Studies on the effects of sewage effluent on gastropod populations in experimental streams

Population density, biomass, growth and reproduction rate of the gastropods Lymnaea peregra (Müller) and Potamopyrgus jenkinsi (Smith) were monitored over a 21 month period in three experimental earth channels, one carrying clean river water and the others 25 and 50% treated sewage effluent mixed with river water. Each channel was divided into riffle and pool stretches; the abundance and biomass of both species were higher in the riffles. The abundance and biomass of L. peregra were significantly greater (P < 0.01) in the riffle in the presence of effluent. Concentration of effluent did not have a significant effect on abundance or biomass. The abundance and biomass of P. jenkinsi were significantly greater (P < 0.001) in riffle and pool in the absence of effluent. In addition, the abundance and biomass of P. jenkinsi were significantly greater (P < 0.05) in the 25% effluent channel than in 50% effluent. No significant differences in the growth of L. peregra between channels were observed. The average number of eggs and of egg masses laid by L. peregra was significantly greater (P < 0.01) in riffle and pool in the presence of effluent. In the riffle, significantly more masses (P < 0.05) and more eggs per adult (P < 0.01) were laid in the 25% effluent channel than in 50% effluent. No differences were observed in the reproduction rate per adult of P. jenkinsi between the 0 and 25% effluent channels. It is concluded that population differences between channels are probably largely the result of differing mortality rates.     

Effect of elevated water temperature on macroinvertebrate communities in outdoor experimental channels

Macroinvertebrates were sampled monthly from December 1976 to September 1977 in two 520m long outdoor experimental channels. One channel was maintained at ambient seasonal Mississippi River water temperatures and the other 10°C higher. Maximum water temperature reached 31.0°C in the ambient and 40.8°C in the heated channel. Elevated temperature seasonally altered macroinvertebrate abundance and life history in the channels. Few animals were found in the heated channel during the period of maximum water temperature. Most macroinvertebrate density and composition differences were confined to the channel riffles rather than the pools. Peak total density in the heated channel riffles occurred 3 or 4 weeks before the ambient channel. Total macroinvertebrate density was appreciably higher in the heated channel riffles during the winter and spring months and in the ambient channel riffles during the summer months. This seasonal alteration was due to composition differences of several identified taxa. Reproductive periods for one snail and one isopod species began approx. 2 and 3 months earlier in the heated channel than in the ambient channel. No marked change occurred in the reproductive activities of an amphipod in the two channels.     

Survival and distribution of aeromonas hydrophila in near-shore coastal waters of Puerto Rico receiving rum distillery effluent

For a period of 1 year, monthly water samples were taken for estimates of Aeromonas hydrophila density at 6 sites in Ensenada de Boca Vieja near San Juan, Puerto Rico. Five sites were associated with the effluent plume of the world's largest rum distillery, the sixth site was 177 m upcurrent. Fifteen water quality parameters were monitored concurrently with A. hydrophila estimates. The toxic and stimulatory nature of the effluent made correlations with any physicochemical parameter difficult. However, a significant multiple regression was obtained against density of A. hydrophila using temperature, total phosphorus, total organic carbon and orthophosphates. Densities of A. hydrophila were always higher in the effluent plume and usually highest at the site closest to effluent outfall. Suspensions of A. hydrophila placed in diffusion chambers at the effluent point source not only survived, but gradually increased in density, while 500 m upcurrent densities of A. hydrophila in diffusion chambers rapidly declined. Significant differences in A. hydrophila density between the two sites could be detected after only 18 h. The diffusion chamber studies confirm natural correlations with water quality that indicate A. hydrophila densities in marine habitats can become elevated under the appropriate conditions. Higher densities of other potential pathogens e.g. Klebsiella pneumoniae, Vibrio cholerae, were also observed in the rum distillery effluent plume.     

CHARACTERISTICS AND CONTROLS OF GRAVEL-BED RIFFLES: AN ANALYSES OF DATA FROM THE RIVER-HABITAT SURVEY

This paper presents an analysis of data from the UK Environment Agency's River Habitat Survey database relating to bedform type and frequency. Emphasis is given to the gravel-bed riffle which (a) traditionally has been considered to be a fundamental morphological unit diagnostic of river stability, and (b) more recently has become an important design component in channel restoration and rehabilitation schemes. Data were sufficient to support the identification of distinct, catchment-scale controls determining the circumstances under which step-pools and riffles occur, and key local-scale influences upon riffle frequency and spacing. This demonstrates that the database can be used to support a broad geomorphological analysis. Suggestions are made for the interpretation of results obtained from the existing database, and for possible future modifications to enhance its geomorphological value.     

Effects of subacute cadmium exposure on a hardwater mountain stream microcosm

Open stream microcosms in the RIFFLE facility were exposed to 22 μg l^?1 cadmium for 21 days. Although less than 0.3% of the metal passing through the streams remained in the microcosms, more than 1000 μg g^?1 dry wt accumulated in the Aufwuchs community, apparently in response to photosynthetically induced CdCO₃ precipitation. Accumulation decreased with increasing trophic level in the order: Aufwuchs > macrophytes > grazers/collectors > predators. Although no effect on periphyton community structure was observed, invertebrate grazers and collectors in the riffles were adversely affected by cadmium exposure, while populations of pool chronomida and riffle predators increased. Open lotic microcosms are shown to provide valuable hypotheses regarding metal fate and effects, but cannot be used as simple screening tools because of the nature of the invertebrate population data likely to be produced.     

Occupational exposure to trihalomethanes in indoor swimming pools

The study evaluated occupational exposure to trihalomethanes (THMs) in indoor swimming pools. Thirty-two subjects, representing the whole workforce employed in the five public indoor swimming pools in the city of Modena (Northern Italy) were enrolled. Both environmental and biological monitoring of THMs exposure were performed. Environmental concentrations of THMs in different areas inside the swimming pools (at the poolside, in the reception area and in the engine-room) were measured as external exposure index, while individual exposure of swimming pool employees was estimated by THMs concentration in alveolar air. The levels of THMs observed in swimming pool water ranged from 17.8 to 70.8 microg/l; the mean levels of THMs in ambient air were 25.6+/-24.5 microg/m3 in the engine room, 26.1+/-24.3 microg/m3 in the reception area and 58.0+/-22.1 microg/m3 at the poolside. Among THMs, only chloroform and bromodichloromethane were always measured in ambient air, while dibromochloromethane was detected in ambient air rarely and bromoform only once. Biological monitoring results showed a THMs mean value of 20.9+/-15.6 microg/m3. Statistically significant differences were observed according to the main job activity: in pool attendants, THMs alveolar air were approximately double those observed in employees working in other areas of the swimming pools (25.1+/-16.5 microg/m3 vs. 14.8+/-12.3 microg/m3, P < 0.01). THMs in alveolar air samples were significantly correlated with THMs concentrations in ambient air (r = 0.57; P < 0.001). Indoor swimming pool employees are exposed to THMs at ambient air levels higher than the general population. The different environmental exposure inside the swimming pool can induce a different internal dose in exposed workers. The correlation found between ambient and alveolar air samples confirms that breath analysis is a good biological index of occupational exposure to these substances at low environmental levels.     

Fragmentation of pine flatwood and marsh communities converted for ranching and citrus

Patterns of change are documented for pineland and marsh, two habitats that are significant for 273 of the 326 native terrestrial vertebrates within the Immokalee Rise region of Florida. Area of both habitats, average patch sizes, and association of patches with patches of the same type and different types changed dramatically from ca. 1900 to 1989. Patterns of change were slightly different from ca. 1900 to 1973 and 1973 to 1989, with more large-scale removal of patches occurring in the former time period. Fragmentation of remaining patches was greatest from 1973 to 1989. In addition to loss and fragmentation of habitat, the association of the two habitat types has been altered. Pineland and marsh have become separated from each other thereby altering, if not destroying, the important upland-wetland linkages naturally present in the region. Drawing from previous studies of species-habitat associations and fragmentation impacts on wildlife in other areas, we form some general conclusions on the implications of these changes on regional biodiversity. Species most severely impacted by the change are most likely those requiring large contiguous areas, requiring interior pineland habitat, and those that use both uplands and marsh. It is probably not a coincidence that 65% of the species rare in the region use pineland or marsh. Continued chipping away at the remaining habitat without regard for the importance of the spatial arrangement and regional context will continue to impact regional biodiversity. A regional perspective to agricultural development is needed to maintain the native biodiversity in the region. Efforts should be made to preserve the remaining large tracts of habitat and seek to restore connections between critical habitats. Maintance of biodiversity will require a regional perspective to agricultural development. Large tracts of remaining habitat must be preserved and connections between critical habitat restored.     

Do landscape factors affect brownfield carabid assemblages?

The carabid fauna of 28 derelict sites in the West Midlands (England) were sampled over the course of one growing season (April-October, 1999). The study aimed to investigate the relationship between carabid assemblages and five measures of landscape structure pertinent to derelict habitat. At each site measurements of landscape features pertinent to derelict habitat were made: (i) the proximity of habitat corridors; (ii) the density of surrounding derelict land; (iii) the distance between the site and the rural fringe; and (iv) the size of the site. Concurrent surveys of the soil characteristics, vegetation type, and land use history were conducted. The data were analysed using a combination of ordination (DCA, RDA), variance partitioning (using pRDA) and binary linear regression. The results suggest that: 1. There is very little evidence that the carabid assemblages of derelict sites were affected by landscape structure, with assemblages instead being principally related to within-site habitat variables, such as site age (since last disturbance), substrate type and vegetation community. 2. No evidence was found to support the hypothesis that sites away from railway corridors are impoverished in their carabid fauna than sites on corridors. 3. There are some suggestions from this study that rarer and non-flying specialist species may be affected by isolation, taking longer to reach sites. We infer from this that older sites with retarded succession, and sites in higher densities of surrounding derelict land may eventually become more species rich and that these sites may be important for maintaining populations of rarer and flightless species. 4. Conservation efforts to maintain populations of these species should focus principally on habitat quality issues, such as maintaining early successional habitats that have a diversity of seed producing annuals and perennial plants and enhancing substrate variability rather than landscape issues.     

The avifaunas of some fragmented, periurban, coastal woodlands in south-eastern Australia

Growth of urban centres world-wide has been so dramatic over the past 100–200 years that many natural habitats have been much altered around large cities. A threatened coastal plant community, Moonah Melaleuca lanceolata woodlands, has been largely destroyed and degraded over a long period by the growth of suburbs into the desirable coastal areas on the fringes of the two main cities of Vic., Australia (Melbourne and Geelong). Here, we describe the avifaunas of 19 remnants of coastal Moonah woodland. The largest remnant is about 50 ha and this was used as a site for positioning ‘virtual’ remnants against which we could compare the avifaunas of the more common size-range of real remnants (≤10 ha). Although remnant habitat structure differed consistently between virtual and real remnants, these differences were not sufficient to alter the native avifaunas in constitution or bird densities. However, species richness was higher in 10 ha and in 2 ha remnants than in 1 ha remnants. Of seven landscape-context variables, only one influenced the avifauna: species richness declined as the degree of urbanization increased (measured by roof-counts). Exotic bird species have not colonized the remnants to a great degree (four species [of 38 in total], 8% of total records).     

基于Maxent模型的深圳湾鸟类热点生境 判别及修复研究

鸟类热点生境判别对于掌握鸟类空间分布格局、 识别保护空缺及指引生境修复策略具有科学价值。采用最大 熵模型确定深圳湾2000与2020年的鸟类热点生境,分析鸟 类生境的变化及其与景观格局演变的关系。结果表明：1)各 环境因子对不同生态类群的鸟类影响程度各不相同,除鸣禽 以外水源距离对其他类群鸟类的影响较大,其次为高程和 年降水量;2)2020年深圳湾的鸟类热点生境占总研究区的 3%(22km2),呈现从自然保护区向城市内陆逐渐减少的趋 势,存在2km2的保护空缺;3)20年间深圳湾鸟类的热点生 境减少了7%,热点生境下降的地区主要集中在深圳湾沿海滩 涂、香港山贝河与屯门河流域中,且猛禽与游禽的生境退化最 为严重;4)鸟类热点生境面积随斑块的数量、密度、形状与用 地类型等景观指数的增加而降低,景观破碎化和景观连通性降 低是导致鸟类生境退化的主要原因。研究为深圳湾鸟类多样性 保护及生境修复提供了参考,对粤港澳大湾区协同生态保护与 城市建设的关系具有重要意义。     

The development of epigeic fauna in new hedges — a comparison of spatial and temporal trends

The colonisation of a linear sequence of nine young hedge plantations (each 400 m²) within an intensely cultivated landscape about 30 km to the west of Bonn has been studied to compare spatial and temporal distribution patterns of epigeic arthropods in order to consider differences obtained concerning an assessment of colonisation characteristics and dispersal trends. The investigation was started in 1982, the year in which the new hedges were planted and continued until 1991. Pitfall traps—usually six as a standard set—were installed in young hedges and in old wooded habitats of an adjacent semi-natural habitat complex, as well as in surrounding arable fields and in meadow strips connecting the hedge plantations. But only in 1990 nearly all the habitats were sampled at the same time. Between 1982 and 1989 catches were continuously performed only in two habitats, since 1986 in four young habitats.Results on species of the taxonomical groups of Carabidae, Opilionida and Araneida show that the analysis of spatial only or temporal only patterns can lead to different interpretations and sometimes wrong conclusions about the colonisation of new hedge habitats. Both types of data, comprehensive spatial and long-term temporal, are complementary and a combination of both is recommended for properly assessing dispersal of species and other dynamic processes in the landscape. As far as the colonisation of new hedges is concerned it is shown that despite high temporal dynamics in species abundances and remarkable differences between the three taxa considered, the development towards a typical hedge fauna progresses very slowly. Small, 9-year-old hedges do not function well as stepping stones for the dispersal of epigeic forest and forest-edge arthropods, and only a small corridor effect could be established for the linear plantation strip. Remarkable differences in colonisation trends between beetle and spider species of similar ecological preferences are discussed.     

Planning and designing for the multiple use role of habitats in urban/suburban landscapes in the Great Basin

Most researchers agree that preserving, creating, and restoring urban wildlife habitats has to be an interdisciplinary undertaking if it is to succeed. Ecologists and wildlife biologists must be key participants. The culturally modified context of most urban habitats suggests that landscape architects also have a primary role to play.Open space in the urban/suburban environment is a scarce and valuable resource. Private and public sector pressure to convert these spaces to commercial or intensive recreational uses are immediate and intense. Presenting arguments to preserve or restore urban open space solely as habitat for wildlife is seldom successful. Decision makers are more likely to support urban wildlife habitat programs if other uses are also accommodated.There is a growing body of research data that suggests that wildlife are being adversely impacted by multiple uses of urban habitats. The challenge for planners and designers is to minimize adverse impacts and capitalize on those attributes of other uses that enhance habitat value. Planning for the temporal as well as spatial dimensions of site uses is required if the needs of wildlife are to be met.The paper presents three general areas in which landscape architects have traditionally contributed to an interdisciplinary approach to urban wildlife habitat planning: contextual perspective, problem solving process, and design/technical execution.Reflecting back on his past 10 years of experience as a landscape architect planning urban wildlife habitats, the author presents several case study projects in which: (A) accommodation of multiple use objectives, including wildlife habitat, was required; (B) interdisciplinary teams participated in the planning and design process; (C) key principles from the fields of landscape ecology, conservation biology and wildlife biology were applied to facility and activity location, habitat configuration, and management.Plans of completed projects are used to illustrate how habitat values were preserved or enhanced and multiple uses accommodated in public open spaces. The paper concludes with a brief summary of keys to success common to each project.     

Implementation of artificial neural networks (ANNs) to analysis of inter-taxa communities of benthic microorganisms and macroinvertebrates in a polluted stream

This study was performed to gain an understanding of the structural and functional relationships between inter-taxa communities (macroinvertebrates as consumers, and microbes as decomposers or preys for the invertebrates) in a polluted stream using artificial neural networks techniques. Sediment samples, carrying microorganisms (eubacteria) and macroinvertebrates, were seasonally collected from similar habitats in streams with different levels of pollution. Microbial community taxa and densities were determined using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and 16S rDNA sequence analysis techniques. The identity and density of macroinvertebrates were concurrently determined. In general, differences were observed on grouping by self-organizing map (SOM) in polluted, clean and recovering sites based on the microbial densities, while the community patterns were partly dependent on the sampling period. A Spearman rank order correlation analysis revealed correlations of several eubacterial species with those of macroinvertebrates: a negative correlation was observed between Acidovorax sp. (from polluted sites) and Gammaridae (mostly from the clean site), while Herbaspirillum sp. and Janthinobacterium sp. appeared to have positive correlations with some macroinvertebrate species. The population dynamics of the tolerant texa, Tubificidae and Chironomidae, appeared to be related with changes in the densities of Acidovorax sp. This study revealed community relationships between macroinvertebrates and microorganisms, reflecting the connectivity between the two communities via the food chain. A further physio-ecological and symbiological study on the invertebrate-microorganism relationships will be required to understand the degradation and utilization of detritus in aquatic ecosystems as well as to elucidate the roles of the inter-taxa in the recovery of polluted aquatic environments.     

The effect of neighbourhood on rodent communities: an example from Pampean agroecosystems

Pampean region agroecosystems are devoted to agricultural and farming activities, but in the crop field matrix there are relicts of remnant natural habitats. Poultry farms mainly harbour commensal species as house mice and rats, which are rarely present in surrounding habitats. We assessed if neighbourhood to poultry farms affect the presence of Mus musculus in crop fields and their borders, and if rodent community in poultry farms is influenced by the species present in surrounding crop fields and borders. We found that habitat had a significant effect on the abundance of M. musculus. This species showed higher abundance in poultry farms than in crop field borders. Calomys laucha was the unique native species that was captured in farm sheds. We found higher abundance of native species in crop field borders than in crop fields independent of the proximity to the poultry farms. We conclude that rodent communities in poultry farms are little influenced by the surroundings, and show a dominance of M. musculus independently of the presence of native rodent species in neighbour habitats. On the other hand, farms do not export M. musculus to surrounding habitats, and borders only function as corridors for dispersal among farms, while crop fields are rarely used.     

Survival and viability of Escherichia coli in a thermally altered reservoir

Escherichia coli survived and grew in a warm, monomictic reservoir receiving thermal effluent from a nuclear production reactor, which suggests that the presence of E. coli in these aquatic systems is not an indication of recent fecal contamination. Known populations of E. coli were placed in sterile diffusion chambers and suspended at various depths throughout the water column. Experiments were conducted during both ambient water conditions (reactor not operating) and thermally altered water conditions (reactor operating). E. coli populations were observed for changes in density by using optical density and direct and indirect counting methods. During both ambient water and thermally altered water conditions, E. coli survived and grew 2–3 weeks at each depth and at all stations. During thermal alteration, cell populations attained higher optical densities and maintained those densities for longer time periods than those during ambient water conditions. In addition, populations suspended in the hypolimnion generally maintained higher optical densities than those in the epilimnion. Data show that E. coli survives and grows for extended periods of time while it is in diffusion chambers in both aerobic and anaerobic portions of the water column.     

Early colonization of stone by freshwater lichens of restored habitats: A case study in northern Italy

This study evaluated the effectiveness and life-strategies of freshwater lichens in colonizing newly constructed stone structures in low-elevation streams in a small nature reserve in northern Italy. Species richness, size of thalli, morphological and ontogenetic traits of the species were related to the age of restored habitats. Lichen colonization was surprisingly rapid, indicating the high potential of these organisms in colonizing restored habitats. However, the species pool found in the restored habitats was different than that found in natural sites in the same study area. The age of newly constructed habitats influenced both species richness and thallus size of the two most frequent Verrucaria species. Verrucaria aquatilis was a rapid colonizer invading the substrate by several small-sized and thin thalli which soon supported a large number of small perithecia whose development began in the earlier phase of thallus formation. V. elaeomelaena, on the contrary, developed according to a different strategy, establishing a thick thallus on which relatively large perithecia were formed much later than in V. aquatilis. As these taxa are important photoautotrophic components of freshwater ecosystems more ecological knowledge is needed to evaluate the effectiveness of different measures of river restoration on lichen communities. The main practical implication of our study is related to the value of small stone structures, such as riffles and ramps, for enhancing the establishment of pioneer freshwater lichens to rapidly colonize newly available substrata.     

成都城区河流廊道自生植物的生境及物种多样性

河流廊道是自生植物生长的重要栖息地,但相关研究较为缺乏.运用均匀布样法,结合典型样地法,选取贯穿成都城区西北到南部的清水河、南河、府河为样段,共223个样方,分析自生植物定居的生境类型,探寻物种组成特征,以期为自生植物生境及景观营造提供参考.结果表明:生境按照距水的远近可分为无驳岸水边、驳岸和岸上三大类,根据基质及绿地...     

Ecological impact of river impoundment using benthic macro-invertebrates as indicators

A study of the benthic macroinvertebrates of a fourth order stream in Southern Nigeria was carried out to assess the ecological impact of impoundment. Three stations 1, 2, and 3 were selected from upstream of the impoundment, the impoundment (reservoir) and its downstream, respectively. There was no significant difference (P > 0.05) in the values of the physical and chemical parameters between the upstream and downstream stations. Water level, transparency, current velocity and dissolved oxygen were, however, significantly lower within the reservoir. The total number of benthic macroinvertebrate taxa and their overall density were significantly higher in the control station (upstream) than within the reservoir and the downstream station. The density of the three dominant taxonomic groups, Diptera, Oligochaeta and Ephemeroptera differed significantly (P < 0.05) among the stations. While chironomid dipterans dominated the up- and downstream stations, Oligochaeta was dominant in the reservoir. Ihe density of Ephemeroptera was significantly reduced within the reservoir and the downstream station. Analysis of faunal similarities showed that the upstream station I was significantly different from stations 2 and 3. Stream impoundment, therefore, alters not only the river hydrology but also the faunal characteristics of downstream stations. This study further strengthens the viewpoint that river management consideration should be implemented to lessen the impact on the downstream ecology. Furthermore, when considering impounding a river, the ecological implication must also be considered.     

基于河流动态自然过程的生境修复策略

全球气候变化和土地利用方式的改变对河流的动态自然过程带来不利影响。而目前人们对河流的修复重治理效果而轻自然过程,特别是风景园林与相关学科的交叉与融合研究较少,缺乏聚焦中、微尺度基于河流动态自然过程的生境恢复方法指导。基于此,从雨洪淹没、潮汐消落的河流动态自然过程规律着眼,提出对应的生境修复策略：1)恢复水陆边界的自然属性,重建泛洪区和河岸的联系;2)梯度式快速恢复近自然河岸带生境植被;3)连通感潮河涌湿地和营建关键生物生境,实现多种共生生物栖息地的再生。该方法有助于恢复河流长期、稳定的自由流动,生境在河流动态潮汐作用下异质性不断提高,从而提高河流湿地的生物多样性,还能为城市中心的居民提供亲近自然的休闲空间,以期在河流生境修复实践方面为风景园林和多学科融合提供新思路。     

A habitat model for Parus major minor using a logistic regression model for the urban area of Osaka, Japan

We developed a habitat model for Great Tits, Parus major minor, in an urban area of Osaka, Japan. Although Great Tits play an important role in the urban food web, there are few in most of Osaka and downtown Tokyo, areas that have low vegetation cover. We derived a habitat model for Great Tits using a logistic regression model with GIS. A bird survey was conducted twice in 85 urban parks using the line census method in the breeding season, May–July 2000. A GIS base map was created from aerial photographs. The following variables were measured for each park from public records and GIS for predicting the habitat: park properties (age, distance to the nearest mountains, distance to the nearest forest of more than 10 ha), the number of other habitats occupied by the tits within 500 m and 1 km and area of tree cover (within it and surrounding parks). Number of nearby habitats and distance from the nearest mountains and forest of more than 10 ha are variables related to the regional populations of the tits. Area of tree cover was measured for five radii (50, 100, 150, 200, 250 m) from park centers, and a logistic regression model was calculated for each of these radii. Variables were selected by a stepwise method. The best fitting model of the five models was selected using Akaike’s Information Criteria. In the bird survey, the tit was recorded in 12 parks. The areas of parks occupied by the tit were 0.56–136.0 ha (mean: 26.0 ha±42.06 S.D., n=12). Variables selected in the best fitting model were area of tree cover in a radius of 250 m from park center and the number of other habitats within 1 km as positive factors. This model shows that area of tree cover within a certain range and number of nearby populations are the keys to the distribution of Great Tits. From this model obtained, 6.0 ha (31%), 4.0 ha (20%), 2.6 ha (13%) and 1.8 ha (9%) of tree area are needed to achieve probability of 0.5 in a radius of 250 m when numbers of other habitats within 1 km was 0–3, respectively. A realistic target figure is 10% of tree cover throughout urban areas to create an ecologically sustainable city.