Ecology and Environmental Problems

Ecology and Environmental Problems

• Dr. Ron Chesser – Lecture #2 - •22 Jan. ‘04

• Science, Decision-making processes, social systems & society.

• READING: – Chapters 1 & 2

Can science ever really prove anything?

• Yes and no. It depends on what you mean by "prove".

• Theories may change as our abilities to observe (measure) improve.

What is Occam's Razor?

• Occam's Razor is the principle proposed by William of Ockham in the fifteenth century that "entities should not be multiplied unnecessarily".

• In more modern terms, if you have two theories which both explain the observed facts then you should use the simplest until more evidence comes along.

Science and the Secular Universe

• Science does not make moral judgments. One can not draw moral lessons from the laws of nature.

• Evolution in particular seems to suffer from this. At

one time or another it seems to have been used to justify Nazism, Communism, and every other -ism in between.

• These justifications are all completely false. Similarly, anyone who says "evolution theory is evil because it is used to support Communism" (or any other -ism) has also strayed from the path of Logic.

What is Dogma?

• Dogma is a statement or concept that is presented as accepted theory or fact, but has not been rigorously tested.

• Dogma is usually widely accepted.

• Dogma is prevalent in science and society.

Faith vs Theory

• Faith, defined as `belief that does not rest on logical proof or material evidence’, does not determine whether a scientific theory is adopted or discarded.

• One does not question faith.

• A theory must be “falsifiable''

Where is the Truth?

• There IS a truth. The universe behaves in a real way that may be difficult to observe, measure, and predict. We have two choices to explain the behavior of the universe:

– To adhere to a stated belief without question– To build hypotheses, experimentation, and

theories that explain the observations

Neither approach guarantees the “truth” is found.

Did Mendel “cook the books”?

• Gregor Mendel was a 19th Century monk who discovered the laws of inheritance (dominant and recessive genes etc.). More recent analysis of his results suggest that they are "too good to be true". It seems from Mendel's raw data that chance played a smaller part in his experiments than it should. This does not imply fraud on the part of Mendel.

• First, the experiments were not "blind". Deciding whether a particular pea is wrinkled or not needs judgement, and this could bias Mendel's results towards the expected. This is an example of the "experimenter effect".

• Second, Mendel's Laws are only approximations. In fact, in some cases inheritance is less random than his Laws state.

• Third, Mendel might have neglected to publish the results of `failed' experiments. It is interesting to note that all 7 of the characteristics measured in his published work are controlled by single genes. He did not report any experiments with more complicated characteristics. Mendel later started experiments with a more complex plant, hawkweed, could not interpret the results, got discouraged and abandoned plant science.

Evidence, evidence, evidence

• If you have an idea, remember that the burden of proof is on you.

• Science is not easy. It is a demanding discipline that is governed by skeptics who require rigorous experimentation. (manuscripts, seminars, teaching, books)

• a • b

Scientific Manuscript

• Abstract (Summary)• Introduction -- Description of the problem

(observation). Statement of the Hypothesis(es).

• Methods and Materials – Complete description of methods used and materials needed.

• Results – Statement of results of methods.• Discussion – What the results likely mean.

Support for or rejection of hypotheses.• Acknowledgements – Who helped in the study.• Literature Cited – Previously published

manuscripts that the authors used to support or build their ideas.

Experimenter Effect

• Sometimes you see what you expect to see

• Sometimes you see what you want to see

• Sometimes you see what you are told to see

• Sometimes you see what you are paid to see

How do you avoid Experimenter Effect?

• Blind Study– Randomly assign samples where the

experimenter doesn’t know what the groups are

– No one is aware of results until end of studyGroup Shift

Change the groups so that the experimenter thinks one group is the other

Replicate Experimentation Different groups analyze the same samples

Science vs Technology

• Science is the search for knowledge through a systematic method of the study of variation

• Technology is the application of science to make products or processes

What Does Society Need?

• Advanced Education and Training• Energy Resources• Natural resources (materials)• Transportation and Communication• Industry, Finance and Technology• People who passionately support and defend the

society• Mechanisms for making decisions (who/how)• Judicial & Police System (Crime & Punishment)

Especially since 1960, several developments have dramatically reduced infant and child mortality

throughout the world

• the use of DDT to eliminate mosquito-borne malaria

• childhood immunization programs against cholera, diphtheria and other often-fatal diseases

• antibiotics. • During the same period, the "Green Revolution"

greatly boosted food output through the cultivation of new disease-resistant rice and other food crops, and the use of fertilizers and more effective farming methods.

r = intrinsic rate of increase

Births DeathsrNumberalive

Growth = there are more born than die.

Models of population growth

Exponential growth: Nt = Nt-1 + rNt-1

= N0er0t

t=generationr=intrinsic increase rateNt = population size at time t.Nt-1=population size in prior generationN0=initial population sizee=exponentialr0=ln(1+r)

t

N

Carrying Capacity

The theoretical number of individuals that can be supported by the resources within an ecosystem.

Earth’s Resources• we have already transformed or degraded 39-50% of the Earth's

land surface (agriculture, urban). • we use 8% of the primary productivity of the oceans. • we have increased atmospheric CO2 concentration by 30% • we use more than half of the accessible surface fresh water • over 50% of terrestrial nitrogen fixation is caused by human

activity (use of nitrogen fertilizer, planting of nitrogen-fixing crops, release of reactive nitrogen from fossil fuels into the atmosphere)

• on many islands, more than half of plant species have been introduced by man; on continental areas the fraction is 20% or more

• about 20% of bird species have become extinct in the past 200 years, almost all of them because of human activity

• 22% of marine fisheries are overexploited or depleted, 44% more are at the limit of exploitation

POPULATION AND AVAILABILITY OFRENEWABLE RESOURCES

1990 2010Total

Change (%)

Per CapitaChange

(%)Population (millions)  5,290 7,030 33

Fish Catch (million tons) 85 102 20 -10

Irrigated Land (million hectares)

237 277 17 -12

Cropland (million hectares)

1,444 1,516 5 -21

Rangeland and Pasture (million hectares)

3,402 3,540 4 -22

Forests (million hectares)

3,413 3,165 -7 -30

Models of population growth

Logistic Population growth: Nt = K/(1+[[K-N0]/N0]e-rt)

t=generationr=intrinsic increase rateNt = population size at time t.K=carrying capacity N0=initial population sizee=exponential

t

N K

Carrying Capacity = 15 Bil

6 000 000 000

7 000 000 000

8 000 000 000

9 000 000 000

10 000 000 000

11 000 000 000

12 000 000 000

13 000 000 000

14 000 000 000

0 20 40 60 80 100 120 140 160 180 200

Years

Po

pu

lati

on

Siz

e

I.Practice problems

A. At the beginning of 2000, the human population had reached a size of 6,000,000,000. Assuming that r=0.001 (the intrinsic rate of growth of Lithuania) and an exponential growth model, what will the size of the human population be in 2025?

B. Now, assuming the same information in A, but with r=0.018 (the intrinsic rate of growth of Rwanda), use the exponential growth model to estimate the size of the human population in 2025?

C. Using the information in Problem A, plus a hypothetical carrying capacity, K=10,000,000,000 for the earth, estimate the size of the human population in 2025, using the logistic growth model?

D. Repeat C, except assume that r=0.018.

I.Practice problems

A. At the beginning of 2000, the human population had reached a size of 6,000,000,000. Assuming that r=0.001 (the intrinsic rate of growth of Lithuania) and an exponential growth model, what will the size of the human population be in 2025?

B. Now, assuming the same information in A, but with r=0.018 (the intrinsic rate of growth of Rwanda), use the exponential growth model to estimate the size of the human population in 2025?

C. Using the information in Problem A, plus a hypothetical carrying capacity, K=10,000,000,000 for the earth, estimate the size of the human population in 2025, using the logistic growth model?

D. Repeat C, except assume that r=0.018.

Press

Press

PressPress

Human Population GrowthWas Thomas Malthus correct?

Human Population Growth

5,950,000,000.00

6,000,000,000.00

6,050,000,000.00

6,100,000,000.00

6,150,000,000.00

6,200,000,000.00

6,250,000,000.00

6,300,000,000.00

6,350,000,000.00

0 10 20 30 40 50

Years

Po

pu

lati

on

Siz

er = 0.001 (as in Latvia)

Human Population Growth

6,000,000,000

7,000,000,000

8,000,000,000

9,000,000,000

10,000,000,000

11,000,000,000

12,000,000,000

0 10 20 30 40 50 60

Years

Po

pu

lati

on

Siz

er=0.001 and r=0.013

Rising Death Rates

• In 1999 the Worldwatch Inst. reported that rising death rates are slowing world population growth for the first time since famine killed 30 million people in China in 1959-61.  Partly because of these rising death rates, the U.N. revised its estimate for world population in 2025 from 9.4 to 8.9 billion.  Three factors are pushing the death rates up, especially in sub-Saharan Africa and the Indian sub-continent:

• the HIV epidemic - between a fifth and a quarter of adults are already infected in Zimbabwe, Botswana, Namibia, Zambia and Swaziland. In India, four million adults are now HIV positive, more than in any other country.

• the depletion of aquifers - another serious problem in India, where water tables are falling annually by 1- 3 meters over much of the country.

• shrinking cropland area per person. More than half of the children in India are already malnourished and underweight.  Dwindling cropland also threatens food security in Nigeria, Ethiopia and Pakistan.