Biodiversity

Introduction

Disharmonic Biota

Research on islands has long played a fundamental part in developing our basic understanding of ecology and evolution. Both Darwin's and Wallace's insights into evolution and speciation were shaped by studies on islands (Darwin 1859 Wallace 1881). It is no coincidence that Darwin felt close to that great fact - that mystery of mysteries - the iirst appearance of new beings on this earth in the Galapagos (Darwin 1845). Even today, the Hawaiian drosophilids provide a primary standard for analyses...

Biodiversity Of Mangroves

Mangrove Ecosystem Structure

Biodiversity is usually defined at three levels, i.e. species, populations and ecosystems (Ray and McCormick 1992). The term biodiversity components has been recommended as an ecological reference to these several hierarchical levels, and the idea is particularly appropriate to describe tropical estuarine ecosystems (Yanez-Arancibia et al. 1994). Biodiversity components of tropical estuaries can refer to the high diversity of species, life histories, habitats and links in food webs, or the...

References

Anderson, R.H., Buys, B. and Johannsmeier, M.F. (1983) Beekeeping in South Africa. Department of Agriculture, Bulletin No. 394, Pretoria. Arianoutsou, M. and Groves, R.H. (Eds) (1993) Plant-Animal Interactions in Mediterranean-Type Ecosystems. Kluwer, Dordrecht. Aschmann, H. (1973) Distribution and peculiarity of Mediterranean ecosystems. In Di Castri, F. and Mooney, H.A. (Eds) Mediterranean-Type Ecosystems. Origin and Structure. Springer, Berlin, Heidelberg, New York, p. 11-19. Atkins, L. and...

Biodiversity controls on nutrient cycling and soil processes

Natural communities have been selected to withstand a wide range of environmental perturbations such as wetting-up after the dry season, intense rain storms, tree throw, synchronous litter falls and outbreaks of defoliating insects. With the exceptions of extreme events such as hurricanes and wildfires, the effects of these events are buffered by the system and have negligible long-term consequences for the sustainable production of the system. In contrast, high-intensity short-rotation...

Conclusion biodiversity and ecosystem function from genes to regions

To conclude, we have identified how biodiversity, from genes to regions, may alfect ecosystem function in coral reefs. At a single reef, diversity in the life-history characteristics of reef biota, both within and among species, provides the basis for occupancy and survival in the broad range of environments that the reef provides. The diversity of a reefs zones is essential to the maintenance and accretion of the overall structure itself, and of its protein resources. Each zone's...

Environmental Gradients In Tropical Forests

Gradients in moisture, soil fertility and elevation constitute the most important variables in tropical forest environments. Changes in any of these environmental attributes are likely to affect the performance of functional groups or to cause shifts in the relative abundance of functional groups within tropical ecosystems. In tropical regions, annual rainfall varies from near zero in the Atacama Desert in northern Chile, and a few centimeters in the Guajira Peninsula of northern Colombia, to...

Humaninduced Changes And Their Effects On Biodiversity And Ecosystem Function

Climate warming The anticipated warming from atmospheric loadings of radiatively active gasses is probably the greatest threat to the boreal region worldwide. Although the global circulation models disagree on the details of the extent of warming and drying, all agree that the greatest warming will take place in high-latitude regions, and most agree that mid-continent areas will become drier while maritime areas will become wetter (Schlesinger and Mitchell 1985). Climate warming will affect the...

Concluding Remarks

Humanity needs to protect and nourish tropical forests for many reasons. Without implying that we think other reasons are less important than the ones we discuss here, we direct attention to those components that derive from the biological complexity of tropical forests. Because of their complexity, tropical forests have an extremely high information content. This information resides in the genomes of the individual species, the interactions among them, and the resulting ecosystem patterns and...

Trophic roles

The primary producers of coral reefs are extremely diverse. Like most shallow hard and sandy substrata throughout both tropical and temperate seas, they are inhabited by all the major algal groups (benthic micro- and macro-algae, coralline algae), and commonly by seagrasses. What sets coral reefs apart are the sj'mbiotic zooxanthellae, the single-celled, dinofiagellate algae of many species (Trench 1987 Rowan and Powers 1991) which live within the cells of many animal calcifiers (notably...

Predictive Capability And Prospects For Learning

How generally predictable are the effects of stress on freshwater ecosystems We chose to test this question by focusing on Chilean ecosystems and their potential stressors. We attempted to develop a series of predictions for these Southern Hemisphere ecosystems. 12.3.1 Characteristics of Chilean lakes The Lake Region in southern Chile, South America, contains large (50 to 870 km2) and deep (up to 350 m maximum depth) lakes. The basins around most of these lakes have some deforested areas that...

Impacts Of Changes In Biodiversity Upon Ecosystem Function

The previous section presented a conceptual model of the effects of changes in biodiversity on ecosystem function. This sections summarizes experimental evidence for this relationship. We organized this section according to different ecosystem processes, such as primary production, decomposition, water distribution, atmospheric properties, landscape structure and biotic linkages. Our use of the term ecosystem processes includes not only water, energy and nutrient cycling, but also atmospheric...

Contributing Authors And Affiliations

David Beilwood Department of Marine Biology, James Cook University, School of Biological Sciences, Townsville, Qld. 4811, Australia. John Benzie Australian Institute of Marine Science, PMB No. 3, Townsville MC, Qld. 4810, Australia. Charles Birkeland Marine Laboratory, University of Guam, UOG Station. Mangilao 96923, Guam, USA. Jorge Cort s C1MAR, University of Costa Rita, San Pedro, Costa Rica. Chris D'Elia Maryland Sea Grant College, 0112 Skinner Hall. University of Maryland, College Park, MD...

Freshwater Ecosystems Linkages of Complexity and Processes

PERSSON, M. POWER AND D. SOTO 12.1 INTRODUCTION 12.1.1 Uses of Freshwaters Freshwater ecosystems are indispensable for life. Unlike some resources, there is no substitute for water. Its availability influences the distribution of Earth's major biomcs and the productivity of agriculture. Historically, fresh-waters have been a magnet for human settlement. Important human uses of freshwaters include drinking, fishing, industry, irrigation, recreation and transportation...

Characteristics of strong interactions

Strong interactors have several characteristics that enable them to exert substantial control over ecosystem processes. Some taxa have the ability to track and constrain fast-growing resources. This ability may derive from behavioral capacities, a steep or non-saturating functional response, or a rapid numerical response. Strong interactors typically have broad diets that enable them to prey on and constrain entire functional groups of taxa. Many strong interactors are able to survive periods...

Maintaining Biodiversity Of Freshwaters

From an ecosystem perspective, the reason to preserve biodiversity is to preserve options for the future. The environment is certain to change because of natural fluctuations in the physical forcing of the biosphere and large-scale anthropogenic effects. We cannot predict which building blocks will be essentia for maintaining ecosystem or landscape processes in future environments. It is prudent to preserve taxa that may be crucial for ecosystem processes under new conditions. At a large scale,...

Summary

In freshwaters, ecosystem processes are linked to biodiversity at several levels. Biodiversity of terrestrial landscapes affects erosion and the flow of silt and nutrients to freshwater systems. Within lakes and streams, species interactions can lead to massive changes in ecosystem components and processes. In other cases, species replacement dampens the response of ecosystem processes to stress. Despite many intriguing examples of connections between biodiversity and ecosystem processes, our...

Vulnerability Of Biodiversity In Tropical Estuaries

A 1991 workshop on the status of mangroves of Southeast Asian coastlines (Sasekumar 1993) reported that the region has lost large areas of mangroves in the Philippines (80 ), Thailand (50 ), Indonesia (50 ) and Malaysia (32 ). This pattern is likely to continue as greater demands are placcd on forest and fishery resources, along with land-use changes along coastlines and in upland watersheds the result will necessarily cause a change in the ecological characteristics of tropical estuaries. Many...

Conclusions

Our effort was to explore the system-level consequences of human-caused changes in open-ocean biodiversity. Of the 15 biomes examined in the course of the SCOPE project, the open ocean is the most underdescribed. It is in many ways premature to describe ccosystem function when we have not become familiar with all of the components. Due to the taxonomic structure of marine assemblages, when an open-ocean creature is newly discovered there is a reasonable likelihood that an entire family, class...

Scope 1 Scope 2 Scope

Global Environment Monitoring, 1971, 68 pp (out of print) Man-Made Lakes as Modified Ecosystems, 1972, 76 pp (out of print) Global Environmental Monitoring Systems (GEMS) Action Plan for Phase I, 1973, 132 pp (out of print) Environmental Sciences in Developing Countries, 1974, 72 pp (out of print) Environmental and Development, proceedings of SCOPE UNEP Symposium on Environmental Sciences in Developing Countries, Nairobi, February 11-23, 1974, 418 pp (out of print) SCOPE 7 SCOPE 8 SCOPE 9 SCOPE...

Pelagicbenthic coupling export of benthic material to the benthos

Since photosynthetic primary production in the open ocean occurs only in the epipelagic zone, (he mesopelagic and abyssal zones are almost totally dependent upon down-transport of nutrients, with the limited exception of hydrotherma vent environments (Honjo 1980 Deuser et al. 1981 Lampitt 1985). Benthic biomass decreases with depth and distance from the coastal areas (Mcnzies et al. 1973 WolH 1977). There are three major processes by which nutrients are transported into abyssal waters. To some...

Nekton Bot Mail

Aber, J.D. and Melillo, J.M. (1982) Nitrogen immobilization in decaying hardwood leaf litter as a function of initial nitrogen and lignin content. Can, J. Bot. 60 2263-2269. Alexander, T.R. (1967) Effect of hurricane Betsy on the southeastern Everglades. Q. J. Flu. Acad. Sci. 30 10-24. Alongi, D.M. (1987a) Intertidal zonation and seasonality of meiobenthos in tropical mangrove estuaries. Mar. Biol. 95 447-458. Alongi, D.M. (1987b) The influence of mangrove-derived tannins on intertidal...

Mangrove Faunal Guilds And Ecosystem Function

Animal species co-occurring in mangrove forests can be separated into guilds characterized by the utilization of available resources (Ray and McCormick 1992). Fauna) guilds described in this section are basically resident species that exploit the habitat with different intensity in space and time, in contrast to the nekton guilds discussed below (Section 13.6). The utilization and exploitation of the mangrove habitat by faunal guilds, both resident and migratory, can contribute to the structure...

Program Publications

Baskin, Y. (1994) Ecologists dare ask How much does diversity matter Science 264 202- 203. Chapin, F.S. III. and K rner, Ch. (Eds) (1995) Arctic and Alpine Biodiversity Ecosystem Consequences in a Changing Climate. Springer, Berlin, 323 pp. Chapin, F.S., III., Schulze, E.-D. and Mooney, H.A, (1992) Biodiversity and ecosystem processes. Trends Eco. Evol. 7 107-108. Davis, G.W. and Richardson, D.M. (Eds) (1995) Mediterrean-Type Ecosystems The Function of Biodiversity. Springer, Berlin, 366 pp....

Water distribution and quality

Because water is the primary limiting resource for many organisms in arid systems, changes in the biota which translate into changes in water distribution or availability will be strong drivers of a change in state. One critical stage is the infiltration of water into the soil (versus its evaporation from the surface or its horizontal transfer or loss to run-off). Vegetative cover modulates the impact energy of raindrops, reducing the amount of sediment dislodged and transported during heavy...

Alteration Of Biodiversity And Its Impacts

Human activity has historically been less intense in arid lands than in some other regions, due to the harshness of the environment and constraints that water availability places on intensive agriculture and urban development. However, extensive grazing of livestock has been a pervasive and strong influence in many semi-arid and arid environments. More recently, technological developments facilitating the acquisition of water from below-ground have fostered intensive disturbance and human...

Energy flow

Energy captured by photosynthesis flows through ecosystems through many pathways, whose variety is correlated with the species richness of the system. Species richness could influence the rates and quantities of energy flowing through the system in a number of ways. Primary productivity and biomass accumulation Primary productivity of tropical forests is apparently affected by plant species richness only at levels far below those that characterize most mainland tropical forests (Vitousek and...

Mte Research And The Global Forum

Critics sometimes argue that funding of, and attention to, MTE research is disproportionate because they occupy only about 2 of the Earth's land surface according to Koppen Cs climate zones (M ller 1982), or less than 1 using the more narrowly circumscribed definition of Aschmann (1973). This supposes that importance is a linear function of area, which implies that the collective GNP of all MTEs is approximately 4 that of the USA (Europa World Yearbook 1994). MTEs, however, have some...

Oceanatmosphere coupling

The physical structure of the ocean is of obvious importance to all pelagic organisms. Less visible, but no less important in the long run, are feedback relationship between living organisms and atmospheric processes. In a controversial but provocative calculation. Takahashi 1989) proposed that the oceans account for more than twice the amount of C02 removed from the atmosphere than terrestrial systems. In fact, there are serious problems with many recent estimates of carbon flux, although most...

Agroecosystems

On simplification and substitution Agroecosystems provide a particularly good example of how we have substituted the services provided by natural ecosystems for those provided by organisms of particular interest to humankind. It would seem, on the face of it, that comparisons of the diversity-function relationship would be easy between natural and managed ecosystems. However, in agroecosystems, no matter how simple or intensive, the services lost, such as nutrient and water regulation, are...

Atmospheric properties and feedbacks

Arid lands are significant determinants of the earth's albino and thus of its global radiation balance. Albedo and spectral characteristics of the surface are influenced not just by total plant cover, but also by the different properties of woody plants versus grass cover, so changes in plant functional group affect this global property. Arid lands are also significant contributors of dust (Pewe 1981 Pye 1987), which influences both the radiation balance of the atmosphere and the transport of...

Microbial Processes And Ecosystem Function

The biodiversity of microbial communities in mangrove ecosystems is poorly documented, but the biomass and metabolism of this guild is well established for tropical intertidal environments (Fell and Master 1980 Newell et al. 1987 Alongi 1988, 1989 Alongi and Sasekumar 1992). The microbial ecology of mangrove sediments and its influence on ecological processes, particularly decomposition, has been related to the chemical diversity of mangrove leaf litter (Benner and Hodson 1985 Benner et al....

Effect Of Species Diversity On Ecosystem Function

We now explore how changes in species diversity affect ecosystem function in order to test our null hypothesis. For this purpose we make use of natural and unplanned human experiments involving the addition and or removal of plant and animal species from natural savanna ecosystems. 8.4.1 Invasion of South American and Australian savannas by African Several species of African grasses (such as Hypharrenia rufa, Melinis minuli-flora and Panicum maximum) have becomc naturalized in the South...

Complexity And Ecosystem Processes In Fresh Waters

Biodiversity applies not only to species, but also to ecological variety at many levels, including genotypes, ecosystem types on the landscape or biogeochemical pathways (Jutro 1993). It is obvious that ecosystem processes and the features that humans desire in systems (including ecosystem services Ehrlich and Ehrlich 1981) are linked with much broader aspects of diversity. Examples include the genetic diversity of fish stocks, biochemical diversity of microbial transformation pathways, and the...

Disturbance And Grassland Biodiversity

Disturbance is such an intrinsic property of grassland ecosystems that it could be argued that the true disturbance is a lack of disturbance. It has been suggested that degradation of Australian grasslands may be as much a consequence of improper fire regimes as of overstocking (WCMC 5992), and the trcelcssness of North American prairies was due in significant part of both lightening-causcd and Amerindian-set fires (Sauer 1952). Perhaps rather than characterizing environmental fluctuations in...

Archipielago De Jambeli

Ecuador Mangroves

Figure 13.9 Photointerpretation of land use in (he southern coastal province of El Oro. Ecuador, based on SPOT image of 1987. Dark blue represents shrimp ponds and lighter blue estuarine waters, while different heights of mangroves are presented in green, brown and grey Figure 13.9 Photointerpretation of land use in (he southern coastal province of El Oro. Ecuador, based on SPOT image of 1987. Dark blue represents shrimp ponds and lighter blue estuarine waters, while different heights of...

Carbon pathways reef function and reef degradation

The essential functional characteristics that distinguish coral reefs from other ecosystems are illustrated in Figure 15.3a. (A representation of the enormous network complexity, not represented here, is provided by Johnson et al. 1995.) Photosynthesis by diverse plant forms (from unicellular dinoflagellates to fleshy macro-algae and coralline crusts) fixes carbon into compounds which are directed into pathways that are primarily bioconstructional (arrows 1 and 2) or trophic (arrow 3) in...

Characterization Of Biodiversity In Arid Lands

We define biodiversity as the number, and the identity or composition, of biological units at different scales the genetic, the species, the guild and functional group, and the ecosystem and landscape levels. Genetic diversity is the diversity of genetic characteristics or features within a biological species. Species diversity, the number and composition of taxa present at a site, is the most frequently considered aspect of biodiversity (although it can be difficult enough to assess, as we...

Human Impacts On Biodiversity Of The Open Ocean

Cognitive Model Ocd

Biodiversity and ecosystem processes are intertwined in a tangled web with complex feedback loops. Changes in one aspect of biodiversity, loss of a top predator for example, will affect some aspect of the food web, which can then lead to changes in other biodiversity and ecosystem processes. Figure 16.5 summarizes the idea that human impacts interact to change biodiversity in Figure 16.5 A conceptual relationship between anthropogenic impact on biodiversity and subsequent effect on ecosystem...

Stability And Species Richness

Discussions of the degree and causes of stability are frequently hampered by vagueness and inconsistency about what is meant by stability (Orians 1975). Stability may simply mean constancy, that is a low level of variation in some measurable property of the system. Stability may also refer to the resistance of the system to alteration by external perturbations (inertia), its speed of return to initial conditions following a perturbation (elasticity or resilience), the domain over which it...

Niche breadth

Consumer Engagement Vivek Model

The epipelagic world is more variable over small spatial and temporal scales, containing generalists with broad diets which are widely distributed in their biogeographic region (low among-region diversity Angel 1993 McGowan and Walker). Broad niche structure among pelagic species does not imply that the niches are overlapping, i.e. that there is high species redundancy. For some marine groups, e.g. cetaceans, the lack of functional redundancy is fairly obvious each species is highly distinct,...

Productivity and nutrient regeneration in the benthos

Limited in scope, chemosynthesis-driven hydrothermal vents are one benthic system which is rich in life. Alternative sources of energy provide the grist for flourishing communities of bacteria worms and molluscs. Hydrothermal vents are deserving of much greater attention than can be devoted here. Most other open-ocean benthic communities are food- rather than space-limited, unlike so many shallow water marine systems. The full functional significance of this difference has yet to be...

Agricultural intensification

The concept of agricultural intensification describes the changes in agroeeosystem structure, functions, management practices and purposes during evolution and change from traditional to modernist forms. The change most directly related to our present concerns is an increasing specialisation in the plant and livestock species that are cultivated (Figure 11.1). Specialisation is associated in the modernist mind with increased efficiency of production, although this is scientifically...

Biodiversity And The Design Of Agricultural Systems

In the last decade cortccrrts for sustainability have replaced the maximisation of productivity as the target for agricultural development. This has generated increased interest in agroecosystem design, a more holistic concept than the commodity-led technology development paradigm which has dominated the post-world-war period of agricultural development. The fundamental features of this sustainability agenda, are that productivity should meet the aspirations of the farmers and society, whilst...

Energy Flow And Material Processing Interfaces

Analyzing the functional significance of biodiversity is a difficult task because there are no widely accepted schemes for classifying functional groups, and no single classification can aggregate organisms appropriately for more than one major ecosystem process. In our analysis of tropical forests we use two major ecosystem processes - energy flow and materials cycling - as the primary basis for establishing junctional groups. We analyze these processes by examining interfaces at which most of...

Research Agenda

In this chapter we have explored the relationships between biological diversity and ecosystem functioning for moist forest, highlighting the shortage of information that is needed to assess biodiversity-ecosystem functional relationships. The shortage is even more dramatic for other types of tropical forests, which have not received the attention that has been directed toward wet forests. Dry forests, montane forests and wetlands are important types of tropical ecosystems. Because of their...

Relationships Between Biodiversity And Function In Agroecosystems

11.3.1 The issue of scale and functional domains The preceding sections provide a contextual framework within which the role of biodiversity in agroecosystems can be evaluated. There has been very little controlled experimentation in agroecosystems in which the effect of species number (or other features of biodiversity) on a specific function or set of functions has been directly examined. We therefore explore the nature of the relationships by means of brief descriptions of a number of...

The plant subsystem

One of the most common practices in tropical ecosystems is intercropping, i.e. the growing of two or more crops in the same field at the same time. A great deal has been written on intercropping and its effects in terms of relationships between biodiversity and function (e.g. Francis 1986 Vandermeer 1989). Intercrops are known to often, although not invariably, produce higher yields than sole crops (Figure 11.4 Trenbath 1976). Intercrops are also thought to reduce farmer's risk (Rao and Wtlley...

Landscape diversity and productivity

A loose global network of free market economies is the backdrop against which much of today's science is being done. Utility of system components is therefore usually a strong motivation for conservation. In the case of biodiversity, landscapes which offer a stable mosaic of opportunity for human exploitation are considered desirable and worthy of conservation, in the Mediterranean basin, humans have for hundreds of years derived sustained benefit from functional attributes of ecosystems, and...

Zooplankton

The analysis of Chilean lakes points out important uncertainties that could he reduced by targeted research. We do not know the critical loading level of nutrients that destabilizes lake ecosystems and impairs their use. The lakes can probably tolerate some enrichment, but how does risk rise with loading What are the implications of human population growth for water quality, and what steps are necessary to maintain nutrient loading below critical levels So far, aquaculture has reduced fishing...

Ecosystem Processes At Scales Of Whole Reefs And Zones

Forty years ago, Odum and Odum (1955) proposed that the high accumulation of biomass on coral atolls compared with the surrounding oceans depended on two factors (a) effective use of a non-limiting supply of solar energy, and (b) tight recycling of potentially limiting nutrients. Solar energy is fixed by the zooxanthellae within coral cells, by micro-aigae covering virtually every non-living surface, and by abundant macro-algae, turfs and corallines. By contrast, planktonic production is close...

Facilitators as links between humans biodiversity and ecosystem function

Three case studies illustrate reef turn-off caused by population fluctuations in echinoderm facilitator species. In the first, the turn-off appears to be rapidly reversible without human intervention in human time scales in the latter two, the situation appears to be irreversible, or at least much slower than expected. Crown-of-thorns starfish. In the 1960s and 1980s, populations of the crown-of-thorns starfish Acanthaster planci, for reasons unknown, increased by several orders of magnitude...

Replenishment of populations

Resilience is the ability of populations to replenish losses incurred as part of norma population fluctuations or as a result of exploitation or other human impact. Given the key functional roles of many coral reef' populations in bioconstruction and protein production, resilience benefits not only the individual populations concerned, but also the maintenance of key ecosystem outputs of framework and protein. However, resilience in a cora reef population is as much a function of the location...

Learning and adapting to surprise

The ecological changes likely to occur in Chilean lakes and the management actions to be recommended are consistent with experience in North Temperate lakes. This convergence may indicate global patterns of ecosystem change which suggest that general guidelines for management can be derived, and that we do not need to study each system as if it was unique. It seems likely that nutrient enrichment and salmonid introductions will cause Chilean lakes to resemble many mesotrophic lakes around the...

Soil structure and nutrients

Soils in arid lands are usually poorly developed, with little profile structure (Dregne 1976). Evaporation rather than leaching is the primary influence of water in the soil, at least for small or moderate rainfall events. Because most precipitation does not penetrate very far, biological activity (and thus organic matter and available nutrients) is usually concentrated near the surface. However, the surface is exposed to wind and water movement, which can dislodge and remove particles thus...

Summary Biodiversity Effects On Ecosystem Processes

Biodiversity plays a crucial role in moderating the harshness and unpredictability of the desert environment. Functional groups arc recognizable and conspicuous in their effects on ecosystem processes. Particularly vivid examples include the cffects of burrowing vertebrates and invertebrates on soil and hydrological properties, the influence of woody plants on the soil, microclimate and food resources for animals, and the distinct cffects of plants with different canopy architectures, rooting...

Global Impacts On Biodiversity In Coastal Regions

Coastal systems can be defined as the general marine region extending from the shore out across the continental shelf, slope and rise (Brink 1993). Other chapters in this volume focus on various portions of the coastal system (Twilley et al., Chapter 13 Done et at., Chapter 15). Our review of impacts on biodiversity considers coastal regions generally the latter portion of the chapter focuses more specifically on rocky iniertida and shallow subtidal communities where more complete information...

Addition and redistribution of chemical substances

The most recent review of ocean pollution concluded that most coastal areas arc contaminated, some extensively, but that the open occan is relatively unimpacted (GESAMP 1990). Despite apparent freedom from human impact, even distant oceanic ecosystems have traces of human activities (Flegal et al. 1993) no oceanic system is free from human influence. Pollution has impacted open-ocean systems through chemical discharges, toxic inputs (oil spills, ocean dumping of PCBs, heavy metals,...

Facilitating roles

In the long term, the persistence of a coral reef requires that its overall rate of mass and volumetric growth of framework equals or cxcecds losses to biological and physical erosion and transport of sediment away from the framework zones. Persistence is thus a function of benthic community structure as well as the vitality of associations between zooxanthellae and individual hosts. Mass bleaching can facilitate the switch between net accretion and net decay. This switch may also be mediated...

General Program Conclusions

The loss of genetic variability within a population of a species of a given area can reduce its flexibility to adjust to environmental change and narrow the options for adjustments to climate change, for example, as well as for rehabilitating specific habitats. 2. The addition or deletion of a species can have profound effects on the capacity of an ecosystem to provide services. We are beginning to develop the potential to predict which species these will be. They are those with unique traits...

Functional mechanisms of biodiversity

Ecological insights into system function, especially in terrestrial systems, arc widely recognized as difficult to obtain because of the connected nature of most ecosystems. Relationships involving only a small number of system components can usually be described, while the bulk of the system's functional attributes remain undetermined. Improving techniques in observation, experimentation and analysis arc, however, affording better and better opportunities for expanding quantitative knowledge...

Mediterranean ecosystems

On disturbance I diversity functioning It has been well documented that disturbance, at a moderate level, can promote diversity. In the Mediterranean basin, human-induced landscape variation - fields, pastures, scrublands and forests -- leads to high diversity at all levels as well as to multiple services to humankind. Even complex manipulation of ecosystems, such as in the dehesa agro-ecosystem in southern Spain, has provided a diversity of organisms and services and has been sustainable, at...

Addition and subtraction of species

Direct take in fisheries has had an immense impact on open-ocean food webs, virtually clearing many parts of the ocean of large predators and marine mammals. Of about 200 fisheries tracked by the FAO, fully one-third are severely depleted, and many are on the verge of collapsing, or have already collapsed, commercially. Many fisheries which were thought to be successfully managed for sustained yield prove to have experienced a scries of sequential collapses of different target species close...

Recommendations

Scientific research needs The scope of work needed to address the issue of ecosystem consequcnces of biodiversity in coral reefs is, in broad terms, similar to that identified for other marine ecosystems (Butman and Carlton 1993) (I) research on the determinants of species distribution and abundance, and (2) biology and ecology of species that play a pivotal role in the maintenance and generation of diversity as it relates to community and ecosystem function and stability. As in other...

Life history strategies resilience and resistance

In corals, diversity of coral growth form, life-history strategies, demographic performance, palatability, protective symbionts and strength of attachment have both phenotypic and genotypic bases (Veron 1986, 1995 Knowlton and Jackson 1994). Such diversity maximizes the chance that long-term accretion of framework will be achieved in the face of periodic disturbance (Connell 1978 Rogers 1993). The intermediate disturbance hypothesis (Connell 1978) holds that a low rate of disturbance allows...

Water quality and land runoff effects on biodiversity and ecosystem function

The water flowing onto a coral reef acts as a transport medium for materials (organic matter, nutrients, sediments, propagules - sec Section 15.3) which are beneficial when delivered at appropriate concentrations and frequencies, but may be deleterious when delivered in excess. Mechanisms for nutrient impacts on coral reefs Four mechanisms for nutrient impact on reefs are rccognised, although cause and effect have been difficult to establish unequivocally (Bell 1992). Should they reach a reef...

Opportunities For Research

Overall, we believe that islands can contribute to the analysis of biological diversity and ecosystcm function, and that wc could make better use of what they have to offer. Four important lines of approach are outlined below. 1. Make use of the striking natural gradients in diversity, in which diversity varies substantially and dircctionally under reasonably constant climatic and other environmental conditions, as a consequence of the remoteness or size of oceanic islands. Wc should set up...

Functional Groups

The number of species in all ecological communities, especially tropical ones, greatly exceeds the number of key ecological processes. We refer to the species that participate in a particular process as a functional group (Vitousek and Hooper 1993). Functional groups are inevitably fuzzy assemblages, but they constitute a useful operational basis for identifying groups of species with potentially similar effects on ecosystem-level processes. If the loss of a species results in a large effect on...

Model Of Savanna Function

The one common feature of all tropica savannas is climatic seasonality. The rhythm of the wet and dry seasons regulates the rhythm of growth and reproduction of the herbaceous and woody vegetation. This rhythm is driven by two major factors rain and fire (Fig. 8.3). Fire, taking place towards the end of the dry season, generates two pulses increased nutrient availability and high PAR radiation at ground level, both favorable to grass growth. The onset of rains represents the third pulse. With...

Landscape structure

Croplands have expanded dramatically during this century from 9.1 x 106 to lSxlO km2 (Richards 1990). This expansion altered landscape heterogeneity in grasslands. Habitat selectivity by domestic livestock has differentially influenced riparian ecosystems and therefore altered landscape diversity. Domestic livestock, and especially cattle, tend to congregate in the topographically lowest portions of the landscape (Senft et al. 1985 Pinchak et al. 1991). Such habitat selectivity has negative...

Conceptual Model

The relationship between biodiversity and ecosystem function in grasslands can be described by two general hypotheses (Lawton and Brown 1993) the redundant species hypothesis which states that species richness is irrelevant for ecosystem function (under existing conditions'), and the alternative hypothesis that each and every species plays a unique role in the functioning of the ecosystem. Experimental evidence does not support either of these extreme hypotheses. Most ecologists prefer a model...

Likely Responses To Global Change

Because some semi-deserts comprise diverse mixtures of plant growth forms and physiologies, changes in temperature, precipitation or the concentration of atmospheric C02 have the potential to alter photosynthetic performance and the relative abundance of C3, C4 and CAM pathway plants (Johnson et at. 1993). Alterations of the amount, the predictability and the seasonality of rainfall will have significant impacts on the nature of arid land ecosystems. For example, Striegl el ai (1992) pointed...

Introduction of nonnative plants

There are relatively few data on the resistance of arid lands to invasion of non-native species. One study (Fox and Fox 1986) found little difference among plant communities in the percentage of non-native species present (with the exception of high invasion rates in Mediterranean-climate regions), suggesting that arid communities are not likely to differ from any others in their susceptibility to invasion. At one Chihuahuan Desert research area, non-native plants make up about 3 of the species...

Effects Of Biodiversity On Ecosystem Processes

Ecologists often equate ecosystem processes with the average (steady-state) flow of energy and nutrients in undisturbed ecosystems. However, there is little reason to think that the process of natural selection which accounts for patterns of biotic diversity is tightly coupled to biogeochemical cycling. To persist, individuals that comprise populations and species must (1) reproduce, and to achieve this must (2) acquire resources to maintain themselves and produce biomass. In the process, they...

Arctic and Alpine Biodiversity Its Patterns Causes and Ecosystem Consequences

STUART CHAPIN, III AN ) CHRISTIAN KORNER Ecological changes altering the Earth System and the loss of biotic diversity that have been major sources of ecological concern in recent years. These processes have been pursued independently, with little attention being paid to the environmental causes and the ecosystem consequences of changes in biodiversity. The two processes are clearly interrelated. Changes in ecological systems cause changes in diversity. Unfortunately, we know much less about...

The Global Biodiversity Assessment

The SCOPE program was expanded somewhat following initiation by the United Nations Environmental Programme (UNEP) of a Global Biodiversity Assessment (GBA). In mid-1993, a group met in Trondheim, Norway, to prepare an outline of such an assessment. It was decided that the SCOPE effort (as well as other DIVERS IT AS components) would be incorporated into the GBA, as noted in the publications below. The GBA is intended to provide the scientific underpinnings for the Biodiversity Convention. The...

The Scope Program

The SCOPE program consisted of a series of activities between 1991 and 1994, culminating in an overall synthesis meeting at Asilomar, California, in 1994. The program was launched in October 1991 with a meeting on background issues held in Bayreuth, Germany. This meeting brought together ecologists and population biologists, both directed toward evaluating the consequences of human-driven disruption of natural systems. In particular, there was an examination of the degree of redundancy within...