Analysis of Abrupt Transitions in Ecological Systems

The occurrence and causes of abrupt transitions, thresholds, or regime shifts between ecosystem states are of great concern and the likelihood of such transitions is increasing for many ecological systems. General understanding of abrupt transitions has been advanced by theory, but hindered by the lack of a common, accessible, and data-driven approach to characterizing them. We apply such an approach to 30–60 years of data on environmental drivers, biological responses, and associated evidence from pelagic ocean, coastal benthic, polar marine, and semi-arid grassland ecosystems. Our analyses revealed one case in which the response (krill abundance) linearly tracked abrupt changes in the driver (Pacific Decadal Oscillation), but abrupt transitions detected in the three other cases (sea cucumber abundance, penguin abundance, and black grama grass production) exhibited hysteretic relationships with drivers (wave intensity, sea-ice duration, and amounts of monsoonal rainfall, respectively) through a variety of response mechanisms. The use of a common approach across these case studies illustrates that: the utility of leading indicators is often limited and can depend on the abruptness of a transition relative to the lifespan of responsive organisms and observation intervals; information on spatiotemporal context is useful for comparing transitions; and ancillary information from associated experiments and observations aids interpretation of response-driver relationships. The understanding of abrupt transitions offered by this approach provides information that can be used to manage state changes and underscores the utility of long-term observations in multiple sentinel sites across a variety of ecosystems.Organismic and Evolutionary Biolog

Effects of tidal-forcing variations on tidal properties along a narrow convergent estuary

A 1D analytical framework is implemented in a narrow convergent estuary that is 78 km in length (the Guadiana, Southern Iberia) to evaluate the tidal dynamics along the channel, including the effects of neap-spring amplitude variations at the mouth. The close match between the observations (damping from the mouth to ∼ 30 km, shoaling upstream) and outputs from semi-closed channel solutions indicates that the M2 tide is reflected at the estuary head. The model is used to determine the contribution of reflection to the dynamics of the propagating wave. This contribution is mainly confined to the upper one third of the estuary. The relatively constant mean wave height along the channel (< 10% variations) partly results from reflection effects that also modify significantly the wave celerity and the phase difference between tidal velocity and elevation (contradicting the definition of an “ideal” estuary). Furthermore, from the mouth to ∼ 50 km, the variable friction experienced by the incident wave at neap and spring tides produces wave shoaling and damping, respectively. As a result, the wave celerity is largest at neap tide along this lower reach, although the mean water level is highest in spring. Overall, the presented analytical framework is useful for describing the main tidal properties along estuaries considering various forcings (amplitude, period) at the estuary mouth and the proposed method could be applicable to other estuaries with small tidal amplitude to depth ratio and negligible river discharge.info:eu-repo/semantics/publishedVersio

Population policies and education: exploring the contradictions of neo-liberal globalisation

The world is increasingly characterised by profound income, health and social inequalities (Appadurai, 2000). In recent decades development initiatives aimed at reducing these inequalities have been situated in a context of increasing globalisation with a dominant neo-liberal economic orthodoxy. This paper argues that neo-liberal globalisation contains inherent contradictions regarding choice and uniformity. This is illustrated in this paper through an exploration of the impact of neo-liberal globalisation on population policies and programmes. The dominant neo-liberal economic ideology that has influenced development over the last few decades has often led to alternative global visions being overlooked. Many current population and development debates are characterised by polarised arguments with strongly opposing aims and views. This raises the challenge of finding alternatives situated in more middle ground that both identify and promote the socially positive elements of neo-liberalism and state intervention, but also to limit their worst excesses within the population field and more broadly. This paper concludes with a discussion outling the positive nature of middle ground and other possible alternatives

Benguela Source and Transport Project (BEST) : current measurements off the coast of South Africa : WOCE ACM-4, June 1992-October 1993

The BEST (Benguela Source and Transport) project was designed to investigate the form of the Benguela Current and ratio of the Aguhlhas Current and South Atlantic Current source waters masses. The transport of the Benguela Current and its variability was measured by a moored array of instruments, inverted echo sounders (IES), inverted echo sounders with pressure gauges (PIES), current meter moorings, and hydrographic surveys as wells as analysis of the TOPEX/POSEIDON satellite altimeter data. This report presents data from the current meter moorings. The BEST mooring array was deployed in June 1992 and recovered in October 1993. The array consisted of 4 subsurface moorings laid off the West Coast of Africa along 30° South. Figs 1 & 2. BEST objectives contribute to the WOCE International plan. The 30° S mooring array is identified by WOCE as ACM-4

Deep western boundary currents in the southwestern Pacific Ocean : WOCE PCM-9 : February 1991-December 1992

This report describes current meter measurements from an experiment to measure the deep western boundary current that carries dense water from the Antarctic to the Pacific Ocean. The field measurements were conducted as part of a joint two year experiment by Oregon State University, Texas A&M University, Woods Hole Oceanographic Institution and the New Zealand Oceanographic Institute. The effective western boundary for deep waters in the South Pacific is located east of New Zealand and consists of the Campbell Plateau, Chatham Rise and the Kermadec and Tonga Ridges. Because there is no substantial source of dense bottom waters in the North Pacific, all the deep and bottom waters of both the North and South Pacific have their origin in the Antarctic, and are carried north in a deep western boundary current (DWBC). Neither the sinking of dense water in a few places near the Antarctic Continent nor the general upwelling of this water throughout the rest of the world ocean are easily measurable; since the DWBC is the sole source of deep inflow for the world's largest ocean, knowledge of its strength and variability is critical to a better understanding of the ventilation and heat balance of the Pacific. No direct measurements had ever been made in the DWBC in the Pacific, and evidence of its width could only be made from hydrographic evidence. It was decided to deploy the U.S. resources along a 1000-km line at 32.5°S extending east from the western boundary (Fig. 1, Table 1). Three nominal depths were instrumented: about 200m above the bottom, 4500m, and 2500m (Fig. 2). The 2500m level was selected because it was anticipated that it is near the top of the DWBC in the west, and should show predominately northward flow in the eastern part of the array. The array was deployed in January and February, 1991 from the RN Rapuhia operated by the New Zealand Oceanographic Institute. It consisted of 20 sub-surface moorings, with a total of 60 current meters. It was recovered in November and December, 1992 by the FN Giljanes. The acoustic releases failed on four of the mooring. Partial instrumentation on three of these were recovered by dragging. Mooring 8 was not recovered. The top instrument on Mooring 14 sunk during recovery. A total of 53 current meters were recovered. The experiment was called MAPKIWI, but nobody remembers why. The MAPKIWI current meter array contributes to the World Ocean Circulation experiment and is identified by that program as PCM-9

Abyssal boundary current studies, current measurements north of the Falkland Plateau: January 1986-April 1987

The data described in this report were collected in support of the program, Abyssal Boundary Current Studies, funded by the National Science Foundation. This program was designed to improve our understanding of the structure and variability of the deep western boundary currents and to estimate their transport of heat and mass. Some of these deep western boundary currents are formed by the northward flow of the Antarctic Bottom Water along the eastern margins of the southern continents and ridges. In particular these data are from the energetic flow of this Bottom Water entering the South Atlantic

Traditional beliefs and practices in the postpartum period in Fujian Province, China: a qualitative study

<p>Abstract</p> <p>Background</p> <p><it>Zuo yuezi </it>is the month postpartum in China associated with a variety of traditional beliefs and practices. We explored the current status of <it>zuo yuezi </it>from social, cultural and western medical perspectives.</p> <p>Methods</p> <p>We interviewed family members (36) and health workers (8) in Fujian Province, selecting one rural and one rapidly developing urban county. We asked about their traditional beliefs and their behaviour postpartum. We used a framework approach to identify main themes. We categorised reported behaviour against their probable effects on health, drawing on Western standards.</p> <p>Results</p> <p>Respondents reported that <it>zuo yuezi </it>was commonly practiced in urban and rural families to help the mother regain her strength and protect her future health. <it>Zuo yuezi </it>included: dietary precautions, such as eating more food and avoiding cold food; behavioural precautions, such as staying inside the home, avoiding housework and limiting visitors; hygiene precautions, such as restricting bathing and dental hygiene; and practices associated with infant feeding, including supplementary feeding and giving honeysuckle herb to the infant. Respondents reported that the main reasons for adhering to these practices were respect for tradition, and following the advice of elders. Categorised against Western medical standards, several <it>zuo yuezi </it>practices are beneficial, including eating more, eating protein rich food, avoiding housework, and daily vulval and perineal hygiene. A few are potentially harmful, including giving honeysuckle herb, and avoiding dental hygiene. Some women reported giving infants supplementary feeds, although <it>zuo yuezi </it>emphasises breast feeding.</p> <p>Conclusion</p> <p><it>Zuo yuezi </it>is an important ritual in Fujian. In medical terms, most practices are beneficial, and could be used by health staff to promote health in this period. Further research on reported potentially harmful practices, such as supplements to breast feeding, is needed.</p