Lecture 20

Question 1

How many are there on average children per woman in developed countries? In underdeveloped countries? What is this predicted to drop to? Under these assumptions what is the population predicted to be in 2050?

Answer 1

. 2.5 children per woman in developed countries
. 4.3 in underdeveloped countries
. Predicted to drop to 3.5 in 2025-2030 and 2.1 in 2095-2100
. So, the population would be ~9.3 billion by 2050

Question 2

Which are the countries with the highest population densities?

Answer 2

China, India and the US (these are the countries that produce the most greenhouse gas and Europe as well to some extent)

Question 3

What is the mean world population density? How does this differ in biodiversity hotspots? Why is this?

Answer 3

. About 50 individuals per km^2
. 16 out of the 25 biodiversity hotspots had a population density above that of the average- lots of people live there due to the fertile soil and beauty

Question 4

What is the average population growth rate per year? How does this compare to biodiversity hotspots?

Answer 4

. Just over 1% per year

. 19 out of the 25 hotspots have an average growth rate above that of the global average

Question 5

What percentage of the earths surface is crop land and pasture?

Answer 5

29%

Question 6

What percent of habitat decline has occurred in different habitats since human disturbance?

Answer 6

. Forest woodland- 29%
. Steppe/ savannah/ grassland- 49%
. Shrubland- 74%
. Desert/ tundra/ ice desert- 14%

Question 7

What percent of the UK is cropland and pasture?

Answer 7

~70% (was ok before herbicides as there were weeds and wild plants)

Question 8

What percentage of the original wet tropical forest habitat remains in eastern Madagascar?

Answer 8

34%

Question 9

What is the global temperature determined by?

Answer 9

. Partly by heat generated in centre of planet heat from formation; friction; radioactive decay
. Largely by radiation from the sun (mainly this)
. Temperature is determined by balance between heat gained from solar energy and loss of heat to space

Question 10

How does the atmosphere affect global temperature?

Answer 10

. Radiation reaching the Earth surface- dust and cloud reduce input from the sun by reflecting and absorbing radiation
. Loss of energy back to space

Question 11

What is albedo?

Answer 11

The reflectivity of a surface

Question 12

What is solar energy which reaches earths surface mostly?

Answer 12

Short wavelengths which are absorbed or reflected

Question 13

How does habitat loss affect the reflectivity of the Earth?

Answer 13

Will decrease the reflectivity of the Earth and increase the heat trapped on Earth

Question 14

Give an example of how changing vegetation cover affects albedo

Answer 14

If you have a full, broken canopy the light tends to be bounced straight off. However, with a broken canopy it can bounce into all the cracks and there is no where it can escape, so the radiation is trapped

Question 15

Which absorbs more heat cities or vegetation?

Answer 15

Cities (concrete albedo=20%, tarmac roads albedo= 10%).
City microclimates can be 4 degrees higher than surrounding regions (so the growth of cities is likely to mean that the Earth will absorb more heat as well)

Question 16

Changing vegetation will affect many animals but some species will increase. What are these species? What is the problem with this?

Answer 16

. Dragonflies, bats, butterflies- some have already spread in recent warmer years from the south where they are more prevalent (UK)
. The issue is that they are vectors of human and cattle diseases- e.g. malarial, African swine fever

Question 17

Give the future climate change predictions

Answer 17

. Effects greater at higher latitudes compared to equator
. Greater frequency of extreme events
. Global temp rise of 1.5-2 degrees in next 50 years? (Depends on the action of the big nations)
. Poleward advance of monsoon rains
. Rise in sea level of 12cm in last 100years-this will carry on
. Expansion of deserts

Question 18

What are the predictions of climate change on vegetation?

Answer 18

. ~55% land area will show shift in vegetation (under climate change actions)
. Temperature climates at higher latitudes- N expansion of Boreal forest into present Tundra
. Drying in tropics- forests to shrublands