Relationships between fluvial aquatic habitat availability and discharge are often assumed to remain static when used with hydrologic datasets to analyze changes in habitat availability over time. ...Despite this assumption, studies have observed significant changes in aquatic habitat availability before and after restoration projects, dam removals, and extreme flood events. However, research is lacking on how aquatic habitat changes as a result of morphodynamic processes during more commonly occurring hydrologic conditions. This study compared Chinook salmon (Oncorhynchus tshawytscha) rearing habitat availability at 19 discharges before and after a relatively mild 8‐year hydrologic period punctuated with modest floods on the lower Yuba River in California, USA. During this time, the total area of rearing habitat remained relatively consistent at discharges <2× bankfull but decreased by up to 25% at discharges >2× bankfull. Significant decreases in rearing habitat area appeared to be the result of widespread erosion on floodplains, terraces, and lateral bars, even after only modest floods. As a result, spatially delineated areas of lost habitat tended to increase in water depth and velocity at baseflow, bankfull, and floodplain‐filling discharges, while areas of gained habitat decreased in depth and velocity. Although these specific results may not apply to all rivers around the world, the finding that habitat–discharge relationships change as a result of morphodynamic processes likely does transfer globally and should be considered when making long‐term regulatory and management decisions, such as instream flow requirements and habitat restoration plans.
The habitat-amount hypothesis challenges traditional concepts that explain species richness within habitats, such as the habitat-patch hypothesis, where species number is a function of patch size and ...patch isolation. It posits that effects of patch size and patch isolation are driven by effects of sample area, and thus that the number of species at a site is basically a function of the total habitat amount surrounding this site. We tested the habitat-amount hypothesis for saproxylic beetles and their habitat of dead wood by using an experiment comprising 190 plots with manipulated patch sizes situated in a forested region with a high variation in habitat amount (i.e., density of dead trees in the surrounding landscape). Although dead wood is a spatio-temporally dynamic habitat, saproxylic insects have life cycles shorter than the time needed for habitat turnover and they closely track their resource. Patch size was manipulated by adding various amounts of downed dead wood to the plots (∼800 m3 in total); dead trees in the surrounding landscape (∼240 km2) were identified using airborne laser scanning (light detection and ranging). Over 3 yr, 477 saproxylic species (101,416 individuals) were recorded. Considering 20–1,000 m radii around the patches, local landscapes were identified as having a radius of 40–120 m. Both patch size and habitat amount in the local landscapes independently affected species numbers without a significant interaction effect, hence refuting the island effect. Species accumulation curves relative to cumulative patch size were not consistent with either the habitat-patch hypothesis or the habitat-amount hypothesis: several small dead-wood patches held more species than a single large patch with an amount of dead wood equal to the sum of that of the small patches. Our results indicate that conservation of saproxylic beetles in forested regions should primarily focus on increasing the overall amount of dead wood without considering its spatial arrangement. This means dead wood should be added wherever possible including in local landscapes with low or high dead-wood amounts. For species that have disappeared from most forests owing to anthropogenic habitat degradation, this should, however, be complemented by specific conservation measures pursued within their extant distributional ranges.
Biodiversity is severely threatened by habitat destruction. As a consequence of habitat destruction, the remaining habitat becomes more fragmented. This results in time‐lagged population extirpations ...in remaining fragments when these are too small to support populations in the long term. If these time‐lagged effects are ignored, the long‐term impacts of habitat loss and fragmentation will be underestimated. We quantified the magnitude of time‐lagged effects of habitat fragmentation for 157 nonvolant terrestrial mammal species in Madagascar, one of the biodiversity hotspots with the highest rates of habitat loss and fragmentation. We refined species’ geographic ranges based on habitat preferences and elevation limits and then estimated which habitat fragments were too small to support a population for at least 100 years given stochastic population fluctuations. We also evaluated whether time‐lagged effects would change the threat status of species according to the International Union for the Conservation of Nature (IUCN) Red List assessment framework. We used allometric relationships to obtain the population parameters required to simulate the population dynamics of each species, and we quantified the consequences of uncertainty in these parameter estimates by repeating the analyses with a range of plausible parameter values. Based on the median outcomes, we found that for 34 species (22% of the 157 species) at least 10% of their current habitat contained unviable populations. Eight species (5%) had a higher threat status when accounting for time‐lagged effects. Based on 0.95‐quantile values, following a precautionary principle, for 108 species (69%) at least 10% of their habitat contained unviable populations, and 51 species (32%) had a higher threat status. Our results highlight the need to preserve continuous habitat and improve connectivity between habitat fragments. Moreover, our findings may help to identify species for which time‐lagged effects are most severe and which may thus benefit the most from conservation actions.
Resumen
La biodiversidad se encuentra seriamente amenazada por la destrucción del hábitat. Como consecuencia de esta destrucción, el hábitat remanente se vuelve más fragmentado. Esto resulta en extirpaciones poblacionales retardadas dentro de los fragmentos restantes cuando éstos son muy pequeños para mantener a las poblaciones a largo plazo. Si se ignoran estos efectos retardados, se subestimarán los impactos a largo plazo de la pérdida del hábitat y la fragmentación. Cuantificamos la magnitud de los efectos retardados de la fragmentación del hábitat para 157 especies de mamíferos terrestres no voladores en Madagascar, uno de los puntos calientes de biodiversidad con las tasas más elevadas de pérdida del hábitat y fragmentación. Depuramos las extensiones geográficas de las especies con base en las preferencias de hábitat y los límites de elevación y después estimamos cuáles fragmentos de hábitat eran muy pequeños para mantener una población durante al menos cien años dadas las fluctuaciones estocásticas de las poblaciones. También analizamos si los efectos retardados cambiarían el estado de amenaza de la especie de acuerdo con el programa de evaluación de la Lista Roja de la UICN. Usamos relaciones alométricas para obtener los parámetros poblacionales requeridos para simular las dinámicas poblacionales de cada especie y cuantificamos las consecuencias de la incertidumbre en estos parámetros estimados mediante análisis repetidos con una gama de valores plausibles de los parámetros. Con base en los resultados promedio, descubrimos que para 34 especies (22% de las 157 especies) al menos el 10% de su hábitat actual tiene poblaciones inviables. Ocho especies (5%) cambiaron a un estado más elevado de amenaza cuando se consideraron los efectos retardados. Con base en los valores del centil 0.95, adherido a un principio precautorio, para 108 especies (32%) al menos el 10% de su hábitat tiene poblaciones inviables y 51 especies (32%) cambiaron negativamente su estado de amenaza. Nuestros resultados resaltan la necesidad de conservar la continuidad de los hábitats y mejorar la conectividad entre los fragmentos. Además, nuestros hallazgos pueden ayudar a identificar especies para las cuales los efectos retardados son más serios y que podrían beneficiarse más con las acciones de conservación.
【摘要】
生物多样性面临着栖息地破坏的严重威胁。栖息地破坏会导致剩余的栖息地破碎化更加严重, 进而在剩余破碎化栖息地的面积不足以长期支持种群发展时, 引发时间滞后的种群灭绝。如果忽视这种时滞效应, 那么将会低估栖息地丧失和破碎化的长期影响。马达加斯加是栖息地丧失和破碎化比例最高的生物多样性热点地区之一, 本研究量化了马达加斯加157种非飞行陆地哺乳动物栖息地破碎化的时滞效应。我们根据物种的栖息地偏好和海拔限制精细划分了其地理范围, 并估计在随机种群波动下, 哪些破碎化栖息地的面积不足以支持种群存活至少100年。我们还根据《世界自然保护联盟红色名录》的评估框架, 评估了时滞效应是否会改变物种的濒危等级。我们使用异速关系得到了每个物种种群动态模拟所需的种群参数, 并通过对一系列合理的参数值进行重复分析, 量化了这些参数估计的不确定性结果。我们发现基于中位数的结果, 有34个物种 (在157个物种中占22%) 当前的栖息地中至少有10% 包含难以存活的种群。如果考虑到时滞效应, 8个物种 (5%) 应被纳入更高的濒危等级。而基于0.95分位数的结果, 则有 108个物种 (69%) 在预防性原则下至少有10% 的栖息地包含难以存活的种群, 51个物种 (32%) 会被纳入更高的濒危等级。我们的结果强调了保护连续栖息地和提高破碎化栖息地连接度的必要性。此外, 我们的研究结果还有助于确定受时滞效应影响最严重且将从保护行动中受益最大的物种。【翻译: 胡怡思; 审校: 聂永刚】
Habitat loss is often considered the greatest near-term threat to biodiversity. Yet the impact of habitat fragmentation, or the change in habitat configuration for a given amount of habitat loss, has ...been intensely debated. We isolated effects of habitat loss from fragmentation on the demography, movement, and abundance of wild populations of a specialist herbivore, Chelinidea vittiger, by removing 2,088 patches across 15 landscapes. We compared fragmentation resulting from random loss, which is often considered in theory, to aggregated loss, which is often observed in the real world. When quantifying fragmentation caused by random vs. aggregated loss, aggregated loss led to less fragmented landscapes than random loss based on patch isolation, but more fragmented landscapes when based on isolation at a larger mesoscale scale defined by dispersal distances of C. vittiger. Overall, habitat loss decreased population size and demographic parameters, with thresholds occurring at approximately 70–80% patch loss. Synergistic effects also occurred, where an aggregated pattern of loss had negative effects at low, but not high, amounts of habitat loss. Effects on population size of C. vittiger were driven by reductions in movement and subsequent reproduction. The direction of habitat fragmentation effects from random and aggregated loss treatments, for a given habitat amount, was conflictingly positive or negative depending on the scale at which fragmentation was quantified. Fragmentation quantified at the scale of dispersal for this species best explained population size and highlighted that fragmentation had negative effects at a mesoscale. Our results emphasize the importance of quantifying habitat fragmentation at biologically appropriate scales.
Although mammalian carnivores are vulnerable to habitat fragmentation and require landscape connectivity, their global patterns of fragmentation and connectivity have not been examined. We use ...recently developed high-resolution habitat suitability models to conduct comparative analyses and to identify global hotspots of fragmentation and connectivity for the world's terrestrial carnivores. Species with less fragmentation (i.e. more interior high-quality habitat) had larger geographical ranges, a greater proportion of habitat within their range, greater habitat connectivity and a lower risk of extinction. Species with higher connectivity (i.e. less habitat isolation) also had a greater proportion of high-quality habitat, but had smaller, not larger, ranges, probably reflecting shorter distances between habitat patches for species with restricted distributions; such species were also more threatened, as would be expected given the negative relationship between range size and extinction risk. Fragmentation and connectivity did not differ among Carnivora families, and body mass was associated with connectivity but not fragmentation. On average, only 54.3 per cent of a species' geographical range comprised high-quality habitat, and more troubling, only 5.2 per cent of the range comprised such habitat within protected areas. Identification of global hotspots of fragmentation and connectivity will help guide strategic priorities for carnivore conservation.
Climate change is causing an increase in the frequency and intensity of marine heatwaves (MHWs) and mass mortality events (MMEs) of marine organisms are one of their main ecological impacts. Here, we ...show that during the 2015–2019 period, the Mediterranean Sea has experienced exceptional thermal conditions resulting in the onset of five consecutive years of widespread MMEs across the basin. These MMEs affected thousands of kilometers of coastline from the surface to 45 m, across a range of marine habitats and taxa (50 taxa across 8 phyla). Significant relationships were found between the incidence of MMEs and the heat exposure associated with MHWs observed both at the surface and across depths. Our findings reveal that the Mediterranean Sea is experiencing an acceleration of the ecological impacts of MHWs which poses an unprecedented threat to its ecosystems' health and functioning. Overall, we show that increasing the resolution of empirical observation is critical to enhancing our ability to more effectively understand and manage the consequences of climate change.
During the 2015‐2019 period, the Mediterranean Sea has experienced exceptional marine heatwaves conditions resulting in the onset of five consecutive years of widespread MMEs across the basin. These MMEs affected thousands of kilometers of coastline from the surface to 45 m depth, across a range of marine habitats and taxa (50 taxa across 8 phyla). By assessing and integrating temperature data with mass mortality records across the basin, our study provides the most up‐to‐date account of the impacts of extreme warming events on Mediterranean marine organisms and ecosystems.
Decades of research suggest that species richness depends on spatial characteristics of habitat patches, especially their size and isolation. In contrast, the habitat amount hypothesis predicts that ...(1) species richness in plots of fixed size (species density) is more strongly and positively related to the amount of habitat around the plot than to patch size or isolation; (2) habitat amount better predicts species density than patch size and isolation combined, (3) there is no effect of habitat fragmentation per se on species density and (4) patch size and isolation effects do not become stronger with declining habitat amount. Data on eight taxonomic groups from 35 studies around the world support these predictions. Conserving species density requires minimising habitat loss, irrespective of the configuration of the patches in which that habitat is contained.
Analysis of a global set of 35 studies suggests that habitat amount, rather than patch area, isolation or fragmentation per se, determined species richness in sample plots at scales ranging from 13 to 11 000 ha. Minimising species losses requires protecting and restoring as much habitat as possible, irrespective of the configuration of that habitat.
The results of a long-term comprehensive study of ecological and biological features of urban flora of various habitats of the cities of the Orel (Oryol) oblast: Orel, Mtsensk, Livny, Bolkhov, ...Maloarkhangelsk, Novosil, and Dmitrovsk are presented in the article. Flora of the city Orel has a population of 913 species, Livny - 786, Mtsensk - 777, Bolkhov - 780, Novosil - 775, Maloarhangelsk - 776, and the Dmitrovsk - 777 species. In the course of research, the taxonomic structure of urban flora is characterized as one of the indicators of floras zonal and ecological-topological confinement. Comparison of complete floristic lists of Orel oblast cities revealed high floristic similarity, which indicates a significant concordance of urban flora and smoothing of zonal distinctions. We also determined large degree of similarity between aboriginal and adventive fraction of flora in various cities. The high correlation between the systematic structure of the dominant families in different habitats is associated with the conformity of regional flora and indicates the close interaction of natural and urban flora.
Quantifying habitat use is important for understanding how animals meet their requirements for survival and provides information for conservation planning. Currently, assessments of range-wide ...habitat use that delimit species distributions are incomplete for many taxa. The Harpy Eagle (Harpia harpyja) is a raptor of conservation concern, widely distributed across Neotropical lowland forests, that currently faces threats from habitat loss and fragmentation. Here, we use penalized logistic regression to identify species-habitat associations and predict habitat suitability based on a new International Union for the Conservation of Nature range metric, termed Area of Habitat. From the species-habitat model, we performed a gap analysis to identify areas of high habitat suitability in regions with limited coverage in the key biodiversity area (KBA) network. Range-wide habitat use indicated that Harpy Eagles prefer areas of 70%–75% evergreen forest cover, low elevation, and high vegetation species richness. Conversely, Harpy Eagles avoid areas of >10% cultivated landcover and mosaic forest, and topographically complex areas. Our species-habitat model identified a large continuous area of potential habitat across the pan-Amazonia region, and a habitat corridor from the Chocó-Darién ecoregion of Colombia running north along the Caribbean coast of Central America. Little habitat was predicted across the Atlantic Forest biome, which is now severely degraded. The current KBA network covered 18% of medium to high Harpy Eagle habitat exceeding a target biodiversity area representation of 10%, based on species range size. Four major areas of high suitability habitat lacking coverage in the KBA network were identified in north and west Colombia, western Guyana, and north-west Brazil. We recommend these multiple gaps of habitat as new KBAs for strengthening the current KBA network. Modeled area of habitat estimates as described here is a useful tool for large-scale conservation planning and can be readily applied to many taxa. LAY SUMMARY Quantifying habitat use is key to understanding animals' requirements for survival and can inform spatial conservation planning by mapping species range limits. Species that inhabit remote, hard-to-survey areas lack sufficient location data and there is a need to be able to predict into poorly sampled areas to estimate the potential area of habitat. Using species distribution models, we identified Harpy Eagle range limits, habitat area, and key biodiversity area coverage across the species range. Harpy Eagles prefer areas of 70–75% evergreen forest cover, high vegetation species richness, and low elevation. Key biodiversity areas covered 18% of highly suitable Harpy Eagle habitat but with key gaps in coverage in north and west Colombia, western Guyana, and north-west Brazil. Our method of calculating habitat area estimates based on a predictive spatial model is a useful tool for large-scale conservation planning and can be readily applied to many taxa. Cuantificar el uso de hábitat es importante para comprender cómo los animales alcanzan sus requerimientos para la supervivencia, y proporciona información para la planificación de la conservación. En la actualidad, las evaluaciones del uso de hábitat a lo largo de todo el rango que delimitan las distribuciones de las especies están incompletas para muchos taxones. Harpia harpyja es una rapaz de preocupación para la conservación, ampliamente distribuida en los bosques neotropicales de tierras bajas, que actualmente enfrenta amenazas por la pérdida y fragmentación de hábitat. Aquí, utilizamos una regresión logística penalizada para identificar asociaciones de especies y hábitats y predecir la aptitud del hábitat basados en una nueva métrica de rango de la Unión Internacional para la Conservación de la Naturaleza, denominada Área de Hábitat. A partir del modelo de especie-hábitat, realizamos un análisis de brechas para identificar áreas de alta aptitud de hábitat en regiones con cobertura limitada en la red de Áreas Clave para la Biodiversidad (ACB). El uso de hábitat en todo su rango de distribución indicó que H. harpyja prefiere áreas con 70–75% de cobertura forestal siempre verde, baja elevación y gran riqueza de especies de vegetación. Por el contrario, H. harpyja evita áreas con más del 10% de cobertura terrestre cultivada y bosques en mosaico, y áreas topográficamente complejas. Nuestro modelo de especie-hábitat identificó una gran área continua de hábitat potencial a lo largo de la región panamazónica, y un corredor de hábitat desde la ecorregión de Chocó-Darién de Colombia que se extiende hacia el norte a lo largo de la costa caribeña de América Central. Se predijo poco hábitat en el bioma del Bosque Atlántico, que ahora está severamente degradado. La red actual de ACB cubrió el 18% del hábitat medio a alto de H. harpyja, lo que excedió la representación del área de biodiversidad objetivo del 10%, según el tamaño del rango de la especie. Se identificaron cuatro áreas principales de hábitat de alta aptitud que no están cubiertas por la red ACB en el norte y oeste de Colombia, el oeste de Guyana y el noroeste de Brasil. Recomendamos que estos múltiples vacíos de hábitat se incluyan como nuevas áreas para fortalecer la red actual de ACB. Las estimaciones del área de hábitat modelada como se describe aquí son una herramienta útil para la planificación de la conservación a gran escala y se pueden aplicar fácilmente a muchos taxones.
Valuation of ecosystem services can provide evidence of the importance of sustaining and enhancing those resources and the ecosystems that provide them. Long appreciated only as a commercial source ...of oysters, oyster reefs are now acknowledged for the other services they provide, such as enhancing water quality and stabilizing shorelines. We develop a framework to assess the value of these services. We conservatively estimate that the economic value of oyster reef services, excluding oyster harvesting, is between $5500 and $99,000 per hectare per year and that reefs recover their median restoration costs in 2–14 years. In contrast, when oyster reefs are subjected to destructive oyster harvesting, they do not recover the costs of restoration. Shoreline stabilization is the most valuable potential service, although this value varies greatly by reef location. Quantifying the economic values of ecosystem services provides guidance about when oyster reef restoration is a good use of funds.
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BFBNIB, DOBA, IZUM, KILJ, NMLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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