Desertification

Question 1

How and why has the global distribution of hot deserts changed over time?

Answer 1

During the height of the last glacial maximum about 18,000 years ago, the extent of arid areas was huge, however almost all of these areas would have not been hot, as global temps were on avg 12 c lower.
About 8,000 years ago, during the ‘Holocene Climate Optimum’, temperatures were much warmer, with similar temperatures as today, but the extent of deserts was confined to very small areas.
Present day deserts extend over considerably larger areas.

Question 2

Explain the process of desertification and its causes?

Answer 2

Desertification is the persistent degradation of dry land ecosystems by human activities and by climate change.

Climate change:
Less rainfall and increased droughts -> rivers and water holes dry up -> vegetation dies - > decrease in vegetation cover -> desertification
Higher temperatures (increased evaporation and reduced condensation) -> less rainfall -> vegetation dies -> soil expoed to wind and rain -> desertification

Human Activities:
Changes in farming -> increase in livestock numbers -> overgrazing: soil depleted of nutrients, land stripped of its protective grass cover -> vegetation cannot reestablish itself - soil exposed to wind and rain -> desertification

Population growth (high birth rates) - >farmers forced to change traditional methods of land use as more crops are needed for food crops -> over-cultivation: reduced soil fertility, soil left exposed - > vegetation removed -> increased risk of soil erosion - > desertification

Population growth (high birth rates) -> increased demand for wood for cooking, heating and building -> deforestation -> vegetation removed -> increased risk of soil erosion -> desetification

Question 3

Explain the global distribution of desertification?

Answer 3

Around boarders of existing deserts. Around 30*N&S of the equator and all are hot deserts
- Sub - Saharan Africa and south- west regions of Africa (increasing in risk of greater desertification)
- Central Australia (and expanding)

Expanding due to climate factors and population pressure

Question 4

Explain the impacts of desertification?

Answer 4

Include impact on landscape and populations …..
ECOSTYSTEM
- habitat ranges -> reduction in habitats
-> changing distributions of diseases, pathogens and parasites-> affect human health, agriculture and fisheries
-> food webs -> one removed species can set off a chain reaction in the food web

POPULATIONS
- rescued soil fertility -> decreased crop yields
- soil erosion -> sedimentation of water courses increases likelihood and intensity of floods
- drought and famine -> malnutrition and starving
- ‘ forced migration’ - > increased pressure on neighbouring areas and can lead to conflict

LANDSCAPE
- increased amounts of sand and dunes -> existing landscapes encroached upon
- soil erosion and loss of top soil
- increased salinity of soils -> development of salt crusts
- vegetation damaged by sandblasting from desert winds

Question 5

Explain the different human responses to desertification?
- resilience
- mitigation
- adaption

Answer 5

Resilience ( the capacity to recover quickly from damage or difficulty )
- remote sensing and ground surveys
- agroforestry - 200M
- new trees
- regeneration

Mitigation (action taken to reduce severity of impact)
- policies - convection to combat desertification and millennium ecosystems assessment
- environmental accounting

Adaption (altering behaviours and technology to cope)
- Intergration of trees, crops and livestock for drought resilient, productive and sustainable agricultural system

Question 6

What are the most effective human responses to desertification and why?

Answer 6

• mention alternative possible futures for local populations
  (If local knowledge and priorities are incorporated into future plans to mitigate vulnerabilities for locals communities and ecosystems, it is less likely that the ‘solutions’ that are proposed make the problem worse or move it elsewhere)

MOST EFFECTIVE
- proactive globalisation because it can hold everyone accountable for preventing climate change and desertification. As well as fairly redistributing the cots of negliegence

LEAST EFFECTIVE
Reactive regionalisation because the sources and impacts of desertification are global and long term issues that need mitigating immediately

Question 7

How is climate change predicted to impact desertification in the future?

Answer 7

(Positive feedback loop) - GET WORSE - especially impacts negatively least developed countries

Climate chnage
Increased extreme weather events
Soil erosion
Desertification
Reduced carbon reservoirs and sequestion
Increased co2 emissions
Climate change