Conservation of Wildlife
Lecture Notes 3
Human Population History:
Human Population facts:
2,000 years ago the estimated human population was 150 million
By 1850, the human population was one billion. By 1930, it was 2
It took 10,000 generations to reach 2 billion.
The human population is now growing at a rate of about 3 people/second
or 260 thousand/day or 1.8 million per week or 93 million/year
Every 3 years, the global environment must support another 285 million
Even the U.S. population is growing fast. We're currently adding the
of three Washington, D.C.s every year; another New Jersey every 4 years.
U.S. at night
How many of us are there? Click on the rotating Earth!
As a result of this rapid growth:
Approximately 1.3 billion of the world's people are impoverished,
on the equivalent of less than 1 dollar a day. And as population
increases, the gap between rich and poor is widening.
Some 60% of the 4.8 billion people in developing countries lack basic
and almost one-third have no access to clean water.
Nearly 1 billion people in the world are illiterate, two-thirds of
Despite increases in grain production that began in the 1950s, thanks
"miracle wheat" and other advances in agricultural
such increases seem to have leveled off in recent years. Some 841
people today are chronically malnourished, and there are 88 "food
countries. This means "they can neither feed themselves nor afford the
imports they need," according to the United Nations Population Fund, a
subsidiary of the UN General Assembly and the largest
source of population assistance to developing countries.
When a country darkens on this map, it represents a
caused by hunger.
Supplies of water for irrigation are declining around the world as
water reserves - aquifers - become depleted faster than nature can fill
them. Groundwater overdrafting is now widespread in the crop-producing
regions of central and northern China, northwest and southern India,
of Pakistan, much of the Western United States, North Africa, the
East, and the Arabian Peninsula.
Nearly half the earth's land mass already has been changed by human
- wetlands filled in, forests cut down, prairies plowed under. Runoff
farms, industries, and urban areas has resulted in some 50 "dead zones"
coastal waters, including one in the Gulf of Mexico.
- Among the ocean's 200 major fish
stocks, 35% are in decline, and another 25% are being fully exploited.
Species are going extinct at a faster rate than ever before, including
the time when dinosaurs were dying out.
Factors Contributing to the Population
The green revolution
Agricultural advances have insured that no
has to starve. For thousands of years, the Earth's carrying capacity
on the available food supply. That is no longer the case.
Advances in medicine
Disease has throughout history always been
definitive factor in the limiting of the human population. However,
research has largely controlled (or eliminated) such diseases as
malaria, & cholera. As a result, death rates have declined
The industrial revolution
An increase in the availability and use of
has lead to a more densely packed society that attempts to make room
an ever increasing population. The influx of new technology into the
market over the past 150 years has made life generally easier in the
nations of the world and led to promising social situations that
the tendency of people to have more children.
In some countries people lack awareness of
control or the ability to limit the size of their families. Recent
Nations statistics indicate that 90% of women in 10 African nations had
not heard of contraception.
People in some developing countries who do
limit the growth of their families lack access to contraception or
services. Family planning methods are simply not available in large
of the world. As many as 500 million women in developing countries live
too far from health centers to obtain contraceptives, & unsafe
kill an estimated 70,000 women a year.
Human reproduction is a matter of great
and cultural importance as well. The religious teachings of many people
prohibit or discourage contraception. And some cultures traditionally
large families as a sign of prestige and power.
The overall rate of population increase depends on the number of births
and deaths, but also on the length of generations -- the age at which
have their first baby.
For example, if all women had three kids with a 15-year average
time, the rate of population growth would be 2.7%. If the average
were 30 years, the growth would drop in half -- to 1.35%.
How does percent population growth translate into 'doubling
Population Age Structure:
Birth and death rates do not tell the whole story of population
A country's TFR can be below replacement level while the population
to grow, if there are a disproportionately large number of couples in
younger age groups. That is the situation in Kenya and, to a lesser
the United States. The age structure of the population, then, is also
important factor in population change (see the population pyramids for
Kenya, Sweden, & the U.S. above). When a substantial proportion of
a country's population is young, high population growth rates in a
are to be expected, even if the average TFR is modest. The reason is
so many females are of childbearing age, that even a modest
TFR results in a large number of births.
Replacement-level fertility = the number of
a couple must bear to replace themselves
slightly more than 2 children because some
die before reaching their reproductive years
reproducing at this level does NOT mean
growth stops; there are so many "future parents" already alive that,
at replacement-level, population will continue to grow for many years
fertility rate (TFR) - estimate of the average number of children a
woman will have during childbearing years
In 1998, the TFR was 2.9 children per woman
in MDCs & 3.2 in LDCs); still far above replacement level
This map shows the average number of children born to
a woman during her lifetime. The darker the color, the greater the
number of children. For example, France at 1.7 children
has a lower fertility rate than Egypt at 3.6 children. The total
rate (TFR) is the average number of children a woman
would have, assuming that current age-specific birth
rates will remain constant throughout her childbearing
years (usually considered to be ages 15-49).
Fertility rates in the United States:
Peaked in 1957 at 3.7 children/woman
At or below replacement level (2.1) since
(& currently about 2.07) because:
widespread use of birth control
availability of legal abortion
social attitudes favoring small families
increasing cost of raising a child to age
for low-income family, $231,000 for middle-income & $335,000 for
increase in average age of marriage
& 1992 (from 20 to 24.4 for women, and from 23 to 26.5 for men)
More women working outside home
of "working" women 1/3 that of women not in paid labor force)
The U.S. population is still growing faster than most MDCs:
In 1995, the U.S. population grew by 1.18% (3.1 million people) more
double mean rate of world's industrialized nations. More recently, the
nation's population grew by 2.8 million people, or 1.0% between July 1,
2002 and July 1, 2003
The U.S. population is projected to increase from 263 million to 345
between 1995 & 2030, with no leveling off anticipated
This projected growth of the U.S. population is due to:
large number of baby boomer women still in child-bearing years (i.e.,
of potential mothers)
increase in number of unmarried mothers (including teen-agers)
higher fertility rates for women in some racial & ethnic groups
for Caucasian women
high levels of legal/illegal immigration (about 40% of current growth)
U.S. population growth is very important because of the impact that
of us has on the environment. For example:
Earth's Carrying Capacity (is the Earth overpopulated?):
Carrying capacity is the number of organisms an environment (e.g., the
Earth) can support
determined by: food production, living space, waste assimilation, &
for humans, carrying capacity can be expanded through advances in
industry, & medicine
Some believe Earth's carrying capacity has already been exceeded as
The world's marine catch has increased more than four times in the past
40 years -- from 18.5 million tons in 1950 to 82.5 million tons by
This staggering growth has resulted in overfishing and wasteful,
fishing practices worldwide which now threaten the lives of hundreds of
millions of people who are vitally dependent on fishing for food and
They face resource depletion, competition from industrial and distant
fleets, and loss of access to traditional marine food supplies.
The last 50 years has seen an
geographic expansion and increase in fishing intensity by industrial
fleets from the core areas in the North Atlantic and North Pacific, to
areas that were unexploited or underexploited in the 1950s. This map
illustrates the pattern of the expansion. Peak catch took place in the
North Atlantic before the 1970s, and as exploitation pattern shifted
towards more underexploited areas Eastern Pacific and Central Atlantic
reached the peak during the 1980s. The pattern has further extended
into South and Western Pacific in 1990s. The percentage in each area
reflects the decline in the fish catch from the peak year to the latest
catch estimates in 1997.
Continued forest loss and degradation will have serious implications at
local, regional, and global levels. Exploitation and clearance of
forests are destroying the environment and way of life for tens of
of indigenous people. Disappearing forest cover also represents
losses in biological diversity and ecological services, including
recycling, watershed management, and climate regulation.
Percentage of Tropical
Forest Cleared by Region Between 1960 and 1990
and so on
Others are more optimistic & believe Earth could support many more
More people = more productivity = more knowledge = better production
+ discovery of new substitutes, and so on
Impacts of continued growth in human populations include:
increased hunger/starvation while food production levels off or even
(i.e., less food/person)
|While grain yields per acre have been
steadily until 1990, the rate of increase has fallen off in the
10 years. Most of the benefits of irrigation, machinery, fertilizer and
plant breeding have already been realized. The production of grain per
acre is close to the maximum obtainable through photosynthesis.
are working on improving the efficiency of photosynthesis, and that may
turn out to be possible, but given that nature has been working on the
problem for several hundred million years, there is no guarantee that
can improve on the process in the next 10 to 20 years.
for more information.
Desertification is the conversion of productive rangeland or cropland
desertlike land. It is usually caused by a combination of overgrazing,
soil erosion, prolonged drought and climate change.
Arable land per person
increased number of refugees
Geographic video & this Geography
Cities may offer opportunities for the people of developing countries.
However, the danger lies in the structural inadequacies typical of many
cities in these countries. The most obvious of these inadequacies are
of public sanitation. Insufficient or non-existent sewage systems in
in many parts of these cities. Water supplies can thereby become
leading to the high incidences of disease.
dying seas & rivers, for example:
Where are we headed?:
Maximum Global Population Guesses (McCluney
|Everyone at the current U.S. standard of
living and with
all the health, nutrition, personal dignity and freedom that most
|Everyone at the same affluence as the U.S.
but with many and onerous restrictions on freedoms relative to
leading to environmental degradation. To accommodate populations
than 2 billion, restrictions such as the following would have to be
Driving restrictions (gasoline rationing,
even to mass transit systems).
Restrictions on the transport of food (food
more than 100 miles for example to its point of retail sales).
Prohibitions against cutting trees on one's
Limitations on the burning of fossil fuels to
complex molecules for more valuable or durable uses, such as in the
of plastics and pharmaceuticals.
Limitations on the areas of open spaces that
can be converted
to renewable energy power plants, such as solar thermal, solar
and wind energy systems. This latter results from the need to preserve
natural areas for food growing.
|Only people in the U.S. and Europe at current
affluence. Everyone else at the current prosperity level of
|Everyone in the world at Mexico's current
|Everyone in the world at the current
level of northwest Africa.
Text of the message of Secretary-General Kofi Annan to mark World
Day, 5 June 2000:
We may be at the dawn of a new millennium, but the environmental
we face are painfully familiar. They may even be
getting worse. Despite the Earth Summit, and despite success stories
like the Montreal Protocol to protect the Ozone Layer,
human beings continue to plunder the global environment. Unsustainable
practices remain deeply embedded in the fabric of our
daily lives. We are failing to protect resources and ecosystems. We
are failing to invest enough in alternative technologies,
especially for energy. We are failing even to keep the debate alive.
These are deeply troubling trends. I recommend four priorities for
Technological breakthroughs that are unimaginable today may well solve
some of the environmental challenges we face. But it
First, we need a major public education effort. Understanding of the
we face is alarmingly low. Corporations and consumers alike need to
that their choices can have significant consequences. Schools and civil
society groups have a crucial role to play.
Second, environmental issues must be fundamentally repositioned in the
policy-making arena. The environment must become better integrated into
mainstream economic policy, and the surest way is through green
Third, Governments must not only create environmental agreements, they
must enforce them. They can, for example, cut the subsidies that
environmentally harmful activities each and every year. They can also
more environment-friendly incentives for markets to respond to.
And fourth, we need sound scientific information. This is the only
for effective policy, yet large gaps in our knowledge remain.
would be foolish to count on them and to continue with business as
usual. The theme for this year's World Environment Day
says it best: the year 2000 begins the environment millennium; the
time to act is now. There will be no easy solutions.
Unpleasant ecological surprises lie ahead. But the start of the new
century could not be a more opportune time to commit
ourselves -- peoples as well as governments -- to a new ethic of
Why six billion?
to BIO 317 Syllabus