79 again with increase in environmental resistance. The equilibrium level may be maintained for sometimes before a gradual decrease.
Fig 11 & 12
Finally, all the above we know that a population is a group of organism, (plant or animal) of the specie occupying, a particular space at a particular point in time. The population, in addition, is an organizational unit (level) through which energy flows and nutrients are cycled. A population is a self-regulating system that helps to keep the ecosystem (or community) in equilibrium (dynamically stable over time.) Populations also have birth rates, death rates, age structures, densities, growth patterns, and dispersion in both time and space (both dispersion within the ecosystem and to different ecosystems).
SELF ASSESSMENT EXERCISE
What do you understand by population?
80 group (23.7 million or 51.4 percent) than males (22.4 million or 48.6 percent). Aging has not become an important feature of the Nigerian population. Only 3.6 percent of males and 3.0 percent of females are aged i.e. above 64 years. The graph below (Fig. 6.7) shows that developing countries are experiencing greater increases in population than developed countries.
Some of the causes of these disproportionate figures are summarized in a tabular form that follows.
Fig 13
Continents
Comparable population Growth in Six Continents variables related to population growth in
developing countries
Variables related to population growth in developed countries
A lower rate and level of education
A culture bound perception of children as being part of the family’s labour force and often times a concomitant desire to produce male.
A tendency to have more children in order to offset the high infant mortality rate.
A lower marrying age which increase number of child bearing years.
Limited access to birth control information and techniques.
Religious beliefs and cultural values, individualism and independent minds and norms which impinge upon reproductive behaviour.
Higher rate and level of education
Higher cost associated with child-bearing and education.
A lower level of mortality with better healthcare delivery system. _
A tendency to delay marrying to a latter age thereby limiting the number of child bearing years.
Greater assess to birth control methods.
Individualisms and independent minds.
Table 1 Factors in Population Growth Developing and Developed countries.
(Source: Ehindero 2006 p.118)
81 Fig. 14
82 The Population-Environment Link
In order to satisfy their basic needs for survival and growth, humans interact with their biophysical environment for resources. There is therefore an expected and ideal proportional relationship between population increase and the degree of human impact on the environment for resources from the biosphere for survival. The number of people in a particular region or country varies and it is an index of how human activities will have impact on the environment. Factors in this relationship are rate of population increase, geographical distribution of people and investment in social services such as health and education.
The idea of earth’s carrying capacity comes into the relationship between human population growth and the degree of environmental impact. Carrying capacity as stated earlier in this unit refers to the long term capability of an ecosystem to sustain a given population without degrading its available resources and, in turn, affecting its own population. Carrying capacity is a function of human resource use and environmental factors.
The impact of human population growth on the environment depends on human ingenuity, government policies, existing legal system, access to capital and technology, the efficiency of industrial production, inequity in the distribution of land and other resources, poverty especially, in the South and conspicuous consumption in the North (WRI 1994-95). In general, the relationship between population and the environment is explicit. Observed growth in popu1ation will heighten demand for basic resources for food, energy, water, health care, sanitation and housing.
There are two major human-induced changes accompanying population growth: habitat alteration and pollution. Habitat alteration results from indiscriminate deforestation to make way for more farmland to grow food for the exploding population it has been estimated that between 1700 to 1980, forest a woodland declined globally from roughly 6.2 billion hectares 5.1 billion hectares, or nearly 20 percent. Over the same period, cropland increased from about 270 million hectares to about 1.5 billion hectares or about 460 percent (WRI 1994-95. Deforestation and the expansion of cropland are usually accompanied by different agricultural activities (inputs efficient and sophisticated use of machines and technology, roads and canals’ construction) the cumulative effect of which is soil degradation.
4.0 Conclusion
The impact of human population growth on the environment depends on human ingenuity, government policies, existing legal system, access to capital and technology, the efficiency of industrial production, inequity in the distribution of land and other resources, poverty especially, in the South and conspicuous consumption in the North
83 5.0 Summary
Globally, irrigated lands cover some 310 million hectares, an estimated 20 percent of it salt-affected (62 million hectares). The inflation-adjusted cost of salt-induced land degradation in 2013 was estimated at US$441 per hectare, yielding an estimate of global economic losses at US$27.3 billion per year. (https://unu.edu/media-relations/releases/world-losing-2000-hectares-of-farm-soil-daily-to-salt-induced-degradation.html visited on 16-09-2016 01:23)
6.0 Tutor-Marked Assignment
Establish the link between the environment and population 7.0 References/Further Readings
Oyeshola D. Essentials of Environmental Issues: The World and Nigeria in Perspective, Daily Graphics Publications, Ibadan, 1995.
Oyeshola D (1998) Politics of Internationl Environmental Regulations: Daily graphics Nig. Ltd.
Oyeshola D.(2008) Sustainable Development Issues and challenges: Daily graphics Nig. Ltd.
Ehindero O. J Environmental Education and sustainable development, Lantern books Literamed Publications (Nig) Ltd 2006
Hardy J. (1975) Science, Technology and the Environment Sauder. Lodon.
Unesco-Unep (1993) Teaching Global Change Through Environmental Education. Connect Vol.
XVIII(1) March.
Kormandy E. (1976) Concepts in Ecology. Prentice Hall Inc. Englewood Cliffs N.J.
84 UNIT 4 ENVIRONMENTAL CHALLENGES
CONTENTS 1.0 Introduction 2.0 Objectives 3.0 Main Content