003

Future coral reef habitat marginality: Temporal and spatial effects of climate change in the Pacific basin

Marginal reef habitats are regarded as regions where coral reefs and coral communities reflect the effects of steady-state or long-term average environmental limitations. We used classifications based on this concept with predicted time-variant conditions of future climate to develop a scenario for the evolution of future marginality. Model results based on a conservative scenario of atmospheric CO2 increase were used to examine changes in sea surface temperature and aragonite saturation state over the Pacific Ocean basin until 2069. Results of the projections indicated that essentially all reef locations are likely to become marginal with respect to aragonite saturation state. Significant areas, including some with the highest biodiversity, are expected to experience high-temperature regimes that may be marginal, and additional areas will enter the borderline high temperature range that have experienced significant ENSO-related bleaching in the recent past. The positive effects of warming in areas that are presently marginal in terms of low temperature were limited. Conditions of the late 21st century do not lie outside the ranges in which present-day marginal reef systems occur. Adaptive and acclimative capabilities of organisms and communities will be critical in determining the future of coral reef ecosystems.

Conference Paper↗
USGS2012

Abiotic and biotic controls of cryptobenthic fish assemblages across a Caribbean seascape

The majority of fish studies on coral reefs consider only non-cryptic species and, despite their functional importance, data on cryptic species are scarce. This study investigates inter-habitat variation in Caribbean cryptobenthic fishes by re-analysing a comprehensive data set from 58 rotenone stations around Buck Island, U.S. Virgin Islands. Boosted regression trees were used to associate the density and diversity of non-piscivorous cryptobenthic fishes, both in the entire data set and on reef habitats alone, with 14 abiotic and biotic variables. The study also models the habitat requirements of the three commonest species. Dead coral cover was the first or second most important variable in six of the eight models constructed. For example, within the entire data set, the number of species and total fish density increased approximately linearly with increasing dead coral cover. Dead coral was also important in multivariate analyses that discriminated 10 assemblages within the entire data set. On reef habitats, the number of species and total fish density increased dramatically when dead coral exceeded ~55 %. Live coral cover was typically less important for explaining variance in fish assemblages than dead coral, but live corals were important for maintaining high fish diversity. Coral species favoured by cryptobenthic species may be particularly susceptible to mortality, but dead coral may also provide abundant food and shelter for many fishes. Piscivore density was a key variable in the final models, but typically increased with increasing cryptobenthic fish diversity and abundance, suggesting both groups of fishes are responding to the same habitat variables. The density of territorial damselfishes reduced the number of cryptobenthic fish species on reef habitats. Finally, habitats delineated by standard remote sensing techniques supported distinct cryptobenthic fish assemblages, suggesting that such maps can be used as surrogates of general patterns of cryptic fish biodiversity in conservation planning.

Coral Reefs↗
USGS2010

Microbial community shifts influence patterns in tropical forest nitrogen fixation

The role of biodiversity in ecosystem function receives substantial attention, yet despite the diversity and functional relevance of microorganisms, relationships between microbial community structure and ecosystem processes remain largely unknown. We used tropical rain forest fertilization plots to directly compare the relative abundance, composition and diversity of free-living nitrogen (N)-fixer communities to in situ leaf litter N fixation rates. N fixation rates varied greatly within the landscape, and 'hotspots' of high N fixation activity were observed in both control and phosphorus (P)-fertilized plots. Compared with zones of average activity, the N fixation 'hotspots' in unfertilized plots were characterized by marked differences in N-fixer community composition and had substantially higher overall diversity. P additions increased the efficiency of N-fixer communities, resulting in elevated rates of fixation per nifH gene. Furthermore, P fertilization increased N fixation rates and N-fixer abundance, eliminated a highly novel group of N-fixers, and increased N-fixer diversity. Yet the relationships between diversity and function were not simple, and coupling rate measurements to indicators of community structure revealed a biological dynamism not apparent from process measurements alone. Taken together, these data suggest that the rain forest litter layer maintains high N fixation rates and unique N-fixing organisms and that, as observed in plant community ecology, structural shifts in N-fixing communities may partially explain significant differences in system-scale N fixation rates.

Oecologia↗
USGS2012

New parasites and predators follow the introduction of two fish species to a subarctic lake: implications for food-web structure and functioning

Introduced species can alter the topology of food webs. For instance, an introduction can aid the arrival of free-living consumers using the new species as a resource, while new parasites may also arrive with the introduced species. Food-web responses to species additions can thus be far more complex than anticipated. In a subarctic pelagic food web with free-living and parasitic species, two fish species (arctic charr Salvelinus alpinus and three-spined stickleback Gasterosteus aculeatus ) have known histories as deliberate introductions. The effects of these introductions on the food web were explored by comparing the current pelagic web with a heuristic reconstruction of the pre-introduction web. Extinctions caused by these introductions could not be evaluated by this approach. The introduced fish species have become important hubs in the trophic network, interacting with numerous parasites, predators and prey. In particular, five parasite species and four predatory bird species depend on the two introduced species as obligate trophic resources in the pelagic web and could therefore not have been present in the pre-introduction network. The presence of the two introduced fish species and the arrival of their associated parasites and predators increased biodiversity, mean trophic level, linkage density, and nestedness; altering both the network structure and functioning of the pelagic web. Parasites, in particular trophically transmitted species, had a prominent role in the network alterations that followed the introductions.

Takvatn Lake↗
USGS2018

Increasing temperature seasonality may overwhelm shifts in soil moisture to favor shrub grass dominance in Colorado Plateau drylands

Ecosystems in the southwestern U.S. are hotspots for climate change, and are predicted to experience continued warming and drying. In these water-limited systems, the balance between herbaceous and woody plant abundance impacts biodiversity and ecosystem processes, highlighting the need to understand how climate change will influence functional composition. However, variability in topo-edaphic conditions, notably soil texture and depth, as well as a long history of disturbance, confound efforts to quantify specific climatic controls over plant functional composition. Here, we utilized a mechanistic soil water model and identified the timing and depth at which soil moisture related most strongly to the balance between grass and shrub dominance in the Southern Colorado Plateau. Shrubs dominate where there is high soil moisture availability during winter, and where temperature is more seasonally variable, while grasses are favored where moisture is available during summer and temperatures are higher. Climate change projections indicate increases in seasonal temperature variability and decreases in summer soil moisture, which both favor shrub dominance. However, projections also include substantial and reliable increases in temperature, which favors grass dominance. Rising temperatures overwhelm both the soil moisture and temperature variability effects favoring shrubs such that our models indicate increasing grasses at these sites. This approach, which incorporates local, edaphic factors at sites protected from disturbance, improves understanding of climate change impacts on plant functional composition and may be useful in other complex dryland regions with high edaphic and climatic heterogeneity.

Colorado Plateau↗
USGS2021

Behaviorally-mediated trophic cascade attenuated by prey use of risky places at safe times

The mere threat of predation may incite behavioral changes in prey that lead to community-wide impacts on productivity, biodiversity, and nutrient cycling. The paucity of experimental manipulations, however, has contributed to controversy over the strength of this pathway in wide-ranging vertebrate systems. We investigated whether simulated gray wolf ( Canis lupus ) presence can induce behaviorally-mediated trophic cascades, specifically, whether the ‘fear’ of wolf olfactory cues alone can change deer foraging behavior in ways that affect plants and soils. Wolves were recently removed from the Cedar Creek Ecosystem Science Reserve (Minnesota, USA), such that consumptively mediated predator effects were negligible. At 32 experimental plots, we crossed two nested treatments: wolf urine application and herbivore exclosures. We deployed camera traps to quantify how white-tailed deer ( Odocoileus virginianus ) adjusted their spatiotemporal habitat use, foraging, and vigilance in response to wolf cues and how these behavioral changes affected plant productivity, plant communities, and soil nutrients. Weekly applications of wolf urine significantly altered deer behavior, but deer responses did not cascade to affect plant or soil properties. Deer substantially reduced crepuscular activity at wolf-simulated sites compared to control locations. As wolves in this area predominantly hunted during mornings and evenings, this response potentially allows deer to maximize landscape use by accessing dangerous areas when temporal threat is low. Our experiment suggests that prey may be sensitive to ‘dynamic’ predation risk that is structured across both space and time and, consequentially, prey use of risky areas during safe times may attenuate behaviorally-mediated trophic cascades at the predator–prey interface.

Minnesota↗
USGS2021

Modeling effects of disturbance across life history strategies of stream fishes

A central goal of population ecology is to establish linkages between life history strategy, disturbance, and population dynamics. Globally, disturbance events such as drought and invasive species have dramatically impacted stream fish populations and contributed to sharp declines in freshwater biodiversity. Here, we used RAMAS-Metapop to construct stage-based demographic metapopulation models for stream fishes with periodic, opportunistic, and equilibrium life history strategies and assessed their responses to disturbance scenarios that approximated the effects of invasion, drought, and the additive effects of both disturbances. Our models indicated that populations respond differentially to disturbance based on life history strategy. Equilibrium strategists were best able to deal with simulated invasion. Periodic strategists did well under lower levels of drought, whereas opportunistic strategists outperformed other life histories under extreme seasonal drought. When we modeled additive effects scenarios, these disturbances interacted synergistically, dramatically increasing terminal extinction risk for all three life history strategies. Modeling exercises that examine broad life history categories can help to answer fundamental ecological questions about the relationship between disturbance resilience and life history, as well as help managers to develop generalized conservation strategies when species-specific data are lacking. Our results indicate that life history strategy is a fundamental determinant of population trajectories, and that disturbances can interact synergistically to dramatically impact extinction outcomes.

Oecologia↗
USGS2002

Effects of stress from mine drainage on diversity, biomass, and function of primary producers in mountain streams

This paper proposes a hypothesis that relates biodi- versity, community biomass, and ecosystem func- tion to a gradient of stress. According to this hy- pothesis, biodiversity has a low threshold of response to stress, whereas biomass and function are stable or increase under low to moderate stress and decrease only under high stress. This hypothe- sis was tested by examining communities of pri- mary producers in streams under stress from mine drainage in the Rocky Mountains of Colorado, USA. Mine drainage exerts chemical stress (low pH, dis- solved metals) as well as physical stress (deposition of metal oxides) on stream biota. Diversity of pri- mary producers was usually more sensitive to stress from mine drainage than community biomass (chlorophyll a) or primary production. Diversity was negatively related to all stresses from mine drainage, but it was especially low in streams with low pH or high concentration of dissolved zinc. Biomass and production were high in streams with only chemical stress, but they were often low in streams with physical stress caused by metal oxide deposition. Stream sites with aluminum oxide dep- osition usually had very little algal biomass. The rate of metal oxide deposition, presence of alumi- num oxides, and pH together explained 65% of the variation in biomass. The rate of net primary pro- duction was highly correlated with biomass and had a similar response to stress from mine drainage. Overall, chemical stresses (low pH, high concentra- tion of zinc) generally led to the hypothesized trends in our model of ecosystems under stress. Physical stress (deposition of metal oxides), how- ever, led to variable responses, and often decreased biomass and function even at low intensity, con- trary to the original hypothesis. Thus, the nature of ecosystem response to stress may differ for chemical and physical stresses

Colorado↗
USGS2025

The structural and functional impacts of invasive Psidium cattleianum in forests on the Island of Hawai’i

During the past century, the proliferation of invasive species has contributed to loss of biodiversity and ecosystem degradation. In forests, invasive tree species can alter ecosystem function, but the underlying mechanisms of these changes are not fully understood. We use the ongoing invasion of P. cattleianum on the Island of Hawai’i to test the hypotheses that invasive structural changes drive changes to forest evapotranspiration (ET). The aim of our study is first to quantify the structural changes to native ‘ōhi‘a -dominated forest impacted by a gradient of P. cattleianum invasion. Our results suggest that invasive P. cattleianum causes significant changes to the vegetation density and structure of native forest on the Island of Hawai’i, including increased vegetation area index, decreased mean leaf height, and decreased structural heterogeneity. Second, we strove to understand the functional implications of structural changes through a biophysical modeling simulation, testing the sensitivity of ET to canopy structure under contrasting scenarios. Modeling the functional impact of structural change, we found that plots with P. cattleianum invasion importance value (IV inv ) above 0.35 have a higher likelihood to increase ET compared to plots with P. cattleianum invasion less than 0.35 IV inv . Modeled increases in ET due to invasion ranged from 19 and 123% relative to native transects. The large variation in ET increases is caused by structural variation because the modeling scenarios did not include potential species differences in leaf physiology. Diagnostic scenario modeling shows the effect size of increased leaf area on modeled ET is constrained by the structural arrangement, that is vertical distribution, of the increased vegetation. Thus, invasion structure that increases vegetation density in taller, more sunlit forest strata will lead to a greater increase in ET compared to invasion structure that increases vegetation density in the shaded forest understory. Overall, we conclude the vertical distribution of vegetation is an important factor shaping the impact of invasive P. cattleianum on the forest water balance.

Hawaii↗
USGS2013

Variation in hair δ 13 C and δ 15 N values in long-tailed macaques (Macaca fascicularis) from Singapore

Much of the primatology literature on stable isotope ratios of carbon (δ 13 C) and nitrogen (δ 15 N) has focused on African and New World species, with comparatively little research published on Asian primates. Here we present hair δ 13 C and δ 15 N isotope values for a sample of 33 long-tailed macaques from Singapore. We evaluate the suggestion by a previous researcher that forest degradation and biodiversity loss in Singapore have led to a decline in macaque trophic level. The results of our analysis indicated significant spatial variability in δ 13 C but not δ 15 N. The range of variation in δ 13 C was consistent with a diet based on C 3 resources, with one group exhibiting low values consistent with a closed canopy environment. Relative to other macaque species from Europe and Asia, the macaques from Singapore exhibited a low mean δ 13 C value but mid-range mean δ 15 N value. Previous research suggesting a decline in macaque trophic level is not supported by the results of our study.

Primates↗
USGS2023

Long-term trends of local bird populations based on monitoring schemes: Are they suitable for justifying management measures?

Local biodiversity monitoring is important to assess the effects of global change, but also to evaluate the performance of landscape and wildlife protection, since large-scale assessments may buffer local fluctuations, rare species tend to be underrepresented, and management actions are usually implemented on local scales. We estimated population trends of 58 bird species using open-population N-mixture models based on count data in two localities in southeastern Spain, which have been collected according to a citizen science monitoring program (SACRE, Monitoring Common Breeding Birds in Spain) over 21 and 15 years, respectively. We performed different abundance models for each species and study area, accounting for imperfect detection of individuals in replicated counts. After selecting the best models for each species and study area, empirical Bayes methods were used for estimating abundances, which allowed us to calculate population growth rates ( λ ) and finally population trends. We also compared the two local population trends and related them with national and European trends, and species functional traits (phenological status, dietary, and habitat specialization characteristics). Our results showed increasing trends for most species, but a weak correlation between populations of the same species from both study areas. In general, local population trends were consistent with the trends observed at national and continental scales, although contrasting patterns exist for several species, mainly with increasing local trends and decreasing Spanish and European trends. Moreover, we found no evidence of a relationship between population trends and species traits. We conclude that using open-population N-mixture models is an appropriate method to estimate population trends, and that citizen science-based monitoring schemes can be a source of data for such analyses. This modeling approach can help managers to assess the effectiveness of their actions at the local level in the context of global change.

Journal of Ornithology↗
USGS2008

Reef fishes have higher parasite richness at unfished Palmyra Atoll compared to fished Kiritimati Island

We compared parasite communities at two coral atolls in the Line Islands chain of the central Pacific (Kiritimati Island and Palmyra Atoll). Palmyra Atoll is relatively pristine while Kiritimati Island is heavily fished. At each island, we sampled five fish species for helminth and arthropod endoparasites: Chromis margaritifer , Plectroglyphidodon dickii, Paracirrhites arcatus , Acanthurus nigricans , and Lutjanus bohar . The surveys found monogeneans, digeneans, cestodes, nematodes, acanthocephalans, and copepods. Parasite richness was higher at Palmyra compared to Kiritimati for all five fish species. Fishes from Palmyra also tended to have more parasites species per host, higher parasite prevalence, and higher parasite abundance than did fishes from Kiritimati. The lower parasitism at Kiritimati may result from a simplified food web due to over fishing. Low biodiversity could impair parasite transmission by reducing the availability of hosts required by parasites with complex life cycles. Most notably, the lower abundances of larval shark tapeworms at Kiritimati presumably reflect the fact that fishing has greatly depleted sharks there in comparison to Palmyra.

EcoHealth↗
USGS2014

Moving beyond too little, too late: managing emerging infectious diseases in wild populations requires international policy and partnerships

Emerging infectious diseases (EIDs) are on the rise due to multiple factors, including human facilitated movement of pathogens, broad-scale landscape changes, and perturbations to ecological systems (Jones et al. 2008; Fisher et al. 2012). Epidemics in wildlife are problematic because they can lead to pathogen spillover to new host organisms, erode biodiversity and threaten ecosystems that sustain human societies (Fisher et al. 2012; Kilpatrick 2011). There have been recent calls for large-scale research approaches to combat threats EIDs pose to wildlife (Sleeman 2013). While it is true that developing new analytical models, diagnostic assays and molecular tools will significantly avance outr abilities to respond to disease threats, we also propose that addressing difficult problems in EIDs will require considerable shofts in international health policy and infrastructure. While there are currently international organizations responsbile for rapidly initiating and coordinating preventative measures to control infectious diseases in human, livestock, and arable systems, there are few comparable instiutions that have the authority to implement transnational responses to EIDs in wildlife. This absence of well-developed infastructure hampers the rapid responses necessary to mitigate international spread of EIDs.

EcoHealth↗
USGS2017

Batrachochytrium salamandrivorans and the risk of a second amphibian pandemic

Amphibians are experiencing devastating population declines globally. A major driver is chytridiomycosis, an emerging infectious disease caused by the fungal pathogens Batrachochytrium dendrobatidis ( Bd ) and Batrachochytrium salamandrivorans ( Bsal ). Bd was described in 1999 and has been linked with declines since the 1970s, while Bsal is a more recently discovered pathogen that was described in 2013. It is hypothesized that Bsal originated in Asia and spread via international trade to Europe, where it has been linked to salamander die-offs. Trade in live amphibians thus represents a significant threat to global biodiversity in amphibians. We review the current state of knowledge regarding Bsal and describe the risk of Bsal spread. We discuss regional responses to Bsal and barriers that impede a rapid, coordinated global effort. The discovery of a second deadly emerging chytrid fungal pathogen in amphibians poses an opportunity for scientists, conservationists, and governments to improve global biosecurity and further protect humans and wildlife from a growing number of emerging infectious diseases.

EcoHealth↗
USGS2012

Influence of salinity and prey presence on the survival of aquatic macroinvertebrates of a freshwater marsh

Salinization of coastal freshwater environments is a global issue. Increased salinity from sea level rise, storm surges, or other mechanisms is common in coastal freshwater marshes of Louisiana, USA. The effects of salinity increases on aquatic macroinvertebrates in these systems have received little attention, despite the importance of aquatic macroinvertebrates for nutrient cycling, biodiversity, and as a food source for vertebrate species. We used microcosm experiments to evaluate the effects of salinity, duration of exposure, and prey availability on the relative survival of dominant aquatic macroinvertebrates (i.e., Procambarus clarkii Girard, Cambarellus puer Hobbs, Libellulidae, Dytiscidae cybister ) in a freshwater marsh of southwestern Louisiana. We hypothesized that increased salinity, absence of prey, and increased duration of exposure would decrease survival of aquatic macroinvertebrates and that crustaceans would have higher survival than aquatic insect taxon. Our first hypothesis was only partially supported as only salinity increases combined with prolonged exposure duration affected aquatic macroinvertebrate survival. Furthermore, crustaceans had higher survival than aquatic insects. Salinity stress may cause mortality when acting together with other stressful conditions.

Aquatic Ecology↗
USGS2023

Ecological benefits of integrative weed management of Melaleuca quinquenervia in Big Cypress National Preserve

The southern tip of North America coalesces into one of the world’s largest freshwater wetlands, the Everglades, Florida, USA. Though this region is much like an island, home to high biodiversity and endemism, it is also the site of a century of development and associated landscape-scale species invasions. Melaleuca quinquenervia (hereafter melaleuca), a tree native to tropical Australia, was planted extensively throughout south Florida as street trees, levee stabilizers, and later to reduce standing water in marshy areas. Through extensive cooperation with the United States Department of Agriculture’s Australian Biological Control Laboratory, several biological control agents were released, three of which later successfully established. Herein we examine evidence that plant community shifts determined from vegetation surveys and remotely sensed images reflect changes from melaleuca-dominated wetlands (before management) to native communities (after management). Melaleuca-dominated community types decreased from 1990 to 2020 by more than 99%. Vegetation surveys also reflect an increase in cypress wetlands, pinelands, and open water wetlands, all of which were dominated by melaleuca in previous decades. We also found the normalized difference vegetation index (NDVI) increased in melaleuca-invaded wetlands during peak infestations but decreased again after communities recovered to sawgrass-dominated wetlands. These responses are concomitant with the development of integrative management techniques for melaleuca that include mechanical, chemical, and biological control. Our results confirm previous findings that biological control likely augments conventional management methods by limiting recovery of invasive species.

Florida↗
USGS2006

Essential elements of online information networks on invasive alien species

In order to be effective, information must be placed in the proper context and organized in a manner that is logical and (preferably) standardized. Recently, invasive alien species (IAS) scientists have begun to create online networks to share their information concerning IAS prevention and control. At a special networking session at the Beijing International Symposium on Biological Invasions, an online Eastern Asia-North American IAS Information Network (EA-NA Network) was proposed. To prepare for the development of this network, and to provide models for other regional collaborations, we compare four examples of global, regional, and national online IAS information networks: the Global Invasive Species Information Network, the Invasives Information Network of the Inter-American Biodiversity Information Network, the Chinese Species Information System, and the Invasive Species Information Node of the US National Biological Information Infrastructure. We conclude that IAS networks require a common goal, dedicated leaders, effective communication, and broad endorsement, in order to obtain sustainable, long-term funding and long-term stability. They need to start small, use the experience of other networks, partner with others, and showcase benefits. Global integration and synergy among invasive species networks will succeed with contributions from both the top-down and the bottom-up. ?? 2006 Springer.

Conference Paper↗