Topic 28: The Human Footprint

Question 1

Explain the processes in which harmful substances can be transported from where they are heavily used to where they are totally not present

Answer 1

• Global fractionation: volatile chemicals evaporate from soils and are carried by winds, esp. from warmer areas to colder regions
• Global distillation: volatile chemicals in the atmosphere can condense into snow or rain
  
  • esp. when at high latitude, condensation rate > evaporation rate
  • The toxic rain or snow can come in contact directly with people or get into waterways and contaminate fishes.
• Very slow breakdown in cold climates

Question 2

Explain how important the size of habitat fragment is in monitoring edge effect.
Effects of edge effects

Answer 2

The smaller the fragment or the narrower or thinner it is, the greater the edge effect will be.

–> more exposed to winds and rain
–> change the microclimate in the area –> more likely to affect the core area
–> accumulated biomass loss results in biomass collapse

Question 3

Describe the effect of habitat fragmentation on the distribution of species

Answer 3

When an area is isolated or fragments, it is less likely to host large vertebrates –> predators loss
–> hyperabundance of smaller invertebrates at lower trophic levels
–> an example of trophic cascade leading to ecological meltdown

Question 4

Identify the key difference between the concept of HIPPO and Evil Quartet

Answer 4

The overpopulation of humanity

Question 5

What are some features of alien/invasive species?

Answer 5

• Maximize reproduction
• Allow great ecological dispersal
• Allow flexible ecological requirements (e.g. generalist)
• Similar to pioneer species in succession

Question 6

Explain the tens rule for invasive species

Answer 6

• 1 in every 10 species brought to a region will escape into the wild.
• 1 in every 10 of the escaped species will become naturalised.
• 1 in every 10 of these species will become invasive and pose negative impacts.

Question 7

Why do alien species pose such huge impact on native ones?

Answer 7

Since these species are new, the native species are naive to their foraging behaviours, smell or signs so they become more vulnerable to predators.

Question 8

How can the extinction debt be understood?

Answer 8

After a habitat is lost or damaged, the effect is not just short-term. Even after the initial habitat loss event, the number of species continued to go down much later on.