Halophytes in deforestation and reforestation - Essay Example

Utilizating halophytes in afforestation and reforestation - reducing pressure on deforestation Deforestation, the depletion of earth’s forests on a massive scale, due to underlying causes (such as development of living areas, industries, economic development, increasing population, corruption, mismanagement) and direct/proximate causes (such as cutting trees to extend land area for agriculture, to provide land for grazing livestock, to utilize woods in paper industries, wood products, wood fuel, urbanization i.e. construction of houses, markets and roads), negatively affects global climate (Geist & Lambin, 2002, Fig.1). Forests serve as habitats for millions of species, therefore, are important in biodiversity conversation (Wilson, 1988; Brook, 2003). Among the several negative impacts caused by deforestation some are: the ultimate decrease in biodiversity due to loss of habitats of many species, the increase in emissions of carbon dioxide and other greenhouse gases, the increasing greenhouse effect, shift of forest water cycle due to loss of forest canopy, and the rapid rise in temperature due to direct exposure of soil surface to sun (Houghton & Hackler, 1999; Fearnside & Laurance 2004). Implementation of remote sensing and satellite data from past years has revealed a very drastic rate of deforestation (Tucker & Townshend, 2000). FAO (2006a, 2007) has reported change in global deforestation by a rate of 13 million ha per year. Fig. 1. Demonstration of Proximate and Underlying causes responsible for deforestation. (Source: Geist & Lambin, 2002). Tremendous increase in world population, at one hand, limits the available cultivable farmlands for crop production while demands increase in crop production simultaneously (Koyro et al., 2011). An estimated increase of about 50% in global food production is estimated to be required by the year 2050 (Flowers, 2004). Forests that were depleted for purpose of agricultural land extension in past years, are now been exploited for urbanization and industrialization as the soil of those lands has been degraded, illustrates various soil problems and hence, led to reduction in availability of cultivable farmlands (Geist & Lambin, 2002). Increase in agriculture by expanding land for crops production in order to secure food for every individual is becoming difficult; for this reason the recent tendency has been to increase the per unit area production of crops which in technical terms is referred to as intensification of agriculture (Binswanger & Ruttan, 1978). This prospect can only be explored if the amount of nutrients that are available in the soil are sufficient to nourish and raise crops in repeated cycles (Lele & Stone, 1989). However, in present scenario, environmental degradation has emerged as one of the undesirable and prominent effects due to such rapid and frequent crop plantation and association of new cultigens and pesticides (Turner et al., 1993). In current situation, even after advancement of current technologies enabling researchers to supress all these environment problems, increase in crop yield is not as much sufficient as it should be to fulfill raising needs of food supply (Berry, 1984; 1993). Furthermore, soil salinity is one of the major environmental stresses intruding severe limitations on plant yeild and quality in various parts of the world (Flower & Colmer, 2008). Youssef (2009) has reported that nearly 20-50% of world’s irrigable land area is affected due to salinity. In the view of Koyro et al., (2008) nearly 7% of world’s total land area demonstrates salinity induced damage. Increasing soil salinization and decreasing fresh water resources, as a consequence of agricultural intensification (as toxic concentrations of salts reach to top most soil layers due to process of leaching) are contradictory to the enhanced production of food for increasing population (FAO, 2004; FAO and IFAD, 2006; Munns et al., 2006; Alcamo et al., 2007) due to salt sensitivity of crop plants. The top most soil layer of forest floor is moist due to dense forest canopy that covers the soil surface and prevents access of the sunlight to the deeper layers of soil. This converts into dry soil due to high concentrations of salt as a result of deforestation where high evaporation rates are recorded as temperature of forest soil increases due to removal of forest canopy (Fearnside, 2000). With increasing awareness and knowledge about greenhouse effect, change in global climate, and possible causes involved in affecting immediate environment, a stringent control on further utilization of forests lands for urbanization after deforestation has been imposed. Although, remediation of deforested lands (reforestation) under prevailing environmental disruptions such as alteration in fresh water resources and increasing soil salinity highlight the importance of identifying alternative plants that can grow on such lands and can also serve as means for food/feed for the future generations. In addition, identifying the potential uses of such plants and educating local citizens to utilize these naturally occurring newly grown (afforested) salt tolerant populations instead of cutting forests may reduce the fastest increasing pressure on deforestation. Furthermore, the complete screening of chemical compounds present in such plants that enable them to tolerate such adverse environmental conditions may increase our understanding of stress tolerance plants. Fig. 2. Graph representing loss of germination in four economically important crop plants with increasing salinity. On X-axis: Saturation effect is the soil salinity. On Y-Axis: Germination % is the water uptake by seeds of these plants. (Source: Ayers & Hayward, 1949). Several researchers have conducted a series of experiments for many years to find out possible solution for remediation of environmental stressed damaged lands, where conventional crop plants have failed to grow (supporting figure: germination of some crop plants in salt solution). These researches include surveys where the researchers visit salt affected lands and analyze chemical properties of soil (Malicki & Walczak, 1999). An increased concentration of salts particularly sodium chloride has been reported in many dry soils (Jefferies et al., 1981; Ab-Shukor et al., 1988). Similarly, the analyses of chemical properties of soil from different areas and monitoring vegetation of such plants has led to identification of ‘halophytes’, the salt tolerant plants, as an ultimate solution (Khan & Ungar, 1986;). The use of ‘halophytes’ in regions of the world facing shortage of fresh water and increase in soil salinization (Huchzermeyer et al., 2004; Koyro et al., 2011) seems an appropriate solution. Halophytes have been defined as plants which complete their life cycle in salty soil have a number of adaptations that enable them to survive under saline conditions; circumstances which are lethal to most of the plants (Khan & Hameed, 2011). Domestication of halophytes in order to their utilization as new crops has been reviewed (Colmer et al., 2005). Another unique characteristic of halophytes is their ability to demonstrate suitable level of growth under saline conditions; for this reason their use in ventures involving saline agriculture needs to be explored (Hameed & Khan, 2011). The potential uses of halophytes are illustrated in Table 1 (Koyro et al., 2011). Among these uses, several purposes of utilizations are under current investigation such as the localization of pharmaceutical compounds present in these halophytes and their role in afforestation. Table 1. Source: Koyro et al., 2011. Burning of wood for purpose of fuel releases Carbon dioxide gas in quantities as greater as obtained by burning of fossil fuels in ten years and wood fuels contribute to about 50-90 percent of the fuel used (FAO 2010). Several halophytes are known to possess carbon dioxide concentrating mechanisms i.e. these plants are capable of taking in carbon dioxide from atmosphere more rapidly and in more amount as compared to releasing water to the atmosphere during the process of transpiration, and are recognized as C4 plants (Ashraf & Harris, 2013). The presence of carbon dioxide concentrating mechanisms in these plants highlights their utilization to reduce effects of global warming at rates higher compared to other plants (Glenn et al., 1992; Toderich et al., 2013). Several studies concerning afforestation (Selby et al., 2005; Ninjik et al., 2012; Yao & Feng, 2012) started from the identification of selective plant candidate that inhabited the particular land of interest and the selection of neighbor plant species able to survive and grew with primary plant species. Determining the number of plant individuals that can populate deforested land in association to each other, the patches formed due to distribution of two or more number of plant species and the technical and economic importance of afforestation methods to be utilized, have also been parameters of great importance. Whereas critical criteria for reforestation (re-establishment of forest cover) has been the selection of plant species able to grew and survive on land as deforested land is severely affected by many environmental hazards. Selection of neighbor plants has also been according to competence of selected species. Several woody halophytic plants such as saltbush and greasewood have been recognized as tolerance of high salt salinity and have been found to rehabilitate the deforested lands (Theodore et al., 2012). Basic studies emphasizing the use of halophytes for afforestation and reforestation of salt affected lands include the research reports of Schofield (1990), Pielke et al. (1993), Khan et al. (2006), Monteverdi et al. (2008), and Li et al. (2012). However, none of them led us to application of true candidate plant for the purpose of afforestation and reforestation, globally. Selection of a halophytic species that can tolerate high saline conditions and therefore, convert barren decertified lands into forests has central importance. Furthermore, trial experiments and their results regarding implementation of halophytes on deforested lands are not available. In addition, the climatic conditions vary across longitudes and latitudes making growing environment of one location entirely different from other one. Therefore, there is need to study the deforestation locally, monitoring the content of soil salts and identifying potential halophyte that can grow optimally under those situations. However, a vast literature exists regarding salt tolerance limits for various halophytes, helping one to take initial steps, as well as clear and immediate steps to be taken for the purpose of afforestation and reforestation in any deforested area. Poor agricultural practices in addition to agriculture intensification on cultivable farmlands are leading to soil salinity as well as deforested lands. The presence of large area of barren land due to saline soil, therefore, draws attention towards the utilization of halophytes. These plants, in addition to their high salt tolerance ability, have many other potential uses such as pharmaceutical, food, feed, wood, landscaping, wild life conservation, carbon dioxide sequestration, environmental and coastal protection. Thereby, reforestation and afforestation of lands that have been depleted from forests, with halophytes arises as environmental friendly and low cost solution. After analyzing chemical properties of soil such as salt content in the soil, halophytes with high salt tolerance can be grew there. In this way, reforestation of already degraded lands can bring positive outcomes regarding change in global climate. The utilization of halophytes for the purpose of afforestation and reforestation is an eminently emerging approach. Deforested lands for the purpose of agricultural extension have greatly contributed to degradation of soil largely due to high evaporation rates of soil moisture leading to increased contents of salts in soil surface. High concentrations of salt ions in soil become toxic and thus endanger survival and growth of many conventional plants due to their salt sensitivity. Halophytes enjoy survival in such harsh conditions because of their ability to adopt to a wide range of saline environments. Deforestation and use of wood for fuel contributes to majority of carbon dioxide emissions which have been previously stored in forests for so many years. Increase in emission of carbon dioxide and other greenhouse gases damages ozone layer in the atmosphere of earth, and cause increase in temperature of earth and a shift in global climate. This has been a topic of fierce debate in the literary circles during recent times. Several halophytes employ the strategy of carbon dioxide concentrating mechanisms and therefore rapidly intake large concentrations of carbon dioxide from atmosphere; participating in normalizing global temperature. Therefore, growing halophytes on salt affected deforested lands, where no other plant can grow well, as well as on new lands that become saline due to poor agricultural practices, seems an ultimate solution for protecting earth environment. References Ab-Shukor, N . A., Kay, Q. O. N., Stevens, D. P. and Skibinski, D. O. E. 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