Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
CLIMATE CHANGE AND THE ENVIRONMENT By Prof. J.O. Ayoade Department of Geography University of Ibadan Ibadan Invited Contribution to the Conference on Climate Change and Sustainable Development holding in University of Ilorin, Ilorin May 1-5, 2011 1 CLIMATE CHANGE AND THE ENV IRONMENT Introduction Since the late 1970’s the average temperature of the earth has been increasing rather steadily giving rise to the fear of global warming and climate change. The 1990’s have been the warmest decade on record while the 20th century has been the warmest century in the last millennium. If this warming continues unabated, it may lead to changes in global climate characterized by shifts in climatic zones, extreme weather events as well as extensive melting of polar ice and mountain glaciers and consequent rise in sea levels. All these will have considerable impact on man, his socio-economic activities and the environment in general. I have been invited by the organizers of this conference to speak on one of the sub-themes of this conference namely climate change and environmental development. It is rather difficult to meaningfully explain what environmental development means or entails unlike economic or social development. In environmental studies we usually talk about environmental management, environmental conservation, environmental degradation, environmental quality etc but not environmental development. I have therefore slightly modified the title of the topic given to me. It seems to me that what the organizers want me to do is to examine the issue of climate change and its possible impact on our environment. This is what I intend to do in this presentation. 2 Climate and the Environment Climate is the synthesis of weather over a long period of time at a given location or area. Environment is the term used to describe the collective of the surrounding external conditions within which an object, usually an organism, exists. A distinction can be made between the natural (or physical) environment and the man-made (socio-economic) environment. In this presentation our concern is with the natural environment although there is hardly anywhere in the world today that does not show the imprint of man in one form or another. The atmosphere (air), the hydrosphere (water), the lithosphere (land) and the biosphere (biota) constitute man’s natural environment (see Fig.1). These four components of man’s environment interact with one another in a very complex manner that is made even more complex by the influence of man through his activities. However, the atmospheric (climatic) environment is the most dominant. Climate exercises a strong control on the type of plants and organisms that can survive and flourish in a given area. It also determines the type of pedological and geomorphological processes that will prevail in a given area. It can therefore be said that the nature of the physical environment of an area is determined more by climate than by any other element of the physical environment. In other words, the nature of the environment in any area is primarily determined by climate. The earth is a habitable planet because of its conducive environment that allows life to flourish. The earth’s atmosphere creates this conducive environment. Without the atmosphere and 3 the climate generated there from there would be no life on this planet. The atmosphere provides and maintains the supply of oxygen required for life. It protects the earth from extremes of heat and cold. The average temperature of the earth is 150c. Without the atmosphere it would have been -180c and the earth would not have been habitable. The atmosphere holds the moisture that gives precipitation. It protects life on earth from dangerous ultraviolet radiation from the sun, cosmic radiation as well as meteorites from outer space. Weathering and various geomorphological processes that shape the earth’s surface are controlled and determined by climate especially moisture and temperature (see Fig 2). Climate is also a major and vital active factor in soil formation. Hence, climatic conditions determine patterns of world pedogenic regimes and major soil types (see Fig 3). Similarly, climate determines the characteristics and patterns of major terrestrial biomes of the world (See Fig.4). It is quite clear from the above that climate plays a pivotal role in determining the characteristics of the physical environment of an area – the land forms, the soil, the plants and organisms. Thus, if there is a significant change in the climate prevailing over an area it will also have impact on the other components of the environment in the long run. These are lessons that we have learnt from palaeoclimatological studies. Climate change will have impact on natural processes operating in the environment and the nature and characteristics of the new environment that will be created. 4 5 6 7 8 9 Observed changes in climate and their impacts on the environment Observational records indicate that the global average temperature has increased especially since about 1950. The rate of warming in the last 50 years is on the average 0.13oC ± 0.03oC per decade. This is nearly twice that for the last 100 years. Urbanization and landuse changes have made insignificant contributions to this warming according to IPCC. (IPCC, 2007). In contrast the stratosphere has cooled by between 0.3oC and 0.6oC per decade since 1979. The land areas of the earth have warmed faster (0.27oC/decade) than the ocean surfaces (0.13oC/decade). Warming has been more widespread in the last 30 years over the globe with the higher northern latitudes recording the greatest warming. Consequently heat waves have increased in frequency in the middle latitudes while the intensity of hurricanes in the North Atlantic has increased since 1970 in sympathy with increase in the sea surface temperature. Snow cover has decreased in most regions in the higher latitude especially in spring as a result of the increase in temperature. Similarly arctic sea ice extent has shrunk by about 2.7 ± 0.6% per decade since 1978 (IPCC, 2007). Mountain glaciers are retreating including those in the Tropics like on Kilimanjaro mountain in East Africa. Consequently, the sea level is rising as a result of the melting of polar ice and mountain glaciers and the thermal expansion of ocean water. Based on tidal gauge data, the global mean sea level rose between 1961 and 2003 by 1.8 ± 0.5mm per year on the average. 10 Satellite measurements between 1993 and 2003 indicate the global average rate of sea level rise is 3.1 ± 0.7mm per year. The rise in sea level has resulted in losses of coastal wetlands and mangroves and the increased salinization of groundwater in coastal areas. The frequency of coastal flooding has also increased with attendant increase in beach erosion and damage to infrastructures. Precipitation has been highly variable spatially and temporally in the last 100 years over many parts of the world. However, significantly increased precipitation has been observed between 1980 and 2005 in eastern parts of North and South America, Northern Europe and Northern and Central Asia. In contrast, reduction in rainfall has been observed in the West African Sahel, the Mediterranean, Southern Africa and parts of Southern Asia. Substantial increases in heavy precipitation have been observed in many land areas of the world since 1950. There have also been increases in rare precipitation events with return period of fifty years. This has resulted in increase in the frequency and intensity of flood events in many areas. In contrast, more intense and longer droughts have been experienced in some areas especially in the tropics and subtropics since 1970’s. Increased drying as a result of higher temperatures and decreasing precipitation has worsened the severity of these droughts. Rising ocean temperature has resulted in changes in phenology and distribution of both marine and freshwater species. There have been poleward shifts in ranges and changes 11 in algae and plankton and hence the abundance of fish in high latitude oceans. Because of the uptake of anthropogenic CO2 by the oceans since 1750, the oceans are becoming more acidic. This may have additional adverse effect on marine life and coral reefs in future. Already some coral reefs are being bleached as a result of this process. continually being refined and updated. Besides these models need to be scaled down to provide reliable forecasts at regional levels. The characteristics of projected future climate of the world as predicted by most General Circulation Models are briefly described (see IPCC, 2002, 2007 for more details). According to the IPCC Third Assessment Report (IPCC, 2002), globally averaged surface temperature is projected to increase by between 1.4oC and 5.8oC by 2100 relative to 1990 level. Nearly all the land areas of the world will warm more than the global average, especially those in the northern latitudes. There will be a tendency towards less severe winters and decrease in the occurrence of cold waves. There will be increase in the frequency of occurrence of heat waves especially in the urban areas of the temperate latitudes. There will be increase in the occurrence of storms including tropical cyclones as a result of the global warming induced intensification of the global hydrological cycle. There will be increase in global atmospheric moisture as a result of increase in evaporation. Consequently there will be overall increase in global precipitation. Precipitation increases of more than 20% are projected for middle and high latitudes in the northern hemisphere and the Antarctica in winter. Decreases in precipitation are projected for the subtropical region of the world. Large year-to-year variations in precipitation are very likely especially in those areas where an increase in average precipitation is projected. 14 More intense precipitation events are very likely in many areas while continental interiors face the risk of drought especially in summer. There will therefore be increase in precipitation extremes giving rise to increase in the occurrences of floods and droughts. A shift in the boundaries of climatic zones world-wide is most likely with global - warming induced increase in the length of the growing season in the middle and high latitudes. As a result of thermal expansion of warm ocean water and melting of polar ice and glaciers there will be a general rise in sea level of between 0.09 and 0.88 metre within a century, leading to the inundation of low-lying coastal areas and some oceanic islands. Ecosystem characteristics are determined by climate (especially temperature and precipitation), soil and human activities. Since soil characteristics are primarily determined by geology (parent material) and climate. Climate is really the critical factor that determines the gross characteristics of an ecosystem. All plants and organisms have their range of temperature and moisture requirements beyond which they find it difficult to function and survive. Plants, organisms and animals that will be most affected by a change in climate are those that are currently managing to survive because the existing climatic conditions are not optimal for them. A change in climate may improve their habitat or destroy it depending on the current conditions. Ecotones will shift in their geographical locations in sympathy with the new climate regime. Apart from causing shifts in boundaries of ecological zones, climate change will also have impact on bio-diversity. A change 15 in climate may cause the death and extinction of some species while encouraging the invasion by new species better suited to the new climatic conditions. Species that are sensitive to a change in climate are those at the edge of or beyond their optimal climatic range, those that are poor dispersers, those that reproduce comparatively slowly and those that occupy specialized niches and are consequently less tolerant of ecological changes. Climate change will also affect the distribution of pests and diseases that affect plants and animals. Some pests and diseases may disappear and be replaced by invasion by new pests and disease pathogens favoured by the new climatic conditions. These will ultimately affect the health and characteristics of ecosytems. The characteristics of ecosystems may also be influenced by fire, natural or man-made. The frequency and severity of forest fire are expected to increase under a warmer climate especially where the warmer climate is accompanied by reduced rainfall. The increase in the CO2 content of the atmosphere will increase photosynthetic rates and primary productivity all things being equal. This will increase both available and dead fuel that can encourage forest fire especially in unmanaged lands. Aquatic ecosystems or wetlands will be affected in diverse ways by global warming – induced climate change. Water is a critical element in the creation of wetlands natural or man-made. Changes in rainfall patterns and water control projects designed to meet water requirements under the new climatic regime as well as the rise in sea level as a result of global warming will affect the characteristics, size and distribution of wetlands worldwide. In coastal areas with mangrove swamp vegetation such as Nigeria’s 16 Niger Delta, sea level rise will result in inland movement of the boundary between the freshwater swamp and the salt water swamp. This is because a sea level rise will increase the salinity of water and cause the death of plants and organisms that cannot tolerate the high level of salinity. What should be our response? Given the various possible impacts of climate change on the environment outlined above, what then should be our response? We can respond in two major ways both of which are in reality complementary. First, we may wish to stop the process of global warming and the climate change that may result. This presupposes that we know the cause of the warming. Global warming may be caused by natural or man-made factors. The temperature of the earth is determined by solar energy output, the amount of this energy intercepted by the earth, the composition of the atmosphere which determines the amounts of energy that the atmosphere absorbs and the albedo of the earth’s surface which determines the amount of energy that the earth’s surface is able to absorb. In most discussions of global warming emphasis has always been on the role of the composition of the atmosphere to the near exclusion of the others. This is the green-house effect of the atmospheric gases such as water vapour, CO2, methane and nitrous oxide. When the amounts of these gases are increased by various human activities the greenhouse effect is enhanced and the earth’s temperature may rise leading to global warming. However, global warming may also occur naturally if there is an increase in solar energy output or the amount of solar energy 18 intercepted by the earth depending on its distance from the sun and the tilt in its axis of rotation. In other words, global warming may be due to natural cause or may be anthropogenic (man-made) in origin or a combination of the two. Measures taken to deal with the causes of global warming are known as mitigation measures. Since there is nothing we can do to influence the amount of solar energy output or the amount of this energy that the earth is able to intercept by virtue of its location and disposition towards the sun, we can only take measures to deal with anthropogenic (man-made) causes of global warming notably the emission of greenhouse gases by man. Mitigation measures are therefore basically anthropogenic interventions to reduce the sources or enhance the sinks of greenhouse gases such as CO2, CFC’s, methane and nitrous oxides. Chlorofluorocarbons (CFC’s) are entirely man-made and their production and usage are already being controlled under the Montreal Protocol of 1987 as amended in 1990, 1992, 1995, 1997 and 1999. The Kyoto Protocol to the United Nations Framework Convention on Climate Change (UNFCCC) of 1997 was designed to control anthropogenic emissions of greenhouse gases such as CO2, methane and nitrous oxides. A great deal of emphasis has unfortunately been put on CO2 which accounts for about 55% of anthropogenically induced global warming (see Table 1). The world is yet to agree on an equitable way of curbing CO2 emissions because of the economic and political implications. 19 Table 1: Greenhouse gases and their contribution to global warming Greenhouse Pre-industrial Concentrations Contributions Gases concentrations in 1994 (ppm) to global warming (ppm) Carbon dioxide 278 358 55% (CO ) Chlorofluorocarbons (CFC’s) 0 0.102 24% Methane (CH ) 0.7 1.7 15% Nitrous Oxide (N O) 0.275 0.311 6% 2 4 2 The second way we can response to the issue of global warming and climate change is to engage in adaptation strategies. For those who do not believe in the anthropogenic causes of global warming adaptation measures are the only credible measures because man does not have the means or capability to control the natural causes of global warming which are sun-related. Adaptation measures are measures taken by man to adjust to global warming and the resultant climate change and cope with its effects. In other words, they are measures taken to moderate the unpleasant consequences of global warming and/or take advantage of the opportunities it may offer. Adaptation measures should go hand-in-hand with mitigation measures especially given the controversial nature of mitigation measures in terms of the science and economics. Developing countries which contribute least to anthropogenically – induced global warming and resultant climate change have the least adaptive capacity to the effects of global warming and climate change because of their poverty and low-level of 20 technology. They should therefore be assisted by the rich countries to cope effectively. Although most of carbon emissions into the earth’s atmosphere emanate from the industrialized countries of the world, the developing countries such as Nigeria also make some contributions through bush burning, deforestation, use of charcoal and fuelwood for cooking and the use of old vehicles in their inefficient transportation. As these countries develop industrially their share of global emissions of CO2 and other greenhouse gases are likely to increase. China recently replaced the United States of America as the world’s largest emitter of carbon dioxide while India’s share of global carbon emissions is also increasing (see Table 2). Nigeria and other developing countries can reduce their carbon emissions through afforestation to encourage carbon sequestration, control of bush burning, the use of gas including biogas for cooking instead of charcoal and fuelwood and improvement in public transportation system that would discourage traffic bottlenecks and the use of old motorcycles and motor vehicles which are veritable sources of air pollution in our cities. Nigeria as an oil producing country should also stop gas flaring and adopt the use of environment – friendly technology in oil exploration, exploitation and transportation. 21 Table 2: CO2 emission by country in 2007 Country Per capita % of world total Rank emission in metric tones China 4.75 21.01 1 USA 19.94 20.08 2 Russia 11.83 5.59 3 India 1.25 4.68 4 Japan 9.91 4.22 5 Germany 10.13 2.79 6 Canada 17.91 1.97 7 U.K. 9.28 1.89 8 South Korea 10.69 1.72 9 Iran 7.5 1.64 10 South Africa 9.35 1.51 14 Nigeria 0.72 0.35 37 Mitigation measures involving curbing of CO2 emissions are based on the premise that the current global warming is CO2 – induced. There are of course other green-house gases such as methane and nitrous oxide that can cause global warming. More emphasis needs to be given to the reduction in the emissions of these green-house gases also. Because global warming could also be caused by changes in solar energy output or the amount of solar energy the earth is able to intercept, we will need to put in place measures to adapt to the effects of solar energy-induced 22 global warming since we have no control over changes in solar energy and the amount of solar energy the earth is able to intercept. Examples of such adaptation measures will now be briefly discussed in relation to some environmental problems that climate change may cause. (a) Increase in the occurrence of heat waves Adaptation measures are designed to protect people against excessive heat. This may be achieved through modification to building design and construction code, more use of air conditioning in homes and offices and improved urban design with a lot of open spaces and green areas to encourage air flow and ventilation and improve air quality. (b) Increase in the intensity of tropical cyclones Adaptation measures should aim at protecting people and properties including infrastructure against floods and high winds. This could be achieved through improved building design, construction of flood protection walls, proper landuse planning to reduce vulnerability to flooding and improved weather forecast and evacuation strategies. (c) Changes in the ecosystem/loss of bio-diversity Adaptation measures will involve conservation of rare species and species under threat, landuse planning that is eco-friendly and protection of rare ecosystems and afforestation programmes. (d) Drought/desertification Adaptation measures will include a well-designed drought containment plan involving water control projects, water 23 conservation, planting of drought-resistant or quick-maturing crops, afforestation programmes (shelter belts), soil conservation and agricultural landuse planning and the control or elimination of bush burning and the use of fuelwood and charcoal for cooking (e) Floods Adaptation measures should be geared towards water control works to regulate river flow, structural and non-structural flood protection measures and urban planning with integrated drainage system. Landuse planning is also required especially in coastal zones to significantly reduce vulnerability to flooding. (f) Erosion With extremes in rainfall and sea level rise there is likelihood of increase in soil erosion in the hinterland and beach erosion in coastal areas. Soil erosion can be controlled through soil conservation measures, afforestation and land use planning. Beach erosion can be controlled by structural measures involving the construction of embarkments and nourishment of beaches by sandfilling. (g) Water Problems Water problems are likely to be exacerbated in a warmer earth especially in current semi-arid environment such as the West African Sahel. Increase in temperature will increase demand for water for human and agricultural uses. On the other hand, decreased rainfall coupled with increase in temperature and evaporation will reduce the amount of water available for various uses. In coastal areas, the increase in sea level will lead to salinization of both surface and groundwater. Adaptation 24 measures will involve water control projects water conservation, management of water demand, modern rainfall harvesting and ultimately the de-salinization of water contaminated by salt-water intrusion. 25 Conclusion Climate is a vital component of the earth’s environment as well as a major factor in shaping and determining the characteristics of the earth’s environment. This is because climate through its attributes such as moisture and heat regulates many of the processes that shape the earth’s physical environment. A change in climate can therefore be expected to affect various environmental processes operating in the earth’s surface whether in the lithosphere, the biosphere or the hydrosphere. A change in climate may therefore result in a change in our physical environment with all the implications for man and his activities. Our environment is our life support system. We should therefore be very interested in the future state of the earth’s environment. Sustainable development is not possible without environmental sustainability. In fact, the foundation of sustainable development is environmental sustainability. Man depends on environmental resources for his sustenance. A change in climate can have a significant impact on some of these environmental resources notably water, soil, flora and fauna. The environment must be conducive for man to continue to thrive on this planet. As we exploit the resources of our environment to meet our various needs we must think of the future generations and ensure that we preserve this precious environment so that they too can meet their needs. This, I submit, is the real essence of sustainable development. 26 Selected References IPCC (2002).Third Climate Change Assessment Reports.3 volumes. IPCC (2007).Fourth Climate Change Assessment Reports. 3 volumes Ayoade, J.O. (2003). Climate Change: A Synopsis of its nature, causes effects and management. Vantage Publishers, Ibadan, Nigeria. Ayoade, J.O. (2004). The effects of global warming on wetlands in Encylopedia for Life Support Systems (EOLSS) EOLSS Publishers, Oxford, U.K. Awosika L. and Folorunsho, F. (2006). Climate change and impact on the coastal environment of Nigeria in Ivbijaro M.F.A. et al (ed) Sustainable Environmental Management in Nigeria Mattivi Productions Ibadan, Nigeria.