Impact of Urbanization on Ecology - Essay Example

Impact of Urbanization on ecology (conservation) 2006 Urbanization is the expansion of a or metropolitan area, the proportion of total population or area in urban localities or areas, cities or towns, or the increase of this proportion over time. Thus, it represents the total level of urban population relative to total population of the area, and also the rate the urban population increases. For example, the United States have a rather higher urbanization level than developing countries, but a rather slower urbanization rate, because its population is living in the rural areas. The urbanization rate itself represents the increase of the urban population proportion over a certain period of time. Urbanization also means an increased scale of settlement and business in the area over time. This process can be either natural expansion of the existing population, or the transformation of population from rural to urban areas, or a combination of these two processes. Besides this, urbanization strongly has effects on the ecology of a region and its economy. With the increase of the activities in the urban area of large cities the volume of waste which accompanies increased affluence and reliance on purchased goods also increases. Moreover, harmful synthetic materials used in packing, household appliances or machinery threatens neighboring rural areas and water sources. [Batten, 1995] Environmental effects due to urbanization have been observed since early in the 18th century, while until the middle of the 20th century the levels of urbanization were too low and the number of cities was too small. But since 1950 the number of large cities has increased rapidly, provoking large metropolitan areas and agglomerations appear. The effects of urban development on ecology can be defined by many factors, the most important of which are air quality, the availability of safe water supplies, provisions of sanitation and waste management. Urbanization often provides people with the contact with wildlife. For example, hunting deer is forbidden in settled areas, and it became tame; puma as a natural predator of deer and pets such as cats and dogs, which becomes at home in the urban setting and thus often addresses people as a source of food. [Fisher, 1976] The increase of the size of urban areas has significant impacts on local airsheds and watersheds. In urban areas the majority of economic activity often occurs outwards from the city core, so that people need to go greater distances to offices and markets, situated in the core. Most of them use cars, which pollute the air with emissions and waters with auto fluids, rubber, metal and grime, and road salts. Very often new urban areas appear in areas with natural water cycle once occurred, such as forests, wetlands, meadows. This harms the recharging of the groundwater table and affects local bodies of water; the natural water cycle is disrupted and new pollutants such as pesticides create problems for the ecology in the area. Urban air is considered to be more polluted than suburban or rural ones due to the transport-related pollution. Besides, city-dwellers occupy less space household, and use less fresh water, herbicides and fertilizer, because they have smaller gardens and lawns than suburbanites. The sprawling urban centers and great tracts of agricultural lands in modern age are both direct and indirect threat to ecosystems through habitat conversion and the effects human populations have on their environment: resource depletion, waste generation, habitat fragmentation, and freshwater consumption. It also includes chemical pollution (pesticides, fertilizers), and the disruption of natural water and nutrient cycles. [Ricketts & Imhoft, 2003] All this has resulted in a biodiversity’s decrease and a reduction in the quality of natural services that various ecosystems provide (fresh air, recreation, clean water, esthetics). [Conroy et al., 2003] Thus, the modern urbanization impact on environment has become a top priority among conservationists. A study conducted by Ricketts and Imhoft (2003) indicates that there exist a significant correlation between species richness (birds, mammals, butterflies, reptiles, land snails, amphibians, tiger beetles, and vascular plants) and urbanization. The species richness increases with the level of urbanization increase within an ecoregion; the correlation also exists between agriculture and species richness. The basic human preference is to settle in ecologically rich areas, and sustain greater urbanization; there also exists a trend towards greater urbanization in areas that support high levels of biodiversity. [Ricketts and Imhoft, 2003] Conroy et al. (2003) outline that ecological problems resulted from the urbanization process are usually highly complex, that must be taken into consideration while planning to implement successful management and conservation strategies for ecosystems. The researches puts out three main components of an adaptive decision-making strategy to deal with any complex ecological problem: assessment of the current state of the ecological system, development of actions and alternative actions that may be taken to correct the problem and the predictions of the expected impact of each action, and the monitoring and assessment of the new current state of the system. Urbanization tends to perturb natural lotic systems by means of increase of drainage, sedimentation, and infiltration, that results in larger volumes of floodwater in short periods of time. Thus, streaming the flow and water development activities, and finer scale local disturbances must be dealt with to combat the degradation of the lotic ecosystem. Various alternative water development scenarios conducted by Conroy et al. (2003) suggest that an optimal strategy for regional water development must be found by looking at the underlying assumptions of system dynamics. The following scenarios can be taken into consideration: development of a few large, regional reservoirs; the use of several small reservoirs located on headwater streams; and the development of several small off-channel reservoirs. The choice of any scenario presupposes that the impact of each on species diversity, assemblage, hydrology, water chemistry, and ecosystem function will be evaluated. Luck et al. (2004) stays that the best way to protect areas of high diversity threatened by urbanization is to purchase these areas for the purpose of conservation. In urban areas local climate is also said to be changed dramatically: temperatures are warmer in the city than in surrounding areas, thus creating a sort of ‘heat-island’ (Harms, 1994); stone, concrete and asphalt tend to act as solar collectors and emit and absorb heat; the burning of fossil fuels emit greenhouse gases like carbon dioxide, heating up the atmosphere around the source, that is usually within urban environments. Urbanization and human activity creates a microclimate that isn’t environmentally healthy: the average relative humidity is less and the average maximum temperature is some degrees higher in urban areas. [Keller, 1996] After the construction phase of urbanization there increases the potential for erosion: disturb of sensitive oil results in the loss of its strength that leads to landslides. This is rather true in the areas of high densities of people and supporting structures – roads, buildings, homes. Urbanization disturb of soil and sediment leads to erosion. [Conroy et al., 2003] Human use of land in the urban areas increases the magnitude and frequency of floods, because the raw land in the process of urbanization is converted and covered with pavement, that causes an increase of runoff amount after rainfall leading to flash floods. Urban runoff can also carry polluted water from cities to streams and oceans, disturbing environments even outside the city. [Dear, 2000] The process of urbanization influences also the wildlife: flora and fauna either lose their homes or are relocated. Urbanization if virtually irreversible, because habitats are eliminated and permanent resources are depleted. [Merrifield & Swyngedouw, 1997] In order to conserve nature and maintain good ecological state, urban ecological policies should clean up and rebuild cities in balance with nature rather than destroy natural environments. [Merrifield & Swyngedouw, 1997] On the example of a huge metropolis, namely Mexico City, that is over 20 million people, we can see the results urban environment influence the ecology of the area. Here most part of sewage water is used mainly for irrigation in parks and public spaces, constituting an important source of agricultural pollution. The effects of inadequate solid water disposal are felt far beyond the city in the form of water, air and land contamination over a wide area. The domestic garbage per day rate is estimated by approximately 10,000 tons. Thus, extending and improving waste collection, processing and disposal services in order to converse the ecology of the area is vital to control also mounting health problems and prevent further damage to the environment. [Ricketts & Imhoff, 2003] Every city built on an underground aquifer is at risk for the water basin to be heavily polluted; aquifers and rivers that supply the city become overextended and polluted, and also cholera risks arise. In time many parts of the city begin to suffer from water shortage and inefficient industrial water use. This example is vivid for the Mexico City, and trying to conserve the natural environments and decrease the level of contaminations, water resources should be protected through the introduction of a variety of techniques within a city system, including: sanitary waste disposal facilities, drainage programs, urban storm water runoff, the promotion of recycling of wastewaters and solid wastes, and the control of industrial pollution sources. [Goudie, 1994] Air contamination has become the urgent problem of urban areas: photochemical smog is critical for winter month, when a temperature inversion stabilizes the atmosphere above the water basins the air pollutants accumulate in the stationary layer of air coming to the cities. Most of the air pollution comes from automobile exhaust, that’s why in many parts of the United States, where the ozone levels are more than normal atmospheric concentration and more than the maximum limit allowed in the USA, the vehicles are under a permanent vehicular restriction program called ‘Hoy No Circula’, and the pollution level is monitored by the Automatic Atmospheric Monitoring Network in order to analyze air quality every minute of the year. [Imhoff, 2004] Urbanization also affects the atmosphere by the difference of temperatures in urban and rural areas that is explained by the fact that city surfaces absorb and store significantly more solar radiation, they are of great thermal capacity and conductivity; because of the high water runoff in the city, less of this energy is used for evaporation. The additional energy in the city is produced by industrial, commercial and domestic users. [Keller, 1996] Many gases and aerosols of the urban environments contaminate the atmosphere that is harmful for humans, animals and plants. Photochemical smog presented in the urban areas is formed of nitrogen and hydrocarbons, which irritate the eyes and damage the respiratory system, also damage some crops. [Merrifield & Swygedouw,1997] Air pollution can affect the amount of cloudiness and the quality and quantity of precipitation, so that urban areas become the sources of condensation of nuclei that enhance cloud development, water vapor that increases the relative humidity, and heat that favors convection. [Dear, 2000] Acid rain that are rather common for the urban areas settle to the ground as dry deposition which lowers the pH of lakes and streams, affecting fish reproduction, aquatic life and microorganisms; removes metals from the soil, washing them into lakes and streams where they may be harmful to fish and plants; weakens or kills trees, especially conifers at high elevation, by leaching nutrients from soil and bottom sediments, that accelerates weathering of building materials and metal corrosion. [Goudie, 1994] The most import human impacts on the urban areas are grazing and logging (Ricketts et al., 1999), and the majority of impacts from urbanization are agriculture are felt by local ecosystems. Stressing on the problem of conservation, it’s worth to more cost-effective conservation opportunities for species richness may lie in neighboring ecoregions with similar habitat types and communities, but with the lower land prices and demand. It’s also important to note that endemic species can be conserved only in their ecoregion of occurrence, that’s why ecoregions containing both high endemism and high human threats are among the clearest conservation priorities. [Batten, 1995] For birds conservation much work is done by the ornithologists who investigate how climate changes resulted from the urbanization activities affect bird diversity and populations, and how this impact differs between temperate and tropical regions; they also monitor bird abundance, nesting success, survival rates, annual and seasonal variations in the abundance of predators and food. All these is done for the birds populations conservation. The studies show that urbanization reduces biodiversity in just every ecosystem, so that the preservation must take place not only in the natural habitats but around urban areas as well. [Imhoff, 2004] For the conservation activities to be successfully applied the step of mitigating the negative impact that is presupposed to be produced by the further urbanization process, critical areas and species should be identified and protected from development, to reduce per capita land consumption, appropriate or higher density of development should be encouraged. [Ricketts & Imhoff, 2003] One of the outcomes of the urbanization process is a landscape change, that include loss of agriculture areas, density of new urbanization, loss of core habitat areas. [Conroy et al., 2003] To sum the result of urbanization impact on ecology up, it’s worth to note that there are four broad interrelated forms of disturbance or degradation that can affect stream energy by altering hydrology, geomorphology or ecological processes such as energy transfer, nutrient cycling and the breeding or recruitment of flora and fauna: disturbance of hydrological and hydraulic patterns, degradation of water quality, habitat degradation or simplification, and disturbance to stream geomorphology. Often rehabilitation is conducted within the paradigm that urbanization is a negative influence on stream condition, however it also includes its positive side, connected with good public access, amenity, and an aesthetically pleasing landscape. Even if they are of little benefit, they may impair native species and ecological function. Protecting local urban waterfalls may require planning or action (for example, adoption of water-sensitive urban design that increases infiltration or the installation of stormwater treatment pond and wetlands to reduce pollutant loads) at sub-cathment, local neighborhood or even house-lot scales. Ecology aspects are marked by the reduced frequency of connection between the stream channel and association floodpain and wetland systems, habitat simplification, less diverse biotic communities, decreased nutrient retention and altered patterns of nutrient and energy cycling, altered production: respiration ratio, reduced landscape and stream-riparian connection; decreased biodiversity values. Recognizing that urban streams are highly modified features of landscapes, humans can design these ecosystems to maximize ecosystem services and minimize risk. For example, Grimm et al. (2000) are talking about integrating of multiple impacts into two elements of landuse: catchment imperviousness and the level of efficient drainage connection between impervious surfaces and local streams via stormwater pipes (‘effective imperviousness’). Disconnection of imperious surfaces will allow to increase infiltration of stormwater that will offer considerable benefits to stream condition and allow improved urban design in the future. A conceptual and planned frameworks need to be promoted for improved management of urban waterways (Lawrence, 2001). This management should occur within the conceptual framework of the total water cycle, which integrates rainfall-runoff patterns with the development and management of water resources, stormwater drainage and wastewater treatment as part of total catchment management. The measures are to be directed to the protection of natural systems, integration of stormwater treatment into the landscape, protection of water quality, reduction of runoff and peak flows, adding value while minimizing development costs. [Luck et al., 2004] The conservation activities must be held in system, at regional and continental scales. Biodiversity conservation recognized the need to provide links between reserves across fragmented natural landscapes; rare species management must include species planning and management that recognized history and spatial context. References 1. Batten D.F. (1995) Network cities: creative urban agglomerations for the 21st century. Urban studies, 32, p.361-378 2. Conroy et al. (2003) Landscape change in the southern Piedmont: challenged, solutions, and uncertainty across scales. Conservation ecology 8(2): 3 3. Dear M.J. (2000) Postmodern urban condition. Oxford: Blackwell 4. Fisher C. (1976) The urban experience. 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