Drylands Flashcards
Why do drylands occur
Atmospheric instability, continentality, topography
What effect does atmospheric instability have on drylands
Intense solar insolation causes evaporation and the air rises and cools to cumulonimbus clouds so rainfall. Air moves sideways after hitting TTL (troposphere meets stratosphere) and sinks so high pressure means dry. Not always 30 degrees North and South as ICTZ shifts
What effect does continentality have on drylands
No water as too far from sea
What effect does topography have on drylands
Orographic rainfall means windward side is wet and leeward side is dry e.g. Gobi desert as Himalayas
Aridosol
Poorly developed with high mineral content and little OM so poor water retention, saltpans
What was the wellbeing assessed as in the drylands
Millennium Assessment: lower than in any other ecological system
What is % of land degrading globally and how many depend on it
24%, 1.5b
Where is the Sahel
S of the Sahara desert as a band from Djibouti to Senegal
Sahel temperatures
27-42 degrees
Sahel precipitation
100-200mm precipitation/yr - Maplecroft water stress index says extreme risk. 50y cycles of rain above and below norm
What is the effect of population pressure on the Sahel
DTM 2 means fallow system breakdown, food shortages causing Sudan conflicts as nomadic people have to settle on owned land
Water conservation techniques in the Sahel
Bamboo drip irrigation: Nougbah village in Jainta hills used for rice, can save 50% water. Rainwater harvesting: save 50% water. Terracing: flattens slopes in Asia rice communities. Khadins, johads and kaltas: Rajsamand Lake dams. Dams: contribute to 16% global food production. Sand bores: Karnataka. Composting, mulching, cover crops, controlled floods. Contour planning: reduce 50% erosion. Conservation tillage, crop selection.
Plant restoration in the Sahel
Important in soil restoration as build OM, conserve water, control erosion, enhance biodiversity. Atriplex shrubs good as adapted and protein rich when animals need. Kitui County, Kenya, planted 50,000 trees
Agroecology in the Sahel
Aligns with 2030 Agenda for Sustainable Development, Cape Verde have targeted agricultural policies to conserve and improve soil structure
Great Green Wall in the Sahel
8000km across 22 Sahel countries, largest living structure, AU launched in 2007, 10m green jobs by 2030, 100m ha restored, needs $33b but $14b raised by world leaders, Tree Aid NGO plants one tree each 19s, Kew Botanical gardens provided science support, only 18m ha in 2023, Senegal most success so far as community work
UN Decade for Deserts
2010-20. Established by UN General Assembly to respond to desertification issues. Lead by United Nations Convention to Combat Desertification, FAO support. Raise awareness, promote sustainable land use, mitigate impacts. UNCCD legacy involved in land management
