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1.
The distribution of epipsammic phytoplankton in the coastal shore (Ibeno beach) of Qua Iboe River estuary was studied in the early summer (between October and December) of 1998. The results revealed the presence of Actinoptychus undulatus, Aphanizomenon flos-aquae, Astasia fustis, Chromulina globosa, Cocconeis pediculus, Cymatopleura solea, Cymbella lanceolata, Euglena intermedia, Lyngbya majusculata, Microcystis sp., Nodularia spumigena, Navicular rhynocephala, Oscillatoria nigroviridis, Pinnularia viridis, Rhoicosphenia curvata, Trachelomonas volvocina and Urceolus cyclostomus in the sandy beach. The mean species density of the epipsammic algae encountered in the beach ranged from 16 to 7600 organisms per hectare. The density, however, decreased with increase in sampling distance from the low tide level. Actinoptychus undulatus was the most abundant and widely distributed phytoplankton while Aphanizomenon flos-aquae was the least encountered species. The occurrence of A. flos-aquae and other toxin producing cyanobacterial species of Lyngbya majusculata, Microcystis sp., N. spumigena and O. nigroviridis in the sandy beach are of serious health significance.  相似文献   

2.
Coastal waters have been significantly influenced by increased inputs of nutrients that have accompanied population growth in adjacent drainage basins. In Tampa Bay, Florida, USA, the population has quadrupled since 1950. By the late 1970s, eutrophic conditions including phytoplankton and macroalgal blooms and seagrass losses were evident. The focus of improving Tampa Bay is centered on obtaining sufficient water quality necessary for restoring seagrass habitat, estimated to have been 16,400 ha in 1950 but reduced to 8800 ha by 1982. To address these problems, targets for nutrient load reductions along with seagrass restoration goals were developed and actions were implemented to reach adopted targets. Empirical regression models were developed to determine relationships between chlorophyll a concentrations and light attenuation adequate for sustainable seagrass growth. Additional empirical relationships between nitrogen loading and chlorophyll a concentrations were developed to determine how Tampa Bay responds to changes in loads. Data show that when nitrogen load reduction and chlorophyll a targets are met, seagrass cover increases. After nitrogen load reductions and maintenance of chlorophyll a at target levels, seagrass acreage has increased 25% since 1982, although more than 5000 ha of seagrass still require recovery. The cooperation of scientists, managers, and decision makers participating in the Tampa Bay Estuary Program’s Nitrogen Management Strategy allows the Tampa Bay estuary to continue to show progress towards reversing many of the problems that once plagued its waters. These results also highlight the importance of a multi-entity watershed management process in maintaining progress towards science-based natural resource goals.  相似文献   

3.
ABSTRACT: Filtering efficiency of the fathead minnow (Pimephales promelas), gizzard shad (Dorosoma cepedianum), carp (Cyprinus carpio), and a freshwater mussel (Elliptio coinpianata) was measured in field and laboratory trials to assess the ability of each species to control phytoplankton and suspended solid densities. All fish species tested were ineffective filterers and generally increased, rather than suppressed, algal and suspended solid concentrations. Filtering efficiencies of fish varied between -354 and 84 percent, depending on the size, shape, abundance, palatability, composition, and resistance to digestion of the particles. Because of poor filtering abilities, unpredictable feeding habits, and sensitivity to stress, the fish species examined are not effective biological controls in waste lagoons. In contrast, the freshwater mussel Elliptio was a highly effective control organism, averaging 66 percent filtering efficiency over a wide size range of algal and suspended particles. Filtration efficiency was positively correlated with mussel density. Elliptio was efficient at filtering small particles, which are particularly difficult to remove. Mean filtration rates ranged from 53 to 134 ml/mussel/h depending on the algal species consumed and algal densities (range 50–180,000 cells/ml) and 3 mg/L/mussel/h on suspended solids (range 14 to 112 mg/L). Water clarification was facilitated by both direct consumption and pseudofeces deposition. Elliptio and probably other mussel species can effectively control algae and suspended solids in wastewater lagoons and eutrophic lakes, if environmental conditions, especially dissolved oxygen levels, are suitable (>5 mg/L) for their survival.  相似文献   

4.
This project is aimed at studying the feasibility of using sewage sludge to prepare culture media for microalgae (Chlorella-HKBU) and the use of the sludge-grown algae as a feed for some aquatic organisms. Part I of the project included results on preparing sludge extracts and their use on algal culture. By comparing two culturing techniques, aeration and shaking, it was noted that both lag and log phases were shortened in the aeration system. A subsequent experiment noted that algal growth subject to aeration rates of 1.0 and 1.5 liters/min had similar lag and log phases. In addition, both aeration rates had a significantly higher (P < 0.05) final cell density than that of 0.5 liters/min. A detailed study on the variation of growth conditions on the algal growth was done. The results indicated that pH values of all the cultures declined below 5 at day 12. The removal rates of ammonia N ranged from 62% to 70%. The sludge-grown algae contained a rather substantial amount of heavy metals (µg/g): Zn 289–581, Cu 443–682, Ni 310–963, Mn 96–126, Cr 25–118, and Fe 438–653. This implied that the rather high levels of heavy metals may impose adverse effects on higher trophic organisms.  相似文献   

5.
The possibility of application of black liquor for oil-riched algae cultivation is inspected. The results show that after ligin removal and enzymatic hydrolysis, the hydrolysate of black liquor contained 9.18 g L?1 of reducing sugar. When the hydrolysate was used for Scenedesmus obliquus (S. obliquus) cultivation, a 1.23 g L?1, 24.52%, and 23.20 mg L?1d?1 was obtained for growth yield, oil content, and the lipid productivity, seperately. The hemicellulose was extracted from black liquor and hydrolyzed. With addition of 3 g L?1 yeast extract, the growth yield of S. obliquus in hemicellulose hydrolysate increased to 2.7 g L?1, an increase of 26.8% than that of in glucose medium, oil content was 25.7% and the final lipid productivity reached 53.37 mg L?1d?1. The results indicate that black liquor can not be directly used by microalgae, but with approprate treatment, the carbohydrate of it could be recovered and uitilized for the oil production from microalgae.  相似文献   

6.
Microalgae biomass is well known as a potential sustainable product for bio-based industry, which has reported encountering numerous difficulties during biomass harvesting and recovering. This study examined the effect of pH (5–12) and alum dosage (30–180 mg/L) for microalgae Botryococcus sp. harvested via flocculation technique. The optimum pH condition for Botryococcus sp. harvesting was measured to be 9.2, and the alum dosage was 100 mg/L. Both optimum values successfully harvested up to 95% microalgae biomass. This study revealed that flocculation efficiencies for alum are highly dependent on the range of pH and coagulant dosage that were applied during the process. Use of flocculation technique with alum as a coagulant represents a convenient technique for Botryococcus sp. biomass harvesting and is recommended for use in both small- and large-scale biomass industries.  相似文献   

7.
Populations of many shorebird species are declining; habitat loss and degradation are among the leading causes for these declines. Shorebirds use a variety of habitats along interior migratory routes including managed moist soil units, natural wetlands, sandbars, and agricultural lands such as harvested rice fields. Less well known is shorebird use of freshwater aquaculture facilities, such as commercial cat- and crayfish ponds. We compared shorebird habitat use at drained aquaculture ponds, moist soil units, agricultural areas, sandbars and other natural habitat, and a sewage treatment facility in the in the lower Mississippi River Alluvial Valley (LMAV) during autumn 2009. Six species: Least Sandpiper (Calidris minutilla), Killdeer (Charadrius vociferous), Semipalmated Sandpiper (Calidris pusilla), Pectoral Sandpiper (C. melanotos), Black-necked Stilt (Himantopus himantopus), and Lesser Yellowlegs (Tringa flavipes), accounted for 92 % of the 31,165 individuals observed. Sewage settling lagoons (83.4, 95 % confidence interval [CI] 25.3–141.5 birds/ha), drained aquaculture ponds (33.5, 95 % CI 22.4–44.6 birds/ha), and managed moist soil units on public lands (15.7, CI 11.2–20.3 birds/ha) had the highest estimated densities of shorebirds. The estimated 1,100 ha of drained aquaculture ponds available during autumn 2009 provided over half of the estimated requirement of 2,000 ha by the LMAV Joint Venture working group. However, because of the decline in the aquaculture industry, autumn shorebird habitats in the LMAV may be limited in the near future. Recognition of the current aquaculture habitat trends will be important to the future management activities of federal and state agencies. Should these aquaculture habitat trends continue, there may be a need for wildlife biologists to investigate other habitats that can be managed to offset the current and expected loss of aquaculture acreages. This study illustrates the potential for freshwater aquaculture to provide habitat for a taxa at risk. With the rapid growth of aquaculture worldwide, the practices of this industry deserve attention to identify benefits as well as risks to wildlife.  相似文献   

8.
Granéli, Edna and Paulo S. Salomon, 2010. Factors Influencing Allelopathy and Toxicity in Prymnesium parvum. Journal of the American Water Resources Association (JAWRA) 46(1):108-120. Abstract: Some microalgae are able to kill or inhibit nutrient-competing microalgae, a process called allelopathy. Inhibiting or killing competitors enable these species to monopolize limiting resources, such as nitrogen and phosphorus. Prymnesium parvum is known to produce such allelopathic compounds, substances that seem identical to the ichthyotoxins identified from this species. Biotic and abiotic environmental factors influence not only growth rates but also toxin/allelopathic compounds production by P. parvum cells. Toxin production, as well as allelopathy, including grazer deterrence, increases dramatically in light, temperature, or nutrient stressed P. parvum cells. Correspondingly, toxicity and allelopathy may decrease, or cease completely, if cells are grown with high amounts of N and P in balanced proportions. However, even under nutrient (N and P) sufficient conditions, P. parvum is able to produce toxins/allelopathic compounds, with negative effects on other phytoplankton species or grazers, if cells densities of P. parvum are high relative to other species. This negative effect might shift the plankton community to more toxin resistant species. Filtrates from nutrient-deficient P. parvum cultures have almost the same strong negative effect on grazers and other phytoplankton species as when Prymnesium cells are grown together with the target organisms. Eutrophication, the increased input of N and P to aquatic ecosystems, besides increasing nutrient concentrations, is usually provoking unbalanced N:P condition for the optimal growth of phytoplankton, deviating from the Redfield ratio, i.e., the phytoplankton cellular nitrogen to phosphorus ratio, N:P = 16:1 (by atoms) or 7.2:1 (by weight). Eutrophication thus both enhances P. parvum growth and increases production of toxins and allelopathic compounds. Supplying N-deficient or P-deficient P. parvum cells with the deficient nutrient reduces toxicity to less than half within 24 h after additions. As P. parvum is mixotrophic, uptake of dissolved or particulate organic N (DON or PON) can also reduce toxicity and allelopathy in the same manner as addition of inorganic N to N-starved cells. In conclusion, P. parvum, by increasing its toxicity and allelopathic ability under poor environmental conditions, outcompetes the co-occurring phytoplankton species.  相似文献   

9.
Enhanced concentrations of Fe, Zn, Mn, Pb, Cu, Cd and total hydrocarbons (THC) determined in fish samples from the Cross River system, Nigeria have been associated with clinical defects (nausea, headache, hepatitis, body rashes) observed in coastal residents who are the major consumers of the fish species. Fish samples were collected from ten locations with varying degrees of exposure to human activities. Heavy metal concentrations in fish followed the sequence: Fe>Zn>Mn>Pb>Cu>Cd with the highest concentration of 243 g/g (Fe) wet weight occurring in Tympanotonus sp. Fe levels were significantly (P<0.001) higher than other metals analysed. The sequence in total hydrocarbon concentrations according to fish species was in the order of O. niloticus (55.1 g/g) > E. fimbriata > P. elongatus > Portonus sp. > C. nigrodigitatus > Tympanotonus sp. Generally, the demersal species showed a marked potential for tolerating high levels of heavy metals while the pelagic species showed preference for the accumulation of hydrocarbons. The degree of contamination depended on pollutant type, fish species, sampling location, trophic level and their mode of feeding. The persistent accumulation and tolerable potential of Tympanotonus, Portonus and P. elongatus suggest that they might be effectively utilized as self-integrating indicators for time-series monitoring of the rate of recovery of the impacted ecosystem by heavy metals. Possible sources of pollutant include leachates from municipal dumps, used crankcase oils from fluvial discharges (mechanic workshops) and occasional oil spills.  相似文献   

10.
Parallel determination of phytoplankton biomass and chlorophyll a concentration were made on spring and summer phytoplankton samples collected from 165 Florida lakes. There was a significant correlation between chlorophyll a concentration and phytoplankton biomass (r=0.80; P < 0.01). Chlorophyll content per unit phytoplankton biomass ranged over two orders of magnitude. Nitrogen seemed to be a major factor influencing the chlorophyll content of Florida algae. Multiple regression analyses indicated that phytoplankton biomass was dependent on both the total phosphorus and total nitrogen concentration. Nutrient-phytoplankton and Secchi-phytoplankton relationships for the Florida lakes had higher coefficients of determination if chlorophyll a concentrations rather than phytoplankton biomass data were used in regression analyses.  相似文献   

11.
This ecophysiological research on the ash deposits from the Nikola Tesla–A thermal power station in Serbia covered 10 plant species (Tamarix gallica, Populus alba, Spiraea van-hauttei, Ambrosia artemisifolia, Amorpha fruticosa, Eupatorium cannabinum, Crepis setosa, Epilobium collinum, Verbascum phlomoides, and Cirsium arvense). This paper presents the results of a water regime analysis, photosynthetic efficiency and trace elements (B, Cu, Mn, Zn, Pb, and Cd) content in vegetative plant parts. Water regime parameters indicate an overall stability in plant-water relations. During the period of summer drought, photosynthetic efficiency (Fv/Fm) was low, ranging from 0.429 to 0.620 for all the species that were analyzed. An analysis of the tissue trace elements content showed a lower trace metal concentration in the plants than in the ash, indicating that heavy metals undergo major concentration during the combustion process and some are not readily taken up by plants. The Zn and Pb concentrations in all of the examined species were normal whereas Cu and Mn concentrations were in the deficiency range. Boron concentrations in plant tissues were high, with some species even showing levels of more than 100 g/g (Populus sp., Ambrosia sp., Amorpha sp., and Cirsium sp.). The presence of Cd was not detected. In general, it can be concluded from the results of this research that biological recultivation should take into account the existing ecological, vegetation, and floristic potential of an immediate environment that is abundant in life forms and ecological types of plant species that can overgrow the ash deposit relatively quickly. Selected species should be adapted to toxic B concentrations with moderate demands in terms of mineral elements (Cu and Mn).  相似文献   

12.
A series of statistical analyses were used to identify temporal and spatial patterns in the phytoplankton and nutrient dynamics of Lake Washington, an mesotrophic lake in Washington State (USA). These analyses were based on fortnightly or monthly samples of water temperature, Secchi transparency, ammonium (NH4), nitrate (NO3), inorganic phosphorus (IP), total nitrogen (TN), total phosphorus (TP), dissolved oxygen (DO), pH and chlorophyll a (chl a) collected during 1995–2000 from 12 stations. Lake Washington has a very consistent and pronounced annual spring diatom bloom which occurs from March to May. During this bloom, epilimnetic chl a concentrations peak on average at 10 μg/L, which is 3 times higher than chl a concentrations typically seen during summer stratified conditions. The spring bloom on average comprised 62% diatoms, 21% chlorophytes and 8% cyanobacteria. During summer stratification, diatoms comprised 26% of the phytoplankton community, chlorophytes 37% and cyanobacteria 25%. Cryptophytes comprised approximately 8% of the community throughout the year. Overall, 6 phytoplankton genera (i.e., Aulacoseira, Fragilaria, Cryptomonas, Asterionella, Stephanodiscus, and Ankistrodesmus) cumulatively accounted for over 50% of the community. These analyses also suggest that the phytoplankton community strongly influences the seasonality of NO3, IP, DO, pH and water clarity. According to a MANOVA, seasonal fluctuations explained 40% of the total variability for the major parameters, spatial heterogeneity explained 10% of variability, and the seasonal-spatial interaction explained 10% of variability. Distinctive patterns were identified between offshore and inshore sampling stations. The results of our analyses also suggest that spatial variability was substantial, but much smaller than temporal variability.  相似文献   

13.
Arsenic levels in seawater, microplankton (diatoms and dinoflagellates), shrimp (Penaeus semisulcatus), mollusc (Cerithium scabridum) and five types of fish (Maid, Nakroor, Nuwaiby, Suboor and Sheim) in five sampling stations (I–V) off the Kuwait coast were determined during the years 1995 to 1999. The maximum mean concentration of arsenic was observed in the order; the five fish (0.50–0.78 g g–1)> mollusc (0.26 g g–1)> shrimp (0.23 g g–1)> particulate matter (0.03 g g–1)> water and phytoplankton (0.02 g g–1) from all the sites of the Kuwait coast. Station II possessed the maximum arsenic levels. In comparison with the arsenic levels in other parts of the globe, low arsenic levels were observed in most of the marine organisms off the Kuwait Coast. However, an increasing trend in arsenic concentrations was anticipated due to rapid local industrialization and on account of recent spills of arsenic compounds.  相似文献   

14.
Soil loss and surface runoff patterns over a four-year period (1997–2000) were studied in erosion plots from three hillslopes under different vegetative covers (Rosmarinus officinalis, Triticum aestivum and natural-spontaneous vegetation) in Lanjaron (Alpujarras) on the south flank of the Sierra Nevada of southeast Spain. The erosion plots were located on the hillslopes at 35.5% incline, at 1,480 m in altitude and with 41.8 m2 (21 m×1.9 m) in area. The vegetative covers were tested for effectiveness in controlling the surface runoff and soil loss production. The highest runoff and erosion values, ranging from 114.1 to 1.7 mmyr–1 and from 14,564.3 to 6.6 kgha–1yr–1, respectively, over the entire study period, were measured under the Triticum aestivum. In the Rosmarinus officinalis, runoff ranged from 7.9 to 1.3 mmyr–1 and erosion from 156.4 to 2.3 kgha–1yr–1, while on the hillslope under natural-spontaneous vegetation, runoff ranged from 4.4 to 0.9 mmyr–1 and erosion from 322.3 to 2.2 kgha–1yr–1. According to the results the vegetative covers of Rosmarinus officinalis and natural-spontaneous vegetation reduced the soil losses by 99 and 98%, with respect to the Triticum aestivum, and the runoff losses by 94 and 96%, respectively. Also, the Rosmarinus officinalis and natural-spontaneous plants influenced infiltration by intercepting much of the rainfall water respect to the Triticum aestivum. Monitoring allowed more direct linkages to be made between management practices and their impacts on runoff and soil erosion, thereby enabling to identify problems and take appropriate preventive measures to improve the management practices.  相似文献   

15.
Reviews     
DESIGN ON THE LAND: the development of Landscape Architecture Norman T. Newton Belknap Harvard

COMMUNITY CENTERS AND STUDENT UNIONS Eugene D. Sternberg and Barbara E. Sternberg Van Hostrand Reinhold Company, New York.

DECISION AND CONTROL by Stafford Beer, John Wiley and Sons, Inc., New York, 1966 (3rd printing, 1970)

INDUSTRIAL DYNAMICS by Jay W. Forrester, M.I.T. Press, Cambridge, Mass., 1961. S.1O.5O.

PRINCIPLES OF SYSTEMS by Jay W. Forrester. Wright‐Allen Press, Inc., Cambridge, Mass., 1968.

PUBLIC INQUIRIES AS AN INSTRUMENT OF GOVERNMENT R.E. Wraith and G.B. Lamb George Allen & Unwin Ltd. for the Royal Institute of Public Administration, London 1971, £4.50.

SYSTEMS APPROACH AND THE CITY M.D. Mesarovic and A. Reisman (eds.) North‐Holland Publishing Co., Amsterdam and London, 1972.

SIMULATION IN THE CLASSROOM John L. Taylor and Rex Walford Penguin Books, London, 1972. 45p.

DEVELOPMENT BUILDING: THE TEAM APPROACH C.W. Griffin John Wiley & Sons, Inc. for the American Institute of Architects, New York, 1972.  相似文献   


16.
A habitat transition model, based on the correlation between individual habitats and micro-elevation intervals, showed substantial changes in the future spatial distributions of coastal habitats. The research was performed within two protected areas in Slovenia: Se?ovlje Salina Nature Park and ?kocjan Inlet Nature Reserve. Shifts between habitats will occur, but a general decline of 42 % for all Natura 2000 habitats is projected by 2060, according to local or global (IPCC AR4) sea level rise predictions. Three different countermeasures for the long-term conservation of targeted habitat types were proposed. The most “natural” is displacement of coastal habitats using buffer zones (1) were available. Another solution is construction of artificial islets, made of locally dredged material (2); a feasible solution in both protected areas. Twenty-two islets and a dried salt pan zone at the desired elevations suitable for those habitats that have been projected to decease in area would offer an additional 10 ha in the Se?ovlje Salina. Twenty-one islets and two peninsulas at two different micro-altitudes would ensure the survival of 13 ha of three different habitats. In the area of Se?ovlje Salina, abandoned salt pans could be terrestrialized by using permanent, artificial sea barriers, in a manner close to poldering (3). By using this countermeasure, another 32 ha of targeted habitat could be preserved. It can be concluded that, for each coastal area, where wetland habitats will shrink, strategic plans involving any of the three solutions should be prepared well in advance. The specific examples provided might facilitate adaptive management of coastal wetlands in general.  相似文献   

17.
Microplastics (MPs) are frequently regarded as environmental and biota contaminants. Yet, research on the accumulation of MPs in living entities, particularly aquatic insects that serve as food resources in the aquatic food chain, is limited. This study to investigate the accumulation of MPs in aquatic insects from water and sediment in an Egyptian wastewater basin. Four typical freshwater insect groups were used. The highest MP load per gram wet weight was reported by collector-gatherers (Chironomus sp. and Hydrophilus sp.), followed by collector-filterers (Culex sp.) with the second highest MP load. However, Predators (Aeshna sp.) had the lowest values. Also, the present results showed a reduction in the number of MPs in all insect taxa tested after a 24 h depuration time, with differences in the observed egestion ability. The mean number of MPs per individual significantly reduced after 24 h in both Chironomus sp. and Culex sp. larvae, where 53% and 40% of MPs particles were ejected from them, respectively. However, the ability of MP egestion decreases in Aeshna sp. nymph (25%), and the lowest proportion of ejection was observed in Hydrophilus sp. adults (9%). Polyethylene terephthalate fibers were the most abundant type of MP in both sediment and water, followed by fragments (polyethylene and polypropylene). Yet, only polyester fibers were detected in the various insect species. The average length of fibers in the various insects was somewhat shorter than in the surrounding environment. The current study reveals that MP ingestion by aquatic insects is not always related to levels of pollution in the environment, since other factors such as feeding strategies may play a role in MP ingestion. Based on these observations, further studies should be carried out on studies on toxicological impacts of MPs on freshwater/aquatic biota.  相似文献   

18.
Book reviews     
Common Property Economics: A General Theory and Land Use Applications

Glenn G. Stevenson

Cambridge, Cambridge University Press, 1992, XIV + 256pp., £35

Controversial Issues in Environmental Policy: Science vs Economics vs Politics

Kent E. Portney

London, Sage, 1992, 181 pp. £22.00 hb., £10.95 pb.

Economics of Natural Resources and the Environment

E. Kula

London, Chapman & Hall, 1992, 287 pp., £40

Policy Implications of Greenhouse Warming: Mitigation, Adaptation and the Science Base

Committee on Science, Engineering and Public Policy (US), Panel on Policy

Implications of Greenhouse Warming

Washington, DC, National Academy Press, 1992, xxiii + 918 pp., $89.95 hb.

Contemporary Rural Systems in Transition, Volume 1: Agriculture and Environment, Volume 2: Economy and Society

I. Bowler, C. Bryant & M.Nellis (Eds)

Wallingford, CAB International, 1992, 288 pp. + 336 pp., £35 + £40 (2 vols. £70) hb.

Third World Cities: Problems, Policies and Prospects

John Kasarda & Allan Parnell (Eds) London, Sage, 1993, 310 pp., £19.50 pb.

Pricing the European Environment

Stale Navrud (Ed)

Oxford, Oxford University Press/Scandinavian University Press, 1992, 288 pp., £30.00 hb.  相似文献   


19.
We study the potentially unnecessary costs imposed by strict performance standards for forest restoration of surface coal mines in the Appalachian region under the Surface Mining Control and Reclamation Act of 1977 (SMCRA) that can vary widely across states. Both the unnecessary private costs to the mine operator and costs to society (social costs) are reported for two performance standards, a ground cover requirement, and a seedling survival target. These standards are examined using numerical analyses under a range of site productivity class and market conditions. We show that a strict (90%) ground cover standard may produce an unnecessary private cost of more than 700/ha and a social cost ranging from700/ha and a social cost ranging from 428/ha to 710/ha, as compared with a 70 standard, may produce an unnecessary private cost of approximately710/ha, as compared with a 70% standard. A strict tree survival standard of 1235 trees/ha, as compared with the more typical 1087 trees/ha standard, may produce an unnecessary private cost of approximately 200/ha, and a social cost in the range of 120 to120 to 208/ha. We conclude that strict performance standards may impose substantial unnecessary private costs and social costs, that strict performance standards may be discouraging the choice of forestry as a post-mining land use, and that opportunities exist for reform of reforestation performance standards. Our study provides a basis for evaluating tradeoffs between regulatory efficiency and optimal reforestation effort.  相似文献   

20.
Book reviews     
Rebuilding the City: Property‐led Urban Regeneration

P. Healey, S. Davoudi, M. O'Toole, S. Tavsanoglu & D. Usher (Eds)

London, E. & F. N. Spon, 1992, 312 pp., £30

Der Wert stadtnaher Wälder als Erholungsraum: Eine ökonomishce Analyse am Beispiel von Lugano (Value of Urban Forests as Recreational Areas: An Economic Analysis on the Case of Lugano)

Claudia Nielsen

Chur (Switzerland), Verlag Rüegger, 1992, 261 pp., SFr 48

Urban Planning under Thatcherism: The Challenge of the Market

A. Thornley

London, Routledge, 1991, 253 pp., £14.99

Sustainable Development and Urban Form, European Research in Regional Science 2

M. J. Breheny (Ed)

London, Pion, Limited, 1992, 292 pp., £28.00.

Tourism, Museums and the Local Economy: The Economic Impact of the North of England Open Air Musuem at Beamish

Peter Johnson & Barry Thomas

Cheltenham, Edward Elgar, 1992, 160 pp., £29.50  相似文献   


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