The Lake Tahoe Basin: A systems analysis of its characteristics and human carrying capacity

A systems analysis of the Lake Tahoe Basin indicates significant and accelerating environmental deterioration within the basin, suggests that Tahoe is poised for yet another round of urban expansion, delineates the portion of Tahoe's resources that are consumed by gaming recreation vis-à-vis outdoor recreation, and identifies the Federal government as a contributor to Tahoe's problems. In response to the need for a holistic approach to basin-wide planning and management, ecological carrying capacity concepts are explored as they may be applicable to the Basin's growth patterns, and ideas on establishing a carrying capacity for Tahoe are developed.     

WATER-ENERGY LINKAGES IN NEBRASKA1

ABSTRACT Nebraska is well endowed with water, particularly groundwater, but has few fossil fuel reserves. However, it is located adjacent to states which have almost no water but have enormous quantities of coal and oil shale. Recent court cases facilitate the movement of water from water-rich states such as Nebraska to water-short states, such as Colorado and Wyoming. The possibility of an energy-water partnership exists and raise numerous policy questions. Within Nebraska, energy consumption patterns are similar to those of the nation's, with consumption of electricity in the agricultural sector growing fastest. Water consumption in the state is dominated by agriculture, and future development of groundwater for irrigation is expected to be intense. Although water and energy are both factors of economic production, an equivalent amount of water consumption provides more jobs in the energy industries than in agriculture. Water and energy are also interdependent. Each is required to produce the other and conservation of one will cause conservation of the other. If both agriculture and electricity are involved, such as in irrigation, the conservation effects are synergistic. Current water policy in Nebraska is biased toward agriculture relative to the energy industries and provides little incentive for water conservation. Given recent court cases and economic conditions, the advantages and disadvantages of the sale of water for export or the use of water with Wyoming coal for energy development need to be compared systematically with those of using water only for agriculture.     

Complex dynamics in the uptake of new farming practices: a case study for organic waste application

Adverse environmental effects of intensive agriculture, together with scarcity in phosphates and water, urge farmers to find more sustainable practices. An example of such a sustainable practice is on-farm processing of organic waste. This paper explores three mechanisms that can lead to a widespread uptake of this technique: (1) economies of scale, (2) information sharing, and (3) adjustment of social norms. Although each of these mechanisms has been studied before, this paper provides new insights by considering the interactions that might exist between the different mechanisms when they are applied to real-life situations. Based on a pilot study, we developed a multi-criteria mathematical programming model at individual farm level. We used this model to simulate the uptake of on-farm processing of organic waste, as a result of the three mechanisms and their interactions. Our results show that each mechanism results in an increased uptake, but is not likely to cause a widespread uptake. Interaction between the mechanisms, will lead to a much higher uptake. This result suggests that simultaneous consideration of multiple mechanisms is essential to understand the behaviour of social–ecological systems.     

Fitness consequences of dispersal decisions for male mountain gorillas (Gorilla beringei beringei)

The fitness consequences of dispersal decisions are difficult to quantify, especially for long-lived species with complex social systems. To calculate those consequences for male mountain gorillas, from the perspective of both subordinate and dominant males, we used behavioral and demographic data obtained over 30 years from the Virunga Volcano population to develop an agent-based model that simulates the life history events, social structure, and population dynamics of the species. The model included variables for birth rates, mortality rates, dispersal patterns, and reproductive skew. The model predicted an average lifetime reproductive success (LRS) of 3.2 for philopatric males (followers) and 1.6 for emigrants. The benefits of philopatry were most sensitive to opportunities for social queuing and to female transfer preferences, but philopatry remained the best strategy over a wide range of group conditions and hypothetical simulations. The average LRS for dominant males was 4.5 when a subordinate stayed and 4.6 when the subordinate emigrated. The dispersal decision of the subordinate male had little impact on the fitness of the dominant male because it came relatively late in the dominant males reproductive life span, and it changed his group composition only incrementally. The fitness consequences for the dominant male were most sensitive to the degree of reproductive skew. Since subordinates suffer a fitness loss when they leave a group, they should accept whatever reproductive restraint is needed to avoid eviction, and the dominant male does not need to offer concessions for them to stay. The dominant male may offer reproductive concessions for other reasons, such as peace incentives or to confuse paternity, or he may not have complete control of reproduction within his group.Communicated by D. Watts     

Socioecological influences on the reproductive success of female mountain gorillas (<Emphasis Type="Italic">Gorilla beringei beringei</Emphasis>)

Over the past few decades, socioecological models have been developed to explain the relationships between the ecological conditions, social systems, and reproductive success of primates. Feeding competition, predation pressures, and risk of infanticide are predicted to influence how female reproductive success (FRS) depends upon their dominance rank, group size, and mate choices. This paper examines how those factors affected the reproductive success of female mountain gorillas (Gorilla beringei beringei) of the Virunga Volcanoes, Rwanda from 1967–2004. Reproductive success was measured through analyses of interbirth intervals, infant survival, and surviving infant birth rates using data from 214 infants born to 67 females. Mountain gorillas were predicted to have “within-group scramble” feeding competition, but we found no evidence of lower FRS in larger groups, even as those groups became two to five times larger than the population average. The gorillas are considered to have negligible “within-group contest” competition, yet higher ranked mothers had shorter interbirth intervals. Infant survival was higher in multimale groups, which was expected because infanticide occurs when the male dies in a one-male group. The combination of those results led to higher surviving birth rates for higher ranking females in multimale groups. Overall, however, the socioecological factors accounted for a relatively small portion of the variance in FRS, as expected for a species that feeds on abundant, evenly distributed foliage.     

TBT in California coastal waters: Monitoring and assessment

Butyltins were monitored at over eighty sites, primarily marinas, in surface waters and sediments of the California coast. Values of tributyltin (TBT) in marina waters ranged from 20 to 600 ppt while lower values were usually found in harbors and on the coast. The origin of the tributyltin is in its use as an antifouling agent in marine paints. In those marinas where the concentrations are greater than about 100 ppt, there is usually a conspicuous absence of native organisms, especially molluscs, which are among the most sensitive animals to the highly toxic TBT. The impact of TBT upon not-target organisms recalls the DDT episode of the 1970s. Increasing uses of TBT-containing antifouling paints in the future may have even more drastic effects on coastal organisms than those observed today. The conclusion is inescapable that TBT should be banned for use in commercially available marine paints.     

Cometary dust studied with infrared photometry

Our knowledge of the physical properties of cometary dust grains derives primarily from measurements of their thermal emission and optical scattering. The infrared data for bright, nonperiodic comets have recently been augmented by observations of fainter periodic comets beyond 1 AU. Small absorbing grains, ? 1 μm radius, are necessary to explain the observed infrared flux at wavelengths 3 to 20 μm while small silicate grains are necessary to explain the excess flux near 10 and 18 μm observed in many comets within 1 AU of the sun. These conclusions are consistent with collected micrometeorites and dynamical analysis of comet dust tails. The thermal emission from all well-observed comets at R≦1.5 AU can be fit by a size distribution function with a change in mean particle size less than a factor 2.5.