POTENTIAL EFFECTS OF CLIMATE CHANGE ON SURFACE‐WATER QUALITY IN NORTH AMERICA1

ABSTRACT: Data from long‐term ecosystem monitoring and research stations in North America and results of simulations made with interpretive models indicate that changes in climate (precipitation and temperature) can have a significant effect on the quality of surface waters. Changes in water quality during storms, snowmelt, and periods of elevated air temperature or drought can cause conditions that exceed thresholds of ecosystem tolerance and, thus, lead to water‐quality degradation. If warming and changes in available moisture occur, water‐quality changes will likely first occur during episodes of climate‐induced stress, and in ecosystems where the factors controlling water quality are sensitive to climate variability. Continued climate stress would increase the frequency with which ecosystem thresholds are exceeded and thus lead to chronic water‐quality changes. Management strategies in a warmer climate will therefore be needed that are based on local ecological thresholds rather than annual median condition. Changes in land use alter biological, physical, and chemical processes in watersheds and thus significantly alter the quality of adjacent surface waters; these direct human‐caused changes complicate the interpretation of water‐quality changes resulting from changes in climate, and can be both mitigated and exacerbated by climate change. A rigorous strategy for integrated, long‐term monitoring of the ecological and human factors that control water quality is necessary to differentiate between actual and perceived climate effects, and to track the effectiveness of our environmental policies.     

The effects of size-dependent predation risk on the interaction between behavioral and life history traits in a stream-dwelling isopod

In field surveys, laboratory observations and field-based assays of behavior, I examined the effects of size-dependent predation risk on the interaction between size at reproductive maturity and maternal care behavior in the stream-dwelling isopod, Lirceus fontinalis. L. fontinalis exhibit population-specific sizes at reproductive maturity which result in population differences in predation risk during the adult phase. Females from streams containing salamander larvae (that prefer small prey) mature at large sizes and then become relatively safe from predation. Females from streams containing fish (that consume all size classes of prey equally) mature at small sizes and remain at risk. I tested whether these differences in expected survival were reflected in the behavior of females during the maternal phase (i.e., the period during which females exhibit maternal care). Female L. fontinalis carry developing juveniles inside a brood pouch. I simulated predatory attacks on gravid female L. fontinalis from the different population types and found that female behavior correlated with population differences in risk. When “attacked”, females from streams with predatory fish (that experience high risk to adult females) released juveniles from the brood pouch, whereas females from populations with predatory salamander larvae (that pose relatively little risk to adult females) did not release juveniles. I discuss the results with reference to the joint evolution of behavioral and life history traits. Received: 6 March 1996 /Accepted after revision: 12 August 1996     

Population Status of the Razorback Sucker in the Middle Green River (U.S.A.)

The razorback sucker, Xyrauchen texanus , in the middle Green River (U.S.A.) has been described as a static population consisting of old individuals that will eventually disappear through attrition. Capture data between 1980 and 1992 indicated a constant length frequency despite a slow but positive growth rate of individual fish. Abundance and survival estimates indicated that the population of razorback sucker in the middle Green River is precariously low but dynamic. Although high variation existed among survival estimates, no significant decrease in the population between 1982 and 1992 could be detected. The low level of recruitment occurring in the razorback sucker population of the middle Green River was related to high-flow years, indicating that floodplain habitats may be necessary for survival of the species.     

Factors associated with occupational injury severity in the New South Wales underground coal mining industry

The relationship between a large number of mine and mine worker characteristics and injury severity was examined using multiple regression techniques. The study was based on data extracted from the New South Wales (N.S.W.) Joint Coal Board's computer based accident/incident reporting system describing 21,372 non-fatal, lost-time injurious incidents that occurred in the N.S.W. underground coal mining industry during the 4 year period from 1 July 1986 to 30 June 1990. The number of days lost as a result of an injurious incident was the best available proxy measure of injury severity. Over the study period, the number of days lost per 100,000 tonnes of raw coal production declined by 73%. Over the same period, injurious incidents involving more than 20 days off work, which constituted only 16% of all injurious incidents in underground mines, resulted in 75% of the total days lost for the whole N.S.W. underground coal mining industry. Factors that had practical importance and that were significantly associated with injury severity included mine worker's age, part of the body injured, type of accident, agency of accident, and mine worker activity. Factors not important or not significant in their relationship with injury severity were: time into shift, previous hours worked, mine location of incident, occupation, work experience, frequency of task, shift, and mining region. This study suggests that factors related to the susceptibility of a mine worker's body tissue to damage or repair, and factors related to the concentration of energy on the mine worker by vehicle and environmental characteristics are important determinants of injury severity.     

Pollen dispersal and intensity as criteria for the minimum viable population and species reserves

In small populations the lack of mating individuals may cause a reduction in reproductive potential which can restrict population expansion or cause further population declines. This is especially true in outcrossing monoecious and self-incompatible dioecious plant species. Principles of pollen dispersal suggest that many small to medium size population reserves of round shape will maximize the pollen interaction within and between island reserves. Diverse and low-density ecosystems require more total area in reserves than low-diversity and high-density ecosystems.     

A PLANNING METHOD FOR EVALUATING DOWNSTREAM EFFECTS OF DETENTION BASINS1

While storm water detention basins are widely used for controlling increases in peak discharges that result from urbanization, recent research has indicated that under certain circumstances detention storage can actually cause increases in peak discharge rates. Because of the potential for detrimental downstream effects, storm water management policies often require downstream effects to be evaluated. Such evaluation requires the design engineer to collect additional topographic and land use data and make costly hydrologic analyses. Thus, a method, which is easy to apply and which would indicate whether or not a detailed hydrologic analysis of downstream impacts is necessary, should decrease the average cost of storm water management designs. A planning method that does not require either a large data base or a computer is presented. The time co-ordinates of runoff hydrographs are estimated using the time-of-concentration and the SCS runoff curve number; the discharge coordinates are estimated using a simple peak discharge equation. While the planning method does not require a detailed design of the detention basin, it does provide a reasonably accurate procedure for evaluating whether or not the installation of a detention basin will cause adverse downstream flooding.     

Desertification Evaluated Using an Integrated Environmental Assessment Model

Desertification has been defined as land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities (United Nations, 1992). A technique for identifying and assessing areas at risk fordesertification in the arid, semi-arid, and subhumid regionsof the United States was developed by the Desert Research Institute and the U.S. Environmental Protection Agency (EPA), using selected environmental indicators integrated into a Geographic Information System (GIS). Five indicators were selected: potential erosion, grazing pressure, climatic stress (expressed as a function of changesin the Palmer Drought Severity Index [PDSI]), change invegetation greenness (derived from the Normalized DifferenceVegetation Index [NDVI]), and weedy invasives as a percentof total plant cover. The data were integrated over aregional geographic setting using a GIS, which facilitateddata display, development and exploration of data relationships, including manipulation and simulation testing. By combining all five data layers, landscapes having a varying risk for land degradation were identified, providing a tool which could be used to improve landmanagement efficiency.     

Pasture diversification to combat climate change impacts on grazing dairy production

Among livestock systems, grazing is likely to be most impacted by climate change because of its dependency to feed quality and availability. In order to reduce the impact of climate change on grazing livestock systems, adaptation measures should be implemented. The goal of this study is to identify the best pasture composition for a representative grazing dairy farm in Michigan in order to reduce the impacts of climate change on production. In order to achieve the goal of this study, three objectives were sought: (1) identify the best pasture composition, (2) assess economic and resource use impacts of pasture compositions under future climate scenarios, and (3) evaluate the resiliency of pasture compositions. A representative farm was developed based on a livestock practices survey and incorporated into the Integrated Farm System Model (IFSM). For the pasture compositions, four cool-season grass species and two legumes were evaluated under both current and future climate scenarios. The effectiveness of adaptation measures based on economic and resource use criteria was evaluated. Overall, the pasture composition with 50% perennial ryegrass (Lolium multiflorum) and 50% red clover (Trifolium pratense) was identified as the best. In addition, the increase in precipitation and temperature of the most intensive climate scenario could significantly improve farm net return per cow (Bos taurus) and whole farm profit while no significant impact was observed on resource use criteria. Finally, the overall sensitivity assessment showed that the most resilient pasture composition under future climate scenarios was ryegrass with red clover and the least resilient was orchardgrass (Dactylis glomerata) with white clover (Trifolium repens).