Paradoxes of leadership: Contingencies and critical learning

No Abstract.South African Journal of Education Vol. 27(3) 2007: pp. 377-39

Desertification : Concept, causes and amelioration

Desertification is a condition of human-induced land degradation that occurs in arid, semiarid and dry sub-humid regions (precipitation/potential evapotranspiration or P/ETP 0.05 to 0.65) and leads to a persistent decline in economic productivity (> 15% of the potential) of useful biota related to a land use or a production system. Climatic variations intensify the decline in productivity, restorative management mitigates it. Drylands or territories susceptible to desertification occupy 39.7% (~ 5.2 billion ha) of the global terrestrial area (~ 13 billion ha). The highest concentration of drylands occurs in Africa, Asia and Australia. Two out of every three hectares of drylands suffer from land degradation of one kind or another. Barring 78 M ha which are irreversibly degraded, the remainder area - affected by desertification - is reclaimable at a price. Desertification is caused primarily by over-exploitation of natural resources beyond their carrying capacity. Solutions to combat desertification lie in the management of the causes of desertification. However, there are no easy options to combat it. While managing demographic pressure should receive priority, the solutions to combat desertification involve local action, guided by land use and climatic conditions and in harmony with local needs and people’s expectations. Drylands are used as rangelands or as croplands, with the latter either irrigated or rainfed. Integrated data on land and soil degradation and on the socio-economic environment within which it occurs are the basis to formulate strategies for reclamation and proper use of drylands. Rangelands constitute the dominant land use (est. 88%) in the territories susceptible to desertification. Of the 3333 M ha rangeland area affected by land degradation 757 M ha are severely affected., 72 M ha irreversibly. Within rangelands, vegetation degradation is the primary cause of desertification – it represents 72% of the total area desertified worldwide (2576 M ha out of 3592 M ha). Overgrazing by excessive numbers of low productivity livestock and fuel wood extraction by man are the principal causes of vegetation degradation. Centralized management of common rangeland resources and insecure tenancy laws stand in the way of communities and herders adopting a long-term view to conserve and invest in range improvement measures. Inadequate dissemination of knowledge on vegetation improvement methods is another cause of rangeland degradation. Five suggestions are made to assure sustainability and effectiveness of rangeland management programs: (1) shifting to community management of rangelands that have been nationalized, (2) granting formal rights to individual transhumance herders that have been settled, (3) providing education and training on range management and improvement, (4) introducing elite breeds of livestock for high productivity, and (5) implementing programs for harnessing alternative sources of energy for cooking (solar and biogas). Rainfed croplands occupy an area of 457 M ha, 216 M ha of which have degraded soils. Some 4 M ha suffer from irreversible degradation. Of the remainder, 29 M ha and 183 M ha are, respectively, affected by severe (reclaimable with engineering works) and moderate degradation. Soil constraints in rainfed croplands arise primarily from their vulnerability to erosion, which leads to loss of organic matter, fertility and rooting depth. Eroded soils are structurally unstable and are prone to crusting and compaction. Risk arising from drought susceptibility and poverty limit the adoption of restorative management. Rainwater conservation to minimize risk is not adopted due to insecure tenancy and centralized management of government supported programs. A lack of adequate knowledge and skills of efficient use and storage of rainwater allow degradation processes to proceed unchecked. The imperatives to succeed are: (1) land tenure policies towards freehold ownership; (2) community participation in the management of rainwater, (3) efficient use of harvested water supported by high value land use options built on indigenous knowledge and (4) government support to facilitate the development of rainfed agriculture. Irrigated croplands occupy an area of 145 M ha. Of this, 2 M ha are affected by irreversible degradation and 41 M ha suffer from reversible degradation, mainly from salinity and waterlogging. The mechanisms of salinity development differ and so do the solutions when canal or underground water is used for irrigation. With canal water irrigation, three key development options are suggested to remove excess salts and water and to minimize conveyance and application losses of water: (1) effective drainage, (2) properly lined or closed water conveyance systems and efficient irrigation techniques, and (3) participatory management of irrigation systems. The costs of installing drainage and leak-proof conveyance systems are high, but so are the economic and ecological gains. With underground water use, salinity develops as the water reserves are depleted due to over-extraction. While efficient methods of irrigation can help in postponing the occurrence of salinity, sustainable solutions lie in balancing the water withdrawals with recharge. Efforts should therefore be made to promote groundwater replenishment through runoff harvesting. Although it is not always possible to recharge the deep aquifers with the limited quantities of runoff produced by the low annual precipitation, still, the use of harvested runoff for irrigation can save groundwater. Once water-efficient systems are operational, cropping systems that maximize productivity per unit of water can be introduced. The entire strategy of reclaiming desertified land revolves around water, the reestablishment of the vegetation of rangelands, the rejuvenation of the productivity of rainfed croplands, and the halting of loss of irrigated farmlands. Humans play a central role in that strategy; desertification begins and ends with human action. Unless it ends, the estimated 900 million people affected today will grow to billions tomorrow

Current Efficiency, Dielectric Measurements & Ion Mobility Studies of Anodic Oxide Films Formed on Tantalum in Aqueous Electrolytes

198-20

Measuring soil processes in agricultural research

Soil and crop management strategies (e.g., tillage, bunding, cropping intensity, and crop sequencing) are location- and season-specific in the way they affect soil processes and resource utilization by crops. Research findings on these effects therefore need to be modeled if they are to be extrapolated to other locations wi th similar soils and climatic conditions. This manual presents practical methods for assessing management effects on such soil processes as water infiltration and erosion by water, and on water, air, and nutrient use by crops. It covers the basic elements of soil physical characterization, and deals principally with the role of soil structure on water infiltration and percolation, heat flow, aeration, and the mobility of roots and soil microorganisms. The authors discuss the agronomic and engineering practices that affect soil processes; and the effects of such strategies as contour cultivation, organic and inorganic amendments, watershed management, and soil surface manipulations are emphasized

Mantle redox state drives outgassing chemistry and atmospheric composition of rocky planets

Volcanic degassing of planetary interiors has important implications for their corresponding atmospheres. The oxidation state of rocky interiors affects the volatile partitioning during mantle melting and subsequent volatile speciation near the surface. Here we show that the mantle redox state is central to the chemical composition of atmospheres while factors such as planetary mass, thermal state, and age mainly affect the degassing rate. We further demonstrate that mantle oxygen fugacity has an effect on atmospheric thickness and that volcanic degassing is most efficient for planets between 2 and 4 Earth masses. We show that outgassing of reduced systems is dominated by strongly reduced gases such as H2, with only smaller fractions of moderately reduced/oxidised gases (CO, H2O). Overall, a reducing scenario leads to a lower atmospheric pressure at the surface and to a larger atmospheric thickness compared to an oxidised system. Atmosphere predictions based on interior redox scenarios can be compared to observations of atmospheres of rocky exoplanets, potentially broadening our knowledge on the diversity of exoplanetary redox states

Exercising D. melanogaster modulates the mitochondrial proteome and physiology - the effect on lifespan depends upon age and sex

Ageing is a major risk factor for many of the most prevalent diseases, including neurodegenerative disease, cancer and heart disease. As the global population continues to age, behavioural interventions that can promote healthy ageing will improve quality of life and relieve the socio-economic burden that comes with an aged society. Exercise is recognised as an effective intervention against many diseases of ageing, but we don’t know the stage in an individual’s lifetime in which exercise is most effective at promoting healthy ageing and whether it has a direct effect on lifespan. We exercised w 1118 Drosophila melanogaster, interrogating effects of sex and group size, at different stages of their lifetime and recorded their lifespan. Climbing scores at 30 days were measured to record differences in fitness in response to exercise. We also assessed the mitochondrial proteome of w 1118 Drosophila that had been exercised for one week, alongside mitochondrial respiration measured using High-Resolution Respirometry, to determine changes in mitochondrial physiology in response to exercise. We found that age-targeted exercise interventions improve lifespan in male and female Drosophila, and grouped males exercised in late life had improved climbing scores, when compared with those exercised throughout their entire lifespan. The proteins of the electron transport chain were significantly upregulated in expression after one week of exercise, and complex II linked respiration was significantly increased in exercised Drosophila. Taken together our study provides a basis to test specific proteins and complex II of the respiratory chain as important effectors of exercise induced healthy ageing

Public Health and the Built Environment: Historical, Empirical, and Theoretical Foundations for an Expanded Role

In 2000, the Center for Disease Control and Prevention\u27s National Center for Environmental Health issued a report that explored some of the ways in which sprawl impacts public health. The report has generated great interest, and state health officials are beginning to discuss the relationship between land use and public health. The CDC report has also produced a backlash. For example, the Southern California Building Industry Association labeled the report a ludicrous sham and argued that the CDC should stick to fighting physical diseases, not defending political ones. In this environment, it is understandable if the CDC looks to such critiques as simply the latest partisan recruit to a political debate. But critics of the CDC\u27s efforts in this area may substantially overstate their case in the other direction. There is now and has long been a demonstrated connection between health, including physical disease, and the built environment. Moreover, government has intervened in the past in response to this connection and it continues to do so. While neither past practice nor current evidence make government intervention inevitable, this paper argues that such intervention is appropriate and supported by theory as well as history and empirical evidence

Mantle redox state drives outgassing chemistry and atmospheric composition of rocky planets

Volcanic degassing of planetary interiors has important implications for their corresponding atmospheres. The oxidation state of rocky interiors affects the volatile partitioning during mantle melting and subsequent volatile speciation near the surface. Here we show that the mantle redox state is central to the chemical composition of atmospheres while factors such as planetary mass, thermal state, and age mainly affect the degassing rate. We further demonstrate that mantle oxygen fugacity has an effect on atmospheric thickness and that volcanic degassing is most efficient for planets between 2 and 4 Earth masses. We show that outgassing of reduced systems is dominated by strongly reduced gases such as H2, with only smaller fractions of moderately reduced/oxidised gases (CO, H2O). Overall, a reducing scenario leads to a lower atmospheric pressure at the surface and to a larger atmospheric thickness compared to an oxidised system. Atmosphere predictions based on interior redox scenarios can be compared to observations of atmospheres of rocky exoplanets, potentially broadening our knowledge on the diversity of exoplanetary redox states