Carnivore predation on livestock often leads people to retaliate. Persecution by humans has contributed strongly to global endangerment of carnivores. Preventing livestock losses would help to ...achieve three goals common to many human societies: preserve nature, protect animal welfare, and safeguard human livelihoods. Between 2016 and 2018, four independent reviews evaluated >40 years of research on lethal and nonlethal interventions for reducing predation on livestock. From 114 studies, we find a striking conclusion: scarce quantitative comparisons of interventions and scarce comparisons against experimental controls preclude strong inference about the effectiveness of methods. For wise investment of public resources in protecting livestock and carnivores, evidence of effectiveness should be a prerequisite to policy making or large-scale funding of any method or, at a minimum, should be measured during implementation. An appropriate evidence base is needed, and we recommend a coalition of scientists and managers be formed to establish and encourage use of consistent standards in future experimental evaluations.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Computed tomography (CT) of sediment cores allows for high‐resolution images, three‐dimensional volumes, and down core profiles. These quantitative data are generated through the attenuation of ...X‐rays, which are sensitive to sediment density and atomic number, and are stored in pixels as relative gray scale values or Hounsfield units (HU). We present a suite of MATLAB™ tools specifically designed for routine sediment core analysis as a means to standardize and better quantify the products of CT data collected on medical CT scanners. SedCT uses a graphical interface to process Digital Imaging and Communications in Medicine (DICOM) files, stitch overlapping scanned intervals, and create down core HU profiles in a manner robust to normal coring imperfections. Utilizing a random sampling technique, SedCT reduces data size and allows for quick processing on typical laptop computers. SedCTimage uses a graphical interface to create quality tiff files of CT slices that are scaled to a user‐defined HU range, preserving the quantitative nature of CT images and easily allowing for comparison between sediment cores with different HU means and variance. These tools are presented along with examples from lacustrine and marine sediment cores to highlight the robustness and quantitative nature of this method.
Key Points
SedCT and SedCTimage are MATLAB tools for standardized and quantitative treatment of CT data
SedCT extracts CT numbers representative of the sediment and are robust to normal coring imperfections
Properly calibrated HU values can be used as density estimates for paleoenvironmental and sedimentological study
Continuous sedimentary records of paleomagnetic directional variability and relative paleointensity (RPI) provide valuable information on the evolution of the geodynamo while also facilitating ...stratigraphic correlation and age control. While the Quaternary RPI record has received much attention, Pliocene records are relatively rare. Here, a u‐channel paleomagnetic study from Integrated Ocean Drilling Program (IODP) Site U1396 in the Caribbean Sea refines the shipboard‐derived polarity stratigraphy and generates an RPI and directional record extending back 4.5 Ma. Rock magnetic data reveal changes in magnetic coercivity around 2.1 Ma that influences the quality of the paleomagnetic record; while the older record is well‐resolved and passes RPI quality criteria, much of the younger section does not. To facilitate the development of the RPI record, spike noise associated with discrete intervals of volcanogenic sediments are filtered from the data set. The resulting record passes RPI reliability criteria between 0–0.6 Ma and 2.1–4.5 Ma and represents the highest resolution RPI record extending into the early Pliocene. We use this record to refine the existing benthic δ18O chronology and open the door to high‐resolution RPI chronostratigraphies during the Pliocene. Although we find no evidence for a previously observed increase in magnetic field intensity after ∼4 million years ago, we do observe an asymmetrical form to RPI in the normal polarity intervals of the Gauss chron. We also find a polarity bias in inclination that cannot be simply explained by a drill string overprint, suggesting polarity‐driven field asymmetries that are particularly pronounced during the Pliocene.
Plain Language Summary
As sediments slowly accumulate on the ocean floor past variations in magnetic field intensity and direction are recorded. While we have a relatively good record of intensity variations over the last 2–3 million years, we know little about earlier time intervals. Here, we reconstruct past magnetic (or paleomagnetic) variations over parts of the last 4.5 million years using a sediment core from the Caribbean Sea collected by the Integrated Ocean Drilling Program. A deterioration in the quality of the paleomagnetic signal occurred about 2.1 million years ago, however, prior to that time, the sediments preserve a high fidelity paleomagnetic record at a temporal resolution higher than any previously obtained. Good agreement to existing data from 2.1 to 3 million years ago builds confidence in the quality of our new observations. Although we find no evidence for a previously observed change in magnetic field intensity at around 4 million years ago, differences in mean inclination during normal as compared to reverse polarity intervals are observed, suggesting field asymmetries during this time interval. The unparalleled quality and length of our new record means we can now begin to define characteristic geomagnetic field behavior during times rarely observed.
Key Points
Rock and paleomagnetic filtering provide a more robust estimate of relative paleointensity (RPI) that is used to refine the Integrated Ocean Drilling Program Site (IODP) U1396 δ18O chronostratigraphy
IODP Site U1396 provides the longest, highest‐resolution, independently dated record of RPI to establish characteristic Pliocene behavior
Plio‐Pleistocene inclination anomaly contains a strong polarity bias and RPI asymmetry may be a characteristic feature of the Gauss chron
Male osteoporosis is increasingly recognized as a major public health issue. This multinational, 2‐yr, randomized, double‐blind, placebo‐controlled study was conducted to determine the efficacy and ...safety of 35 mg once‐a‐week risedronate in men with osteoporosis. Patients had to be men ≥30 yr old, with lumbar spine T‐score ≤ −2.5 and femoral neck T‐score ≤ −1 SD or lumbar spine T‐score ≤ −1 and femoral neck T‐score ≤ −2 SD (based on young normal men). Patients were randomized 2:1 to risedronate 35 mg once a week or placebo for 2 yr; all patients took 1000 mg elemental calcium and 400–500 IU vitamin D daily. Lumbar spine BMD at month 24 using last observation carried forward was the primary endpoint. Other endpoints included lumbar spine BMD at time points other than month 24, proximal femur BMD, bone turnover markers (BTMs), new vertebral fractures, clinical fractures, and adverse event (AE) assessment. There were 284 men enrolled in the study. Treatment with risedronate resulted in a significant increase from baseline to endpoint in lumbar spine BMD compared with placebo (4.5%; 95% CI: 3.5%, 5.6%; p < 0.001). Few new vertebral and nonvertebral fractures were reported, with no differences in fracture rates between the two groups. There was a significant (p < 0.01) reduction from baseline in BTMs for the risedronate group compared with placebo at all time points. No apparent differences in the pattern or distribution of AEs including serious and upper gastrointestinal AEs were observed. Risedronate therapy was well tolerated during this 2‐yr study and was rapidly effective as indicated by significant BTM decreases at month 3 and BMD increases at month 6 (the earliest time points tested). The effects of risedronate treatment on BMD and BTMs in this study were similar to those previously shown to be associated with fracture risk reductions in women with postmenopausal osteoporosis.
Oxygen isotope data from planktonic and benthic foraminifera, on a high‐resolution age model (44 14C dates spanning 17,400 years), document deglacial environmental change on the southeast Alaska ...margin (59°33.32′N, 144°9.21′W, 682 m water depth). Surface freshening (i.e., δ18O reduction of 0.8‰) began at 16,650 ± 170 cal years B.P. during an interval of ice proximal sedimentation, likely due to freshwater input from melting glaciers. A sharp transition to laminated hemipelagic sediments constrains retreat of regional outlet glaciers onto land circa 14,790 ± 380 cal years B.P. Abrupt warming and/or freshening of the surface ocean (i.e., additional δ18O reduction of 0.9‰) coincides with the Bølling Interstade of northern Europe and Greenland. Cooling and/or higher salinities returned during the Allerød interval, coincident with the Antarctic Cold Reversal, and continue until 11,740 ± 200 cal years B.P., when onset of warming coincides with the end of the Younger Dryas. An abrupt 1‰ reduction in benthic δ18O at 14,250 ± 290 cal years B.P. likely reflects a decrease in bottom water salinity driven by deep mixing of glacial meltwater, a regional megaflood event, or brine formation associated with sea ice. Two laminated opal‐rich intervals record discrete episodes of high productivity during the last deglaciation. These events, precisely dated here at 14,790 ± 380 to 12,990 ± 190 cal years B.P. and 11,160 ± 130 to 10,750 ± 220 cal years B.P., likely correlate to similar features observed elsewhere on the margins of the North Pacific and are coeval with episodes of rapid sea level rise. Remobilization of iron from newly inundated continental shelves may have helped to fuel these episodes of elevated primary productivity and sedimentary anoxia.
Key Points
Regional deglaciation of the northwest Cordilleran Ice Sheet
North Pacific observations of climate change
Potential drivers of deglacial high‐productivity events
The general importance of interspecific competition as an ecological factor for carnivores is unknown and its conservation significance may have been inflated by intensive research conducted on a few ...vulnerable species. We therefore examined the potential for interspecific competition across carnivores on one continent, Africa, by calculating, for each of 70 carnivore species, the number of other carnivore species that overlapped it in geographic range, habitat, and diet, and that could potentially kill the species in question. The average carnivore in Africa shares some of its geographic range and habitat with 26 other species suggesting competition could be pervasive. More specifically, carnivores may have to share food resources with 22 other carnivore species, on average, although the potential for food stealing is far lower. The average African carnivore may be vulnerable to predation by 15 other species although it is unlikely to be eaten by other carnivores. These analyses indicate that exploitative competition and interspecific killing are of potential widespread importance for a large number of carnivores in Africa, rather than being restricted to a few selected carnivores highlighted in the current literature.
• This study examined the effects of infection with barley and cereal yellow dwarf viruses (BYDVs) on wild grass species in California, a region in which native perennial bunchgrasses have been ...largely replaced by exotic annual grasses. We sought to determine whether these widespread viruses compromise the fitness of wild hosts and thus have the potential to influence grassland dynamics. Plant viruses have been long overlooked in ecological studies, and their influence on wild hosts has often been assumed to be minimal. • We examined the short-term and long-term consequences of infection on field-grown individuals from 18 different populations of wild California grasses (from seven native and one exotic species). • Barley yellow dwarf virus infection was aggressive in most hosts and markedly impaired host fitness by reducing growth, survivorship, and fecundity. • Previous work indicates that the presence of exotic grasses can more than double BYDV incidence in natives. Given the ubiquity of BYDVs, our results suggest that apparent competition and other virus-mediated processes may influence interactions among native and exotic grasses and potentially contribute to shifts in grassland community composition.
Radiocarbon reconstructions of past ocean ventilation rates constrain oceanic sources and sinks of CO2 and mechanisms of subsurface hypoxia. Here, 14C in coexisting benthic and planktonic ...foraminifera from a sediment core 682 m deep off Southeast Alaska documents paleoventilation over the past ∼17,000 years. A chronology based on calibrated planktonic foraminiferal dates, consistent with independent terrestrial dates for regional glacial retreat, yields deglacial projection ages moderately greater than those of the Holocene, suggesting comparatively limited ventilation. The observed Holocene increase of apparent ventilation at intermediate depths tracks inundation of the Bering Strait between ∼11,800 and 13,200 years ago, suggesting that flooding of continental shelves and export of low-salinity surface waters to the Arctic enhanced intermediate water formation in the North Pacific. An abrupt increase in the benthic–planktonic radiocarbon age gradient, implying homogenization of abyssal radiocarbon in deep and intermediate waters, aligns with the younger of two episodes of rapid rise of atmospheric CO2 and depletion of atmospheric ΔC14 during deglaciation (∼11,500–13,000 years ago), suggesting the North Pacific as a possible pathway for venting of oceanic CO2 to the atmosphere during the second half of the deglacial transition.
•Gulf of Alaska marine radiocarbon records deglacial circulation and CO2 pathways.•Sealevel rise and Bering Strait throughflow enhanced intermediate depth ventilation.•The younger deglacial atmospheric CO2 jump, 12.5–12 ka, had a North Pacific source.
Abstract
Our understanding of the climatic teleconnections that drove ice-age cycles has been limited by a paucity of well-dated tropical records of glaciation that span several glacial–interglacial ...intervals. Glacial deposits offer discrete snapshots of glacier extent but cannot provide the continuous records required for detailed interhemispheric comparisons. By contrast, lakes located within glaciated catchments can provide continuous archives of upstream glacial activity, but few such records extend beyond the last glacial cycle. Here a piston core from Lake Junín in the uppermost Amazon basin provides the first, to our knowledge, continuous, independently dated archive of tropical glaciation spanning 700,000 years. We find that tropical glaciers tracked changes in global ice volume and followed a clear approximately 100,000-year periodicity. An enhancement in the extent of tropical Andean glaciers relative to global ice volume occurred between 200,000 and 400,000 years ago, during sustained intervals of regionally elevated hydrologic balance that modified the regular approximately 23,000-year pacing of monsoon-driven precipitation. Millennial-scale variations in the extent of tropical Andean glaciers during the last glacial cycle were driven by variations in regional monsoon strength that were linked to temperature perturbations in Greenland ice cores
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; these interhemispheric connections may have existed during previous glacial cycles.
Sediment records from deep-drilling projects such as those carried out by the International Continental Scientific Drilling Program are often tens to hundreds of meters in length. To ensure the ...complete recovery of a stratigraphic section, a basin is usually cored multiple times in adjacent holes so that gaps between sequential cores, poorly recovered sections, or intervals affected by disturbance can be bridged or replaced with sediments from another hole. Stratigraphic correlation, the alignment of stratigraphically-equivalent horizons in cores from different holes in a common-depth scale, and splice generation, the integration of the most-representative core sections into a composite-stratigraphic section, are essential steps in this process to both evaluate and synthesize the recovered-sediment record and focus the scientific analyses. However, these undertakings can be complex and are inherently subjective, making the need for the development of a single robust stratigraphic section early in the project critical to its success. Despite this, the steps between core recovery and on-splice data generation are rarely published in sufficient detail to allow reconstruction, or refinement, of the composited record at a later date. To increase the transparency of how the composite record is created, and to provide a template for future projects, we detail the step-by-step approaches and decisions involved in generating the composite-depth scale and complete-stratigraphic splice following recovery of sediments from Lake Junín, Peru. We first explain the details and nuances of different drilling-depth scales before describing how we integrated different physical property records to generate the composite-depth scale and complete-stratigraphic splice. Here, we show that due to the complex stratigraphy in the Lake Junín sediments, high-resolution line-scan images of the cores offer millimeter-scale precision for construction of the primary-stratigraphic splice at a resolution not afforded by other physical property data. Finally, through comparison of the spliced record to physical-property records acquired in situ on the borehole, we demonstrate that the stratigraphic splice is an accurate representation of the sediment accumulated in the Lake Junín basin.
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