Current and emerging priority issues for environmental research: freshwater resources, coastal zones, biodiversity, vulnerability of ecosystems, impacts of climate change, impacts of land use, natural hazards.
Chair: Jerry M. Melillo President, SCOPE;
Session co-ordinator: Veronique Plocq Fichelet Executive
Director, SCOPE, France
Global problems related to biodiversity
Public awareness about the accelerated loss of species at both the local and global scales has increased in the last decade, and has crystallised in international consensus about the relevance of the subject. The most important such consensus is represented by the Convention of Biodiversity (CBD), which together with the Convention on Climate Change have become key components of the international agenda on global environmental issues, triggered by the 1992 Rio de Janeiro meeting.
The CBD recognises clearly that the conservation of Biodiversity, as well as the factors that threaten it, are problems that transcend economic, political, religious and cultural frontiers (UNEP, 1992). They also transcend the merely quantitative aspect of the loss of species belonging to many different taxonomic groups in a certain region, which in it constitutes a very important issue. It expands both to a Global scale problem and to a variety of factors fundamental for maintaining life as we know it, for us and for the rest of organisms with which we share this Planet.
All those factors are linked and dependent on the biological diversity which composes the variety of ecosystems of the world, either natural or man-made, often in ways which make them difficult to be understood and predictable. Additionally, the complexity of those factors is not limited to the realm of the bio-geo-physical sciences, but includes in a very central way, intricate social issues.
Human activity is causing changes in the environment which, directly or indirectly are causing the extinction of scores of species in both terrestrial and aquatic systems at a rate that, if it is maintained, will represent the most severe process of extinction in the recorded history of our planet since life developed in it. The most serious loss, besides that of taxa, is the loss of the multiple and fundamental services, which the ecosystems formed by the complex interactions of those species, provide to mankind. These processes of ecosystem loss are presented and discussed.
The second most important factor in the loss of Biological diversity at a Global scale is the accidental or purposeful introduction of exotic species which become aggressive invasive in the new areas they are introduced, causing besides the disappearance of populations and entire species, enormous economic hardship. The factors involved in this process are presented and discussed.
The environmental consequences
Carlos Cerri Universidade de São Paulo, Brazil
At the close of the twentieth century, there are approximately 3,5000 million hectares of forest in the world. Of this total forest area, 2,000 million hectares are found in tropical regions (FAO, 1997).
Tropical forest offers a very wide range of highly valuable services. To illustrate, the forest serves important watershed and climate control functions, especially in regulation of stream flows by intercepting rainfall, absorbing the water into the underlying soil, and gradually releasing it into the streams and rivers of its watershed. The forest absorbs albedo (reflectivity of the sun's rays) from the sun, and stores a sizeable share of the world's carbon. Forests absorb atmospheric carbon and replenish the oxygen in the air we breathe. The tropical forest is the most important source of biodiversity on earth. They are the home to 70 percent of all the earth's species (Roper & Roberts, 1999). Industrial wood products account for US$ 400 billion worth of global production. Tropical forest account for approximately 25 percent of this production (WCFSD, 1998). Undisturbed tropical forests furnish essential foods, clothing, and implements for indigenous forest people.
Deforestation is the permanent loss of forest to other land uses such as agriculture, grazing, new settlements, infrastructure, and dam reservoirs (WCFSD, 1998).
At the present time, 14 to 16 million hectares of tropical forests are being converted to other land uses, mostly agricultural. FAO (1997) has estimated the annual rates of deforestation in developing countries at 15.5 million hectares for the period 1980-1990 and 13.7 million hectares for 1990-1995. The total forest area lost during the 15-year period was approximately 200 million hectares. The tragedy lies in the fact that most of these deforested lands are not suited for long-term farming or grazing and they quickly degrade once the forest has been cut and burnt (Roper & Roberts, 1999).
The principal agents of deforestation, those individuals who are cutting down the forests, include slash-and-burn farmers, commercial farmers, cattle ranchers, livestock herders, loggers, commercial tree planters, firewood collectors, mining and petroleum industrialists, land settlement planners, infrastructure developers and others.
The predisposing conditions that favour deforestation include poverty, greed, and quest for power, population growth, and illiteracy. The indirect causes of deforestation include inappropriate government policies, land hunger, national and global market forces, and the undervaluation of natural forests, weak government institutions, and social factors. The more visible direct causes of deforestation include the land uses that compete with the natural forests (e.g. agriculture, ranching, infrastructure development, and mining and petroleum exploration). Logging, fuelwood collection, and tree plantations also have a role in the deforestation phenomena.
In some cases, deforestation can be beneficial. Given the right mix of social needs, economic opportunities, and environmental conditions, it can be a rational conversion from one type of land use to a more productive one (Roper & Roberts, 1999).
The economic and environmental consequences of deforestation are profound, making it one of the most critical issues facing our global society. In economic terms, the tropical forest destroyed each year represent a loss in forest capital valued at US$ 45 billion (WCFSD, 1998). Tropical deforestation is a major component of the carbon cycle and has profound implications for biological diversity. Deforestation increases atmospheric CO2 and other trace gases, possibly affecting climate (Bruce ET al., 1999). Conversion of forests to cropland and pasture results in a net flux of carbon to the atmosphere because the concentration of carbon in forests is higher than that in the agricultural areas that replace them. The paucity of data on tropical deforestation limits our understanding of the carbon cycle and possible climate change (IPCC, 1998). Probably the most serious and most short-sighted consequence of deforestation is the loss of biodiversity. Deforestation affects biological diversity in three ways: destruction of habitat, isolation of fragments of formerly contiguous habitat, and edge effects within a boundary zone between forest and deforested areas. This boundary zone extends some distance into the remaining forest. In this zone there are greater exposure to winds; dramatic micrometeorological differences over short distances; easier access for livestock, other nonforest animals, and hunters; and a range of other biological and physical effects. The result is a net loss of plant and animal species in the edge areas (Roper & roberts, 1999). The long-term impact of deforestation on the soil resource can be severe. Clearing the vegetative cover for slash and burn farming exposes the soil to the intensity of the tropical sun and torrential rains. This can negatively affect the soil by increasing its compaction, reducing its organic material, leeching out its few nutrients available, increasing its aluminium toxicity of soils, making it marginal for farming. In many cases, political decision-makers knowingly permit deforestation to continue because it acts as a social and economic safety valve.
While it is impossible to stop deforestation in the foreseeable future, there are many opportunities for bringing it under control and minimising its negative impacts. Alternatives include the protection and management of remaining forests socio-economic development in rural areas, and policy and institutional reforms.
Water resources for human use:
María Concepción Donoso Director
Water promises to be the single most important issue in the coming century. It will engage development leaders, activists and critics all in the next decades. Of all the water that exists on earth only 2.5% is not sea or salt water, of which 0,3% is available in lakes and rivers. Therefore, as far as human use is concerned, less than 0.08 of 1 per cent of all of the water on the planet is considered freshwater. The amount and distribution of freshwater in space and in time, varies considerably at a global scale. Some regions experience an annual rainfall of over 2000 mm, evenly distributed throughout the year, while others barely reach a few millimeters. However, a vast majority of the countries suffer frequently from a distinct seasonal pattern, where precipitation reaches extreme high amounts during the wet season, serious water shortages and droughts may occur during the rest of the year. Anomalous precipitation patterns, in the form of extremely severe drought or excessive rainfall, are modulated by climate variability. Complex air-sea-land interaction processes regulate climate variability at different global scales. Climate variability is a natural phenomenon and humanity has to deal with it. The negative impact of droughts or excess precipitation can be increased due to human activities. Anthropogenic processes put additional stress on water resources. Overpopulation, together with extensive agriculture, industrialization, and soil erosion due to changes in land cover, are the major man-induced stress agents on water resources in the region. Consequently, a comprehensive integrated water management system is extremely difficult to develop and to implement at a global scale.
In the next century, a priority objective in Science is to acquire better understanding of the air-sea-land interactions that dominate climate variability at global and regional scales. The sometimes severe repercussions of these interactions stresses the need for assessing their impacts while improving our knowledge of the complex mechanisms that control these physical processes. One of these interactive processes is the El Niño (also known as El Niño - Southern Oscillation, or ENSO), and its counterpart La Niña (also known as the cold ENSO phase). The present work focuses on the effect of El Niño and La Niña on water distribution and availability for human use, with especial emphasis on the 1997-1998 El Niño event. and the 1998-1999 La Niña phase. Assessment is performed on the effects of these climatic events on crucial economic sectors, such as health, agriculture, energy, and others Water is the linking element that dominates the activity of all these sectors. Finally, an overview of the political and social consequences of these impacts is presented.
Global climate change and cycling of toxic metals
This presentation will explore the relationships between and global climate change (GCC) and the cycling of toxic metals in the environment. Among other things, GCC is expected to result in (a) an increase in the amount of UV-B radiation reaching the earths surface, (b) a change (increase) in temperature of the atmosphere and earths surface, and (c) a change in the hydrological regime, especially the incidence of catastrophic weather incidents such as floods, storms and droughts. These changes will link GCC to heavy metal cycle in many ways. (I) For some metals (especially mercury), the ratio of emissions from industrial sources and natural processes (sources) is expected to change; GCC may also change the current deposition pattern and can result in further dispersion of already deposited toxic metals. (II) Sites around the world are heavily contaminated with mercury (including abandoned gold and silver mines and chlor-alkali plant graveyards) and a change in climate may lead to increased exhalation of mercury from these so-called "chemical time bombs". (III) Many natural and anthropogenic sources emit toxic metals in forms that can undergo photochemical reactions in the atmosphere. For instance, the removal of mercury from the atmosphere is driven by the formation of reactive Hg(II) species by direct and indirect photochemical processes which are temperature-dependent. GCC can thus alter the current deposition pattern for atmospheric mercury in many parts of the world. (IV) Global climate change is expected to trigger an increase in rates of biogenic production and release of volatile metal compounds, especially the methylated compounds of mercury, arsenic, selenium and lead which are more readily taken up by the biota. (V) Increased remobilization of previously deposited pollutant metals may convert some areas (such the northeastern region of the United States) from being a sink to an area source of toxic metals. (VI) Bioaccumulation of toxic metals by fish is closed linked to production of dissolved organic carbon (DOC) and water temperature, and these habitat characteristics are strongly influenced by GCC. (VII) Extensive flooding of coastal and low-lying areas would exert a drastic influence on the mercury cycle by increasing the efficiency and rates of mercury methylation as well as the levels in water, zooplankton, benthic invertebrates and fish in the newly formed bodies of water. The downstream effects of the flooded areas may expose a significant fraction of the rich fisheries resource of many coastal areas to risk of mercury contamination. (VIII) In temperate lakes, changes in food chain structure and function tend to be non-linear so that small changes due to climate may result in rapid and drastic changes in bioaccumulation rates. (IX). Tropical and arctic ecosystems are particularly sensitive to heavy metal pollution. Because of the unique features of the food web, top predators of tropical and arctic ecosystems are more vulnerable to heavy metals compared to temperate species, and global warming can further exacerbate the exposure of the most sensitive organisms to toxic metal pollutants.
Human activities have changed the natural biogeochemical cycle of toxic metals in many ecosystems. The presentation will show that global climate change can increase the risk of exposure of many people to toxic metals by changing the forms as well as the remobilization and bioaccumulation rates of this class of pollutants.
The role of the oceans in global climate change
John C. Field
One of the challenges facing oceanographers at the turn of the millennium is predicting the nature and consequences of global warming. The enormous heat capacity of the oceans and their huge capacity to store dissolved CO2 are important characteristics. Understanding the role of the oceans is therefore central to predicting global change. This talk highlights a few of many factors and unknowns involved in predicting future scenarios in the ocean. Transport of CO2 in the oceans is strongly influenced by the physical "solubility pump" whereby the solubility of gases such as CO2 increases in seawater as it is cooled in winter at high latitudes. The prime site is in the Arctic North Atlantic where Atlantic Deep Water is formed by convective sinking of the cool, denser water, taking with it newly dissolved atmospheric CO2 . This forms the basis of the deep ocean thermohaline circulation, which takes of the order of a thousand years to complete its slow conveyer belt circulation through the ocean basins and back up to the surface, sequestering CO2 from the atmosphere for many centuries. This has now been shown to have varied strongly (possibly even reversed) between the ice-ages and interglacial periods. The changes in this circulation pattern have not happened gradually but suddenly, as if triggered at a threshold. This has profound implications for the storage of the anthropogenic CO2 accumulating in the atmosphere. The biological pump, based on sinking of organic matter produced by phytoplankton, depends on the physical environment and the supply of nutrients to the sunlit surface ocean. Until recently, nitrate was assumed to be the main limiting nutrient in the oceans but it has been convincingly shown that vast areas of the Equatorial Pacific, the temperate northern Pacific and now the Southern Ocean, are limited by the supply of trace amounts of iron, not nitrate. It is suggested that many coastal areas, and ocean areas downwind of deserts, are not iron limited because of the aeolian transport of iron in the dust blown off the land and into the oceans, e.g. the North Atlantic is largely fertilized by the Sahara Desert. Thus the activity of the biological CO2 pump may be strongly influenced by other elements, including trace elements, in a strongly non-linear fashion, making prediction very difficult. The situation becomes more complicated when one considers that the composition of biological communities of organisms is strongly influenced by small changes in their physical and chemical environment. Dimethyl sulphide (DMS) is the major naturally-produced source of sulphur to the atmosphere. DMS produces aerosol particles which affect the radiative properties of stratus clouds, with a strong cooling effect on climate, thus damping global warming. DMS production in turn depends on the composition of phytoplankton communities in surface waters, which is sensitive to their environment. Climate models, which include aerosols, have performed better than those that do not have.
Natural hazards of geological origin
A geologic hazard is a potentially destructive agent -- a process or an event -- whose direct interaction with the material environment could cause harm to man and his investments. Geologic events such as earthquakes, volcanic eruptions, landslides and tsunami are, in reality, normal earth processes that have been occuring and recurring even before historic time. These events or processes are manifestations of natural forces at work, indications that our Planet Earth is alive and dynamic. They have become hazards and thus a risk to people, properties and infrastructures because people have chosen to build settlements and structures on sites likely to be impacted by these phenomena on flat terrains, near the coasts, at river mouths, at the bases of mountains, on the slopes of active volcanoes, or in areas traversed by or near active faults.
Almost all types of geologic hazards occur in the Philippines. Just by looking at the geologic map of the archipelago, one finds proof of the reality of these hazards in the physical presence of their generators active and potentially active volcanoes, criss-crossing, active and potentially active faults, steep slopes, active subduction zones, trenches, and others. Moreover, in view of its geographic location, being near the equator and the edge of the Pacific Ring of Fire, the Philippines has also been the object of some foreign-sourced geologic hazards.
The magnitude 7.8, July 16, 1990, Northern Luzon earthquake generated a 125 km long ground rupture with maximum horizontal displacement of 6.6 m and vertical displacement of 2.0m. Strong ground shaking caused many buildings to collapse or sustain heavy damage and triggered shallow landslides in the mountainous regions and liquefaction in the coastal areas and fluvial environs of Central Luzon. The combined effects of surface faulting, ground shaking, landslides, liquefaction and lateral spreading took a toll of 1200 lives and more than P18 billion in actual damage to properties and infrastructures and losses in agricultural and industrial production. The Pinatubo Volcano eruption in 1999 is one of the worlds most violent and destructive eruptions of this century. Pinatubos major eruptive episodes on 12-16 June 1991 spewed out some 7 cu km of pyroclastic flows and about 3 cu km of ashfall. The powerfully ejected and tall eruption plumes reached well into the stratosphere and affected global climate. The huge volume of pyroclastic flow deposits buried and rendered uncultivable agricultural lands and agro-forest farms. Continuous heavy rains later remobilized these ashfall and pyroclastic flow deposits into another destructive agent - which in turn inundated, buried and/or destroyed more agricultural lands, settlements and infrastructures. Casualties directly attributed to the eruption are few less than 300, but the environmental and economic impacts are considerable and are still being felt as Pinatubo lahars continue to plague the country.
Human-induced changes in the global nitrogen
During the last half of the 20th century human activities have resulted in approximate doubling the rate of production of biologically available, ìfixedî nitrogen on a global basis (Vitousek, P. et al., 1997. Ecological Applications 7: 737-750). This is the result of the increases in the manufacture of chemical fertilizers to support the needs of agricultural production, the combustion of fossil fuels that released fixed-nitrogen into the atmosphere, the planting of nitrogen-fixing crops (legumes and rice), and the mobilization of N from long-term biological storage pools. Much of this has occurred in developed nations in which there is intensive use of industrial fertilizers and large releases of nitrous and nitric oxides into the atmosphere that ultimately fall to the Earthís surface. There, the rate of fixed N input to the terrestrial N cycle has increased 5-20 fold (Howarth, R. et al., 1996. Biogeochemistry 35:181-226). The rapid increase in fixed N has greatly outpaced the rate of human population growth, release of CO2, and deforestation.
The consequences of this substantial human alteration of the global N cycle include not only the dramatic increase in the worldís agricultural production but also: increased release of nitrous oxide (N2O), a greenhouse gas; formation of photochemical smog; losses in other soil nutrients, such as calcium and potassium; acidification of soils, streams and lakes; increases in the quantity of organic storage in some ecosystems; loss of biodiversity, especially plants and microbes adapted to efficient use of nitrogen; and increased transfer of bioavailable N via rivers and the atmosphere to coastal waters.
The increased loading of N to estuaries, bays and continental shelf environments has resulted in major changes in these ecosystems, including increased organic production (eutrophication), algal blooms that decrease water clarity and may otherwise be harmful, loss of seagrasses and coral reefs due to shading and overgrowth, depletion or elimination of dissolved oxygen in bottom waters, and losses in fishery production. Not only have restricted estuaries and lagoons been affected, but ecosystems of open continental shelf waters that receive substantial riverine inputs from agricultural or heavily populated regions have been greatly altered since the 1950s. These include the northwest shelf of the Black Sea, into which the Danube among other rivers drains, the northern Adriatic Sea, the Baltic and North Seas, and the Gulf of Mexico off of the Mississippi River. Based on the growing use of industrial fertilizers in the developing world, particularly south and east Asia, similar problems are anticipated. Through more efficient application of fertilizers and the restoration of aquatic ecosystems that serve as a sink for fixed N, returning it to the atmosphere as nonreactive N2, N loadings to coastal systems can be halved without loss of agricultural production.