The importance of periodic droughts for maintaining diversity in the freshwater environment

Whereas some species may rely on periodic drought conditions for part of their life histories, or have life strategies suited to exploiting the habitat or changed environmental conditions that are created by drought, for other organisms it is a time of stress. Periodic drought conditions therefore generate a series of waves of colonization and extinctions. Studies on lowland wet grassland, in winterbournes and in the toiche zone of both ponds and rivers, also demonstrate that different organisms are competitively favoured with changing hydrological conditions, and that this process prevents any one species from overwhelming its competitors. Competitive impacts may be inter- and intraspecific. It is therefore apparent that the death of organisms such as adult fish during severe drought conditions, though traumatic for human onlookers and commercial interests, may be merely a regular occurrence to which the ecosystem is adapted. The variability of climatic conditions thereby provides a direct influence on the maintenance of biological diversity, and it is this very biodiversity that provides the ecosystem with the resilience to respond to environmental changes in both the short and the longer term

Water quality objectives as a management tool for sustainability

The aim of this paper is to explore the potential role that quality objectives, particularly when backed by statutory force, may play in the sustainable management of river water quality. Economic valuation techniques are discussed, as well as the theory of "critical natural capital". A brief history of water quality legislation includes the implementation of the National Water Council classification in 1979, and the statutory water quality objectives introduced under the Water Resources Act 1991

Aquatic ecology, economy and society: the place of aquatic ecology in the sustainability agenda

This article explores aspects of sustainability and the importance of sustainable development, including the place of the crucially important resource of fresh water and of freshwater ecosystems. It examines the treatment of natural resources by the economic system that underpins global business, outlines some progress towards more sustainable approaches to business, and recommends steps to re-establish science as the driver of wise policies that contribute to sustainable development

Soil Moisture as a Mediator for Nitrogen Competition: Implications for Species Invasion and Climate Change

Simple models of competition for one and two resources have been well investigated for both nitrogen and water. Ecosystem models of nitrogen and water, including their interactions are also well known, but competition and ecosystem processes have rarely been considered together. Using a simple ecosystem model of the nitrogen and water cycles including the dependence of the nitrogen cycle on soil moisture I examine the outcome of competition for nitrogen. This model shows that when there are species specific effects on soil moisture, the competitive outcome for nitrogen can be coexistence or alternative stable states. The last century has seen widespread invasion of Californian grasslands by annual grasses and forbs from the southern Mediterranean region. Both nitrogen and water have been shown to be limiting in this system. The native perennial grasses deplete the soil moisture and nitrogen to a lower level than the invasive annual grasses, suggesting that natives should be better competitors. Parameterising my model for a Californian grassland system I show that in fact the invasive annual grasses are the superior competitor for nitrogen at lower soil moisture when nitrogen competition is mediated by soil moisture. The competitive outcome at current rainfall levels in California is limited to competitive exclusion by the annuals or coexistence. Climate change caused by anthropogenic emissions of CO2 is already affecting communities and ecosystems. Global climate models predict changes in both mean amount and distribution of precipitation. I investigate the effect of changing precipitation distributions on both ecosystem and community processes in nitrogen limited systems. There is wide variation in ecosystem response to increased variation in rainfall. The outcome of N competition was more predictable, with the best competitor at lower soil moisture being consistently favoured with increasing rainfall variability. This might prove another problem in restoring native grasses in Californian grasslands

The effects of fire on the Podocarpus latifolius forests of the Royal Natal National Park, Natal Drakensberg

Tree species composition within, and on the margins of forests in areas with different burning histories was recorded. Stands were ordinated and classified and related to burning history, altitude, aspect, slope, soil pH, soil organic content and soil moisture content. Regularly burnt margins were shown to be different in both structure and composition to less frequently burnt or unburnt margins. The importance of a dense margin, containing margin associated species is stressed when considering the conservation of the forests

Rebirthing the landscape

An account of the community-based groundwater recharge activities of the NGO Tarun Bharat Sangh in semi-arid north Rajastha

Investing in our rivers

This article makes the case for investment in the natural infrastructure of rivers, highlighting the societal benefits that would flow from it yet their substantial externalisation from current economic thinking with associated deterioration of social and economic opportunit

Are We Preaching a Gospel Free from Law?

Let us state the question which heads this paper more specifically: When we speak of the Gospel (grace, forgiveness of sin, Cross of Christ, Christ Crucified), is it permissible to mix elements of the Law into this concept? One would like to view this question as rhetorical, having for its answer the strongest possible negative. In view of its subject matter, however, one is left with a sense of that kind of interrogative which anticipates a negative answer yet searches deeply for whatever reason may motivate it

The Isles of Scilly and the Channel Islands: "bench-mark" hydrographic and geodetic surveys 1689-1980

PhDThe English Channel has been both a major maritime artery and a navigator's nightmare for many centuries. Two archipelagoes, the Isles of Scilly to the north and the Channel Islands to the south, have been and remain major hazards. The two archipelagos have long cartographic histories which have yet to be fully documented. The present study is, with two limited exceptions, confined to British official hydrographic surveys and more specifically to those that may be regarded as 'bench-mark' surveys , i. e. surveys that made significant advances in 44& charting the two archipelagoes. The study is further restricted to describing and assessing the progressive attempts to fix accurately the latitudes and longitudes of the two archipelagos and their relationships to west Cornwall on the one hand and the Cotentin peninsula on the other. The emphasis is upon the MS charts, Remark Books and notes etc. of the surveyors. The earliest survey discussed here is that of the Isles of Scilly by Capt Collins in 1689, published in 1693 in his Great Britain's Coasting Pilot, followed by Tovey and Ginver (1731), Robert Heath (1744/1750), Graeme Spence (1792-c1812) Joseph Huddart (1795); Ordnance Survey (Mudge: 1796; Clarke 1858; 1959). The first Channel Islands official hydrographic survey was initiated by Capt Martin White, as late as 1803, but not officially recognised until 1812 and not published until 1824/6; other surveys mentioned are Carte de France (1818-45; ) Begat (1829); Beck (1942-3); Service Hydrographique (1948); Ordnance Survey (1980)

False Stereotypes

Despite the Latinx community being misrepresented in mainstream American media, countless Latinx individuals have accomplished prestigious milestones throughout history in America. The stereotypical notions that have formed over the years towards Latina/o’s are both insulting and undermining. Common traits that these stereotypes follow often include the idea that Latinx people are poor, uneducated, violent and unsuccessful. My intent is to discuss self and societal impacts of these stereotypes and to nullify these negative stereotypes toward Latinx individuals by identifying positive traits that outstanding Latinx citizens possess, along with important positive impacts the Latinx community has made in American society. Through compare and contrast analysis, of peer review and scholarly sources logically rational statements are formed to solidify the conclusion stating that Latinx individuals are not what these stereotypes claim