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USGS2009

The Ecology of Parasite-Host Interactions at Montezuma Well National Monument, Arizona - Appreciating the Importance of Parasites

Although parasites play important ecological roles through the direct interactions they have with their hosts, historically that fact has been underappreciated. Today, scientists have a growing appreciation of the scope of such impacts. Parasites have been reported to dominate food webs, alter predator-prey relationships, act as ecosystem engineers, and alter community structure. In spite of this growing awareness in the scientific community, parasites are still often neglected in the consideration of the management and conservation of resources and ecosystems. Given that at least half of the organisms on earth are probably parasitic, it should be evident that the ecological functions of parasites warrant greater attention. In this report, we explore different aspects of parasite-host relationships found at a desert spring pond within Montezuma Well National Monument, Arizona. In three separate but related chapters, we explore interactions between a novel amphipod host and two parasites. First, we identify how host behavior responds to this association and how this association affects interactions with both invertebrate non-host predators and a vertebrate host predator. Second, we look at the human dimension, investigating how human recreation can indirectly affect patterns of disease by altering patterns of vertebrate host space use. Finally - because parasites and diseases are of increasing importance in the management of wildlife species, especially those that are imperiled or of management concern - the third chapter argues that research would benefit from increased attention to the statistical analysis of wildlife disease studies. This report also explores issues of statistical parasitology, providing information that may better inform those designing research projects and analyzing data from studies of wildlife disease. In investigating the nature of parasite-host interactions, the role that relationships play in ecological communities, and how human activities alter these associations, scientists usually make inferences by methods of statistical hypotheses testing. This type of hypothesis testing places additional importance on the analysis and interpretation of parasite-host interactions. We address these ideas in this report, focusing on the following questions: (1) How do two parasites with complex life cycles alter the behavior of a novel amphipod host, and how do host and non-host predators respond to infected amphipod prey? (2) Does human recreation affect spatial patterns of infection in an otherwise natural ecosystem? (3) How is hypothesis-testing applied in studies of wildlife disease? (4) What conclusions can we make about the relative usefulness of these methodologies? and (5) How can the analysis and interpretation of wildlife disease studies be improved? Each chapter of this report contains its own literature-cited section, with tables included in appendixes at the end of the full report.

Open-File Report↗

USGS2019

Perspective: Developing flow policies to balance the water needs of humans and wetlands requires a landscape scale approach inclusive of future scenarios and multiple timescales

Maintenance of the natural flow regime is essential for continued wetland integrity; however, the flow regime is greatly influenced by both natural and anthropogenic forces. Wetlands may be particularly susceptible to altered flow regimes as they are directly impacted by water flows at a variety of time scales. In Puerto Rico, contemporary water management is decreasing freshwater recharge to wetlands and contributes to the salinization of important coastal wetlands as sea levels rise. Further, downscaled climate models predict an increase in drought frequency, intensity, and duration by mid-century. Conflicts over water allocation seem imminent between human and ecological needs. Current minimum flow policies are insufficient given the complexities of ecosystem processes and the changes in precipitation patterns and sea level rise that are expected in the future. Improved flow policies need to be established that reflect the functional relationships between specific representative ecological resources and components of the natural flow regime across all relevant time scales. Similarly, flow policies need to be developed within a landscape scale to implicitly address the socio-ecological trade-offs as well as the complexities of water management. Multi-disciplinary collaborations will be essential for increasing our resiliency to anticipated future changes.

Wetlands↗

USGS2009

The Drenchwater deposit, Alaska: An example of a natural low pH environment resulting from weathering of an undisturbed shale-hosted Zn-Pb-Ag deposit

The Drenchwater shale-hosted Zn-Pb-Ag deposit and the immediate vicinity, on the northern flank of the Brooks Range in north-central Alaska, is an ideal example of a naturally low pH system. The two drainages, Drenchwater and False Wager Creeks, which bound the deposit, differ in their acidity and metal contents. Moderately acidic waters with elevated concentrations of metals (pH ??? 4.3, Zn ??? 1400 ??g/L) in the Drenchwater Creek drainage basin are attributed to weathering of an exposed base-metal-rich massive sulfide occurrence. Stream sediment and water chemistry data collected from False Wager Creek suggest that an unexposed base-metal sulfide occurrence may account for the lower pH (2.7-3.1) and very metal-rich waters (up to 2600 ??g/L Zn, ??? 260 ??g/L Cu and ???89 ??g/L Tl) collected at least 2 km upstream of known mineralized exposures. These more acidic conditions produce jarosite, schwertmannite and Fe-hydroxides commonly associated with acid-mine drainage. The high metal concentrations in some water samples from both streams naturally exceed Alaska state regulatory limits for freshwater aquatic life, affirming the importance of establishing base-line conditions in the event of human land development. The studies at the Drenchwater deposit demonstrate that poor water quality can be generated through entirely natural weathering of base-metal occurrences, and, possibly unmineralized black shale.

Applied Geochemistry↗

USGS2023

Influence of human development and predators on patterns of Virginia opossum occupancy, abundance, and activity

As human development continues to expand, wildlife must relocate or adapt to survive. Many mammalian mesopredators, such as the Virginia opossum ( Didelphis virginiana ), have adapted to living alongside human development. Furthermore, top-down predation pressure may be altered in nuanced ways within the human environment. Species such as opossums may be shielded from predation by human development or behavioral changes in predators. Understanding how dominant and subordinate mesopredators co-exist across natural and developed areas will provide insight into how wildlife communities are structured. Our objective was to evaluate how opossum occupancy, abundance, and activity were associated with human development and the relative abundance of their predators. We used data from a nationwide camera trapping study, Snapshot USA, to estimate opossum occupancy, abundance, and activity. We related these measures to the surrounding landscape and urbanization variables. We found that opossum occupancy was positively associated with anthropogenic sound (a surrogate for human activity). Furthermore, opossums in heavily forested areas were more likely to be detected in locations with higher predicted anthropogenic sounds. In areas with a high density of human housing, opossum relative abundance increased when predator abundance increased. We also found opossums were strictly nocturnal and shifted their activity to earlier in the evening in the presence of high predator abundance. Our results suggest that humans and their urban development can have multidimensional impacts on opossum behavior and occurrence, and could facilitate changes in predator–prey dynamics. Future research should evaluate if the association of opossums with urban areas is due to human-subsidized resources or caused by reduced mortality from altered predator–prey dynamics.

Journal of Zoology↗

USGS1994

Seabird population trends along the west coast of North America: Causes and the extent of regional concordance

We compared trends in breeding population size among cormorants, gulls, alcids, and others, among the Farallon Islands, and sites in northern California and Washington, Gulf of Alaska, and Bering Sea, but in most cases only during the last two decades. For a given species, trends were usually concordant within the same oceanographic domain, except for Rhinoceros Auklet, which increased across all domains in its northeastern Pacific range. Overall, humans and their domestic animals have had severe negative impacts to individual islands, but recent restoration efforts have had spectacular results. On the other hand, the California Current and the eastern Bering Sea now seem unable to support historic populations of natural, top-trophic predators. The major factor responsible appears to be overfishing by humans of important seabird prey, especially, in a period when climate has been unstable. Notable trends indicating these general patterns were as follows: 1) The Ashy Storm-Petrel on the Farallon Islands, where 80% of this species breeds, may have decreased in response to the increase of gulls in the storm-petrel breeding habitat. 2) Brandt's and Pelagic cormorants in the central California Current declined radically owing to El Nino and antropogenic factors in the early 1980s, and have since failed to recover, contrary to trends in the 1970s; farther north, populations fluctuated slightly but at low levels during this period. 3) Large Larus gulls have increased. 4) Common Murres in the central and northern portions of the California Current exhibited a marked decline during the early 1980s and have since failed to recover. 5) Most Common Murre populations in the Gulf of Alaska appear to be stable; whereas those in the eastern Bering Sea are decreasing. 6) Rhinoceros Auklet has increased throughout its range and has (re-)colonized new sites in the southern portion of it. 7) Tufted Puffin has ceased recovery in the California Current, but in Alaska it has continued to recover from former anthropogenic impacts. 8) Cassin's Auklet has declined in the central California Current region.

Studies in Avian Biology↗

USGS1997

Modeling fish dynamics and effects of stress in a hydrologically pulsed ecosystem

Many wetlands undergo seasonal cycles in precipitation and water depth.This environmental seasonality is echoed in patterns of production of fishbiomass, which, in turn, influence the phenology of other components of thefood web, including wading birds. Human activities, such as drainage orother alterations of the hydrology, can exacerbate these natural cycles andresult in detrimental stresses on fish production and the higher trophic levels dependent on this production. In this paper we model theseasonal pattern of fish production in a freshwater marsh, with specialreference to the Everglades/Big Cypress region of southern Florida.The model illustrates the temporal pattern of production through theyear, which can result in very high densities of fish at the end of ahydroperiod (period of flooding), aswell as the importance of ponds and other deep depressions, both as refugia and sinks during dry periods. The model predicts that: (1) there is an effective threshold in the length of the hydroperiod that must beexceeded for high fish-population densities to be produced, (2) large,piscivorous fishes do not appear tohave a major impact on smaller fishes in the marsh habitat, and (3) therecovery of small-fish populations in the marsh following a major droughtmay require up to a year. The last of these results is relevant toassessing anthropogenic impacts on marsh production, as these effectsmay increase the severity and frequency of droughts.

Journal of Aquatic Ecosystem Stress and Recovery↗

USGS2019

Distinguishing disturbance from perturbations in fire-prone ecosystems

Fire is a necessary ecosystem process in many biomes and is best viewed as a natural disturbance that is beneficial to ecosystem functioning. However, increasingly we are seeing human interference in fire regimes that alter the historical range of variability for most fire parameters and result in vegetation shifts. Such perturbations can affect all fire regime parameters. Here we provide a brief overview of examples where anthropogenically driven changes in fire frequency, fire pattern, fuels consumed and fire intensity constitute perturbations that greatly disrupt natural disturbance cycles. These changes are not due to fire per se but rather anthropogenic perturbations in the natural disturbance regime.

International Journal of Wildland Fire↗

USGS2019

Black bears alter movements in response to anthropogenic features with time of day and season

Background With the growth and expansion of human development, large mammals will increasingly encounter humans, elevating the likelihood of human-wildlife conflicts. Understanding the behavior and movement of large mammals, particularly around human development, is important for crafting effective conservation and management plans for these species. Methods We used GPS collar data from American black bears ( Ursus americanus ) to determine how seasonal food resources and human development affected bear movement patterns and resource use across the Commonwealth of Massachusetts. Results We found that though bears moved more and avoided human development during crepuscular and daylight hours than at night, bears preferentially moved through human dominated areas at night. This indicates bears were mitigating the risk of human development by altering their behavior to exploit these areas when human activity is low. This behavioral shift was most prominent in the spring, when natural foods are scarce, and fall, when energetic demands are high. We also observed a high degree of inter-individual variability among our sample of bears. Bears with a higher density of houses in their home ranges (~ 75 houses/km2) displayed less avoidance of human development than more rural bears. Furthermore, bear movement models had different explanatory variables, with preference or avoidance of a variable being dependent on the individual bear. To account for this individuality in our predictive surfaces, we projected the probability of movement for each season and time of day using a spatially weighted surface centered on each bear’s home range. Conclusions We found that black bears in Massachusetts are operating in a landscape of fear and are altering their movement patterns to use developed areas when human activity is low. We also found seasonal and diel differences among individual bears in resource selection during movement. Accounting for these individual, seasonal, and diel differences when assessing movement for large mammals is especially important if predictive surfaces are to be used in identifying areas for conservation and management.

Movement Ecology↗

USGS2018

Pharmaceuticals, hormones, pesticides, and other bioactive contaminants in water, sediment, and tissue from Rocky Mountain National Park, 2012–2013

Pharmaceuticals, hormones, pesticides, and other bioactive contaminants (BCs) are commonly detected in surface water and bed sediment in urban and suburban areas, but these contaminants are understudied in remote locations. In Rocky Mountain National Park (RMNP), Colorado, USA, BCs may threaten the reproductive success and survival of native aquatic species, benthic communities, and pelagic food webs. In 2012–2013, 67 water, 57 sediment, 63 fish, 10 frog, and 12 quality-control samples (8 water and 4 sediment) were collected from 20 sites in RMNP. Samples were analyzed for 369 parameters including 149 pharmaceuticals, 22 hormones, 137 pesticides, and 61 other chemicals or conditions to provide a representative assessment of BC occurrence within RMNP. Results indicate that BCs were detected in water and/or sediment from both remote and more accessible locations in RMNP. The most commonly detected BCs in water were caffeine, camphor, para-cresol, and DEET; and the most commonly detected BCs in sediment were indole, 3-methyl-1H-indole, para-cresol, and 2,6-dimethyl-naphthalene. Some detected contaminants, including carbaryl, caffeine, and oxycodone, are clearly attributable to direct local human input, whereas others may be transported into the park atmospherically (e.g., atrazine) or have local natural sources (e.g., para-cresol). One or more pharmaceuticals were detected in at least 1 sample from 15 of 20 sites. Most of the 29 detected pharmaceuticals are excreted primarily in human urine, not feces. Elevated net estrogenicity was observed in 18% of water samples, and elevated vitellogenin in blood was observed in 12% of male trout, both evidence of potential endocrine disruption. Hormone concentrations in sediment tended to be greater than concentrations in water. Most BCs were observed at concentrations below those not expected to pose adverse effects to aquatic life. Results indicate that even in remote locations aquatic wildlife can be exposed to pharmaceuticals, hormones, pesticides, and other bioactive contaminants.

Colorado↗

USGS2010

The present and future role of coastal wetland vegetation in protecting shorelines: Answering recent challenges to the paradigm

For more than a century, coastal wetlands have been recognized for their ability to stabilize shorelines and protect coastal communities. However, this paradigm has recently been called into question by small-scale experimental evidence. Here, we conduct a literature review and a small meta-analysis of wave attenuation data, and we find overwhelming evidence in support of established theory. Our review suggests that mangrove and salt marsh vegetation afford context-dependent protection from erosion, storm surge, and potentially small tsunami waves. In biophysical models, field tests, and natural experiments, the presence of wetlands reduces wave heights, property damage, and human deaths. Meta-analysis of wave attenuation by vegetated and unvegetated wetland sites highlights the critical role of vegetation in attenuating waves. Although we find coastal wetland vegetation to be an effective shoreline buffer, wetlands cannot protect shorelines in all locations or scenarios; indeed large-scale regional erosion, river meandering, and large tsunami waves and storm surges can overwhelm the attenuation effect of vegetation. However, due to a nonlinear relationship between wave attenuation and wetland size, even small wetlands afford substantial protection from waves. Combining man-made structures with wetlands in ways that mimic nature is likely to increase coastal protection. Oyster domes, for example, can be used in combination with natural wetlands to protect shorelines and restore critical fishery habitat. Finally, coastal wetland vegetation modifies shorelines in ways (e.g. peat accretion) that increase shoreline integrity over long timescales and thus provides a lasting coastal adaptation measure that can protect shorelines against accelerated sea level rise and more frequent storm inundation. We conclude that the shoreline protection paradigm still stands, but that gaps remain in our knowledge about the mechanistic and context-dependent aspects of shoreline protection.

Climatic Change↗

USGS2020

Assessing the water quality impacts of two Category-5 hurricanes on St. Thomas, Virgin Islands

Managing waterborne and water-related diseases is one of the most critical factors in the aftermath of hurricane-induced natural disasters. The goal of the study was to identify water-quality impairments in order to set the priorities for post-hurricane relief and to guide future decisions on disaster preparation and relief administration. Field investigations were carried out on St. Thomas, U.S. Virgin Islands as soon as the disaster area became accessible after the back-to-back hurricane strikes by Irma and Maria in 2017. Water samples were collected from individual household rain cisterns, the coastal ocean, and street-surface runoffs for microbial concentration. The microbial community structure and the occurrence of potential human pathogens were investigated in samples using next generation sequencing. Loop mediated isothermal amplification was employed to detect fecal indicator bacteria, Enterococcus faecalis . The results showed both fecal indicator bacteria and Legionella genetic markers were prevalent but were low in concentration in the water samples. Among the 22 cistern samples, 86% were positive for Legionella and 82% for Escherichia-Shigella . Enterococcus faecalis was detected in over 68% of the rain cisterns and in 60% of the coastal waters (n = 20). Microbial community composition in coastal water samples was significantly different from cistern water and runoff water. Although identification at bacterial genus level is not direct evidence of human pathogens, our results suggest cistern water quality needs more organized attention for protection of human health, and that preparation and prevention measures should be taken before natural disasters strike.

Water Research↗

USGS2011

Geology for a changing world 2010-2020-Implementing the U.S. Geological Survey science strategy

This report describes a science strategy for the geologic activities of the U.S. Geological Survey (USGS) for the years 2010-2020. It presents six goals with accompanying strategic actions and products that implement the science directions of USGS Circular 1309, 'Facing Tomorrow's Challenges-U.S. Geological Survey Science in the Decade 2007-2017.' These six goals focus on providing the geologic underpinning needed to wisely use our natural resources, understand and mitigate hazards and environmental change, and understand the relationship between humans and the environment. The goals emphasize the critical role of the USGS in providing long-term research, monitoring, and assessments for the Nation and the world. Further, they describe measures that must be undertaken to ensure geologic expertise and knowledge for the future. The natural science issues facing today's world are complex and cut across many scientific disciplines. The Earth is a system in which atmosphere, oceans, land, and life are all connected. Rocks and soils contain the answers to important questions about the origin of energy and mineral resources, the evolution of life, climate change, natural hazards, ecosystem structures and functions, and the movements of nutrients and toxicants. The science of geology has the power to help us understand the processes that link the physical and biological world so that we can model and forecast changes in the system. Ensuring the success of this strategy will require integration of geological knowledge with the other natural sciences and extensive collaboration across USGS science centers and with partners in Federal, State, and local agencies, academia, industry, nongovernmental organizations and, most importantly, the American public. The first four goals of this report describe the scientific issues facing society in the next 10 years and the actions and products needed to respond to these issues. The final two goals focus on the expertise and infrastructure needed to ensure the long-term sustainability of the geological sciences in the USGS. The ultimate goal of USGS science and of the strategy laid out in this document is to contribute to the development of a sustainable society that operates in harmony with the Earth systems that society depends upon. As we begin the second decade of the 21st century, our Nation faces growing challenges in resource availability, climate and environmental change, and natural hazards. Meeting these challenges will require strong collaboration across the natural and social sciences and extensive partnerships with both the public and private sectors. The six goals described in this document represent a mix of scientific focus areas and operational necessities that together provide a comprehensive roadmap for USGS geologic science to effectively contribute to the USGS mission, providing science for a changing world.

Circular↗

USGS2014

Respiratory transmission of an avian H3N8 influenza virus isolated from a harbour seal

The ongoing human H7N9 influenza infections highlight the threat of emerging avian influenza viruses. In 2011, an avian H3N8 influenza virus isolated from moribund New England harbour seals was shown to have naturally acquired mutations known to increase the transmissibility of highly pathogenic H5N1 influenza viruses. To elucidate the potential human health threat, here we evaluate a panel of avian H3N8 viruses and find that the harbour seal virus displays increased affinity for mammalian receptors, transmits via respiratory droplets in ferrets and replicates in human lung cells. Analysis of a panel of human sera for H3N8 neutralizing antibodies suggests that there is no population-wide immunity to these viruses. The prevalence of H3N8 viruses in birds and multiple mammalian species including recent isolations from pigs and evidence that it was a past human pandemic virus make the need for surveillance and risk analysis of these viruses of public health importance.

Nature Communications↗

USGS2020

Landscape drivers of dynamic change in water quality of US rivers

Water security is a top concern for social well-being and dramatic changes in the availability of freshwater have occurred as a result of human uses and landscape management. Elevated nutrient loading and perturbations to major ion composition have resulted from human activities and have degraded freshwater resources. This study addresses the emerging nature of stream water quality in the 21st century through analysis of concentrations and trends in a wide variety of constituents in streams and rivers of the U.S. Concentrations of fifteen separate water quality parameters including nutrients, major ions, sediment, and specific conductance were analyzed over the period 1982-2012 and a targeted trend analysis was performed from 1992-2012. Although environmental policy is geared toward addressing the long-standing problem of nutrient overenrichment, these efforts have had uneven success, with decreasing nutrient concentrations at urbanized sites and little to no change at agricultural sites. However, freshwaters are being salinized rapidly in all human-dominated land use types. Increasing salinity negatively affects biodiversity, mobilizes sediment-bound contaminants, and increases lead contamination of drinking water but the effects are poorly quantified. Therefore, while efforts to control nutrients are ongoing, rapid salinity increases are ushering in a new set of poorly-defined issues.

Environmental Science & Technology↗

USGS2026

Conflicts and collisions with an endangered carnivore: Landscape drivers and spatial risk pattern

Human–wildlife conflicts and anthropogenic mortality are expected to increase with the continuous encroachment on natural habitats within and around protected areas, yet the processes governing these risks remain poorly understood. We investigated the spatiotemporal dynamics and drivers of two distinct processes involving the endangered Florida panther ( Puma concolor coryi ; hereafter, panther): (1) direct human–panther interactions and livestock depredation (hereafter, conflicts), and (2) vehicle collisions (hereafter, collisions). Using long-term data collected between 2006 and 2022 within the panther's breeding range in Southwest Florida, USA, we applied dynamic occupancy models to estimate probabilities of occurrence, colonization, and extinction of conflicts and collisions while accounting for imperfect detection. A total of 277 conflicts and 239 collisions were recorded during the study period. Occurrence probabilities for both conflicts and collisions increased during the early years of the study and subsequently stabilized. Landscape configuration consistently showed strong associations with both processes. Conflicts were more likely in areas with fragmented but closely spaced habitat patches, whereas collisions were more likely along road segments characterized by connected landscapes with low resistance to panther movement. In contrast, areas that showed greater distances between habitat patches and increased proportions of protected area were associated with lower probabilities of conflict or collision persistence over time. A predictive map was created to highlight areas with high probability of conflict and road segments with high probability of collision in Southwest Florida, USA. Identifying areas with elevated risk can inform targeted mitigation strategies, including habitat management, wildlife crossings, and outreach efforts, and further support long-term coexistence between humans and large carnivore populations.

Florida↗

USGS2012

Threats and stressors to the health of the ecosystems of Lakes Mead and Mohave: Chapter 6 in A synthesis of aquatic science for management of Lakes Mead and Mohave

Ecosystem impacts from visitor activities or natural environmental change are important concerns in all units of the National Park system. Possible impacts to aquatic ecosystems at Lake Mead National Recreation Area (LMNRA) are of particular concern because of the designation of Lakes Mead and Mohave as critical habitat for the federally listed endangered razorback sucker (Xyrauchen texanus), the significance of the sport fishery, and the regional importance of its habitats to more than 90 documented species of waterbirds. Potential threats to shoreline habitats are of concern not only for their ecosystem values but also for maintaining the recreational setting. Many areas adjacent to the shorelines of Lakes Mead and Mohave are designated wilderness areas. For purposes of this document, stressors are any chemical, biological, or physical agent that has a detrimental effect on aquatic ecosystems at the organism, population, or community level. Human-made stressors at Lakes Mead and Mohave include direct effects of recreation on the lakes, like boating and fishing, as well as indirect effects of activities away from the lakes, such as growing population and increasing urbanization. Common natural environmental stressors include extended changes in climate (precipitation or temperature), or the erosion, transport, and loading of chemical constituents in rocks and sediments to aquatic environments. Human activity also can exacerbate natural stressors in a variety of ways.

Circular↗

USGS2008

Comparison of effects of humans versus wildlife-detector dogs

The use of dogs ( Canis lupus familiaris ) trained to locate wildlife under natural conditions may increase the risk of attracting potential predators or alter behavior of target species. These potentially negative effects become even more problematic when dealing with threatened or endangered species, such as the Mojave Desert tortoise ( Gopherus agassizii ). We addressed three concerns regarding use of dogs trained to locate desert tortoises in the wild. First, we looked at the potential for dogs to attract native and non-native predators to sites at a greater rate than with human visitation alone by comparing presence of predator sign before and after visitation by dogs and by humans. We found no significant difference in predator sign based upon type of surveyor. Second, we looked at the difference in risk of predation to desert tortoises that were located in the wild by humans versus humans with wildlife-detector dogs. Over a 5-week period, during which tortoises were extensively monitored and a subsequent period of 1 year during which tortoises were monitored monthly, there was no predation on, nor sign of predator-inflicted trauma to tortoises initially encountered either by humans or wildlife-detector dogs. Third, we looked at movement patterns of tortoises after encounter by either humans or wildlife-detector dogs. Movement of desert tortoises was not significantly different after being found by a human versus being found by a wildlife-detector dog. Based upon these initial results we conclude that use of trained wildlife-detector dogs to survey for desert tortoises in the wild does not appear to increase attraction of predators, increase risk of predation, or alter movement patterns of desert tortoises more than surveys conducted by humans alone.

Southwestern Naturalist↗

USGS2014

Agricultural conversion without external water and nutrient inputs reduces terrestrial vegetation productivity

Driven by global population and standard of living increases, humanity co-opts a growing share of the planet's natural resources resulting in many well-known environmental trade-offs. In this study, we explored the impact of agriculture on a resource fundamental to life on Earth: terrestrial vegetation growth (net primary production; NPP). We demonstrate that agricultural conversion has reduced terrestrial NPP by ~7.0%. Increases in NPP due to agricultural conversion were observed only in areas receiving external inputs (i.e., irrigation and/or fertilization). NPP reductions were found for ~88% of agricultural lands, with the largest reductions observed in areas formerly occupied by tropical forests and savannas (~71% and ~66% reductions, respectively). Without policies that explicitly consider the impact of agricultural conversion on primary production, future demand-driven increases in agricultural output will likely continue to drive net declines in global terrestrial productivity, with potential detrimental consequences for net ecosystem carbon storage and subsequent climate warming.

Geophysical Research Letters↗