Remote Sensing of the Coral Reefs - Coursework Example

Introduction: Coral reefs are being degraded almost 20 percent globally, the coral ecosystem faces threats that span from; over fishing, oil spillage contamination, bleaching as a result of elevated sea temperatures, enhanced sedimentation, eutrophication as well as the specter of a warming planet. Monitoring of these reefs is therefore an imperative aspect in identifying threats and measures to address them. Remote sensing is the acquirement of information using imaging sensor expertise. Landscape ecologists have been doing well in the field of remote sensing by trying to come up with means of protecting habitat but less has been done in the management of coral reefs ecosystem. Coral reefs are productive ecosystem and diverse habitats in the world because of their economic and social importance including food provision, tourism among others. There is a high rate of global degradation of coral reefs and these calls for their sustainable management. Their reduction has fueled the local and international communities to come up with approaches of monitoring coral reefs. Ecology involves the study of organisms in the environmental surroundings which require spatially accurate data given the distribution of spices. In the past manual and field observation methods were used to gather ecological information. These methods were labour intensive and time consuming. As a result, remote sensing became widely incorporated in the ecological duties because of its large coverage, cost effectiveness and accuracy. This called for the venture into new technologies to enable easy and faster access of remote sensed information in the management and monitoring of ecological species. (Knight, D., E. LeDrew, et al. 1997). Coral ecosystem is one of the important habitats in the world. Coral reefs play a significant role in checking the amount of carbon dioxide in the sea. Without them regulating the level carbon dioxide in water could be difficult and many species on earth including human being could be at a high risk. Although, that is the current situation in the world because people have destroyed the reefs due to the level of impurities in the water bodies this has resulted in global warming. They are also a habitat to millions of fish species, source of employment, food provision, tourism attraction sites and protect the shores fro waves. In short they are source of livelihood to millions of people around the globe (Goodman, J. A., M. Velez-Reyes, et al. 2006).This paper addresses landscape remote sensing approaches of mapping coral reefs. Discussion By 2100 coral reefs will be degraded if no measures are taken. They only cover 2 percent of the total ocean area and annually they provide a home for almost 33 percent of thousands on marine species. As mentioned above, coral reefs are threatened by a number of factors. For example, coral diseases resulting from ruining the reefs, coral reefs can be in danger of water related coastal development as it is in the case in the Caribbean. (Gledhill, D. K., R. Wanninkhof, et al. 2008). As a result of a variety of biological species in the coral ecosystem, over fishing can also be harmful because they interact and depend on one another for food and competition. Harvesting of coral reefs can be classified into controllable, Malthusian-over fished and poisonus.Studies show that reduction of species in the coral ecosystem can lead to prolification of algae. (Manus, J. W., L. A. B. Menez, et al. 1999).In response to this damage a 5 year project was launched and it was funded by the centre for sponsored coastal ocean research (CSCOR).The research key provisions were to provide adequate data on coral reefs, tool and approaches to help marine scientists and identify phenomena that caused the degradation of coral reefs. The research addressed four major areas namely; interaction between water related activities and coral reefs, causes of biological pressure, assessment of marine protected areas and the overall nature of coral ecosystem (Hallock, P., B. H. Lidz, et al. 2003). Researchers are mapping coral reefs and the bordering land areas. The current level of knowledge about such measures is inadequate and the total area of coral reefs in the world is not sufficient for monitoring. Studies attempting to identify the risk factors for decline of coral reefs are also faced with inadequate maps on coral reefs and adjacent land uses. Coral reef researchers are making decisions that impact the health of coral reefs and the economies of the communities that depend on them. Coral reefs are essential part in the earth ecosystem they are measures of determining the health of marine ecosystem. They are important economically for they provide employment opportunities, food, raw material and tourism attraction sites. Remote sensing provides an efficient way of mapping and separating shallow coral reefs. (Andrefouet, S.2004) Most of the coastal habitat mapping is conducted on a temporary basis with little consistency. These limitations hinder interpretation and integration of maps for coral reef science and management, mainly at the international scales where standardization is urgently required. Use of Satellite Satellite offers the possible probability of mapping a coral reef that has never been surveyed before. Conversely, getting significant information from the satellite is difficult therefore electronic signal that relate to that coral ecosystem must be in place. Use of satellite images in cartographical maps have been used to identify changes coastal areas. Maps for coral reef habitat are useful in planning for allocation of boundaries and identifications of other coral reefs with the help of satellites bleaching of coral reefs can be detected. Coral reefs and coastal areas call for habitual collection of accurate data for their long term management. Information from satellite image and the resultant maps provide guidance on the monitoring of reef environment. Satellite image can extort biophysical information of coral reefs in a non-intrusive and relatively inexpensive manner. The availability of high-resolution image data has provided the reef research community with new information. Up to now, image processing techniques developed for the intention of coral reef mapping and monitoring has concentrated on the use of spectral information, without giving much consideration to the spatial context of the pixels. Recent studies have produced promising results on the use of texture-based methods for extracting biophysical attribute information from high-resolution satellite image data sets of coral reefs. Monitoring underwater coral ecosystems are restricted by reef characteristics in humid waters, inadequate knowledge about spectral components of coral reefs and restricted mapping guidelines. In Fiji for instance, using satellite image measurements can be determined up to the depth of 10metres (Knight, D., E. LeDrew, et al. 1997). Aerial photography satellites have also been used to map coral reefs. In the Turks and Caicos Islands which provided precise information and today is one of the remote sensing techniques that provide accurate data on coral colonies. However, it has low penetration rate in deep waters therefore useful in shallow and low altitude areas (D. R., S. Narumalani, et al. 2007). Landsat satellite for many years contributed in the gathering of data from Earth’s surface, including data on coral reefs. These satellites have moderate spatial-resolution that provides exhaustive information about reef ecosystem and these has made it widely satisfactory for marine research. Applications of Landsat have increased not only in collecting information for marine science but also in other areas such as agriculture, forestry and land use. It has also played role in human population growth that causes loss of coral species. In agricultural production Landsat has assisted in developing measures to control adverse effects caused by agricultural chemical siltition into the sea and deforestation. Landsat imaginary has three broad bands (red, green and blue) that provides a platform for locating coral reefs and mapping their general distribution and also offers several observations (Lourie, S. A. and A. C. J. Vincent 2004). The government, national park boards and the ministry of environment plays a fundamental duty in the management and monitoring of coastal role areas. Each of these agencies has different responsibilities in the protection of coral reefs. For instance, in Singapore remote sensing of coral reefs has provided strategies for the management of coastal areas. With the use of satellite images to map coral reefs the information obtained is later used in the environmental audit to ensure there are minimal or no threats to hot spots area such as coral reefs. These data may be used to recognize and identify oil spills discharged into the water bodies and consequently guide in the clean up programmes of the affected coastal areas. The use of satellite images could also help in the prevention of solid waste dumping in the coastal areas hence reducing loss of biological species and silting. For the protection and management of marine habitat SPOT 5 and Ikonos satellites were used in the Mediterranean lagoons as they showed potential data on mapping. The research showed wider distribution of sea grass whereas comparing their accuracy SPOT 5 was more precise than Ikonos. Further, SPOT 5 did not distinguish other species in the lagoon and the coral reefs, even though IKONOS has lower accuracy it provided information on diverse species. Ikonos satellites were used in Bunaken Island, Indonesia to project coral cover and the data was used for the protection of coral reefs and their ensure their long term sustainability. The SPOT 5 satellite was launched in May 2002.It was used for mapping beds of Posidonia oceanica in the Mediterranean Sea, where it is a dominant species forming monospecific beds namely algae on rock, patchy sea grass beds and continuous sea grass beds. This tool provided accurate mapping of posidonia oceanica (Chen, J. Y., Z. H. Mao, et al. 2007).However, SPOT 5 can fail to identify smaller reefs as it is not ideal for under sea reef mapping and can not go through deep surfaces. In addition SPOT 5 cannot differentiate between bottom sand and coral reefs. CASI (Compact Airborne Spectrographic Imager) can also be used in mapping and monitoring coral reefs. This is an accurate tool for mapping and monitoring coral reef over large geographic areas. However, there are various limitations that hinder the accuracy with which coral reefs can be monitored remotely. The major one is optical similarities in the coral reef environment that can lead to accuracy It was the first approach used n the monitoring of coral reefs and use in West Indies and use to view 1 m pixels in 8 spectral bands. CASI maps are accurate after processing than those in satellite imagery. (Mumby, P. J. and A. J. Edwards (2002).Using CASI one can determine the health of coral reefs. CASI has been used to monitor bleaching in coral reef bleaching with the use of radioactive transfer Landsat TM images. The radioactive transfer simulation indicates that the blue and green bands of Landsat TM can detect bleaching to a margin of 23 percent of the coral surface (Yamano, H. and M. Tamura 2004) CASI images have been found to detect coral bleaching resulting from high sea temperature, diseases and solar radiation these has been witnessed in Indian ocean in 1991 the in 1995.According to CASI sensors bleached corals provide a powerful optical signal. Nevertheless, depth of water, surface cover of the coral prevents the application of CASI in monitoring reefs bleaching. (Andrefouet, S.2004) .Lidar (light detection and ranging) is an airborne laser applied in the acquiring topographical data of reef structure. It is ideal in shallow waterslide maps are better compared to aerial photography because they are able to penetrate deeper. The airborne visible infrared spectrometre (AVIRIS) was used for mapping coral reefs along the coastal areas New Caledonia reef ecosystems because it was allowed the evaluation of water and could be able to determine the health of coral reefs. Using these information researchers could come up with measures to control such an ecosystem as a result of its high spatial resolution (Bouvet, G., J. Ferraris, et al. (2003). Bleaching occurs when a white colour forms on the coral and other algae called zooxanthellae which are found in healthy reef-building corals. Through photosynthesis this algae provide oxygen and light to the coral. Bleaching makes coral to reduce zooxanthellae causes them to appear white extreme caused of bleaching leads to death of coral. The main cause of bleaching is high level of temperature in water. Other elements that can have increasing effects are sunlight, agricultural related activities, siltition and dredging. Coral bleaching has adverse effects on fish species human being because they can not be protected from the influence hurricane and tidal waves. Bleached corals also reduce species in the coral and this is likely to lead to death as there are species that depend on each other for food. They (coral reefs) are less attractive (Maina, J., V. Venus, et al. 2008). Furthermore, Juvenile fish are likely to be found in areas with high and healthy coral cover .This was common in Papua New Guinea and this proved that fish species reduce with reduction in coral communities. Moreover, fish that relied on coral juvenile recruitment sites were likely to die. Bleaching that occurred in 1998 was the highest recorded (Mellin, C., S. Andrefouet, et al. 2007). In Kuroshima Island and the nearby areas CASI was applied to manage and monitor coral reefs during flight courses. Whereby CASI satellites were inserted on the flight at an altitude of 9,000 feet from there professional drivers could see coral reefs distribution and the findings were similar as to the marine researchers (Miyazaki, T., Y. Nakatani, et al. 1995). Environmental degradation reveals the stress coastal ecosystem are facing as a result there is an increasing demand for integrating these threats. Coral reef management is concerned with spatial data and that is why GIS was discovered to take into account to take care of these complex issues. GIS enables marine researches to anticipate, explore data and retrieve new information from existing one (Mumby, P. J. and A. J. Edwards 2002). There are a variety of resources in the coastal ecosystem that support man globally. Although policy makers are hampered with the information to help them plan for these resources.GIS can also be applied in the management of coral reefs. For management and sustainability of coral reefs one has to reflect on the effects of man both directly and indirectly on reef ecosystem then use appropriate tool to effectively and efficiently minimize the degradation, such tools can be GIS. It has contributed in the research of submerged coral reefs. It has been useful in Australia’s Ningaloo reef, an area potential for tourists that has contributed to understanding and distribution of coral reef biodiversity. Using a global positioning system, colour satellite images and aerial photography 16 types of reef habitat were identified, monitored and mapped (Cassata, L. and L. B. Collins 2008). Since GIS is an effective technique. It can analyze, store, use, recover and control technological and systematic information useful in mapping coral reefs. Further, the tool can also analyze erosion along the water bodies and other human activities that can possible cause degradation of coral ecosystem. Remote sensing and GIS offer solution to the sustainable development of many fragile ecosystems including the coral reefs through generating information for analysis of these areas. For instance in Mauritius it has a well developed water bodies but due to its topography that allows run off in to the water bodies and these make the responsible authority to come up with measure and guidelines to control these risks from happening. As a result they are using GIS to map and information that can be used to by marine researchers to plan the coastal are and also document health coral reefs come up with measure to monitor them so that they are not affected (Hochberg, E. J. and M. J. Atkinson 2003). Reef components like the sand-sediment were measured using generalized additive models (GAMs) applied to Ikonos satellite images and a reef digital topographic model (DTM) to foretell coral community including hard coral, sea-grass and algae it has been used in Akumal Reef in the Mexican Caribbean. Ikonos sensors are prepared depending on the physical features of the area. Then using GIS these maps are compared with thematic maps (Garza-Perez, J. R., A. Lehmann, et al.2004). In Ishigaki Island in Japan Ikonos sensor have been used to map coral reefs. Because they can observe coral spread all over the oceans as it is the case with this island. Bottom index (BI) can also be combined with the Ikonos satellites to reduce the effects of the depth of water on the satellite results. Although, they very expensive if the research is global basis (Matsunaga, T., A. Hoyano, et al. 2000). Conclusion In the struggle to meet reefs protection there has been a problem in the access of thematic maps and geographical information. Remote sensing is a very essential tool in the management of coastal zone as it is the only approach that can retrieve reef information on a global scale. The main concern is to determine how to protect coral reefs because there is high growth in population, industrialization and tourism throughout the world. But important to know is remote sensing coral reefs in humid areas is difficult as a result of could cover. Marine researches are challenged because working under water is costly and difficult and also the development of coastal zones is increasingly and this calls for monitoring and mapping of these areas. Protection and management of reefs ecosystems requires accurate and latest data about ecosystem health and the distribution of species and habitats, but such information is expensive to gather and interpret in the field. Remote sensing has proven capable of collecting information on coral reef environments, and is cost-effective when information is needed for large area. This information may be used for routine planning requirements, navigation, research, coastal management, economic exploitation and locating the boundaries of management zoning schemes. (YAMANO et al. 2006). Coral reefs are the rain forests of the water bodies. The worst enemy of coral reefs has been man through over fishing, as well as the global issues like climate change. Remote sensing of the floor of the sea using geographical information systems (GIS) is also inadequate because satellite images and aerial photographs are not ideal for studying the habitats of the seafloor. Nevertheless, there is an increasing need for mapping and monitoring marine ecology, for coral reef management programmes, and environmental conservation purposes. Maps from reef habitat are important planning tool. Preferably, these maps could be used to identify other problems in reef ecosystem for recurring study and manage the area. Reference Andrefouet, S. and B. Riegl (2004). 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