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Lecture content• Population and Environment

– Exponential Growth Review

– Logistic Growth Curve

– Replacement Level Fertility

– Forecasting Population Change

– Age Structure

– Human Population’s Effects on the Earth

– Group exercise rules and topic allocation

Exponential Growth

An exponentially growing population theoretically increases forever.

Exponential growth rate: the annual growth rate is a constant percentage of the population

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Human Population as a LogisticGrowth Curve

• On Earth, which is limited in size, exponential growth is not possible, as Thomas Henry Malthus pointed out in the 18th century.

• If a population cannot increase forever, what changes in the population can we expect over time?

• S-shaped curve known as the Logistic Growth Curve.

Thomas Henry Malthus

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Logistic Growth Curve• A logistic population would

increase exponentially only temporarily. After that, the rate of growth would gradually decline until an upper population limit is reached.

• The upper population limit is called the logistic carrying capacity.

• Once that had been reached, the population would remain at that number.

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This was first suggested in 1838 by P. F. Verhulst

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Exponential growth curve

Logistic growth curve

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Replacement level fertility

• Replacement fertility is the total fertility rate at which women would have only enough children to replace themselves and their partner.

• The replacement fertility rate is roughly 2.1 births per woman for most industrialized countries.

World population, 1950-2150: three possible features

Between these three population features which one do you think is going to happen?Lec 6; MrL 7

Forecasting Population Change• Populations change in size through births, deaths, immigration (arrivals),

and emigration (departures).

• Population change in terms of actual numbers in a population:

P2 = P1 + (B - D) + (I - E)

o P1 is the number of individuals in a population at time 1 (e.g., 1000), o P2 is the number of individuals in that population at some later time 2

(?) o B is the number of births in the period from time 1 to time 2 (e.g., 700), o D is the number of deaths from time 1 to time 2 (e.g., 200),o I is the number entering as immigrants (e.g., 600), and o E is the number leaving as emigrants (e.g., 100).

= 2000

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Age Structure

• Population age structure is the proportion of the population of each age group.

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• The age structure of a population affects birth rates, death rates, and growth rates; has an impact on the environment; and has implications for current and future social and economic conditions.

Declining growth

Slow growth

Rapid growth

Bangladesh

Rapid growth

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11

Human Population’s Effects on Earth

• When there were few people on Earth and limited technology human impacts on environment was local but not necessarily less. Human has impacts on environment for a surprisingly long time such as use of fire to clear land.

• The problem now is that there are so many people and our

technologies are so powerful that our effects on the environment are even more global and significant. This could cause a negative feedback—the more people, the worse the environment; the worse the environment, the fewer people.

Early stage vs modern stage

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• Modern technology increases the use of resources and enables us to affect the environment in many new ways,

• For example, before the invention of chlorofluorocarbons (CFCs), which are used in spray cans and in refrigerators and air conditioners, we were not causing depletion of the ozone layer in the upper atmosphere.

• Similarly, before we started driving automobiles, there was much less demand for steel, little demand for oil, and much less air pollution.

• Others

The Human Population’s Effects on the Earth

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The Human Population’s Effects on the Earth

The danger that the human population poses to the environment is the result of two factors: the number of people and the environmental impact of each person.

Total impact (T) of the human population on the environment:

• T = P × IP is the population size, and I is the average environmental impact per person

• The impact per person varies widely, within the same nation and also among nations.

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• The average impact of a person who lives in high technology country is much greater than the impact of a person who lives in a low-technology society.

E.g., CO2 emissions in 2010 (tons/capita): Bangladesh - 0.4; USA - 17.6, Norway – 11.7

• But even in a low-technology nation the higher number of people leads to large-scale environmental effects.E.g., Population (in 2014): Bangladesh - 157,058,000; Norway – 5,090000Total CO2 emissions: Bangladesh– 157m × 0.4= 62.8mT (low-technology)

Norway– 5.09m × 11.7 = 59.55mT (high technology)

• What will happen if high technology country plus higher number of population?USA – 318 m×17.6=5596.8mT

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References for today’s lecture

• BOTKIN, D. B. & KELLER, E.A. 2011. ENVIRONMENTAL SCIENCE: EARTH AS A LIVING PLANET. JOHN WILEY & SONS, INC.

• Some figures are from internet • If you find anything in the slides but NOT in

Botkin and Keller, then read directly from the slides. E.g., some examples of slide 13.

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• Group exercise rules and topic allocation

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Group exercise (20 marks)17

Group name Topics

G1 Green economy and Bangladesh

G2 Natural environmental hazards in Bangladesh

G3 Deforestation in Bangladesh

G4 Global warming and Bangladesh

G5 Electronic waste

G6 Environmental effects of industry in Bangladesh

G7 Sustainable Development Goals (SDGs)

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Instructions18

The group exercise will have two parts: report and presentation

A. Report (10 marks) Group work is needed. Each would contribute equally. The report would have at least 5 sections. Each student will present at least one section in which he/she

contributed more.

For writing the report follow any standard format can be followed such as http://education.exeter.ac.uk/dll/studyskills/assignment_presentation.htm

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Instructions19

Total length of the report would be 3,000- 4,000 words;

1st page will have the exercise title, students’ names, IDs and part of the report prepared by him/her, date of submission, and course details;

2nd page would contain table of contents; report writing would start after that.

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Presentation20

Presentation (10 marks) (4 mins for each);

Assessment criteria Marks allocated (10)

Content (quality and quantity) 4

Fluency/style 3

Quality of slides 2

Timing 1

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Deadline of report/assignment submission is 22 October for all groups

Presentation will be on the following week.Both hard and soft copies (in my email

containing file name: section_Group number_title) need to be submitted.

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Selection of group members and topic22

You select 5 members and a topic by yourself and give me in the next class.

In a page write group name, assignment title, students/members name and IDs

Group exercise: roundtable meeting by each group

• Objectives:• know each other • explore research

topic more• Making a table of

contents for the report/assignment

• Length (words) of each sub-section in the report

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Topic Length Who is contributing?

1. Introduction

150 words Anika

2. 500 Anika

3. 500 Zahir

4. 600 Faiz

5. 700 Zia

6. 400 Farzana

7. Conclusion

200 Farzana

Table of contents

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Any question?