Today, the world's population is approximately 6.7 billion and increasing rapidly despite a recent decline in overall rates of population growth. Population growth is distinctly uneven worldwide and these differences are reflected in the allocation and use of resources. This article gives a brief overview of population growth processes and surveys recent trends in population statistics, including fertility, contraception, sex ratios, nutrition, HIV/AIDS, urbanization, aging, migration, income distribution, consumption, and biocapacity. Current population trends are indicators of the near future, providing a basis for ongoing attention and research on population issues.
Demographers track several population processes to estimate and project population change. For most of history, and likely pre-history, the world's population change has been marked by high fertility rates, high crude birth rates, high infant mortality rates, high crude death rates, high mortality rates, and low life expectancy. When added together, this means that the world's population turned over rapidly, but absolute numbers grew only slightly or not at all. In demography, a relatively stable condition of no net decrease or increase in numbers is called a population replacement rate.
By 1830, the global population had reached one billion. The second billion in population increase took only 100 years, the third billion about 30 years, the fourth billion 15 years, and the fifth billion only 12 years (Population Reference Bureau, 2007). Figure 1 illustrates this exponential growth of world population since 1950, providing projections through the year 2050 (US Census Bureau, 2011).
By 2013, the world's population had reached approximately 7.1 billion, increasing by around 2.5 individuals per second (US Census Bureau, 2013). Around 1990, we see the beginning of a downward trend in the overall population growth rate. As shown in Figure 2 (US Census Bureau, 2012), if this decreasing trend continues, the rate of population growth will have slowed significantly by 2050.
However, as Figure 1 shows, a decrease in the rate of population growth does not lead to a decrease in overall population. In absolute terms, the global population is projected to increase to over 9 billion people by 2050. According to the Population Reference Bureau, this increase is approximately the size of the combined populations of China and India, the two most populous countries representing two of the highest population growth rates in the world (2007).
Factors Affecting Population Growth
Obviously, genetic, biological, geographical, and ecological factors affect population processes. One of the most well-known theories of population growth was put forth in 1798 by Robert Malthus, who held that world population would grow at a rate just slightly higher than food production. Though "natural" population-limiting processes exist, such as disease, drought, and natural disasters, which tend to increase mortality rates, Malthus predicted a future in which widespread starvation would occur.
Cultural and social factors also have had a tremendous impact on population processes. It is no coincidence that the statistical techniques of demography became more sophisticated around the same time as the term "sociology" was first coined by Auguste Comte. The two fields are complementary to one another, just as social change and population change go hand in hand. For example, the potential of war to dramatically affect population numbers cannot be overstated. If natural conditions produce widespread starvation, social conditions that spur conflict and war can arise.
Demographic Transition Theory
A more recent and even better-known theory of population growth is known as demographic transition theory, which holds that populations move through four distinct stages of growth and decline processes, linked to the technological or developmental state of a given society.
In Table 1, the first stage is representative of most of human history up until the last few centuries. According to demographic transition theory, stages 2 and 3 are periods of expected increases in overall population as societies undergo processes of industrialization and the accompanying changes in food supply, sanitation, medicine, and working conditions. In stage 3, decreasing birth rates and increasing life expectancy begin a period of population decline. In stage 4, the birth rate can either stabilize or decrease. If birth rates are stable, the population again reaches replacement rate.
Table 1: Stages of Population Growth during Demographic Transition
Stage 1 Stage 2 Stage 3 Stage 4 Production Rates (economic goods) Low Increase Increase Stable Fertility Rates High Decrease Decrease Stable Birth Rates High High Decrease Stable Death Rates High Decrease Decrease Stable NET EFFECT: Replacement Growth Declining Replacement
Demographic transition is descriptive of population growth during the era of widespread industrialization. Certainly, global population growth and decline have been geographically uneven, and patterns do differ between more and less industrialized nations, as demonstrated in Figure 3.
Demographic transition theory will be put to the test as India and China, with the world's largest populations, continue to industrialize and we see the outcomes of other recent trends in population processes over the next 40 years.
Recent Trends in Population Processes Fertility & Contraception
Fertility rates in industrialized nations have been declining since the early twentieth century. In many less industrialized countries, the idea of planning and timing children was quite revolutionary. Traditionally, with high rates of infant mortality, larger families held better chances of survival, gaining more status and wealth over time.
During the latter part of the twentieth century, attitudes toward childbearing began to change. The global fertility rates began to decline after 1960, as women in less industrialized countries began to limit the number of their children. Many factors contributed to the changes in fertility patterns in the less industrialized world. Some studies credit organized family planning programs with at least half of that decline (Kent & Haub, 2005).
Growing acceptance of the idea of family planning opened the door to multiple changes in childbearing behavior. In the 1960s and 1970s, surveys to measure knowledge and use of family planning were first conducted in a small number of countries around the world. These surveys found that less than 10 percent of women were using any family planning method. Family planning programs worldwide began to introduce women to more effective pregnancy prevention methods, including female sterilization, intrauterine devices (IUDs), and oral contraceptives. Condom usage, which protects from sexually transmitted diseases (STDs) as well as pregnancy, ranks in popularity below these others in every country; only around 5 percent of women worldwide rely on condoms. Vasectomy, or male sterilization, is used by only about 4 percent of the worldwide population (Kent & Haub, 2005).
By the 1980s, most women were using at least one effective method of contraception, and by 2000, more than half of the world's women of reproductive age were using some method of birth control. In less industrialized nations, the total fertility rate fell from about 6.2 in the 1950s to around 3.0 in 2005. At that time, contraceptive use was higher in some less industrialized countries than in many European countries (Kent & Haub, 2005).
A large body of research over the last several years links higher education for women and girls with reduction in fertility levels. Indeed, recent data from many countries show that women with at least a secondary-level education eventually give birth to onethird to one-half fewer children than do women with no formal education whatsoever. Educated women tend to delay marriage and opt for more control over their reproductive lives (Haub, 2007).
Across countries and time periods, both the sex ratio at birth and the population sex ratio generally varies little between human populations. In 2013, just over half of the human population was male, with males accounted for 50.3% of the global total. In some areas of the world the ratio of males to females is higher, while in other countries, including the United States, females outnumber males. Small variations do occur naturally, but reports began to appear in the 1990s of 100 million or so "missing women" across the developing world (Hesketh & Wei Xing, 2006; Sahni, et al., 2008).
Cultural traditions of preference for sons are seen in almost all patrilineal societies, which link inheritance of property to the males in a family. However, there seems to be some evidence that son preference has distorted expected sex ratios in large parts of Asia and North Africa in particular. The contention is that son preference is now practiced actively in these countries through the increasing availability and use of sex-selective abortion and through discrimination in caregiving practices for girls, which leads to higher female mortality (Hesketh & Wei Xing, 2006; Sahni et al., 2008).
Differential gender mortality in some areas has now been a documented problem for some time. Since the early 1990s, improved health care and conditions for women have resulted in reductions in female mortality, but these advances have now been offset by large numbers of "surplus" males now reaching adulthood. These males are predominantly of low socioeconomic class, and concerns have been expressed that their lack of marriageability and consequent marginalization in society may lead to antisocial behavior and...
Table of Contents
List of Figures
Impacts of Rapid Human Population Growth on Biodiversity 1
Human activities related to rapid population growth
Manufacturing and Resource Exploration
List of Figures
Figure 1. Estimated world population and projections: 2000-2050 (Source: UN, 2004)
Human activities modify the environment in many ways; you are affecting the ecosystem by just reading this publication. Some of the major human activities include: agriculture, fishing, mining and exploration, urbanization, manufacturing, transport and communication, warfare among others. These activities have intensified with the continued growth in human population and this has had catastrophic consequences on the planet’s biodiversity, man included. There are multiple measures, locally, regionally and globally, that seek to tame the rapidly growing human population in a bid to salvage the planet’s biodiversity and its environment at large. This publication will highlight some of these human activities and how they negatively affects Earth’s biodiversity. The data/information used in this publication is primarily secondary, drawn from several credible and reliable online sources.
Keywords: Population, Population Growth, Environment, Biodiversity, Agriculture, Forestry, Fishing, Urbanization, Manufacturing, Mining, Resource Exploration, Transport, Communication, Warfare, Pollution.
Impacts of Rapid Human Population Growth on Biodiversity
Biology online (2008) defines population as, “a group of organisms of one species that interbreed and live in the same place at the same time.” The term population will be used to refer to the global human population in general. Population growth is the increase or decrease in numbers of a species over a defined period of time. It is believed that the world population first clocked the one billion mark in 1804, two billion in 1927, three billion in 1960, four billion in 1974, five billion in 1987, six billion in 1999 and seven billion somewhere between late 2011 and early 2012. The UN (2013) projects that the world will have about eight billion people come 2030 and around nine billion by 2050.The UN (2004) predicted that the human population would grow at an average annual rate of 0.77from 6.1 billion in 2000 to 8.9 billion in 2050. The figure below illustrates human population growth trends from 1950 to 2050.
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Figure 1. Estimated world population and projections: 2000-2050 (Source: UN, 2004)
Human activities refer to all the things that people do. These are a function of people’s intrinsic (e.g. personality and genetic disposition) and extrinsic (e.g. culture, norms and faith) factors (Human behavior, 2014) and they have an anthropogenic effect on both the biotic and abiotic environments. We intend to look at the various human activities with both direct and indirect effects on our planet’s biodiversity.
UNEP (2014) describes biodiversity as, “a term used to describe the number, variety and variability of living organisms on Earth.” Some say that there are roughly 30 million species on earth, others 15 million while the lowest estimate is 7 million. Scientists are said to find and describe about 15,000 new species every year. It is believed that 5 billion species have lived on Earth but only 2 in every 1,000 of these species have survived to today’s Age of Mammals (Cincotta & Engelman, 2000).
It would be impossible to list all the things (activities) that people do and how they affect Earth’s biodiversity but we can narrow down this list to those activities that are caused by our rapidly growing population. The term environment and biodiversity will be used interchangeably in this publication.
According to Sala, et al. (2000), the unprecedented rate at which Earth’s biodiversity is declining can be blamed primarily on the rapidly growing human population. The surging human population means that more arable land is needed for crop production and livestock grazing, and for wood for fuel, construction, and energy. This in turn leads to virgin lands, rich in biodiversity, being violated! Also, increased human activities cause land, water and air pollution; alters the concentration of CO2 in the atmosphere; affects the nitrogen cycle to bring about acid rains; alters the climate and brings about the introduction of exotic species.
Ehrlich and Holdren (1971) proposed that the product of population size (P), affluence (A, output per capita also the level of consumption) and technology (T, per unit output or efficiency in production) gives a people's impact on their environment (I).
In other words, the increased pressure on the environment is as a direct result of increased affluence (more consumption, pollution and waste) and persistent poverty (constrained resources and limited technology). Growth in human numbers, P, affects both the A and T variables.
Human activities related to rapid population growth
Here is the scenario, more people demand for more resources but in reality, the planet’s resources are limited. Hence, out of necessity, the inflated population will naturally intensify its activities and consequently exerts enormous pressure on its delicate environment. The impacts that emanate from the intensified human activates are ignorantly accrued over time. This is because there are either limited environmental degradation indicators or the planet is just too big for us to notice them until these impacts are experienced on a larger scale.
When world governments developed the 2010 biodiversity target in 2001, they intended to achieve a significant reduction in the loss of biodiversity at the global, regional and national levels. However, as highlighted in the Global Biodiversity Outlook 3 report (2010), this target, “has not been met.” The report attributes the escalating trend in loss of biodiversity to intensified human activities.
Human activities that intensify with population growth include: agriculture, fishing, mining and exploration, urbanization, manufacturing, transport and communication, warfare among others. Let us describe some of these activities and see how they impact biodiversity (when related to population explosion).
Agriculture is the science, art and activity of cultivating plants and domesticating animals mainly for food and products that sustain and enhance human life. Agriculture brought about human settlement over 10,000 years ago and with this sedentism, came civilization (Science Experiences and Resources for Informal Educational Settings (SERIES), 2006). Farming is done on land and today over 30% of all land is dedicated to agriculture.
There are several microorganisms e.g. bacteria and fungi and macroorganisms e.g. worms, mites, ants and spiders that dwell in the soil. The UNEP (2008) states that, “burrowing organisms mix the upper layers, redistribute nutrients and increase the amount of water absorbed by the soil when they dig to move through the soil.”
As the human population keeps growing, more and more land has to be brought under cultivation. This is necessary in order to sustain the diverse dietary and growing energy demands that come along with this sprawling population. With this in mind, EuropaBio (n.d.) then believes that this puts natural plant and animal life is at risk. Agriculture along with unsustainable forest management, are the two major drivers of species extinctions today.
According to EuropaBio (n.d.), farming practices have extensive effects on Earth´s biodiversity, “especially when new land is brought into cultivation.” When fresh lands are farmed, native species get displaced/destroyed while foreign life is introduced. The Convention on Biological Diversity (CBD, n.d.), tries to articulate how this happens; conversion of wild lands to agriculture leads to the loss of terrestrial ecosystems and natural habitat e.g. the Miombo woodlands of South Africa (Secretariat of the Convention on Biological Diversity, 2010), are threatened by clearing land for Agriculture.
The augmented use of synthetic fertilizer to increase agricultural production has led to excess levels of nitrogen and phosphorus in natural ecosystems. Excess nitrates and phosphates lead to increased eutrophication. For instance, the increased buildup of these compounds in inland waters and coastal ecosystems (due to surface runoff from croplands) causes more algae to grow in rivers and bays. These algae block out sunlight needed by sea grass for photosynthesis. The decaying algae consumes oxygen from the water. These two factors depopulate fish species. In addition, temperate grasslands, that thrive in nitrogen deficient ecosystems are outpaced by those species that do well in nitrogen rich environments.
The abstraction of inland water for farming (aquaculture included) accounts for 70 per cent of the world's withdrawals of fresh water. CBD (n.d.) goes further to say that, “The construction of dams and flood levees on rivers also causes habitat loss and fragmentation, by converting free-flowing rivers to reservoirs, reducing connectivity between different parts of river basins, and cutting off rivers from their floodplains.” In addition, mariculture e.g. shrimp farming and bottom-trawling also causes loss of seabed habitat.
Changes in land management tactics also alters the local biodiversity every time. Other crop management approaches e.g. the cultivation of insect-resistant plant varieties translates to starving the native insect species to death.
The Wikimedia Foundation, Inc. (2014), defines fishing as the (human) activity of trying to catch fish in the wild by either hand gathering, spearing, netting, angling, trapping or other techniques. Humans hunt fish for food and fun. Dietrich and Lundbeck (1992) believed that fishing techniques had not changed since the inception of the activity 40,000 years back. However, continuous technical improvements in fishing techniques had increased fish production. Today, over 100 million tons of fish are harvested every year.
Two decades ago, 15 million people were directly engaged in fishing. The Food and Agriculture Organization (FAO) of the United Nations estimated this figure to be 36 and 38 million in 2000 and 2009 respectively. These numbers continue to swell with the surging human population.
FAO (2000) declared that over one billion people relied on fish as their primary source of protein, half of these being from developing nations. Mora, et al. (2009) estimated that at least 15% of all animal protein consumed directly by humans comes from marine fishing yet 80% of the world's fish stocks had experienced severe exploitation by 2008. Come 2030, when the human population is expected to increase by an estimated 1 billion people, demand for fish will have increased by 35 million tons.
The growth in human population directly translates into increased fishing activities. Increased fishing means accelerated rate of extinction for marine life. Consider this, 5 known marine species disappeared in the last 300 years while 16 marine species have vanished since 1972 to date. Note that in this period, the human population increased by approximately 3 billion people. Today, fishery scientists and wildlife conservatives label the fish situation as a severe global fish crisis. This is because the available wild fish cannot sustain the demand brought about by the current human population growth rate. Advanced fishing techniques have also intentionally and accidentally contributed to this extinction of species. Eilperin (2005) noted that the New Zealand grayling fish and the Caribbean monk seal were intentionally exploited to extinction while other, such as six out of the seven known sea turtles species, are endangered owing to their increased mortality. This high mortality is as a result of commercial fishing bycatch i.e. accidental victims of lines or nets meant for other catches.