L6-8 Drought Summary Notes

Drought Definition: Occurs when there is a water deficit over a specific period; in the UK, it is defined as 15 consecutive days with less than 0.2mm of rainfall.
Key Concepts:
- Positive Feedback: Change leading to instability.
- Negative Feedback: Change leading to stability.
- Resilience: Ability of a system to recover from disturbances.
- Tipping Point: Point of no return in system change.
- Water Deficit: Insufficient water to meet demand.
Types of Drought:
- Meteorological Drought: Significant drop in long-term precipitation.
- Agricultural Drought: Insufficient soil moisture for crops.
- Hydrological Drought: Deficiencies in surface and subsurface water supplies.
- Socio-economic Drought: Water demand exceeds supply due to various factors.

Brazil faced its worst drought in 80 years, affecting water supply and agriculture.
Causes included high-pressure systems diverting rain-bearing winds, resulting in dry conditions despite heavy rains in neighboring countries.
Impacts:
- Water rationing for 4 million people.
- Protests in São Paulo regarding water access inequality.
- Significant crop failures, especially in coffee, leading to a 50% rise in global coffee prices.

Deforestation in Brazil may have passed a tipping point, exacerbating drought severity through positive feedback mechanisms.
This includes:
- Loss of carbon sink capacity.
- Changes to regional water cycles.
- Increased wildfire risks.

Wetland Ecosystems: Loss of habitat, reduced water storage capabilities, carbon release from organic soils.
Forest Ecosystems: Trees take 2-4 years to recover post-drought; reduced carbon sequestration; increased vulnerability to pests and diseases, leading to dieback (e.g., Piñon Pines).

Human activities such as water abstraction, land-use changes, and deforestation contribute to drought severity.
Climate change further complicates drought risk through altered weather patterns.

Examples include reducing illegal groundwater wells and changing land management practices (e.g., banning burning by cattle herders).
Effectiveness of strategies may be limited by implementation challenges and not addressing root causes of water scarcity.