Role Of Human Disturbance Research Articles

A newly invasive species may promote dissimilarity of pest populations between organic and conventional farming systems

Insect taxa vary in their phenology across space creating dissimilar patterns of species abundance over time. The role of human disturbances and invasive species in these patterns of temporal dissimilarity (phenological differences) across space, however, remain largely unexplored. To dissect these patterns, we evaluated four common pests and one newly invasive species (Contarinia nasturtii; Swede midge) at 220 time points across 2 years on organic and conventional farms. We first summarized across time and evaluated differences in pest abundance between farm management (organic and conventional). We then used generalized additive models to describe temporal patterns of abundance, disentangling phenological differences across management systems. Last, we conducted a temporal beta diversity analysis to identify which species and management practices contribute most to dissimilarity. We found that aggregating pest abundance across time and species masked differences in pest phenology across management systems and concealed variation in pest abundance that was strongly driven by an invasive species, respectively. Overall, our results suggest that organic and conventional farms may be only superficially similar in pest abundance. Rather, by accounting for time, we demonstrate a more nuanced understanding of pest communities moving beyond abundance that may be particularly important for management of newly invasive species.

Space use and activity of capybaras in an urban area

Abstract Due to the rapid growth of urban environments, interactions between animals and humans in cities are increasingly common. Large mammals, such as capybaras (Hydrochoerus hydrochaeris), provide benefits to people and biodiversity of urban areas, but can also result in conflicts, such as animal–vehicle collisions or disease transmission. As a consequence, understanding the space use of urban capybara, and the effect of human activity on capybaras, is conducive to the promotion of coexistence. We studied the home range and the role of human disturbance on activity and habitat selection of urban capybaras in the city of Campo Grande (Brazil). We monitored nine groups of capybaras living at four parks: two parks subjected to high human visitation on workdays and two on weekends. Home range of the urban capybaras in the study is larger than those reported in previous studies of wild capybaras. The capybaras under study presented a bimodal activity pattern, which was delayed on days of high human presence, increasing animals’ nocturnality. In addition, habitat selection was completely altered on days of high human presence, leading animals to increase avoidance of urban areas and reversing the selectivity patterns for forests, grasslands, and water bodies, that capybaras show on days with low human presence. Even when completely surrounded by an anthropic environment, our results indicate that a mosaic of grasslands near a water body and forested areas will allow capybaras to maintain daily activity and large home ranges. However, human presence significantly altered the daily activity patterns and habitat selection of capybara. Urban planners should account for these data to improve the coexistence of capybaras with humans and thereby minimize the potential for conflicts.

Damage in Cactaceae, their geographic distribution and new evidences

Background: Field observations of damage in columnar cacti of central Mexico, and previous evidence in scientific literature, indicated the absence of systematic information about kinds of damage, vectors, and pathogens, in this botanical family.
 Questions: How is the knowledge of damage and defense mechanisms in cacti? Is there a pattern in causal agents and their geographical distribution in the Americas?
 Methods: A database of 58 taxa by 51 types of damage was developed from literature recorded in ISI Web of Knowledge, Cabdirect, and Google Scholar, and it was analyzed by multivariate methods.
 Results: From 1,500 species of Cactaceae, only 58 have been studied through this scope. Subfamily Cactoideae has been the most studied, in particular tribe Echinocereeae (= Pachycereeae columnar cacti). Multivariate analysis grouped cacti according to the kind of damage: biotic, or abiotic. Damage due to biotic factors was sub-grouped depending on the herbivores. Damage by abiotic factors is more frequent in extreme latitudes. Fourteen species of columnar cacti were reported with herbivory and rot damage in Central Mexico, of which eight represent new records of damaged cacti. 
 Conclusions: The evidence from field observations, and few recent publications suggest that some generalist herbivores are becoming dangerous in this region, Future research is necessary in order to understand the dynamics of the dispersion of some kinds of damage, the role of human disturbance, and the role and changes in defense mechanisms in wild and domesticated cacti.

Recognizing the importance of an all-inclusive approach to brown bear conservation now and into the future.

In their critique of our recent article in Oecologia (Pigeon et al. Oecologia 181:1101-1116, 2016a) investigating the influence of ambient temperature on brown bear habitat selection, Ordiz et al. (2017, current issue) argue that we downplay the role of human disturbance on bear behavior, and that we wrongly report on the findings of Ordiz et al. (Oecologia 166:59-67, 2011). We argue that our previous article in Oecologia (Pigeon et al. 2016a) by no means downplays the influence of human factors on bear behavior, and that we correctly stated that Ordiz et al. (2011) did not adequately consider the potential influence of temperature on their findings. Finally, we stress the relevance of considering all-inclusive approaches to the common goal of successful wildlife conservation.

Staying cool or staying safe in a human-dominated landscape: which is more relevant for brown bears?

Pigeon et al. (2016) Staying cool in a changing landscape: the influence of maximum daily ambient temperature on grizzly bear habitat selection. Oecologia 181:1101. doi:10.1007/s00442-016-3630-5 analyzed the effect of ambient temperature on the habitat selection of grizzly bears (Ursus arctos) in Alberta, Canada. They concluded that temperature played a significant role in bear habitat selection and that it was unlikely that human activity introduced biases to the habitat selection of bears. However, Pigeon et al. did not consider variables related to human activities in their analyses. They also misinterpreted previous research that has accounted for temperature in the habitat selection of brown bears. There is much literature published on the negative effects of human disturbance on wildlife in general and on bears in particular. Downplaying the role of human disturbance could have important negative consequences if, in fact, human disturbance were a more important factor than thermoregulation. Indeed, dismissing the importance of human influence, in the face of contradictory evidence, could tempt managers to disregard an important factor that is difficult and often unpopular to deal with in their conservation plans.

HUMAN DISTURBANCE AND THE PHYSIOLOGICAL RESPONSE OF ELK IN EASTERN WASHINGTON

Stress hormone measures have proven useful for assessing effects of human disturbance on wildlife populations. However, most studies are of short duration or limited geographic scope (i.e., without spatial replication), leading to concerns about confounding effects of biotic conditions. Previous research correlated fecal glucocorticoid metabolites (FGMs) of elk (Cervus elaphus) with human disturbance, but this factor also co-varied with seasonal climatic conditions, making it difficult to make broader inference regarding the role of human disturbance. In this study we attempted to simultaneously evaluate the effects of climatic conditions and human disturbance by comparing the year-round physiological stress response of elk to varying levels of human disturbance at three study sites in south-central Washington State. FGMs were consistently elevated throughout the year at the study site receiving the greatest amount of human disturbance. We observed support for a positive effect of precipitation and increasing temperature on FGMs at the low-disturbance site, but less support for importance of climatic variables in explaining FGMs at the high-disturbance sites - suggesting that climatic variables were likely of secondary importance compared to anthropogenic stressors in elk at those sites. Collectively, while we were unable to disentangle the effects of site- specific stressors, our findings suggest that in this environment, humans were a dominant stressor influencing FGM levels. Therefore, interpreting results of physiological studies requires that researchers account for a broad combination of biotic and abiotic stressors at a particular study location. We particularly encourage future investigators to account for the potential confounding effect of human disturbance that could override other stressors.

The role of human disturbance in island biogeography of arthropods and plants: an information theoretic approach

AbstractAimRecent progress in island biogeography indicates that classical island biogeography alone cannot encapsulate the complex and dynamic nature of island biogeographical processes. Factors such as habitat complexity and connectivity, and in the face of the Anthropocene, human disturbance and invasive species, may influence insular communities. The relative importance of these factors, however, may differ among groups of biota. Here we employed an information theoretic approach to investigate factors likely to explain patterns in species richness and assemblage composition of five different groups of arthropods (ants, beetles, flies, spiders and cockroaches) and native and exotic plants within an insular community.LocationCapricornia Cays located at the southern end of Great Barrier Reef, eastern Australia.MethodsArthropods were sampled from 14 cays using pitfall and Malaise traps and hand collecting. Plants were comprehensively surveyed on each island. We used univariate and multivariate generalized linear models with a model averaging technique, to calculate summed Akaike weights which quantified the relative importance of predictor variables in explaining variation in species richness and assemblage composition.ResultsWe found that infestation of the invasive ant Pheidole megacephala was negatively correlated with the species richness of ants, beetles and flies. Unlike species richness, only the assemblage composition of ants was related to P. megacephala infestation. Assemblage composition of other arthropod groups and plants was related to various factors, including island size (native plants), native plant species richness (beetles, flies and spiders) and presence of human disturbances (exotic plants and cockroaches).Main conclusionsThe information theoretic approach proved useful in determining the relative likelihood of factors influencing both univariate and multivariate data of insular fauna and flora. The results demonstrated that human disturbance and proliferation of invasive species can override other biogeographical processes. The relative importance of these factors, however, varied depending on the taxonomic groups studied.

New data on the recent history of the littoral forests of southern Cameroon: an insight into the role of historical human disturbances on the current forest composition

Background and aims–Prior to European colonisation of Central Africa, human populations were dispersed through the forests, where they practiced slash-and-burn cultivation. From the 19th century they were progressively concentrated in villages along roads, leaving large areas of forest derelict. In south-western Cameroon, and elsewhere in Central Africa, forest canopy is dominated by long-lived lightdemanding tree species, suggesting a possible role of human disturbance. The aim of this study was to bring new insights into the possible effect of historical human disturbances in terms of timing and spatial extent on the current forest composition. Location–Wet evergreen littoral forest in south-western Cameroon. Methods and key results–A combined vegetation sampling and archaeobotanical survey were conducted. Potsherds, oil-palm endocarps, and charcoal were found throughout the study area, suggesting generalised human occupation and anthropogenic fire. Human occupancy occurred in two periods: between 2200 and 1500 BP, and, more recently, beginning three centuries ago. High frequency of fire and the presence of Elaeis guineensis both dated recently (between 260 and 145 BP) suggest slash-and-burn shifting cultivation practices. These human-induced disturbances may coincide with the age of the current emergent lightdemanding species, the age of which can be estimated around 200 years, or with the phases of drying climate recorded in the Central African forest in the early 18th century. Conclusions–These results support the idea that historical human disturbances are one of the major factors that shaped the current forest composition in Central Africa.

Plant hybridization: the role of human disturbance and biological invasion

AbstractAimAnderson & Stebbins (1954,Evolution,8, 378–388) posited that human activities promote species hybridizations by creating opportunities for hybridization and new habitats for hybrids to persist through disturbances (i.e. the ‘disturbance hypothesis’). While the first part of this hypothesis appears to be well supported, the second part has not been corroborated with empirical evidence, probably because of the lack of appropriate data. In this study, I (1) document the richness and distribution of hybrid plants in the United States; (2) examine the relationships between hybrids of different origins and between hybrid plants and native or exotic plants; and (3) examine possible mechanisms for these relationships and test the disturbance hypothesis.LocationThe United States.MethodsThe richness and distribution of plant hybrids was examined at the county level according to origin, that is, formed between native–native species (N × N), native–exotic species (N × E) and exotic–exotic species (E × E), using data from the Biota of North America Program.ResultsThe three hybrid types (N × N,N × EandE × E) were positively related to each other and showed stronger positive relationship with exotic richness than with native richness. They also exhibited similar spatial patterns, with richness hotspots concentrated in the north‐east United States and Great Lakes region. However, the richness of hybrids of exotic origin (E × EandN × E) was not related to county area, as often observed for native species; instead, it showed strong positive relationships with human population density. Thus, the overall patterns of hybrid richness and distribution support the ‘disturbance hypothesis’.Main conclusionsThe results are generally consistent with the disturbance hypothesis. The relationship between the number of hybrids of exotic origin and overall exotic richness provided stronger evidence for human‐induced than for naturally caused hybridization, although other possible explanations may also exist.

Determinants of pollen dispersal in the East Asian steppe at different spatial scales

Two sites from the East Asian steppe, the Mu Us Sandland as a regional case and the Anguli Nuur catchment as a local one, were chosen to detect roles of vegetation, climate, landform, and human disturbance on pollen dispersal. 1) Vegetation: The semi-arid steppe vegetation is characterized by Artemisia and Chenopodiaceae pollen under various vegetation conditions; however, no evident correlation between pollen percentages and corresponding plant species cover is found. 2) Climate: Samples under different Mean Annual Precipitations (MAPs) clearly distinguish themselves in the Mu Us Sandland, implying MAP-determined surface pollen spectra in regional scale. 3) Landform: Surface pollen assemblages in the azonal psammophytic vegetation and lowland meadow, show insignificant variance from the zonal steppe vegetation. The azonal halophilous vegetation, mostly distributed in the lowland or near the lake shore, leads to higher than average percentages of Chenopodiaceae pollen. Signal of exotic Pinus pollen is also strengthened in the lowland and lake sediment. 4) Human disturbance: The role of human disturbance on surface pollen assemblages is weak, as shown in the Mu Us Sandland. This study also provides theoretical bases for quantitative reconstructions of palaeoclimate and palaeovegetation based on fossil pollen spectra from lake sediments and lowland soils in the semi-arid East Asian steppe. We suggest that calibration against locally dispersed pollen taxa is necessary to reliably reconstruct changes in vegetation pattern through time, for example, a factor of 1.75 for the widely used A/C ( Artemisia/Chenopodiaceae) ratio is suggested according to the pollen assemblages in the surface layers of the lake sediment vs. slope soil in Anguli Nuur. However, uncertainties also exist for such calibration considering the dynamics of local-scale azonal vegetation.

Can human disturbance promote nestedness? A case study with breeding birds in urban habitat fragments.

Several factors, singly or in combination, have proven relevant in promoting nestedness in animal communities (area, isolation, habitat structure, etc.); however, little empirical evidence exists about the role of human disturbance. The goal of this paper was to assess whether human disturbance (pedestrians) may affect bird species composition in such a way as to generate a nested distributional pattern. The study was conducted in an urban fragmented landscape, the city of Madrid, where wooded parks were suitable fragments for many bird species, and had different levels of human visitation. At the community level, the distribution of species was significantly nested in two consecutive breeding seasons. Using two different procedures ("temperature" and "departures" methods) to analyse causality in nestedness, I found that pedestrian rate, fragment size and the diversity of stems were significantly correlated to the nested pattern. When analysed simultaneously, and controlling for their independent effects, these factors still accounted for nestedness. Pedestrian rate was the only factor significantly associated with changes in species composition between years. At the individual species level, 74 and 41% of species were significantly nested in relation to pedestrian rate in 1997 and 1998, respectively; however, these percentages were independent of foraging substrate and body size. Besides the classic area and habitat diversity effects, human disturbance can also promote nestedness: locally, by restraining the time and space of foraging and breeding opportunities, thus reducing fragment suitability, and regionally, by increasing extinction and decreasing colonization probabilities in highly disturbed fragments.

Selective Mortality in Chinook Salmon: What Is the Role of Human Disturbance?

Selective Mortality in Chinook Salmon: What Is the Role of Human Disturbance?

The role of human disturbance in Late Holocene vegetation changes on Kullaberg, southern Sweden

A pollen record from a small peatland located on Kullaberg in northwestern Skane, southern Sweden, revealed that grazing pressure might have been the major disturbance agent controlling the vegetation, at least from ca. 1500 B. C. until the latter part of the nineteenth century. The pollen data also indicate a step-by-step increase in grazing pressure, expressed as a marked increase in non-arboreal pollen representation at ca. 1500 B. C., A. D. 650 and A. D. 1650. The increase at A. D. 650 probably indicates a more regular and intensive use of the area, resulting in a forest structure that was much more open than earlier, together with an expansion of Fagus, which rapidly replaced Quercus as the local forest dominant. At about this time the first patches of heath vegetation originated, but they probably only covered a small part of Kullaberg. Larger areas with an intensively grazed Calluna heath, as shown by eighteenth century maps, probably evolved around ca. A. D. 1650, when much of Kullaberg seems to have been deliberately deforested.

Role of Human Disturbance in Response Behavior of Laysan Albatrosses (Diomedea immutabilis)

Role of Human Disturbance in Response Behavior of Laysan Albatrosses (<i>Diomedea immutabilis</i>)

An investigation of the influence of human disturbance on selected soil nutrients in Narok District, Kenya

Selected soil nutrients were analysed purposely to establish whether they display a spatial pattern due to environmental factors and whether the pattern has been affected by human activities. Data analysis involved descriptive and canonical variate analysis. Except for grassland and shrubland sites, mean carbon, nitrogen, phosphorus, most base cations and copper in the 0–10 cm depth is low for disturbed sites. Within profile data are closer to each other than to data between profiles, suggesting that the former are chemically similar, and that the combined effects of underlying factors is similar. A two-dimensional ordination using canonical discriminant analysis suggests three soil sample clusters that are largely determined by altitude and moisture gradient. Sample ordination of group means show differences between disturbed and undisturbed forest and grassland site categories, suggesting the overriding role of human disturbance over environmental factors on soil nutrients.

The role of human disturbance in the local Late Holocene establishment of Fagus and Picea forests at Flahult, Western Sm�land, Southern Sweden

A pollen record from a small alder carr located in the centre of aFagus stand near the hamlet of Flahult in southern Smaland has shown thatFagus became established in a semi open cultural landscape about 900 B.P. Human disturbance seems to have controlled the local establishment ofFagus at this site through an expansion of pastoral farming. TheFagus dominance in the present stand seems to be of recent origin, asFagus pollen percentages and influx values have increased considerably only during the last 50 years. The modern composition and structure of theFagus stand are probably an effect of changes in land-use and decreased human activity at the end of the last century. Today, only occasionalPicea individuals occur in the studied stand, andPicea does not appear to have been more abundant in the recent past. The regional expansion ofPicea has probably occurred during this century and has been favoured by modern forestry during the last 50 years.