Lecture 5Ecosystems, Biodiversity and Human Populations

7

DelhiIndia

MumbaiIndia

Sao PauloBrazil

DhakaBangledesh

Mexico CityMexico

KolkataIndia

ShanghaiChina

KarachiPakistan

LagosNigeria

KinshasaDemographic Republic of the Congo

What country is the city in??

DelhiIndia

MumbaiIndia

Sao PauloBrazil

DhakaBangledesh

Mexico CityMexico

KolkataIndia

ShanghaiChina

KarachiPakistan

LagosNigeria

KinshasaDemographic Republic of the Congo

Living beyond the planet’s means

Humanity’s global ecological footprint surpassed Earth’s capacity to support us in 1987

FIGURE 6.18

What is natural selection ?

Natural selection

Natural selection is the gradual, non-random, process by which biological traits become either more or less common in a population as a function of differential reproduction of their bearers.

It is a key mechanism of evolution. Ecology and evolution are tightly intertwined

Natural selection is the means by which beneficial variations in a population tend to be preserved while unfavorable variations tend to be lost.

One of the key concepts behind the theory of natural selection is that there is variation within populations. As a result of that variation, some individuals are better suited to their environment while other individuals are not so well-suited. Because members of a population must compete for finite resources, those better suited to their environment will out-compete those that are not as well-suited.

Natural selection

Natural selection acts on genetic variation

• Directional selection drives a feature in one direction• Stabilizing selection produces intermediate traits, preserving the status quo• Disruptive selectiontraits diverge in two or more directions

If the environment changes, a trait may no longer be adaptive

FIGURE 3.2

Some species are more vulnerable to extinction than others

• Extinction occurs when the environment changes too rapidly for natural selection to keep up

• Many other factors also cause extinction– Severe weather– New species– Specialized species

Endemic species a species only exists in a certain, specialized area. These species:

– Are very susceptible to extinction– Usually have small populations

http://www.mnn.com/earth-matters/animals/photos/endemic-species-top-9-lonely-animals/sinarapan

Ecology is studied at several levels

• Biosphere the total living things on Earth and the areas they inhabit• Ecosystem communities and the nonliving material and forces they interact with• Community interacting species that live in the same area

FIGURE 3.9

Population Ecology: investigates how individuals within a species interact with one another.

Community Ecology : Focuses on interactions among species.

Ecosystem Ecology : Studies living and nonliving components of systems.

Population Ecology

http://home.comcast.net/~sharov/PopEcol/lec1/whatis.html

Habitat, niche and degree of specialization are important in organizational ecology.

Habitat: The specific environment in which an organism lives. Each organism has patterns of habitat use.

Niche: A species’ niche reflects its use of resources and its functional role in a community.

Specialists: Species with very specific requirements.Generalists: Species with broad tolerances, able to use a wide array

of habitats or resources.

Population Ecology

Populations exhibit characteristics that help predict their dynamics.

Important Characteristics of a population are:

Population Size: the number of individual organisms present at a given time.Population Density: the number of individuals in a population per unit area.Population Distribution (dispersion): the spatial arrangement of organisms within a particular area.

Population Ecology

(continued) Important Characteristics of a population are:

Populations sex ratio: Proportion of males to females.

Age distribution (structure): The relative numbers of organisms of each age within a population.

Birth and death rate:Measure the number of births and deaths per 1000 individuals for a given time period.

The likelihood of death varies with age; this can be graphically shown in survivorship curves.

Population Ecology

Type I: high survival rate of young, live most of expected life span and die in old age (example : Humans ).Type II: relatively constant death rate. Death could be due to hunting or diseases (examples: squirrels, honey bees).Type III: many young, most of which die very early in their life. Plants, oysters and sea urchins are examples.

Population Ecology

Survivorship Curves

Population characteristics

• Population distribution (dispersion) = spatial arrangement of organisms within an area – Random – haphazardly

located individuals, with no pattern

– Uniform – individuals are evenly spaced due to territoriality

– Clumped – arranged according to availability of resources

• Most common in nature

FIGURE 3.11

Populations are dynamic, they can:GrowShrinkRemain stable

Population growth or decline is determined by :BirthsDeathsImmigrationEmigration

Population Ecology

Growth rate =

( + ) - ( + )

• Unregulated populations increase by exponential growth• When a population increases by a fixed percentage each year, it

is said to undergo exponential growth.

Population Ecology

crude birthrate

immigration rate

crude deathrate

emigrationrate

Original Population = O

Births = B

Deaths = D

Immigration = I

Emigration = E

Growth rate = G

G = (B + I ) - (D + E) ______________ O

Population Ecology

X 100

Population Ecology

Researchers studied a population of 34 peregrine falcons for one year to analyze the effect of pesticides on population growth.

In the first spring, 20 hatched and lived. During the season, 9 baby falcons dies from severe birth defects, 11 died as a result of direct pesticide exposure, 8 were captured and were taken to a conservation area. During the last three months, 4 birds migrated into the area.

Calculate the population growth of peregrine falcons in this study (Show your work)

How would you describe the overall health of this population?What are the consequences for the future?

http://dictionary.reference.com/browse/extirpation

Population Ecology

Extirpation :

The growth rate for a population of 90 field mice in six months was 429%. If the number of birds was 342, the number of deaths was 43, and there was no emigration , calculate the number of mice that migrated into the field.

Population Ecology

Limiting factors: factors which restrain population growth

Every population is eventually contained by limiting factors, which can be:

PhysicalChemicalBiological characteristics of the environment.

The interaction of the limiting factors determines the carrying capacity.

Population Ecology

Examples???

Water, space, food, predators, and disease

Carrying Capacity:

The average population density or population size of a species below which its numbers tend to increase and above which its numbers tend to decrease because of shortages of resources.

The carrying capacity is different for each species in a habitat because of that species' particular food, shelter, and social requirements.

Population Ecology

Unregulated populations

• Steady growth rates cause exponential population growth– Something increases by

a fixed percent– Graphed as a J-shaped

curve• Exponential growth cannot

be sustained indefinitely– It occurs in nature with

a small population and ideal conditions

FIGURE 3.14

Also called geometric growth

Carrying capacity• Carrying capacity the maximum population size of a species that its environment can sustain

– An S-shaped logistic growth curve

– Limiting factors slow and stop exponential growth

Carrying capacity changes

Humans have raised their carrying capacity by decreasing the carrying capacity for other species

FIGURE 3.15

• Carrying Capacities can change• Some factors are density-dependent, others are density-

independent

Biotic potential and reproductive strategies vary amongst species

K-selected: Species that devote large amounts of energy and resources to caring for a few offspring - their populations tend to stabilize over time at or near their carrying capacity. R-selected: Species that have high biotic potential and devote their energy and resources to producing as many offspring as possible in a relatively short time.

Changes in populations influence the composition of communities

Population Ecology

Conclusion

• Natural selection, speciation, and extinction help determine Earth’s biodiversity.

• Understanding how ecological processes work at the population level is crucial to protecting biodiversity

http://www.ted.com/talks/catherine_mohr_builds_green.html

Trying to be environmentally friendly…..

The conservation of BiodiversitySocial and economic factors affect species and communities.Costa Rica took steps to protect its environment and had active ecotourism.

Conclusion:Speciation and extinction determine Earth’s biodiversity.Many human activities are playing a role in biodiversty loss.

Biodiversity

http://wwf.panda.org/about_our_earth/biodiversity/threatsto_biodiversity/

http://polarbears.wwf.ca/

http://www.cbd.int/doc/publications/cbd-ts-50-en.pdf

Biodiversity

What is it??

Svalbard Seed Bank

Located in an old copper mine on remote northern island of Spitsbergen, Norway.

The main storage is 120m inside a sandstone mountain, on a tectonically dead island.

Seeds are packaged in special four-ply packets and heat sealed to exclude moisture. A local coal mine and powerplant supplies the electricity for refrigeration control.

The remote northern location also serves as a natural fridge. In the case of complete power failure at least several weeks will elapse before the temperature rises to the temperature of the surrounding sandstone bedrock.

There are many types or "cultivars" of any given fruit.

A cultivar is a cultivated plant which is chosen and given a special name because of its desired characteristics. Various types of cultivars (for example in apples, the Red Delicious in the 1870s) come in and out of favour over the years.

In the middle of 20th century the dominant banana cultivar exported to North America and Europe was the Gros Michel. Around 1950 the Gros Michel become virtually extinct due to the rapid spread of the so called "Panama Disease," a fungal infection that attacks the roots of the banana plant.

The Gros Michel was replaced with more resilient but notably less tasty Cavendish cultivar

Svalbard Seed Bank

Modern agriculture is generally focused on maximizing profit by extracting maximal possible crop yield.

A small number of specially selected cultivars of any given crop are planted throughout the world, displacing in the process numerous other local varieties. This approach guarantees consistently high yields under normal conditions.

Biodiversity

Essentially, every single commercially grown plant is a clone of one of only a few specially selected strains of genetic material. Diversity of genetic material is thus reduced to a bare minimum, leaving crop species exposed to any disease which can exploit that single strain.

With corn, wheat, and rice being grown world wide in such a fashion, there is a concern that a newly mutated strain of fungus could wipe out an entire world crop in matter of months, and cause massive food shortages.

Biodiversity

“We can no longer see the continued loss of biodiversity as an issue separate from the core concerns of society: to tackle poverty, to improve the health, prosperity and security of present and future generations, and to deal with climate change. Each of those objectives is undermined by current trends in the state of our ecosystems, and each will be greatly strengthened if we finally give biodiversity the priority it deserves.”

Convention on Biological Diversity's 'Global Biodiversity Outlook 3' report

Biodiversity

http://gbo3.cbd.int/

Biodiversity has declined by more than a quarter in the last 35 years.The Living Planet Index (LPI), which tracks nearly 4,000 populations of wildlife, shows an overall fall in population trends of 27% between 1970 and 2005.

Population growth and our consumption are the primary reasons.

Specifically, habitat destruction and wildlife trade are the major causes of population decline in species.

Click me....

Biodiversity

Human Population

Population: Human growth, demography, education

and ecological footprinthttp://perspectivesinnature.blogspot.com/2009/12/implications-of-human-population-growth.html

“As you improve health in a society, population growth goes down. You know. I thought it was…before I learned about it, I thought it was paradoxical.”

– Bill Gates, Microsoft Corp.

http://www.gatesfoundation.org/Pages/home.aspx

Human Population and Growth

http://www.prb.org/pdf11/2011population-data-sheet_eng.pdf

Is population growth really a problem?

It has resulted in technological innovations, improved sanitation, better medical care, increased agricultural output, a decline in death rates and a drop in infant mortality.

Perspectives on human population have changed over time

• 1700s

more children meant better support in old age and more labour for factory work

• 1766:

Thomas Malthus – growing population is eventually checked by limits on births or increases in deaths

• 1968:

Paul Ehrlich – population is growing too fast and must be controlled

Cornucopian view:Resource depletion as a consequence of greater numbers of people, is not a problem if new resources can be found to replace the depleted ones.

Even if resource substitution could enable indefinite population growth, could we maintain the quality of life that we would desire, or would our descendants have less space, less food, and less material wealth than the average person does today?

Many governments have found it difficult to let go of the notion that population growth increases a nation’s economic, political, and military strength.

Human Population and Growth

IPAT model:How humans’ total impact(I) results from the interaction among three factors: (P) (A) (T)

I = P x A x T

A sensitivity factor (S) can be added to the equation to denote how sensitive a given environment is to human pressures : I = P x A x T x S.

Impact generally relates to either pollution or resource consumption. Modern-day China shows how all elements of the IPAT formula can combine to result in environmental impact in very little time.

Human Population and Growth

Population Affluence Technology

One-Child PolicyUnder Mao Zedong’s leadership (1949-1976), improved food production and distribution and better medical care allowed China’s population to swell, causing environmental problems

Human Population and Growth

• Started with education and outreach efforts encouraging late marriage and fewer children, and increasing the accessibility of contraceptives and abortion.

• In 1979 instituted a system of rewards and punishments, in forcing a one-child limit per family.

• China’s growth rate is down but there have been unintended consequences such as widespread killing of female infants and an unbalanced sex ratio.

The government instituted a population-control program in the 1970’s.

Demography

Demography: The science of human population: The application of population ecology principles to the study of statistical change in human populations is the focus.

The principles of population ecology apply to humans

Like other organisms, humans have a carrying capacity set by environmental limitations on our population growth.Estimates of the human carrying capacity have ranged greatly, from 1-2 billion people living prosperously in a healthy environment to 33 billion living in extreme poverty in a degraded world without natural areas.

Demography

People are very unevenly distributed over the globe.This uneven distribution means that certain areas bear far more environmental impact than others

At the same time, areas with low population density are often vulnerable to environmental impacts. The reason they have low populations may be that they are sensitive and cannot support many people.

http://www.navdeep-humanpopulation.blogspot.com/

Rates of growth vary with region• At today’s 2.1% annual growth rate, the population will double in

33 years• If China’s rate had continued at 2.8%, it would have had 2 billion

people in 2004.

FIGURE 6.3

Age structure diagrams show the relative sizes of each age group in a population and are especially valuable to demographers in predicating future dynamics of a population.

• The ratio of males to females, the sex ratio can also affect population dynamics.

• The naturally occurring sex ratio in human populations at birth features a slight preponderance of males.

This ratio can be skewed, examples are China and Sarnia

Demography

• Live male births in the Aamjiwnaang First Nation has been declining from the early 1990s to 2003, from an apparently stable sex ratio.

• Likely due to environmental and occupational chemical exposures.

• This community is located immediately adjacent to several large petrochemical, polymer, and chemical industrial plants.

• A community health survey is currently under way to gather

more information about the health of the community.

http://ehp03.niehs.nih.gov/article/fetchArticle.action?articleURI=info:doi/10.1289/ehp.8479

- Mackenzie, Lockridge and Keith (2005)

Demography

- Mackenzie, Lockridge and Keith (2005)

Age structure affects future population dynamics

• Having many individuals in young age groups results in high reproduction and rapid population growth

FIGURE 6.10

Population growth depends on what 4 factors?Birth, death, immigration and emigration

Immigration and emigration are increasingly important in the modern world:

flow of refugeestransportation

Natural rate of population change: is the change due to birth and death rates alone, excluding migration.

Population growth

Since 1970s growth rates in many countries have been declining and the global growth rate has declined partially because of a steep drop in birth rates.

Total Fertility Rate (TFR): is the average number of children born per female member of a population during her lifetime.

Replacement Fertility: the TFR that keeps the size of a population stable, for humans it is 2.1.

Population growth

Demographic transition is a theoretical model of economic and cultural change that explains the trend of declining death rates and birth rates that occurs when nations become industrialized.

Pre industrial: characterized by condition in which both death rates and birth rates are highTransitional stage: death rates decline and birth rates remain high.Industrial stage: creates employment opportunities, particularly for women causing birth rate to fallPost-industrial stage: both birth rates and death rates remain low and populations stabilize or decline slightly.

Population growth

4 stages of demographic transition

Population growth is seen as a temporary phenomenon

FIGURE 6.14

Women’s empowerment greatly affects population growth ratesDrops in TFR have been most noticeable in countries where women have gained improved access to contraceptives and education, particularly family planning education.

Many women still lack the information and personal freedom of choice to allow them to make their own decisions about when to have children and how many to have.

In societies in which women are freer to make reproductive decisions, fertility rates have fallen, and the children are better cared for, healthier, and better educated.

Female literacy is associated with birth rates

Female literacy is associated with birth rates

FIGURE 6.15

Is the demographic transition universal?

• It has occurred in Europe, U.S., Canada, Japan, and other nations over the past 200-300 years

• But, it may or may not apply to all developing nations• The transition could fail in cultures that

– Place greater value on childbirth– Grant women fewer freedoms

For people to attain the material standard of living of North Americans, we would need the natural resources of four and a half more Earths

Population policies and family-planning programs are working around the globe.

The government of Thailand has relied on an education–based approach to family planning that has reduced birth rates and slowed population growth.

India has had long-standing policies, but some think they need to be strengthened. http://www.indexmundi.com/g/g.aspx?c=in&v=31

Brazil, Mexico, Iran, Cuba and other developing countries have instituted active programs consisting of population reduction targets, incentives, education, contraception and reproductive health care.

Is the demographic transition universal?

http://www.indexmundi.com/map/?v=31

• In 1994 the united Nations hosted a conference in Cairo on population and development at which 179 nations endorsed a platform calling for all governments to offer universal access to reproductive health care within 20 years.

• Despite the successes of family planning internationally, the United States has often declined to fund family –planning efforts by the United Nations.

• Cancelling this funding was one of George W. Bush’s first acts upon becoming a U.S. President in 2001

Is the demographic transition universal?

Poverty is strongly correlated with population growth

Consumption from affluence creates environmental impact

Individuals in affluent societies leave a larger “ecological footprint”

In 1999 the richest 20% of the world’s people: used 86% of the world’s resourceshad over 80 times the income of the poorest 20%

The wealth gap and population growth contribute to violent conflict

Is the demographic transition universal?

HIV/AIDS is a major influence on human populations in parts of the world

Of the 38 million people around the world infected with HIV/AIDS in 2004, 25 million lived in the nations of sub-Saharan Africa.

The AIDS epidemic is unleashing a variety of demographic changesPremature deaths, of both infants and young adults are reducing the average life expectancy in African nations.

Severe demographic changes have social, political, and economic repercussions.

Other factors

Everywhere in sub-Saharan Africa, AIDS is undermining the ability of developing countries to make the transition to modern technologies because it is removing many of the youngest and most productive members of society.

Other factors

Although global populations are still growing, the rate of growth has decreased nearly everywhere.

There has been progress in expanding rights for women worldwide.

In addition to the clear ethical progress of this development, it also helps to slow population growth.

True sustainability demands that we stabilize our population size in time to avoid destroying the natural systems that support our economies and societies.

Is the demographic transition universal?

Low growth does not mean fewer people

FIGURE 6.13

Conclusion• The human population is larger than at any time in the past• However, the rate of growth has decreased because of:

– Demographics– Better rights for women

• How will the population stop rising?– demographic transitions– governmental intervention– disease – social conflict