in the world's population cannot continue through the 21st century and will
come to an end either by human decision and action or by an uncontrollable
increase in deaths.
past 70 years - roughly one lifetime in many countries - the human population
grew from 1.8 billion to 5.4 billion. For every person alive 70 years ago,
there are now three. Such rapid growth cannot continue for even another generation.
Fertility must decline, or mortality will increase.
now the growth continues. Currently the world's population is growing faster
than ever before. Each year, 90 million people are added to our numbers, the
demographic equivalent of another Mexico. Just a lifetime ago, we were adding
only 15 million people per year.
declines in human fertility (or very large increases in mortality) occur over
the next five years, it would be possible to stabilize the human population
at about twelve billion within a century. Virtually all of the additional
growth - more than six billion - would occur in the poorest, least industrialized
countries of the world, often called the "South." The population
in the South would grow to over ten billion. The population in the industrialized
countries of the "North" would remain at about its current size,
a little over one billion.
a rapid drop in human fertility to occur, it will be necessary to change the
religious, social, economic and legal factors that shape couples' decisions
on the number of children they have. Safe and effective contraceptive services
must be available, but most important, religious teachings and social, economic
and legal circumstances must shift to encourage small families. Child labor,
for example, must cease to provide an economic benefit to parents.
be difficult to provide 11 to 12 billion people with even such basic necessities
as food. Of the 14 billion hectares of land on Earth, only 3.3 billion hectares
are potentially arable. At current yields, 0.26 hectares per person are needed
to feed the human population; thus at current yields, 3.1 billion hectares
would be needed to feed 11 to 12 billion. Only 1.5 billion hectares are currently
in production. Since in most cases the best lands are already in use for agriculture,
and the remaining lands are already used for grazing or some other use, a
doubling of the land in agricultural production would be expensive and disruptive.
the world's agricultural lands would also cause enormous environmental damage.
The potentially arable land that is not now in use - especially land in the
tropics - is habitat for a large number of species. Doubling the amount of
land in agricultural production would lead to massive extinctions. Even with
modest growth in the amount of land in production, a third of all the species
that were alive a lifetime ago will become extinct - gone forever - within
another decade or two. By 2015, hundreds of species are projected to disappear
If we are
to meet the food needs of up to 12 billion people by the end of the 21st century,
it is essential that agricultural yields continue to be increased - and in
ways that are sustainable. Although conventional technologies can probably
double yields, there are increasing questions about the sustainability of
conventional agricultural technologies. Furthermore, the promised benefits
of yield increases through genetic engineering may be delayed and more modest
Green Revolution began about 1950. For the first time, yield-increasing technologies
(plant-breeding genetics, fertilizers, pesticides and pumped irrigation) were
applied extensively and systematically during the last half of this century,
increasing yields dramatically and preventing serious food shortages.
Green Revolution also changed agriculture radically, making it dependent both
on environmentally destructive practices (especially the use of pesticides,
fertilizers and irrigation) and on fossil fuels. Energy used for corn production
in the United States, for Example, has increased by a factor of four since
1945. The future of human food supplies is now closely linked to the future
of energy supplies.
supplies and prices are likely to become more unstable and erratic in the
decades ahead. Even at present rates of consumption, most of the world's petroleum
would be burned within the lifetime of a child born today. If consumption
were to increase enough to fuel economic growth in the South, the petroleum
supplies of the world would disappear even more quickly. The most pressing
constraint on the use of petroleum, however, may not be supply of the resources,
but disposal space for its principle combustion product - carbon dioxide.
of carbon dioxide in Earth's atmosphere is increasing around the world, largely
because of the combustion of fossil fuels in the industrialized North. Within
the lifetime of today's children, global concentrations of carbon dioxide
are likely to reach twice pre-industrial concentrations. Such high concentrations
are expected to cause planet-wide changes in temperature and weather patterns.
Such changes would seriously disrupt agriculture throughout the world as early
as the first half of the 21st century, and during the second half would lead
to a sea level rise of 20 to 30 centimeters - enough to force the resettlement
of hundreds of millions of people and the abandonment of some island nations.
Edited by tatee - Dec 11 2012 at 4:24pm