3.2 Human impact on biodiversityIB Environmental Systems and Societies HL: Subtopic test

1. 1
   The brown tree snake (Boiga irregularis) is native to Australia, Papua New Guinea and the Solomon Islands. It was accidentally transported to the Pacific island of Guam in cargo after the Second World War. Guam had no native snakes that eat birds, and its birds had not evolved defences against them. Within a few decades the snake had reached very high densities, and 10 of the 12 native forest bird species had disappeared from most of the island. The Guam kingfisher (sihek) survives only in captive breeding programmes.

   (a)

   Which factor best explains why the brown tree snake population grew so rapidly on Guam?

   [1 mark]

   • AThe snake is a pioneer species adapted to colonise bare ground
   • BNative prey had no defences against it and there were few natural predators or controls
   • CGuam had many other snake species competing with it
   • DThe snake reproduces asexually

   (b)

   The Guam kingfisher survives only in captive breeding programmes. In which IUCN Red List category is it placed?

   [1 mark]

   • AExtinct
   • BCritically Endangered
   • CExtinct in the Wild
   • DData Deficient

   (c)

   Explain how the loss of native birds from Guam's forests could indirectly affect the plants of the forest.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   The Atlantic Forest of Brazil is classed as a biodiversity hotspot. Hotspots are regions with at least 1,500 endemic species of vascular plant that have lost at least 70% of their original habitat. Only around 12–16% of the Atlantic Forest remains, mostly in small fragments, after clearance for farming, plantations and the growth of cities such as São Paulo and Rio de Janeiro. It is the home of species found nowhere else, such as the golden lion tamarin.

   (a)

   Which two features define a biodiversity hotspot?

   [1 mark]

   • AA high number of endemic species and a high proportion of habitat already lost
   • BA large human population and low rainfall
   • CA small area and many introduced species
   • DMany protected areas and no habitat loss

   (b)

   Why are hotspots often prioritised for conservation?

   [1 mark]

   • AThey have the fewest species, so are cheap to protect
   • BThey are the only places where biodiversity is found
   • CTheir habitats have not been affected by human activity
   • DA large number of unique species can be protected in a relatively small area that is under severe threat

   (c)

   Explain why destruction of habitat in a tropical hotspot could lead to a significant loss of biodiversity.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A national agency has assessed 8,000 species in its country using the IUCN Red List categories. The results were: Extinct 40; Extinct in the Wild 10; Critically Endangered 400; Endangered 800; Vulnerable 1,000; Near Threatened 600; Least Concern 5,000; Data Deficient 150. The agency has a limited budget and must decide which species to give priority.

   (a)

   Calculate the percentage of assessed species that are threatened (Critically Endangered, Endangered or Vulnerable).

   [3 marks]

   (b)

   Discuss how the agency could use the Red List information to set conservation priorities, and one limitation of relying on it alone.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   Indigenous territories in the Brazilian Amazon, such as the Xingu Indigenous Park, have had much lower rates of deforestation than the cattle and soya farmland that surrounds them. Traditional management includes rotating cultivation, limited hunting and fishing, and the use of fire in small, controlled amounts. These communities now face illegal gold mining, logging and land-grabbing on their territories, droughts linked to climate change, and growing populations that need more land and income. The governments' enforcement has varied from one administration to the next, and some communities were not consulted when conservation areas were created.

   (a)

   Explain why traditional indigenous approaches to land management can be seen as more sustainable, and the challenges they face.

   [6 marks]

   (b)

   Evaluate the importance of environmental justice when undertaking conservation efforts.

   [6 marks]

   Total for question 4: 12 marks

End of questions