Rainfall and Soils, Not Grazing Intensity, Determine the Composition and Productivity of Annual Plants in a Biodiverse Arid Winter Rainfall Region

Concentration of grazer activity around watering points and stock posts has led to well-documented vegetation impacts in arid and semi-arid rangelands. Effect of grazing and abiotic factors on perennial plant diversity have been reported in the bio-diverse winter rainfall vegetation of the Succulent Karoo in South Africa, but the impact on annuals had not been investigated. The aim of this study was to assess the effect of rainfall, soil nutrients, land forms and grazing on forage depletion, soil chemistry and the composition, diversity, richness and biomass production of annual plants in the Richtersveld National park, which is a contractual national park used by semi-nomadic pastoralists to herd goats and sheep. A grazing gradient away from stock posts at 100m, 500m and 1000m on sandy plains and rocky foothills at five study sites with different mean annual rainfall and vegetation types were used. Distance from stock posts corresponded to a gradient of forage depletion and resulted in changes in soil chemistry with distance. Biomass production, richness and diversity of annuals were correlated with rainfall but not significantly affected by landform or distance from stock posts. Rainfall and soil variables had a greater influence on species composition than grazing in this arid ecosystem. The decrease in perennial cover and richness near the stock posts was not accompanied by increase in biomass production or richness of annuals, which is expected to have adverse effects on overall plant diversity and forage availability. Keywords: Piosphere, Pastoralists, Rangeland, Succulent Karoo DOI: 10.7176/JNSR/12-10-04 Publication date:May 31st 202

Persistent anthrax as a major driver of wildlife mortality in a tropical rainforest

Anthrax is a globally important animal disease and zoonosis. Despite this, our current knowledge of anthrax ecology is largely limited to arid ecosystems, where outbreaks are most commonly reported. Here we show that the dynamics of an anthrax-causing agent, Bacillus cereus biovar anthracis, in a tropical rainforest have severe consequences for local wildlife communities. Using data and samples collected over three decades, we show that rainforest anthrax is a persistent and widespread cause of death for a broad range of mammalian hosts. We predict that this pathogen will accelerate the decline and possibly result in the extirpation of local chimpanzee (Pan troglodytes verus) populations. We present the epidemiology of a cryptic pathogen and show that its presence has important implications for conservation

On a robust estimation of option-implied interest rates and dividend yields

In this paper, a simple no-arbitrage methodology to estimate option-implied interest rates and dividend yields simultaneously via a regression model is employed. Since the mean-based least squares estimation places equal weights on all data points making it sensitive to outliers, a robust median-based estimation approach is proposed. The proposed methodology is only valid for European options; consequently, an empirical analysis is conducted on options on the S & P 500 Index. Robust forward-looking model-free estimates of the risk-free interest rate and dividend yield, based exclusively on market prices of options, are thus obtained

Valuation of harvested goods in Mida Creek with application of the TESSA approach

Mangroves are considered a highly productive blue forests resource providing services that are important to the community both locally and globally. In recent times there has been an increase in studies on valuation of ecosystem services provided by mangroves. However, there is need to provide a simplified approach to identify, assess and quantify ecosystem services. In this study the Toolkit for Ecosystem Services Site-based Assessment (TESSA) was used to assess the value of harvested goods provided by the mangroves of Mida Creek in the current state and under plausible alternative scenarios. Spatial methods (GIS) were used to collect data for the period 1985-2019, and household interviews were used to collect data on harvested goods. Descriptive statistics were used to summarize quantitative data. Results show that the estimated current annual value of harvested goods in Mida Creek is US$11.2 million. This value increased to US$ 14.3 million under the conservation scenario and reduced to US$ 10.9 million under the business as usual scenario (BAU). These findings add to the growing literature on ecosystem service valuation and the need to use site-specific non-modelling tools like TESSA

A computation of implied volatility leveraging model-free option-implied information

This paper takes inspiration from recent model-free techniques for estimating the risk-free rate and dividend yield from European-style option prices. It proposes a methodology for computing implied volatility (IV) that integrates this option-derived information. Instead of relying on traditional inputs like treasury yields and historical dividend yields, our approach incorporates forward-looking estimates of the dividend-adjusted underlying asset price and the implied discount factor into the IV computation. This results in a simpler yet more informative adjustment that may prove useful in updating the computation of IV

International citizen science: making the local global

The Earthwatch Institute is an international non-profit organization that works with scientists and scientific institutions to develop citizen-science-based research and environmental monitoring programs. Each year, Earthwatch supports close to 80 different projects in more than 30 countries and recruits over 3000 volunteers to aid scientists in collecting data. Participants recruited by Earthwatch seek to tap into their passion for learning about science by volunteering to act as assistants for authentic research projects