Hot deserts: Desertification Flashcards
What is desertification?
The persistent degradation of dryland ecosystems, that all have aridisols, by human activities and climate change
What is meant by the last glacial maximum?
The most recent time during the last glacial period when ice sheets were at their greatest extent
What is meant by the holocene climate optimum?
A warm period about 5000-9000 years ago with the thermal maximum around 8000 years ago (North Pole reaching 4ºC)
What is meant by grassroots?
The ordinary people in a society or an organisation (e.g. a political party)
What is globalisation?
A process by which national economies, societies and cultures have become increasingly integrated through the global network of trade, communication, transportation and immigration
What is regionalisation?
The set of processes that lead states to work together in an international system on a regional scale
What is the ‘top-down’ solution?
When the decision to undertake projects or developments is made by a central authority such as government with little or no consultation with local people whom it will affect
What is the ‘bottom-up’ solution?
When local people are consulted and supported in making decisions to undertake projects or developments that meet one or more of their specific needs
Describe the extent and distribution of extreme deserts in the Last Glacial Maximum?
18 000 years ago
- greatest amount of extreme desert
- widespread distribution
- all continents have an area of extreme desert with the longest extent in Northern Africa and Central Asia
Describe the extent and distribution of extreme desert in the Early Holocene?
8 000 years ago
- very little extreme desert
- small extent in central Asia and along the coasts of South Africa and America
- very significant decrease in extent of extreme desert, reduction from widespread areas to confined small areas of extreme desert (lost in Europe, Australia, N.America)
Describe the extent and distribution of extreme desert in the present potential vegetation?
- intermediate extent of extreme deserts
- return of an extreme desert across Northern Africa, now the largest extent and smaller extent in Central Asia and S.American coast
- moderate increase in extent from almost no desert in the Early Holocene
What is the ITCZ?
The intertropical conversion zone
a meteorological equator moves N/S leading to seasonal rains which hit margins of deserts most
Why is the greatest risk of desertification found on the margins of deserts where it’s least dry?
- land in the centre of deserts has little to no soil to degrade
- greatest population pressure is on the margins of the desert as there is soil and vegetation still (cultivation and animal grazing)
- margins of the desert experience the greatest seasonal variation due to proximity of the ITCZ and other seasonal rains
What are the factors that are causing long-term natural climate change?
- Milankovitch Cycle -> variations in the 3 orbital characteristics varies solar radiation received
- CO2, water vapour and CH4 can absorb longwave radiation increasing amount of heat energy in the Earth’s climatic system
- Volcanic eruptions cause periods of cooling, SO2 reacts with water forming a dense haze that reduces transmission of insolation
- 11 year cycle solar output, more sunspots = less solar output
Describe the global distribution of desertification risk?
Often located along southern margins of deserts in Northern Hemisphere
Southern Hemisphere this pattern is less clear
