Pedictive and diagnostic model Essays

Pedictive and diagnostic model Essays Pedictive and diagnostic model Essay Pedictive and diagnostic model Essay Any predictive and diagnostic model of environmental change is dependent on the accuracy of its data and the soundness of its premises (Mortimore, 1998). In terms of form (or physical manifestation of the process of desertification), the received narrative promoted images of moving deserts and the southward movement of the Sahara (Swift, 1995). Yet there is considerable evidence to suggest that rather than a linear encroachment of such conditions, desertification occurs at particular points (Bernus, 1977 cited in Mortimore, 1998). The limitations of the method of analysis used by Lamprey (1975) and Ibrahim (1984) have been further exposed by subsequent studies. Following a series of investigations by Lund University throughout the 1980s, Helleden (1991) was able to state that; none of these studies verified the creation of long lasting desert-like conditions in the Sudan during the 1962-1984 period there was no trend in the creation or growth of desertification patches around 103 examined villages and water holes over the period 1961-1985. No major shifts in the northern cultivation limit were identified [and there were] no major changes in vegetation cover and crop productivity which cannot be explained by varying rainfall characteristics. Similar results were evident in the Manga Grassland survey by Mortimore in 1989. By comparing aerial plots of the dunes over the period 1950 -1969 with the boundaries delimited by the Forestry Commission Survey in 1937, he concluded that many of the basic characteristics of the area showed continuity over time (Mortimore, 1989). Also this time span covered a period of considerable settlement, agricultural intensification and expansion leading to doubt over the basic hypothesis of desertification (ibid, 1989). In terms of a process, it has already been noted that desertification may be more usefully considered with reference to its individual constituents of desiccation, drought and degradation (Warren, 1996). But a further point should also be raised here. Namely, that the desertification is often perceived as a disruption to a stable, equilibrial natural system. There is considerable evidence to suggest adequately represent dryland environments; they are unstable and disequilibrial in the short term and transitional in the longer term (Mortimore, 1998). In terms of both the form and process of desertification, the accuracy of its premises and data may be found wanting on both counts. The utility of the concept may be further questioned when the its structural causation mechanisms of population growth is considered. The very definition of desertification automatically limits the conceptualisation of dryland sustainability, through the inherent assumption of the failure of human management systems to cope with increasing population pressure (Adams, 2003). Within a desertification narrative therefore, there is little room for the possibility of adaptation and flexibility of management techniques and practices by ordinary people (Mortimore, 1998; Adams, 2003). The dominance of large-scale studies that have an emphasis on quantitative analysis (such as remote sensing) rather than micro-scale perspectives that focus upon the social science aspect of the problem may explain this omission (Mortimore, 1998). A number of studies in the last decade have sought to de-link the implicit connotation of population growth and environmental degradation that has been central to the desertification narrative. Such analyses draw on the ideas of Boserup (1965), suggesting that increasing population pressure can provide the stimulus for innovation and agricultural intensification, for example through increased cropping intensities and the introduction of land saving techniques. Tiffen et al. (1994) examine the case of the Machakos District in Kenya, where there has been considerable concern over the sustainability of agriculture since 1930s colonial administrators attempted to implement soil conservation measures. They used a variety of historical and current sources, such as oral history, to undertake the study. They show that increasing population densities have facilitated more productive agriculture and greater specialization and exchange within society (ibid, 1994). Specific strategies include migration, the diversification of incomes (including non-agricultural incomes) and agricultural intensification (ibid. , 1994). The area cultivated increased from 15 percent of the district in the 1930s to between 50 and 80 percent in 1978, and the land supports a population that has grown almost fivefold, from about 240,000 in the 1930s to about 1. 4 million in 1989 (ibid, 1994). The photographs of Kiima Kimwe in 1937 and 1991 (below, left and right respectively) clearly illustrate the use of careful terracing and subsequent increases in productivity through the planting of banana and other trees (Drylands Research website, 2003). Tiffen et al. s (1994) study illustrates how local communities can respond spontaneously to land degradation and make land improving investments that significantly increase productivity over time. Applying the desertification framework in this situation would be of little utility in the explanation of population growth concurrent with continued or even improved prospects of sustainability. Incorporating the idea of sustainable livelihoods and of social, human and human-made capital may be a further help to examining what the concept of desertification has missed through its biophysical sustainability bias (Serageldin, 1996). Such ideas open the possibility for a number of other inputs that may compromise, or indeed uphold, the sustainability of dryland production systems. An analysis of the social system in dryland production can point to the need for a sustainable social as well as natural system for the continuing use of the environment. Through the integration of this perspective, Murton (1997) is able to question whether Tiffen et. als (1994) these examples of sustainable resource use have been compatible with the maintenance of sustainable livelihoods in such marginal African environments such as the Machakos. Murtons research (1997) adds further dimensions the consideration of dryland production systems, including a requirement to consider how polarization and global markets can also impact upon the sustainability of this environment. The integration of the complex social and economic adjustments that embody the everyday decisions of local people has considerable potential to explain the disjuncture between the doomsday predictions of desertification narratives and small-scale evidence on the ground (Mortimore, 1998). An analysis of the history of the concept of desertification can easily lead to conclusions about how science got it wrong, with a consequent attribution of blame which is all too resonant with earlier desertification narratives (Thomas, 1997). A more thorough consideration will recognise that science necessitates the constant refinement and evaluation of ideas by default (ibid. , 1997). This points to the need to ensure the transmission of uncertainty at the science-action interface and a careful reconsideration of how scientific concepts can be taken selectively or used out of context (ibid, 1997). In this way, the legacy of the desertification narrative may yet prove useful as an important reminder of the differential needs of science and policy and the need for a more cautious approach to scientific truth and objectivity. This has been neatly conceptualised as the tension between models of environmental change as heuristics or truth machines by Wynne Sackley (1994, cited in Mortimore, 1998). From a slightly different perspective, an understanding of desertification may be considered critical precisely to move beyond it (Swift, 1996). Until the ghost of the received narrative is laid to rest in national governments and in major NGOs, the deconstruction (versus the understanding) of desertification will be key to the comprehension of dryland production systems (ibid., 1996). In conclusion, the narrative of desertification may be considered as particularly unhelpful to an accurate understanding of the many facets of sustainability in dryland production systems. Definitions of the terms are problematic, contested and confused, leading to problems for clear and concise communication on the topic. Moreover, the scientific evidence and data upon which the narrative is premised has been shown to be seriously flawed and also coloured by ignorance and prejudice towards indigenous livelihoods and technologies. As such the consideration of dryland sustainability in the framework of desertification may be seen to incomplete and also misguided. However, this is not to say that credible work on drylands has not been performed, nor that real environmental problems do not exist in these ecosystems. Although the term has continued to be adopted in policy circles, the use of an alternative, such as dry land degradation, may prove useful in the longer term and particularly when trying to identify effective interventions. Knowledge of the desertification narrative however, may be seen to provide an important reminder of the need to actively manage the use of science as a basis for policy, particularly when in complex issues that contain a substantial element of uncertainty. An analysis of the way in which powerful institutions have harnessed the power of the desertification narrative is also important for its deconstruction and for the possibility of its succession by a concept that is more attuned to the real and substantive issues of dryland sustainability. References Adams, W.M (2001) Green Development: environment and sustainability in the Third World. Routledge: London Adams, W. M Mortimore, M. J. (1997) Agricultural intensification and flexibility in the Nigerian Sahel Geographical Journal 163:150-160 Drylands Research Organisation Website (accessed 19/11/2003) The Machakos Study (available online at drylandsresearch. org. uk/dr_machakos. html) ICIHI (1986) The Encroaching Desert: The Consequences of Human Failure A Report for the Independent Commission on International Humanitarian Issues. Zed Book Ltd: London.

Forest transpiration is an element in the water cycle

Forest transpiration is an element in the water cycle Transpiration From Forest Woody Plants Transpiration is a term used for the release and evaporation of water from all plants including trees that is released out and into the Earths atmosphere. Nearly 90% of this water exits the tree in the form of vapor through small pores called  stomata  on leaves. The leaf cuticle covering located on the surface of leaves and corky lenticels located on the surface of stems also provide some moisture. The stomata are also specially designed to allow carbon dioxide gas to exchange from air to assist in  photosynthesis  that then creates the fuel for growth. The forest woody plant locks up carbon-based cellular tissue growth while releasing residual oxygen. Forests surrender large volumes  of water into the earths atmosphere from all vascular plant leaves and stem.   Leaf transpiration  is the main source of evapotranspiration from forests and, at some cost during dry years, give up much of its valuable water to the Earths atmosphere.   Here are the three major tree structures that aid in forest transpiration: Leaf stomata  -   microscopic openings on the surfaces of plant leaves that allow for the easy passage of water vapor, carbon dioxide, and oxygen. Leaf cuticle  - a protecting film covering the  epidermis or skin of  leaves, young shoots, and other aerial plant organs. Lenticels  -  a small cork pore, or narrow line, on the surface of woody plant stems. In addition to cooling forests and the organisms within them, transpiration also helps to cause a massive flow of mineral nutrients and water from the roots to the shoots. This movement of water is caused by a decrease in hydrostatic (water) pressure throughout a forests canopy. This pressure difference is mainly caused by water endlessly evaporating from the tree leaf stomata into the atmosphere. Transpiration from forest  trees is essentially the evaporation of water vapors from plant leaves and stems. Evapotranspiration is another important part of the  water cycle of which forests play a major role. Evapotranspiration is the collective evaporation of plant transpiration from the Earths land and sea surface into the atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies.   (Note: An element (such as a forest of trees) that contributes to evapotranspiration can be called an   evapotranspirator.) Transpiration also includes a process called guttation, which is the loss of water dripping off uninjured leaf margins of the plant but plays a minor role in transpiration. The combination of plant transpiration (10%) and the evaporation from all bodies of water to include the oceans (90%) is responsible for all of the earths atmospheric moisture. The Water Cycle The interchange of water between air, land and the sea, and between organisms living in their environment is accomplished through the water cycle. Since the Earths water cycle is a loop of occurring events, there can be no starting or ending point. So, we can start learning about the process by beginning where most water exists - with the  sea. The driving mechanism of the water cycle is ever-present solar heat (from the sun) which warms the waters of the world. This spontaneous cycle of naturally occurring events creates an effect that can be diagrammed as a spinning loop. The process involves evaporation, transpiration, cloud formation, precipitation, surface water runoff, and the percolation of water into the soil. Water at the seas surface evaporates as vapor into the atmosphere on rising air currents where the resulting cooler temperatures cause it to  condense  into clouds. Air currents then move clouds and particulate materials which collide continuing to grow and eventually falling out of the sky as precipitation. Some precipitation in the form of snow can accumulate in polar regions, stored as frozen water and locked up for long periods. Annual snowfall in temperate regions will usually thaw and melt as spring returns and that water returns to fill rivers, lakes or soaks into the soil. Most precipitation falling onto land will, due to gravity, either percolate into the soil or will flow over the ground as  surface runoff. As with snow-melt, surface runoff enters rivers in valleys in the landscape with  streamflow  moving water towards the oceans. There is also groundwater  seepage that will  accumulate and is  stored as freshwater  in aquifers. The series of precipitation and evaporation continually repeats itself and becomes a closed system. Sources:     Ecology and Field Biology, R.L. Smith (buy from Amazon)         Transpiration and the Water Cycle, USGS