Diversity Of Natural Systems Research Articles

Land and water systems: managing the hydrological risk

The paper suggests that the expansion of irrigated agriculture in the 20th century has de-coupled the water user from the inherent risk of exploiting both surface and groundwater resources. The apparent reliability of storage and conveyance infrastructure and the, relative cheapness and flexibility of groundwater exploitation offered by mechanised drilling and pumping have sheltered the end user from natural hydrological risk. The imperative for in-field irrigation efficiency has been effectively removed since the physical and economic management of the resource is determined by command area authorities or, in the case of some groundwater pumping, by the performance of power utilities, who have no direct interest in integrated resource conservation. As a result, the resource base has been degraded, and in some cases irreparable damage has occurred. It is argued that the rigidity of the resource management in many irrigation systems is not attuned to the inherent variability of natural systems upon which they depend. Further, the paper argues that irrigation management systems can work toward sustainability by spreading risk equitably, and transparently, amongst the resource regulators, managers and users. This has to involve a much more flexible approach to natural resource management that is conditioned not only by natural parameters, but also by the socio-economic settings. A range of examples highlights the variability and scale issues involved.

210Pb Atmospheric Flux and Growth Rates of a Microbial Mat from the Northwestern Mediterranean Sea (Ebro River Delta)

Environmental archives are needed to study the variability of natural systems and the impact of man on them. Microbial mats, modern homologues of stromatolites, can be found in extreme environments such as the Ebro River Delta and were studied as potential environmental archives of atmospheric deposition. {sup 210}Pb, a radiotracer widely used in geochronology studies, was used both to determine the growth rates of a microbial mat from this environment and to estimate the {sup 210}Pb atmospheric flux in the northwestern Mediterranean Sea. The {sup 210}Pb profile showed the presence of three distinct peaks related to low growth-rate periods. This variability indicted the sensitivity of the system to external forcing. The annual atmospheric flux of {sup 210}Pb was 81.2 {+-} 1.4 B1 m{sup {minus}2}yr{sup {minus}1}, which is similar to other values found in the literature. The age profile showed two layers of differing growth rates, being 0.99 {+-} 0.10 mm yr{sup {minus}1} from the surface down to 10 mm depth. The accumulated mass profile showed a change at about 9 mm depth, corresponding to year 1983 {+-} 1. It is noteworthy that this is coincident with a strong El Nino Southern Oscillation event during 1982--1983, which has been shown tomore » affect other ecosystems, including some in the Mediterranean area.« less

CAN THE ECOSYSTEM MIMIC HYPOTHESES BE APPLIED TO FARMS IN AFRICAN SAVANNAHS

The first ecosystem mimic hypothesis suggests clear advantages if man-made land use systems do not deviate greatly in their resource use patterns from natural ecosystems typical of a given climatic zone. The second hypothesis claims that additional advantages will accrue if agroecosystems also maintain a substantial part of the diversity of natural systems. We test these hypotheses for the savannah zone of sub-Saharan Africa, with its low soil fertility and variable rainfall. Where annual food crops replace the natural grass understorey of savannah systems, water use will decrease and stream and groundwater flow change, unless tree density increases relative to the natural situation. Increasing tree density, however, will decrease crop yields, unless the trees meet specific criteria. Food crop production in the parkland systems may benefit from lower temperatures under tree canopies, but water use by trees providing this shade will prevent crops from benefiting. In old parkland trees that farmers have traditionally retained when opening fields for crops, water use per unit shade is less than in most fast growing trees introduced for agroforestry trials. Strong competition between plants adapted to years with different rainfall patterns may stabilise total system productivity - but this will be appre- ciated by a farmer only if the components are of comparable value. The best precondition for farmers to maintain diversity in their agroecosystem hinges on the availability of a broad basket of choices, without clear winners or 'best bets'.

Florida Bay: A History of Recent Ecological Changes

Florida Bay is a unique subtropical estuary at the southern tip of the Florida peninsula. Recent ecological changes (seagrass die-off, algal blooms, increased turbidity) to the Florida Bay ecosystem have focused the attention of the public, commercial interests, scientists, and resource managers on the factors influencing the structure and function of Florida Bay. Restoring Florida Bay to some historic condition is the goal of resource managers, but what is not clear is what an anthropogenically-unaltered Florida Bay would look like. While there is general consensus that human activities have contributed to the changes occurring in the Florida Bay ecosystem, a high degree of natural system variability has made elucidation of the links between human activity and Florida Bay dynamics difficult. Paleoecological analyses, examination of long-term datasets, and directed measurements of aspects of the ecology of Florida Bay all contribute to our understanding of the behavior of the bay, and allow quantification of the magnitude of the recent ecological changes with respect to historical variability of the system.

Testing Species Phylogenies and Phylogenetic Methods with Congruence

We assessed the utility of congruence and multiple data sets to test species relationships and the accuracy of phylogenetic methods. The ongoing controversy about whether to combine data sets for phylogenetic analysis was evaluated against the naturalness of different types of data (as com­ monly recognized by systematists) and character independence. We defend the recommendation that independent data sets (defined in terms of process partitions; sensu Bull et aI., 1993, Syst. BioI. 42:384-397) should rarely be combined but should be kept separate for phylogenetic analysis because their independence increases the significance of corroboration. Trees of natural taxa, well supported by many independent lines of evidence, should be used in the same way as the known phylogenies of simulations and of certain laboratory and domesticated groups, i.e., as standards for evaluating the accuracy of different phylogenetic methods. Although compromised by their imperfect reliabilities, such tests using well-supported trees of wild taxa provide important reality checks on the conclusions of the other two approaches by encompassing more of the complexity and diversity of natural systems and their evolutionary processes. In this way, a combination of testing with the well-supported trees of natural groups, with simulations, and with those laboratory and domesticated taxa with known phylogenies is most likely to prove effective in establishing the strengths, weaknesses, and assump­ tions of different phylogenetic methods. (Accuracy; taxonomic congruence; character congruence; process partitions; character independence; well-supported trees; phylogenetic methods.)

The importance of long time-series in understanding the variability of natural systems

The Marine Biological Association possesses long time-series of data on the biota and environment of the western English Channel. These series are of value in tracing the influence of climate change on marine communities and show the importance of continuity and length for detection of cycles and prediction of future changes.

Statistical Procedure for Evaluating Hydrologic/Water Quality Models

Input parameters are used in hydrologic/water quality models to describe specific situations. These input parameters are never known with certainty. The models, although largely physically based, are not capable of describing the exact hydrologic and chemical processes that take place under natural conditions. Evaluation of models by a comparison of observed and predicted results is fraught with ambiguities resulting from the large number of parameters that must be estimated and the inherent variability in natural systems. This article puts forth a model evaluation protocol based on a simulation procedure which transforms parameter uncertainty into prediction uncertainty using probability density functions. Confidence intervals are placed on model results and decisions regarding model acceptability are made based on the magnitude of measured data, confidence intervals, and performance criteria placed on the model.

Biological monitoring and tropical biodiversity in marine environments: a critique with recommendations, and comments on the use of amphipods as bioindicators

Preoccupations with regulatory and legal liability issues in marine environmental monitoring have led to programmes based on reductionist models that use nonbiological parameters which are indirect measures of biotic condition. The ability to assess the effectiveness of current monitoring programmes to protect the marine environment at regional and national scales does not currently exist. Current monitoring programmes rarely serve the function for which they were intended: an accurate and sensitive source of information from which conditions and trends can be defined and recognized, and management decisions made. In addition, the natural variability of systems is problematic and must be documented in order to distinguish natural from anthropogenic changes in environmental conditions. Owing to their ecological importance, numerical abundance, and sensitivity to a variety of toxicants and pollutants, amphipod crustaceans have long been known as sensitive environmental indicators. However, application and use of amphipods in such programmes is limited to the few regions where ongoing comprehensive taxonomic and natural history investigations have been undertaken. Potential for amphipods as bioindicators exists in a wide variety of environments, especially in the tropics, but their incorporation into such programmes is dependent upon completion of taxonomic surveys and inventories.

Effects of Temperature and Illumination on Feeding Rates of Green Frog Tadpoles (Rana clamitans)

ate significantly less than at those at 23 C or 26 C, but feeding rates did not differ at the two higher temperatures. Feeding rates in the laboratory were similar to those measured in open areas of a pond at the same temperatures; temperature alone may explain some feeding rate variation in natural systems. Tadpoles in the light and in the dark ate similar amounts. A nocturnal decline in feeding rates observed in nature cannot be attributed to darkness.

Biotechnology and biodiversity — the interrelationships

Although the two current high profile scientific fields of biotechnology and biodiversity have extremely different scientific foundations and philosophies, they are still closely interrelated. Useful forest biotechnology is dependent on the availability and maintenance of a broad genetic foundation. Such a foundation is best achieved over time by maintaining the biological diversity of natural systems. In contrast, it is conceivable that with the release of genetically engineered organisms, natural biological diversity could be negatively impacted. The possibility of such an influence will be discussed. Finally, the politics of the relationship between these two emerging scientific fields will be briefly reviewed.

Can Fisheries Agencies Learn from Experience?

The essential steps in learning from experience are documentation of decisions, evaluation of results, and organizational response to the evaluation. Learning is slow in fisheries management because of the difficulty of replication and control and, to a lesser extent, the variability of natural systems. Thus, it may take a long time to determine which kinds of management actions are best, and we stand a significant chance of making false conclusions about the efficacy of specific actions. Even when decisions are documented and evaluated, fisheries agencies have few mechanisms of institutional memory to retain the lessons learned. Agencies need to develop a systematic plan for learning, including listing of identified uncertainties, methods for resolving the uncertainty, how to evaluate existing actions, and mechanisms for retaining the lessons learned in the institutional memory.

Nuclear Waste Disposal: The Interface Between Performance Assessment and Research

ABSTRACTThe potential impact of the post-closure phase of a nuclear fuel waste disposal project is radiation dose to man. Radiation dose is estimated as the end product of a total systems analysis. Field and laboratory research must be assimilated in a form that can be accepted by the total systems analysis procedure. A central focus of this assimilation must be the consideration of uncertainties in the analysis and data used. Irreducible uncertainty arises because of the wide variability in natural systems and the unprecedented extrapolation into the distant future. The SYVAC computer program provides a framework for assimilation of the results of the field and laboratory research with a systematic treatment of uncertainty. A SYVAC assessment of the post-closure performance of a Canadian nuclear waste disposal facility is presented with particular illustrations of the interface between the assessment models and data and the field and laboratory research.

Environmental Geologic Atlas, Texas Coastal Zone: Role of Geology in Land-Use Planning: ABSTRACT

The Environmental Geologic Atlas of the Texas Coastal Zone, which required 25 man-years of research, was initiated in 1969 to meet a growing need for basic land resource information about one of the most rapidly developing regions of Texas. The coastal zone, covering about 20,000 sq mi, is not only an area of accelerating, competitive, and, sometimes, conflicting land use, but it is also a region of dynamic natural processes and delicately balanced environments. The coastal zone is underlain by a wide variety of Pleistocene and Holocene/modern facies with differing physical properties and land-use capabilities. Large-scale mapping (1:24,000) of first-order units, including substrates, biology, processes, and man-made features, resulted in the principal environmental resou ce document--the Environmental Geology Map. This map, at a scale of 1:125,000, displays the distribution of 130 units, which comprise both Pleistocene and Holocene/modern fluvial, deltaic, barrier-strandplain-chenier, offshore, bay-lagoon-estuary, marsh-swamp, eolian, and man-made coastal systems. A series of 8 Special-Use Environmental Maps at a scale of 1:250,000 were, in part, derived from the Environmental Geology Map, and, in part, compiled from other extensive data sources. The special-use map series includes: Physical Properties; Environments and Biologic Assemblages; Current Land Use; Mineral and Energy Resources; Active processes; Man-Made Features and Water Systems; Rainfall, Stream Discharge, and Surface Salinity; and Topography and Bathymetry. These maps, which contain about 150 units, were designed for the special requirements of various users; an almost unlimited number of such special-use and thematic maps can be generated from the basic map data. A further step toward application of environmental geologic information in land-use planning was derivation of fundamental planning units based on carrying capacity. These units alternately have been termed resource-capability units and land-resource units. Each land-resource unit is an areally defined entity that exhibits a unique set of properties, which limits or sustains its use for the wide variety of human activities. The properties of land-resource or resource-capability units, which can be quantified and digitized, may serve as principal input into land-use inventory and planning systems being devised to support future land-use decisions. A land-use planning system that is based realistically upon the nature and variability of natural systems and coastal substrates can provide a commonsense, flexible, and fair approach to land-use planning. Such a system provides potential users with options long before development becomes a reality, enabling users to plan for necessary engineering improvements and/or economic trade-offs. Fundamental geology is a critical element in such a land-use decision system. End_of_Article - Last_Page 2207------------