A higher birth rate than the death rate of a species will lead to an increase in the population size of the species. Secondly, immigration into a given habitat at a faster rate than the emigration will also result to an increase in the population of the area.
Immigration is the movement of new species into the habitat from another habitat and this may be influenced by the presence of food and other resources in the new habitat that are unavailable from where the species are emigrating. Another factor that leads to the increase of the population is a reduction in the mortality rate.
When the mortality rate reduces for a particular population, the number of newly born surviving to grow into adulthood rises thus increases the population size (Zavaleta, Hobbs, & Mooney, 2001). Lastly, the total fertility rate of the population influences the rate of change in the population size.
The fertility rate of a given species will depend on the life history characteristics of the species such as the number of reproductive periods in the lifetime of the species and the number of offspring produced at each reproductive period (Berg & Hager, 2009).
In the nutria case, the high fertility rate and life history characteristic of the animal affect its population. The nutria reach the reproductive age when they are six months old and a mature female is capable of forty births in three years. Another factor affecting their population is the lack of a predator, which leads to a low infant mortality and death rate of the adult population. The absence of a predator causes the replacement rate of the nutria population to be much higher than its depletion rate (Messing & Wright, 2006).
When the land is depleted of the nutria’s food source, the population of the nutria will rapidly decline because of starvation. The nutria has a high daily food demand of about a quarter of their body mass. It would be difficult for the population to find a replacement food source within the same habitat that can sustain their population (Messing & Wright, 2006). Therefore, the nutria population will decrease significantly or wipe out entirely.
Environmental Benefits and Challenges of Urbanization
The term “Urbanization” refers to the transformation of a rural area into an urban area. An area that previously had the characteristics of a rural area gradually transforms into an urban area as its population increases and the dominant economic and social activities of the area change.
Contrasting urban areas and rural areas adequately offer the description of urbanization. While rural area populations work in occupations that directly extract natural resources such as fishing, logging and farming, their urban counterparts, as a result of industrial specialization, engage in occupations that relate to the transformation of the already harvested natural resources or the provision of services not directly related to the harvest of natural resources (Berg & Hager, 2009).
Cities represent urban areas that have fully passed the transition from being rural area and have the characteristic of diversity in race, ethnicity, religion and the social economic status of residents.
Challenges of Urbanization
As areas transform into urban areas they become more populated because they attract immigrants looking for better economic opportunities. The growth in population and the subsequent development of facilities to support the large population creates environmental problems in the urban areas.
One direct environmental impact is the encroachment of forests, wetlands, agricultural land and wildlife habitats. This encroachment changes the primary use of the given land and disrupts the environmental balance, which has consequences on the life of the urban residents and that of the biodiversity around them.
Encroachment into agricultural land leads to an immediate decrease in the food supply capacity of the adjacent rural area that supplies food to the urban area. Therefore, urban residents have to look further for food supplies and seek ways to make the dwindling agricultural land to produce more food per unit land size.
Another challenge of urbanization is the increased commuting distance necessitated by the large urban area. As cities grow geographically, residents have to commute longer distances to their work places, schools, hospitals and to access other social amenities or meet other people.
The increase in the commuting distance comes with an increase in the reliance on motorized transport with comes at a cost to the environment. Vehicles use fuels and emit airborne gases as their byproducts. The larger the number of vehicles used in a city, the greater the emission of the airborne gases to the atmosphere.
These airborne gases are pollutants to the environment because they affect the supply of clean gases such as oxygen beneficial to human and animal life. Vehicles also emit smoke that pollutes the environment by making visibility difficult. Moreover, the sound of vehicles especially in traffic jams as drivers hoot is disturbing to the listeners and is a form of noise pollution.
Another environmental challenge of urbanization is pollution of water. A characteristic of urban areas is the paving of roads, paths and parking lots. In addition, buildings cover any open grounds such that rain and wastewater has to be channeled over the surface through drainage systems into outlets or treatment facilities before it leaves the cities to join the natural river system.
The problem of artificial overflow of water is that it lacks the ability to sift toxic materials from the water before it joins the waterways. As water overflows on roads and other paved surfaces and roofs, it collects a lot of toxic materials that are later transferred into water ways and are consumed by aquatic life, animals and humans who are using the water.
When the rate of population increase in urban areas is much higher than the development of economic opportunities to sustain the population an imbalance arises. Additionally, developments of systems that adequately control the social character of the population have to match the population growth to prevent the social imbalance that arises.
Unprecedented growth of the urban population results to a strain on resources that can support such a high population, otherwise referred to as the carrying capacities of the urban area. An ideal population growth should be at a rate that matches the development of the necessary social amenities and economic capacities such as employment opportunities to support the growing population. Population problems blamed on urbanization lay squarely on the insufficiencies of the urban area to support its large population.
Urbanization becomes undesirable when it results to urban problems of matching facilities and the population that it supports. These challenges occur as sewage treatment, pollution, congestion, inadequate supply of clean water, limited availability of medical facilities, and few transport systems to match population growth among other challenges.
Benefits of Urbanization
Cities and other urban areas have more job opportunities than rural areas and can therefore support large number of people seeking opportunities for social and economic development. The concentration of diverse occupations and cultures in urban areas makes them the center for economic, education and cultural development.
Residents of urban areas have a faster and easier access to the available opportunities for interaction and personal growth that would otherwise require travelling long distance for the rural area resident. Urban areas also make it easy for authorities to conduct their administration duties.
In most cultures of the world, women, the disabled and the minority have limited access to economic opportunities; however, in urban areas the same marginalized people get employment in a variety of industries (Berg & Hager, 2009). In the following section we discuss two winning projects and how they overcame the challenges of urbanization discussed earlier.
Project on Sites and Services for Low-Income Family Groups Argentina
This project aims to address the challenges of providing a good quality residence to urban residents lacking the necessary economic ability to obtain their own land for development of houses. The project identified that despite the availability of land, the poor could not afford the high selling prices.
After the realization that speculators were responsible for the high price of land, the project acquired land that was later subdivided and allocated to poor residents who would afterwards pay for the land in installments without having to suffer the rising cost arising out of the speculation.
In addition, to ensure that the quality of life within the new residents was desirable, the project included the development of physical infrastructure for the low-income residents. The project included the development of roads, drainage facilities, light pillars and street lighting.
The project also addressed the supply of key services like electricity and clean water. To make the project sustainable, the development of the low-income site used the concept of a land bank where land is set aside for future allocation to low-income earners who would otherwise be unable to afford the speculative prices (UNESCO, n.d. a).
The Bronx Center Project – “Don’t Move, Improve” USA
This is a collaboration of the communities around the South Bronx area, which aims to revitalize 300 deteriorated blocks. In the revitalization plan, the project intended to create job opportunities for the community and avail job-training programs that would expand the economic opportunities for South Bronx workers, entrepreneurs and investors.
In coming up with the project, its managers realized that the urban area had been neglected and offered very little social and economic support to its residents making most of them to emigrate to look for better opportunities (UNESCO, n.d. b).
Overcoming Challenges: The Bronx Center Project – “Don’t Move, Improve” USA
In the Bronx center project, the managers focused on the redevelopment of dilapidated and abandoned buildings and using them as economic centers or administrative centers.
For example, an old courthouse was rehabilitated and designated as a community labor exchange building for residents seeking all types of employment. Throughout the implementation period of the project, the project managers engaged the community through different participating avenues so that the final development plans and designs benefited all community members.
Limited economic opportunities of the area led to an inadequate supply of affordable housing as residents earned low incomes. As a remedy, the project included the identification and addressing of the constraints that affect the low-income earners quest for housing.
This included provision of grant and loans for purchase of houses. The project also included the development of a new senior citizen’s residency. Finally the project, addressed the supply of social amenities be redesigning open spaces and streets in addition to development of transport facilities (UNESCO, n.d. b).
Overcoming challenges: Project on Sites and Services for Low-Income Family Groups Argentina
The project was able to provide a land bank for the low-income earners to shield them from the high land prices caused by speculation. It also made the land more affordable to low income earners by giving them an opportunity to pay in monthly installments in addition to letting them construct semi-permanent houses as they seek funds to develop their planned houses.
To make the project sustainable, beneficiaries were allowed to construct houses using their own resources so that there would be no dependencies associated with the success of the project.
To ensure the new residency remained desirable in providing a good quality of living, the project put in place measures limiting the number of houses that can be constructed on a single piece of land; and provided social services like roads, electricity and clean water to the site (UNESCO, n.d. a).
Berg, L. R., & Hager, M. C. (2009). Visualizing environmental science (2nd ed.). John Wiley and Sons, Inc.
Messing, R. H., & Wright, M. G. (2006). Biological control of invasive species: solution or pollution. Frontier Ecological Environment, 4(3), 132-140.
UNESCO. (n.d. a). Project on sites and services for low-income family groups Argentina. Retrieved 15 June 2011, from Most Clearing House Best Practices: http://www.unesco.org/most/southam1.htm
UNESCO. (n.d. b). The Bronx Center Project – “Don’t Move, Improve” USA. Retrieved 15 June 2011, from Most Clearing House Best Practices: http://www.unesco.org/most/usa1.htm
Zavaleta, E., Hobbs, R. J., & Mooney, H. A. (2001). Viewing invasive species removal in a whole-ecosystem context. Trends in Ecology and Evolution, 16(8), 454-459.