Nature and Human Society The Quest for a Sustainable World (1997) / Chapter Skim
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5 Threats to Sustainability
5 Threats to Sustainability
Pages 301-334
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From page 303... ...
Population growth enlarges the scale and extent of the human enterprise and hence inflates the likelihood that human activities will push native nonhuman populations and biotic communities past critical thresholds of tolerance and renewal. Demands for housing (Mason 1996)
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From page 304... ...
Beyond that expectation, however, no one can be certain that world population will ever rise to greater levels. There is equal uncertainty that population will stop growing at any particular time in the not too distant future.
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From page 305... ...
The average of all uneven rates of growth worldwide is equivalent to that of Asia, or about 1.5% per year. Despite the ever~larger population base, world population growth is gradually slowing.
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From page 306... ...
As world population increases, more modest rates of growth can add larger an' nual increments to the population base. That has occurred although the highest rates of global population growth, estimated to have occurred around 1970, saw only about 72 million people added to world population each year.
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From page 307... ...
Given the hodgepodge of modern demo' graphic trends, all that can be said with certainty about future trends and end points is that Eve cannot be certain. The UN Population Division, which produces the most widely cited tables of international population information, has addressed such uncertainty by computing every 2 years a three~piece set of population projections.
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From page 308... ...
and migration, adding all national populations for each year computed, the UN arrives at a continuous medium variant trajectory for world population. The 1996 UN medium variant projects a global population of about 9.4 billion people around the middle of the 21st century, compared with the known 2.5 billion in 1950 and the 5.9 billion in 1998.
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From page 309... ...
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From page 310... ...
Those two scenarios project a 2050 world population between 7.9 billion and 11.9 billion (figure 3~. A SEPARATE DEMOGRAPHIC REALITY The demographic experience of the world suggests that total fertility is dynamic and highly responsive to the circumstances of women and couples.
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From page 311... ...
In practice, most journalists and analysts take the UN's "medium variant," or middle trajectory, to be the most probable one, whether for national, regional, or global population figures. It is often expressed inaccurately as the "expected" population future.
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From page 312... ...
How, then, should scientists view and represent the prospects for world population? Certainly not in terms of any inevitable figure.
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From page 313... ...
1992. A concise history of world population.
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From page 314... ...
1992. Long-range world population projections: two centuries of population growth, 1950-2150.
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From page 315... ...
At the same time, much of the industrial development also happens there. On the other hand, in the foreseeable future, because of transition in the population, global population is expected to level off at 12-14 billion.
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From page 316... ...
But science and technology alone are not enough. Global policies are urgently needed to promote more rapid economic development throughout the world, more environmentally benign patterns of human activity, and more rapid stabilization of world population.
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From page 317... ...
The demographic transition will be accompanied by a marked change in the age structure of the population. Currently, people younger than 15 years make up 32% of the world population and people older than 65 years, 7%; after the transition, the numbers will be 18% and 22%, respectively.
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From page 318... ...
They indicate that if we take into account the finite human life span and reproductive time, we can expect the whole pattern of growth to change. The development of this phenomenon, following well-established methods of systems analysis and physics, envisages an asymptotic transition to a stabilized world population of 12-14 billion, with 12 billion reached in 2100.
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From page 319... ...
Calculations show that the time of the development of all humankind should be shown logarithmically, reckoning time from the year 2007 the peak of the demographic transition so that the whole human story can be shown in the same table (see figure 1~. A table like this also offers an explanation of the nonuniform way in which time has passed during the course of our development.
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From page 320... ...
Epoch B the time of quadratic growth, began 1.6 million years ago and culminated in 1965 in the ad' vent of the demographic transition.
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From page 321... ...
Population growth now practically has reached the peak of the transit tion to a stabilized world population for the foreseeable future, and the period 1965-2050 is the time of this transition. The transition is remarkably short if we compare it with the million years of our development, but 10% of all the people who ever lived will experience this period of rapid change.
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From page 322... ...
We must look into the meaning of sustainability in a world of zero or very low population growth. We should assume that the world population is moving rapidly toward stabilization and that, in promoting and propagating the idea of a sus' tainable world, this must be taken into account.
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From page 323... ...
As recent environmental research has shown, we can expect to lose biodiversity mainly during the period of rapid growth, as happened in the developed world two or three generations ago, during the first stage of the demographic transition the stage of rapid growth. Today, many see the very fast growth of the developing world as the primary menace to the global environment, with biodiversity in first place over the short term, compared with long-term environmental issues.
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From page 324... ...
A mathematical model of the world population system. Science Spectra 2(4)
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From page 325... ...
Now, over 280 million passengers use commercial airliners each year worldwide, as do millions of tons of cargo. The brown tree snake (Boiga irregularis)
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From page 326... ...
For example, on the island of Hawaii, the eastern Atlantic island shrub Myrica faya has invaded nitrogen~poor lava flows and ash deposits. A nitrogen' fixer, it favors other introduced species over the native plants adapted to low ni' trogen (Vitousek 1986~.
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From page 327... ...
In addition to ecosystem effects, nonindigenous species have myriad effects on particular native species or groups of them. They can eat them, for example.
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From page 328... ...
Routine purging of ship's ballast water has released hundreds of nonindigenous species in waters throughout the world (Carlton and Geller 1993~. Tourists can easily import species inadvertently in baggage, even if they heed warnings about which items are the most likely carriers of immigrants.
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From page 329... ...
It is difficult to imagine finding funding sources sufficient to mount risk assessments for all the challenges that might appear even to an educated layperson to be justified on prima facie grounds. Virtually every specialist in invasion biology who has examined the matter concludes that aspects of the ecological impact of a nonindigenous species are inherently unpredictable (for example, Hobbs and Humphries 1995)
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From page 330... ...
In each instance, the natural enemies maintain populations in perpetuity without further human intercession. More recently, biological control has been subjected to critical scrutiny on the grounds that nontarget species, some of conservation concern, have been attacked and even driven to extinction (Howarth 1991; Simberloff 1992~.
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From page 331... ...
Although the extent of such problems is controversial, the fact that biological control agents can both disperse and evolve, just as any other introduced species can, suggests great caution in their use and extensive preliminary testing before their release. ACTION NEEDED NOW Burgeoning international interest in invasive nonindigenous species has led to several international meetings (for example, Sandlund and others 1996)
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From page 332... ...
Having agreed that risk assessment will be the appropriate procedure to adjudicate disputes, we must determine how to do risk assessments en masse for nonindigenous species. REFERENCES Atkinson IAE.
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From page 333... ...
1996. International instruments, processes, organizations, and nonindigenous species introductions: is a protocol to the convention on biological diversity necessary?
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From page 334... ...
1993. Harmful nonindigenous species in the United States.
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