Lecture 1: The Biodiversity Crisis: Science and Understanding

Question 1

What is the biosphere?

Answer 1

“The zone where life is found; the outer portion of the geosphere and the inner portion of the atmosphere. This extends from 3 m below the ground to 30 m above it.” Mayhew (1997), pg. 53.

“The zone occupied by living organisms at the common boundary of Earth’s lithosphere, hydrosphere and atmosphere and depending for its raw materials on geological fractionation and photosynthesis.” Smithson et al. (2002) pg. 586.

Question 2

Biomes

Answer 2

The biosphere can be broken down into component parts according to spatial variations in environmental characteristics and consequently ecology and biology

These are termed ‘biomes,’ and are classified according to dominant vegetation formations, e.g. temperate rainforest, tropical rainforest, desert, arctic tundra, montane forest etc.

Biome definition: “a large, stable terrestrial ecosystem characterized by specific plant and animal communities” Christopherson (2005), pg. 627.


Question 3

What is biogeography?

Answer 3

“…the study of distributions of organisms, both past and present, and of patterns of variation over the earth in the numbers and kinds of living things.” Brown and Lomolino (1998), pg. 3.
“The study of the distribution of plants and animals and related ecosystems; the geographical relationships with their environment over time.” Christopherson (1995), pg. 674.
• Spatial and temporal distribution of biota (organisms)

Question 4

Biogeography species

Answer 4

Almost every location on earth supports some species, but no one location supports all species, and no single species can live everywhere
• Each species has a restricted geographical range in which it will encounter certain environmental conditions to which it is adapted
• There are many inter-related reasons for this, making biogeography a complicated but highly useful scientific discipline

Question 5

The biodiversity crisis

Answer 5

Best estimates of species diversity is somewhere between 10- 80,000,000, with app. 1,600,000 recorded so far
• Suggested 40,000 species lost globally each year (Myers 1979; Myers and Lanting, 1999)
• Much of this attributed to continued loss of the highly diverse tropical rainforest
This has spurred a drive for conservation around the world

Question 6

Deforestation in the tropics

Answer 6

Deforestation in the tropics
• Human population pressure (and associated land for cultivation)
• Land ownership which forces peasant families and landless people into forests
• Commercial agriculture and plantation crops
• Commercial logging and forest road building


Question 7

Growing population

Answer 7

increased urbanization with many direct and indirect consequences

Question 8

Natural invasions

Answer 8

As well as natural invasions (e.g. Homo sapiens themselves), there is a long history of Homo sapiens introducing species into environments where they are not native
• Often this has happened so far in the past that people do not realise that they were introduced at all
e.g. before the development of pollen analysis techniques we did not know that Sweet chestnut is not a native species – in this case naturalised species have been well incorporated into our natural environment

Question 9

Examples of naturalised species

Answer 9

Rabbit (introduced by Normans, 12th C)

Pheasant (introduced by Normans, 12th C)Brown rat (1704 or later)

Question 10

Examples of extinct species

Answer 10

Extinct species
Bear Beaver Wolf
Wild pigs and boars
Fallow deer (introduced by Normans, 12th C) 
Grey squirrel (1876-1929)

Question 11

Examples of exotic species

Answer 11

Exotic species
Walnut (Roman)
Horse-chestnut (introduced from Albania in the 1600s)