8,297 research outputs found

    Climate change amplifies plant invasion hotspots in Nepal

    Get PDF
    Aim Climate change has increased the risk of biological invasions, particularly by increasing the climatically suitable regions for invasive alien species. The distribution of many native and invasive species has been predicted to change under future climate. We performed species distribution modelling of invasive alien plants (IAPs) to identify hotspots under current and future climate scenarios in Nepal, a country ranked among the most vulnerable countries to biological invasions and climate change in the world. Location Nepal. Methods We predicted climatically suitable niches of 24 out of the total 26 reported IAPs in Nepal under current and future climate (2050 for RCP 6.0) using an ensemble of species distribution models. We also conducted hotspot analysis to highlight the geographic hotspots for IAPs in different climatic zones, land cover, ecoregions, physiography and federal states. Results Under future climate, climatically suitable regions for 75% of IAPs will expand in contrast to a contraction of the climatically suitable regions for the remaining 25% of the IAPs. A high proportion of the modelled suitable niches of IAPs occurred on agricultural lands followed by forests. In aggregation, both extent and intensity (invasion hotspots) of the climatically suitable regions for IAPs will increase in Nepal under future climate scenarios. The invasion hotspots will expand towards the high‐elevation mountainous regions. In these regions, land use is rapidly transforming due to the development of infrastructure and expansion of tourism and trade. Main conclusions Negative impacts on livelihood, biodiversity and ecosystem services, as well as economic loss caused by IAPs in the future, may be amplified if preventive and control measures are not immediately initiated. Therefore, the management of IAPs in Nepal should account for the vulnerability of climate change‐induced biological invasions into new areas, primarily in the mountains

    The Changing Demographic Profile of the United States

    Get PDF
    [Excerpt] The United States, the third most populous country globally, accounts for about 4.5% of the world’s population. The U.S. population—currently estimated at 308.7 million persons—has more than doubled since its 1950 level of 152.3 million. More than just being double in size, the population has become qualitatively different from what it was in 1950. As noted by the Population Reference Bureau, “The U.S. is getting bigger, older, and more diverse.” The objective of this report is to highlight some of the demographic changes that have already occurred since 1950 and to illustrate how these and future trends will reshape the nation in the decades to come (through 2050). The United States Is Getting Bigger. U.S. population growth is due to the trends over time in the interplay of increased births, decreased deaths, and increased net immigration. The United States Is Getting Older. Aside from the total size, one of the most important demographic characteristics of a population for public policy is its age and sex structure. This report illustrates how the United States has been in the midst of a profound demographic change: the rapid aging of its population, as reflected by an increasing proportion of persons aged 65 and older, and an increasing median age in the population. The United States Is Becoming More Racially and Ethnically Diverse, reflecting the major influence that immigration has had on both the size and the age structure of the U.S. population. This section considers the changing profile of the five major racial groups in the United States. In addition, trends in the changing ethnic composition of the Hispanic or Latino Origin population are discussed. Although this report will not specifically discuss policy options to address the changing demographic profile, it is important to recognize that the inexorable demographic momentum will have important implications for the economic and social forces that will shape future societal well-being. There is ample reason to believe that the United States will be able to cope with the current and projected demographic changes if policymakers accelerate efforts to address and adapt to the changing population profile as it relates to a number of essential domains, such as work, retirement, and pensions; private wealth and income security; the federal budget and intergenerational equity; health, healthcare, and health spending; and the health and well-being of the aging population. These topics, among others, are discussed briefly in the final section of this report. This report will be updated as needed

    Sequential Procedure for Testing Unit Roots in the Presence of Structural Break in Time Series Data

    Get PDF
    Testing for unit roots has special significance in terms of both economic theory and the interpretation of estimation results. As there are several methods available, researchers face method selection problem while conducting the unit root test on time series data in the presence of structural break. This paper proposes a sequential search procedure to determine the best test method for each time series. Different test methods or models may be appropriate for different time series. Therefore, instead of sticking to one particular test method for all the time series under consideration, selection of a set of mixed methods is recommended for obtaining better results.Time Series, Stationarity, Unit Root Test, Structural Break, Sequential Procedure

    ARDL Modelling Approach to Testing the Financial Liberalisation Hypothesis

    Get PDF
    It is a stylised fact that financial "repression" retards economic growth. Hence, financial liberalisation is advocated to remove the stranglehold on the economy. Financial liberalisation policy argues that deregulation of interest rate would result into a higher real interest rate which would lead to increased savings, increased investment and achieve efficiency in financial resource allocation. Past studies have reported inconclusive results regarding the interest rate effects on savings and investment. This paper examines the financial liberalisation hypothesis by employing autoregressive distributed lag (ARDL) modelling approach on Nepalese data. Results show that the real interest rate affects both savings and investment positively.Financial Liberalisation, Interest Rate Effects, Unit Roots, Cointegration, ARDL Modelling


    Get PDF
    We use panel data from Nepal to examine the effect of climate in inducing technology to understand potential agricultural adaptation to climate change in rice and wheat crops. We find different degree of climate-technology interaction in the productivity of two crops.Crop Production/Industries,

    Enhancement of reinforced soil wall performance under dynamic loading

    Full text link
    University of Technology, Sydney. Faculty of Engineering and Information Technology.Reinforced soils have been widely used in a variety of applications because of their satisfactory performance and cost effectiveness. A number of investigations to determine the seismic deformation modes of reinforced soil walls with conventional horizontal inclusions have already been conducted, but only limited investigations with the partial inclusion of vertical elements have been conducted, and then they did not consider the performance of reinforced soil walls under dynamic loading. This research presents a new concept of soil reinforcement using vertical fortification designed to connect layers of conventional horizontal reinforcement together. For this proposed system, as with conventional reinforced soil, the selected granular material is compacted over the horizontal reinforcement up to a given height, and then subsequent layers of horizontal reinforcement are laid down. Afterwards, reinforcements are inserted vertically or at an inclined angle, as per the design requirements. Each layer is then tied to another so that it acts as one integrated system, reducing the total force at the back of the facing panels. This concept is modelled numerically using PLAXIS 2D version 9.0 using the Kobe earthquake loading. The convincing results from this numerical analysis encouraged me to conduct an experimental program that included shake table tests. The selections of materials were then tested to determine which materials were readily available on the market. Four reduced scale physical models, with and without vertical reinforcement, with angled reinforcement towards the facing and against the facing were tested on a shake table under stepped-up sinusoidal acceleration input. The results of the four models tested were then compared to evaluate the performance enhancement of a soil wall with vertical reinforcement. The results showed that the wall with vertical reinforcement improved its performance under dynamic loading remarkably. Finite element models based on the same parameters used in the shake table experiments and with a PLAXIS 2D program were developed, from which the numerical outcomes generated similar patterns of better performance when vertical fortification was included. Those results are matched against the experimental outcomes, and the results show a reasonable agreement between the measured and calculated displacements, backfill surface settlements and accelerations, albeit there were some discrepancies. These slight dissimilarities could be the result of implementing, to some extent, different physical properties in the numerical model and their variability within the measured data. An array of parametric studies with varying design parameters was also carried out, with the results indicating that the magnitude of dynamic response increases with a decreasing angle of friction and the extent of dynamic response decrease with an increasing Young’s modulus. It is also found that the vertical reinforcement with very close spacing (less than three times the spacing of horizontal reinforcement), adds no extra benefit for the wall system. According to the findings of this study, the proposed inclusion of vertical components to reinforced soil walls enhances the stability of the walls compare to the conventional reinforced soil systems under earthquake loading. The vertical components increase the integrity of the reinforced wall and create blocking actions, which reduce deformations at both facing wall and backfill surface. These outcomes point out the potential benefits of inserting vertical elements into a conventional soil reinforcement system under dynamic loads

    Maximum Likelihood Estimation of ARMA Model with Error Processes for Replicated Observations

    Get PDF
    In this paper we analyse the repeated time series model where the fundamental component follows a ARMA process. In the model, the error variance as well as the number of repetition are allowed to change over time. It is shown that the model is identified. The maximum likelihood estimator is derived using the Kalman filter technique. The model considered in this paper can be considered as extension of the models considered by Anderson (1978), Azzalini (1981) and Wong and Miller (1990)ARMA model, Kalman filter, maximum likelihood estimation


    Get PDF
    Meta-analyses of past research outcomes are becoming more popular, however, the issue of the panel nature of data has not been empirically investigated. We test various forms of data stratifications into panels for outdoor recreation economic studies but do not find any significant effects, possibly because of inherent data complexity.Environmental Economics and Policy, Resource /Energy Economics and Policy,