Land use change, climate change and biodiversity
Some Highlights of Land Use Change, Climate Change and Biodiversity
Mohamed Tawfic Ahmed
Suez Canal University, Egypt

Biodiversity is the web of life that distinguishes planet Earth from the other lifeless spheres in our solar system, if not the universe.
Biodiversity is short for biological diversity. It describes the variety of living organisms of all kinds -- animals, plants, fungi, and microorganisms -- that inhabit a particular area.
Most commonly, biodiversity is measured by the number of species present in an ecosystem, but genetic diversity within those species and the diversity of different ecosystems across the landscape are also important.
The diversity of subdivisions of species, such as subspecies and populations, is important as well, since it is the raw material for the evolution of new species in the future.
Scientists have identified and described about 1.4 million species.
Only a small proportion of these are the organisms we're commonly acquainted with:
of the 1.4 million known species, only about 4,000 are mammals and 9,500 are birds.
Over half of all known species are insects. Far more species in the world remain unknown to science.
Estimates of just how many vary, but there are probably between two and twenty times as many unknown species as known ones.

  1. Biodiversity, A Generic View
    The number and types of organisms inhabiting the planet have varied immensely during geologic history.
    In part, these variations have been caused by the evolution of new types of organisms and the elimination of others due to environmental changes and mass extinctions, as occurred at the end of the Mesozoic period 65 million years ago which saw the extinction of the dinosaurs.
  1. Now, however, human transformations of the earth's surface are a force of geologic proportions
    that is affecting biodiversity in almost every corner of the world.
    Changes are occurring rapidly enough that the result is a net loss of species rather than a proliferation
    of new life forms.

    Species have been disappearing at 50-1000 times the natural rate, and this is predicted to rise dramatically. Based on current trends, an estimated 34,000 plant and 5,200 animal species - including one in eight of the world's bird species - are critically endangered.

    According to the IUCN Red List (2000), almost 10 percent of animal species and 14 percent of plant species are critically endangered. A threatened species is one at significant risk of extinction in the near future.
    Of the threatened species listed world-wide, as of mid­ 1996, 1,029 are birds, 507 are mammals and l,800 are freshwater fish.

    As countries have come to understand the great value and irreplaceable heritage of their wildlife,
    many have taken steps to preserve them.
    National legislation often places high priority on the protection of wild flora and fauna.
    It often prohibits a range of activities such as recreational hunting, commercial exploitation and trade
    in certain wild species and their products.

    Most of the planet's biodiversity is in the tropics. Tropical forests, which take up only about 7 percent
    of the Earth's land area, house about half its species. The canopies of tropical trees are especially diverse.
    In a single tree in Peru, for example, 43 species of ants were found -- about the same number as live in the entire British Isles.

    The great majority of species are rare. In most ecosystems, there are just a few common species
    (e.g., white oak in eastern US forests) and a much larger number of rare species
    (e.g., bitternut hickory, hackberry, slippery elm, Kentucky coffee tree, shingle oak).
    This rarity is one of the reasons why so many species remain unknown and also why so many are vulnerable to extinction.

    Biodiversity and ecosystems
    Biodiversity and ecosystems are closely related concepts. Biodiversity is defined by the CBD as
    "the variability among living organisms from all sources including, inter alia, terrestrial, marine and other aquatic ecosystems
    and the ecological complexes of which they are part; this includes diversity within species, between species and of ecosystems"
    (United Nations1992:Article 2).

    Diversity thus is a structural feature of ecosystems, and the variability among ecosystems is an element of biodiversity.
    The parties to the convention have endorsed the "ecosystem approach" as their primary framework for action.
    Global diversity is usually considered under three fundamental categories - genetic diversity, species diversity and ecosystem diversity.

    Genetic diversity:
    In simple terms, differences in genetic material dictate whether we have blue or brown eyes,
    blond or black hair and are tall or short.
    Genetic variation determines the characteristics of all species and individuals that make up the living world.
  1. Species diversity:
    To date 1.7 million species have been described world­ wide.
    Estimates of the total number of species on earth range from 5 to 100 million, 13­ 14 million being a conservative working estimate.
    Biologists are studying both species ­ rich groups (such as insects) and species­ rich areas
    (such as moist tropical rain forests) in order to provide a more reliable picture of patterns and estimates
    of the number of species on Earth.

    Ecosystem diversity:
    The enormous range of terrestrial and aquatic environments on Earth has been classified into a number of ecosystems. Major habitat types include tropical rain forests, grasslands, wetlands, coral reefs and mangroves.
    Some of the world's richest habitats are tropical rain forests. Although they cover only 7 per cent of the world's surface, these areas contain at least 50 per cent, and possibly up to 90 per cent, of all plant and animal species.
  1. Factors Affecting Biodiversity
    A variety of factors determine the biodiversity of a certain place. These factors include:

    • The mean climate and its variability
    • The availability of resources and overall productivity of the site, measured in terms of the primary productivity and soil characteristics, including availability of adequate substrate, energy, water and nutrients.
    • The disturbance regime and the occurrence of perturbations of cosmic, tectonic, climatic, biologic or anthropologic nature
    • The original stock of biodiversity and dispersal opportunities or barriers
    • The level of spatial heterogeneity
    • The intensity and interdependency of biotic interactions such as competition, predation, mutualism and symbiosis.
    • The intensity and kind of sexual reproduction and genetic recombination.

    Biodiversity is therefore not a static concept as the dynamics of evolution and ecological processes includes a background rate of change.

    The Benefits of Biodiversity to Humans
    Humans benefit from biodiversity in many ways. Besides the animals and plants that we use for food,
    shelter, raw materials, and companionship, there are thousands of species whose natural products
    are literally life-saving.
    Indeed, many ecosystems provide invaluable services to humanity without most of us even realizing it.
  1. Useful Products from the Wild
    A large number of drugs currently on use are originated from plants.
    Aspirin, quinine and penicillin are some of the well known examples of these widely used drugs.
    One of the best-known examples of the medical value of a species previously considered worthless is the anticancer drug taxol which was extracted from Taxus brevifolia, a small tree of the old growth forests of the Pacific Northwest.

    Taxol has become the standard treatment for advanced cases of ovarian cancer, which strikes 24,000 women every year.
    Until the discovery of taxol's effectiveness, the Pacific yew was considered a "weed tree" of no economic value.
    Another plant whose economic value was recently discovered is the Lake Placid mint, a rare herb of the scrublands of central Florida. This species occurs in only 300 acres on a protected biological station.
    It has been found to contain a natural insect repellent that deters ants, as well as a powerful antifungal compound with potential medical uses.
  1. Two compounds derived from African plants are now being used as sugar substitutes.
    Thaumatin, derived from the katemfe bush of West African rain forests, is 100,000 times sweeter than table sugar.
    Brazzein, a protein derived from the fruit of an African vine, was discovered as a spin-off from studies of the eating habits of monkeys.
    It is 2,000 times sweeter than sugar and, unlike substitutes such as saccharin and aspartame, it retains its flavor over time, is nontoxic, and remains stable when heated.

    Since only about 5 percent of the 250,000 known plant species have been analyzed for their medicinal properties, thousands more such compounds may be waiting to be discovered.

    Genetic Diversity
    Beyond the number of species that exist, it's also important to conserve genetic diversity within individual species.
    Populations that fall below 1,000 breeding adults may suffer severe genetic problems that can threaten their long-term viability. Called "inbreeding depression," this phenomenon can lower the fitness of offspring to the point that the population's survival is threatened.

    Genetic diversity is particularly important in domesticated plants and animals and their wild relatives.
    The breeding of new strains of pest-resistant crops and livestock is critically dependent on the supply of new genetic variability.
    This variability has been provided to scientists by wild relatives of domestic plants and animals, and by the thousands of cultivated varieties grown by peasant farmers around the world.
    The importance of such genetic diversity was proved by the southern corn leaf blight outbreak of 1970, which destroyed 15 percent of the crop -- the greatest economic loss in a single crop in a single year in the entire history of agriculture.
    This devastating blight spread rapidly across the United States because of the lack of genetic diversity in US corn varieties.

    The Role of Even Smaller Organisms
    Songbirds in Missouri were recently found to increase the productivity of white oak forests by controlling the populations of leaf-damaging insects that feed on white oak saplings. Without the birds, the saplings had twice as many insects feeding on them and lost twice as much of their leaf area.

    Soil nitrogen -- a key element for agricultural productivity -- depends on bacteria such as Rhizobium, which live in the roots of leguminous plants. Although three-fourths of our atmosphere is nitrogen, crop plants cannot absorb the gas directly.
    It must first be converted to the nitrate form by a process known as fixation. The legume-Rhizobium symbiosis is responsible for the fixation of 80 million tons of nitrogen each year -- twice as much as the total industrial production of nitrogen fertilizer.

    Microorganisms often prove to have unexpected values to science because of their ability to carry out chemical reactions.
    A major breakthrough in genetic engineering -- the polymerase chain reaction technique used to make copies of DNA -- was only possible because of the discovery of a heat-stable enzyme in bacteria living in the hot springs of Yellowstone National Park.
    The lesson of these examples is simple: even the most obscure organisms in an ecosystem are worth conserving.

    The Value of Diverse Ecosystems
    Biodiversity underlies the goods and services provided by ecosystems that are crucial for human survival and well being.
    These can be classified along several lines. Supporting services maintain the conditions for life on Earth including, soil formation and retention, nutrient cycling, primary production; regulating services include regulation of air quality, climate, floods, soil erosion, water purification, waste treatment, pollination, and biological control of human, livestock and agriculture pests and diseases; provisioning services include providing food, fuelwood, fibre, biochemicals, natural medicines, pharmaceuticals, genetic resources, and fresh water; and cultural services provide nonmaterial benefits including cultural diversity and identity, spiritual and religious values, knowledge systems, educational values, inspiration, aesthetic values, social relations, sense of place, cultural heritage, recreation, communal, and symbolic values.

    The quality of the water we drink, the air we breathe, and the soil in which we grow our food depends on the integrity of natural ecosystems. People have long recognized the role of healthy forests in reducing erosion, preventing flooding, maintaining the purity of the water, and tempering climatic fluctuations. In recent years we've come to see that other ecosystems have similar values.

    Wetlands such as swamps, marshes, and mangroves filter large quantities of pollutants from the water.
    They also serve as breeding grounds for thousands of species of wildfowl, fish, and shellfish, and thus are vital to the productivity of our lakes and oceans.

    Current State of Biodiversity
    Massive extinctions have occurred five times during the earth's history -- most notably about 65 million years ago, when about 15 percent of living species, including the dinosaurs, died out; and about 245 million years ago when over 60 percent of all living species disappeared.

    There is strong scientific evidence that we are now in the opening phase of a sixth massive extinction.
    This extinction is unprecedented in both its breadth and speed. In the past 10,000 years, and especially the past 500, the rate of extinction of species has increased to somewhere between 100 and 1,000 times what it was before human history began.

    Scientists' conservative estimates suggest that a significant percentage of the world's species are likely to become extinct within the next several decades. Unlike all previous episodes of mass extinction, the one now under way is human-caused and can be stopped by timely action.

    The concentration of many endangered species in small areas also makes them especially vulnerable to climate change.
    Species on mountaintops or islands, for example, cannot easily migrate to new areas if global warming makes their environment too hot or too dry for them. In some areas, the ranges of endangered species are extremely small, and the dangers correspondingly great.

    The current levels of human impact on biodiversity are unprecedented, affecting the planet as a whole, and causing large-scale loss of biodiversity. Current rates and magnitude of species extinction, related to human activities, far exceed normal background rates. Human activities have already resulted in loss of biodiversity and thus may have affected goods and services crucial for human well being.
  1. Humans have affected the environment for many centuries through hunting, land clearance, urbanisation and other activities.The damage to biodiversity caused by human activities is rapidly increasing as species are over­ exploited, and ecosystems are destroyed for agriculture and urban, economic or recreational development.
    Islands are especially vulnerable to species extinction. Because of their isolation, many unique species have evolved on islands.
    When predators are introduced or habitat is destroyed, these species have nowhere to escape. As many as 2,000 species of birds have become extinct in the Pacific since human settlement: nearly 20 percent of the number of bird species that exist worldwide today.
    This is why ecologists are so concerned about the fragmentation of terrestrial ecosystems into "habitat islands."
    According to The Nature Conservancy and Nature Serve, more than 6,700 animal and plant species in the United States are vulnerable to extinction (Stein et al. 2000). The federal Endangered Species Act currently lists only about 1,300 of those species as endangered or threatened. Losing these species could severely affect the diversity of life and the biological processes on which all living things, including humans, depend.
    Habitat loss and diminishing biodiversity may be the most urgent environmental problems we now face.
    Loss of species is significant in several respects. First, breaking of critical links in the biological chain can disrupt the functioning of an entire ecosystem and its biogeochemical cycles. This disruption may have significant effects on larger scale processes. Second, loss of species can have impacts on the organism pool from which medicines and pharmaceuticals can be derived.
    Third, loss of species can result in loss of genetic material, which is needed to replenish the genetic diversity of domesticated plants that are the basis of world agriculture (Convention on Biological Diversity).
  1. The survival of species is threatened by:

    • habitat loss or modification;
    • over­ exploitation for commercial or subsistence reasons;
    • accidental or deliberate introduction of exotic species;
    • disturbance, persecution and uprooting; and
    • disease.

    Habitat loss is the most significant threat to biodiversity. As many other reports and scientific papers have shown, the loss, degradation and alteration of habitat are the primary factors responsible for the worldwide decline in numbers of wild animals and plants.

    Uncontrolled growth, often referred to as "sprawl", plagues communities across the globe. It permanently fragments contiguous habitat into marginal pieces of land. Species become extinct when the places where they live are destroyed: when forests are cut down, wetlands are polluted, or prairies are plowed up.

    Factors of potential impact on biodiversity would also include

    Overharvesting, overcultivation or over-exploitation of natural resources is also a big threat to biodiversity.
    This human activity refers to a rate of exploitation or utilization that exceeds the cycling capacity of the natural resource.
    Classifying natural resources it has been traditional to distinguish between those that are renewable and those that are nonrenewable.
    The former were considered to be the living resources--e.g., forests, wildlife, and the like--because of their ability to regenerate through reproduction. The latter were considered to be nonliving mineral or fuel resources, which, once used, does not replace themselves.
    Because all natural resources in fact form a continuum, from those that are most renewable in the short term to those that are least renewable, they do not readily lend themselves to a single system of classification. It is useful, therefore, to examine the various types of natural resources in relation to their cycling time; i.e., the length of time required to replace a given quantity of a resource that has been utilized with an equivalent quantity in a similarly useful form.

    Environmental pollution
    Environmental pollution or pollution is the addition of any substance (nutrients) or form of energy (e.g., heat, sound, radioactivity) to the environment at a rate faster than the environment can accommodate it by dispersion, breakdown, recycling, or storage in some harmless form. A pollutant need not be harmful in itself. Carbon dioxide, for example, is a normal component of the atmosphere and a by-product of respiration that is found in all animal tissues; yet in a concentrated form it can kill animals. Human sewage can be a useful fertilizer, but when concentrated too highly it becomes a serious pollutant, menacing health and causing the depletion of oxygen in bodies of water.

  1. By contrast, radioactivity in any quantity is harmful to life, despite the fact that it occurs normally in the environment as so-called background radiation. Pollution has accompanied mankind ever since groups of people first congregated and remained for a long time in any one place.

    Primitive human settlements can be recognized by their pollutants--shell mounds and rubble heaps.
    But pollution was not a serious problem as long as there was enough space available for each individual or group.
    With the establishment of permanent human settlements by great numbers of people, however, pollution became a problem and has remained one ever since. Cities of ancient times were often noxious places, fouled by human wastes and debris.
    In the Middle Ages, unsanitary urban conditions favoured the outbreak of population-decimating epidemics.

    During the 19th century, water and air pollution and the accumulation of solid wastes were largely the problems of only a few large cities. But, with the rise of advanced technology and with the rapid spread of industrialization and the concomitant increase in human populations to unprecedented levels, pollution has become a universal problem.

    Persistent Organic Pollutants (POPs)
    Of all the pollutants released into the environment every year by human activity, Persistent Organic Pollutants or POPs are among the most dangerous. They are highly toxic, causing an array of adverse effects, notably death, disease, and birth defects, among humans and animals. Specific effects can include cancer, allergies and hypersensitivity, damage to the central and peripheral nervous systems, reproductive disorders, and disruption of the immune system.

    These highly stable compounds can last for years or decades before breaking down. POPs released in one part of the world can, through a repeated and often seasonal process of evaporation, deposit, evaporation, deposit, be transported through the atmosphere to regions far away from the original source. In addition, POPs concentrate in living organisms through another process called bioaccumulation. Though not soluble in water, POPs are readily absorbed in fatty tissue, where concentrations can become magnified by up to 70,000 times the background levels. Fish, predatory birds, mammals, and humans are high up the food chain and so absorb the greatest concentrations.

    A number of persistent organic pollutants are known as Endocrine Disturbing Agents. These agents which include among others DDT, PCBs, and TBTs have the ability to disturb endocrine and reproductive systems of several organisms, hence affecting the population density to some serious extent.
  1. Lake Apopka wildlife Lake Apopka, Florida, has been the subject of extensive study since a chemical spill in 1980 dumped a number DDT-related compounds into the water, after which the alligator population declined sharply. Runoff from farming in the area has also added several other pesticides, including dieldrin and toxaphene. Ongoing research continues to reveal aspects of chemical endocrine disruption in wildlife. and because mothers are known to transfer POPs to their offspring, maternal levels during pregnancy and lactation would be an important source of exposure. The study found that concentrations of the chemicals were significantly higher in the mothers of men with testicular cancer than in the control group.
  1. Lake Apopka wildlife Lake Apopka, Florida, has been the subject of extensive study since a chemical spill in 1980 dumped a number DDT-related compounds into the water, after which the alligator population declined sharply.
    Runoff from farming in the area has also added several other pesticides, including dieldrin and toxaphene.

    Ongoing research continues to reveal aspects of chemical endocrine disruption in wildlife. and because mothers are known to transfer POPs to their offspring, maternal levels during pregnancy and lactation would be an important source of exposure.
    The study found that concentrations of the chemicals were significantly higher in the mothers of men with testicular cancer than in the control group.

    About 3,6 billion of the world's 5.2 billion hectares of useful dryland for agriculture has suffered erosion and soil degradation.
    In more than 100 countries, 1 billion of the 6 billion world population is affected by desertification, forcing people to leave their farms for jobs in the cities. Desertification takes place in dryland areas where the earth is especially fragile, where rainfall is nil and the climate harsh.
    The result is the destruction of topsoil followed by loss of the land's ability to sustain crops, livestock or human activity.
    The economic impact is horrendous, with a loss of more than $40 billion per year in agricultural goods and an increase in agricultural prices. Climatic changes can trigger the desertification process, but human activities frequently are the proximate cause.

    Deforestation removes trees that hold the soil to the land. Overgrazing of livestock strips the land of grasses.

    Desertification create conditions that intensify wildfires and stirring winds, adding to the tremendous pressure to earth's most precious resource, water, and, of course, the animals dependant on it. According to the World Wide Fund for Nature, the world lost about 30% of its natural wealth between 1970 and 1995.
    Dust from deserts and drylands are blown into cities around the world. Dust from Africa reaches Europe through the Pasat wind, and even reaches US cities. Dust particles, which are less than 2,5 millionths of a metre in size, are inhaled, causing health problems and have been shown to boost death rates.

    Biodiversity, Land Use Change, and Climate change
    Land is the stage on which all human activity is being conducted and the source of the materials needed for this conduct.
    Human use of land resources gives rise to "land use" which varies with the purposes it serves, whether they be food production, provision of shelter, recreation, extraction and processing of materials, and so on, as well as the bio-physical characteristics of land itself. Hence, land use is being shaped under the influence of two broad sets of forces - human needs and environmental features and processes. Neither one of these forces stays still; they are in a constant state of flux as change is the quintessence of life.

    Land cover refers to the natural vegetative cover types that characterize a particular area. These are generally a reflection of the local climate and landforms, though they too can be altered by human actions. Examples of broad land cover categories include forest, tundra, savannah, desert or steppe, which in turn can be sub-divided into more refined categories representing specific plant communities (e.g., oak-pine scrublands, mangroves, seasonally flooded grassland, etc.).

  1. Humans are increasingly being recognized as a dominant force in global environmental change (Moran 2001, Turner 2001, Lambin et al. 2001). Changes in land use are likely the most ancient of all human-induced environmental impacts. Land-cover change, especially the conversion of forested areas into other uses, has been identified as a contributing factor to climate change, accounting for 33 percent of the increase in atmospheric CO2 since 1850, and a leading factor in the loss of biological diversity.

    Overgrazing and other agricultural practices in developing countries are causes of land degradation and desertification. Water diversion for land irrigation consumes about 70 percent of all water withdrawals and is sufficiently significant to stop the flow of such large rivers as the Colorado (US), Huang Ho (China), and Amu Darya (Central Asia) from reaching the sea during the dry season.
  1. Drivers of Land Use Change
    Farmar-Bowers(2003) suggested that most of the land use change in the last two centuries has been done to create 'wealth'. '
    Wealth creation' for centuries has aimed at generating products that can be sold, and this puts land into the category of a 'producer good' used to produce products that eventually reach the consumer.

    The paradigm in 'wealth creation' is a cost reduction, the productivity-orientated approach of 'how to do more with less'.
    Producing more per person involves the vigorous application of science and technology; genetic engineering and gene patenting are recent phenomena, but typical of this paradigm1. Golüke (2002) refers to this paradigm as a 'material constrained' history of humanity. This global paradigm is resulting in the development of specific kinds of rural landscapes throughout the world, so that forest and woodland is converted to arable land or grazing land and looks the same whether it is in America, Brazil or Australia. The development paradigm is not likely to change in the foreseeable future, not even for 'sustainable development'.

    Drivers of Landuse Change
    Drivers of land use change are classified into two major classes, indirect and direct drivers.
    The main indirect human drivers (underlying causes) include: demographic; economic; sociopolitical; scientific and technological; and cultural and religious factors.
    The main direct human drivers (proximate causes or pressures) include: changes in local land use and land cover (the major historical change in land use has been the global increase in lands dedicated to agriculture and grazing); species introductions or removals; external inputs (e.g., fertilizers and pesticides); harvesting; air and water pollution; and climate change.

    The focus for land use change is on those changes that have a special relevance to biodiversity maintenance in the landscape.
    These are likely to be different from land use changes that are significant for agricultural production.
    These changes can be positive or negative for biodiversity. Knowing why both occur is important, since we wish to promote the positive changes and alter the negative changes so they become either neutral or positive for biodiversity. It is these special kinds of land use change that the study is focused upon and on which the questions relating to fundamental human needs are addressed

    Changes in the uses of land occurring at various spatial levels and within various time periods are the material expressions, among others, of environmental and human dynamics and of their interactions which are mediated by land.

    Land use changes can have either positive or negative effects for native biodiversity. More intensive land uses tend to have the most negative impacts, both on-site and off-site. A change in enterprise from grazing to broad acre cropping would have negative outcomes for native biodiversity if native vegetation is present. Meanwhile, changes in management practices such as altering the intensity of grazing in a particular part of the farm might change the distribution and abundance of native species.

    Research has shown that the overall impact on native biodiversity of a land use change is related to how the land use change alters the extent, pattern and quality of native vegetation.

    Biodiversity/ Landuse Indicators
    Biodiversity indicators are information tools summarizing data on complex environmental issues to indicate the overall status and trends of biodiversity. They can be used to assess national performance and to signal key issues to be addressed through policy interventions and other actions.

    The development of indicators is therefore important for monitoring the status and trends of biological diversify and in turn feeding back information on ways to continually improve the effectiveness of biodiversity management programmes.

    Biodiversity indicators when used to assess national or global trends and to build a bridge between the fields of policy making and science. Policy makers set the targets and measurable objectives while scientists determine relevant variables of biodiversity, monitor current state and develop models to make projections of future biodiversity status. Once they are selected indicators give direction to monitoring and research programmes

    There have been several efforts at all levels from the local to the global to develop indicators for land use that would capture the effects of changing land use patterns on biodiversity. However, there is no consensus framework for measuring or tracking these impacts. In addition, there has been little work that attempts to link indicators of land use that are valid at the local level (i.e. the level of the individual landowner) and the regional and national level indicators that are important to the publicpolicy debate.

    Another approach for indicators of biodiversity and land use is to focus on the issue of
    the functions of the ecosystem, rather than its specific components. In looking at system function, we might look at ground cover, soil fertility, the interaction of land and water and so forth. Focusing on these issues, especially as they pertain to plant species coverage might give good indicators of the environmental state of the system.

    Climate Change
    In 1896, the Swedish chemist, Svante Arrhenius, was among the first to stress the possibility of a greenhouse effect whereby the global climate would be warmed through the increased burning of coal and oil-based fossil fuels. Very little concern was expressed as to the impacts of this greenhouse effect until 1979, when the United Nation's World Meteorological Organization (WMO) sponsored the first World Climate Conference. An article in Nature that year stated that "The release of carbon dioxide to the atmosphere by the burning of fossil fuels is, conceivably, the most important environmental issue in the world today."

    Climate change refers to the effect of human-induced increase in the concentration of greenhouse gases in the atmosphere, enhancing the natural greenhouse effect. Combustion of fossil fuels, cement production and land use changes have led to CO2 concentration increasing by almost 30 percent since the 18th century. Other greenhouse gases are also increasing in concentration in the atmosphere due to human activities, mainly use of landfills, agriculture in general and rice paddy cultivation in particular, animal rearing, fossil fuel use and industrial production.

    These gases include methane, which has more than doubled since pre-industrial times, as well as nitrous oxide, sulphur dioxide and ozone (Schimel et al. 1996). As the concentration of these gases increases, so does the radiative forcing, and global mean surface temperature. The magnitude of the human-induced effect is not fully resolved, but surface temperature observations indicate that there has been a global mean warming of 0.3 to 0.6 degrees centigrade over the past one hundred years (Schimel et al. 1996).

    The effects that a global mean change in temperature may have on local and regional scales are extremely variable and uncertain due to the influence of atmospheric circulation and ocean bodies (Mitchell and Jones 1997). In addition to changes in the mean climatic conditions (such as temperature and rainfall), the frequencies of irregular seasons and extreme events, including fires, hurricanes and droughts, are likely to change and in some places increase (Parry 1986; Peters 1992). Given the potentially dramatic effects on local climate, natural resources, infrastructure and economic activities, Africa may be particularly physically vulnerable to and at risk from climate change.
  1. Intergovernmental Panel of Climate Change
    The 1980'sproved to be the warmest ten-year period on record - and every decade since then has been warmer than the preceding one
    In 1988 the Intergovernmental Panel on Climate Change (IPCC) was officially established. Their first Scientific Assessment of Climate Change was the most comprehensive scientific study on climate change to date, and was published in 1990. That year was also notable as being the warmest year in recorded history until that date.

    In 1992, during the Earth Summit in Rio de Janeiro and afterwards, more than 154 countries signed the United Nations Framework Convention on Climate Change (UNFCCC). This convention entered into force on 21 March 1994, 90 days after receipt of the 50th ratification.

    Climate Change, An Analytical View
    Projected rate and magnitude of changes in climate change during the 21st century are unprecedented compared to those in the last 1.8 million years and the ability of species to adjust given present human dominated landscape is questionable.

    While shifts in the average temperatures for a given locality in the range of 1-3 ○C above those of the pre - industrial present have been experienced from time to time during Pleistocene inter glacials, increases beyond that range will create climates not encountered for millions of years.

    During the Pleistocene, atmospheric CO2 level have not reached those of the present day, let alone those of the near future. The rate of warming induced by greenhouse gas emission seems historically unprecedented and there must be questions as to the ability of species to adjust to existing human dominated landscapes an many species exist in fragmented, weed and pest infested localities, confined to small areas within their previous ranges reduced to small population with reduced genetic diversity and therefore constrained to any adjustment to climate change through migration.

    Three is therefore no reliable model in the recent past of what to expect with sustained greenhouse driven global climate change. Warming beyond the Pleistocene temperature range can be expected to lead to large biotic turnover and extinctions besides the expected substitution of present biotic communities by non - analogue communities. Species at the northern or southern limit of their distribution might be affected differently by climate change and some could become extinct while others could become pests.

    Although past changes in the global climate resulted in major shifts in species ranges and marked reorganization of biological communities, landscapes, and biomes during the last 1.8 million years, these changes occurred in a landscape that was not as fragmented as it is today, and with little or no pressures from human activities. On the one hand, current climate change coupled with other human pressures is stressing biodiversity far beyond the levels imposed by the global climatic change that occurred in the recent evolutionary past. On the other hand, the human component needs to be incorporated when dealing with the impacts of climate change on biodiversity that is, activities aimed at mitigating and adapting to climate change in which biodiversity considerations.
  1. Climate Change and Biodiversity
    Unlike the introduction of invasive species, land conversion, and other threats to biodiversity, because climate is globally pervasive, it will affect even remote wilderness areas that to date have experienced little of anthropogenic change. Walker and Steffan predict that more natural ecosystems will be in an early successional state, and that the biosphere will be "weedier" and structurally simpler, by comparison with ecologically complex old-growth areas.

    The study of climate change impacts on biodiversity is still in its infancy, but several path breaking workshops and research initiatives suggest future research directions for those interested in how humanity can mitigate the impacts of climate change on other species (Global Change in Terrestrial Ecosystems, IAI 1994). There is also increasing interest in how to address, at the policy level, the complex linkages between climate change and biodiversity (IUCN 2001, Convention on Biological Diversity).
  1. Major Drivers of Biodiversity
    There are a number of major issues at the interface of biodiversity, land use and climate change. As climate changes, ecosystems will respond to changes in temperature and precipitation as well as changes in the carbon-dioxide concentrations in the atmosphere. These changes are likely to favour some species and to negatively affect others, which will alter competitive relationships and may cause invasions by "generalist" species (Walker et al., 1999). Perhaps most significantly, there is a risk that climatic changes will occur more rapidly than individual species are able to adapt. For those species that are able to migrate with climate change(seeking appropriate habitat as it literally moves out from under them), there is a risk that migration"escape routes" will be closed due to anthropogenically altered landscapes or natural barriers, such as mountains, rivers and oceans (Malcolm and Markham 2000). The ultimate result could be large-scale extinctions.

    Shifts in distribution of plants and animals
    At the simplest level, changing patterns of climate will change the natural distribution limits for species or communities. In the absence of barriers it may be possible for species or communities to migrate in response to changing conditions. Vegetation zones may move towards higher latitudes or higher altitudes following shifts in average temperatures. Movements will be more pronounced at higher latitudes where temperatures are expected to rise more than near the equator. In the mid-latitude regions (45 to 60º), for example, present temperature zones could shift by 150 ­ 550 km.

    In most cases natural or man-made barriers will impact the natural movement of species or communities. Arctic tundra and alpine meadows may become squeezed by the natural configuration of the landscape, while these and many other natural systems may be further confined by human land-use patterns. Many national parks and protected areas are now surrounded by urban and agricultural landscapes which will prevent the simple migration of species beyond their boundaries.

    Rainfall and drought will also be of critical importance. Extreme flooding will have implications for large areas, especially riverine and valley ecosystems. Increasing drought and desertification may occur in tropical and sub-tropical zones, and at least one model has predicted a drying out of large parts of the Amazon.

    Changes in seasons are already being noticed in many temperate regions. Birdsong is being reported earlier and spring flowers are emerging when it was once winter. In agricultural landscapes changes in the length of growing seasons may improve productivity in mid-latitudes and increase the potential for arable crops at high latitudes. Negative impacts may include increased ranges of insect pests and diseases, and failure of crops in some regions from drought or flooding.

    Responding to change
    The majority of international political activity has been ffocused towards the reduction in outputs of greenhouse gases. This is important, but even if successful, the changes to the global climate will not be stopped immediately and the predicted impacts will increase, probably for many decades. Despite this, there have been few detailed attempts to develop strategies in order to respond to the changing conditions in our biosphere.

    There is an urgent need for more research into the impacts and implications of climate change on biodiversity, looking at geographical changes, and at differing sensitivities of species and habitats.
    There is also a need to greatly develop and advance policies and ground level response strategies which may alter the degree of impact on biodiversity.

    Immediate response strategies may follow three paths - avoidance, mitigation and adaptation. Certain measures may be controversial, ineffective, or even counter-productive, however the science and the debates will need to be held in order to test out such measures. A number of strategies and measures are provided, as examples, below:

    • Utilisation of irrigation, drainage or other artificial means to maintain habitats for particular species;
    • Building sea-walls/dykes to prevent the influx of rising sea levels into low-lying terrestrial habitats;
    • Riverine management and other water conservation or drainage measures to reduce impacts of increased drought or flooding;
    • Artificial removal of invasive species;

    • Planting of new forests or re-afforestation, currently being promoted as a means of sequestrating global carbon dioxide, could be utilised to encourage biodiversity conservation in new areas;
    • Expansion of the protected areas network and creation of wildlife corridors to allow natural species migration;
    • Translocation of species, especially where these are prevented from natural movements by landscape configuration or natural ability to migrate;
    • Habitat creation in new areas;

    • Managed retreat from coastlines, allowing natural processes to operate within the framework of rising sea levels;
    • Allowance of natural 'succession' of communities, including processes of desertification, inundation and migration.

  1. References Cited

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    Malcolm, J.R.and A. Markham, (2000), Global warming and terrestrial biodiversity decline. World Wild Life Fund, Gland, Switzerland, 34pp.

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