Database results:
examBoard: Cambridge
examType: IGCSE
lessonTitle: Drought Effects on Ecosystems
Drought is one of the most devastating natural hazards affecting ecosystems worldwide. Unlike sudden disasters like earthquakes or floods, droughts develop slowly but can have profound and long-lasting impacts on the natural environment.
Key Definitions:
Meteorological drought: Defined by lack of precipitation over an extended period.
Agricultural drought: Occurs when soil moisture is insufficient for crop growth and production.
Hydrological drought: Happens when water reserves in aquifers, lakes and reservoirs fall below average.
Ecological drought: When water shortages create stress on ecosystems and habitats.
Visible signs: Wilting plants, dried-up water bodies, cracked soil
Measurement tools: Precipitation records, soil moisture levels, streamflow data
Drought indices: Palmer Drought Severity Index (PDSI), Standardized Precipitation Index (SPI)
Biological indicators: Changes in plant growth, animal migration patterns
Plants are usually the first organisms to show signs of drought stress. As primary producers, their suffering has cascading effects throughout the ecosystem.
When water becomes scarce, plants undergo several physiological changes to survive:
Plants conserve water by closing stomata (tiny pores in leaves), which reduces water loss but also limits photosynthesis. Leaves may curl, wilt, or be shed entirely to reduce water demand.
Plants redirect energy from growth to survival. This leads to stunted development, reduced flowering and decreased seed production, affecting future generations.
Plants may extend their roots deeper into the soil in search of water. Some species develop specialized root structures to increase water absorption efficiency.
Animals face numerous challenges during drought conditions, from direct water scarcity to habitat changes and food shortages.
Migration: Many animals relocate to areas with better water access.
Altered behaviour: Changes in feeding patterns, activity times and reproductive cycles.
Physiological adaptations: Some animals can concentrate urine or extract water from food to survive with less drinking water.
Population stress: Increased competition for limited resources leads to weakened individuals and higher mortality rates.
Reproductive decline: Many species reduce breeding or skip reproduction entirely during drought.
Population crashes: Death rates increase while birth rates decrease, leading to significant population reductions.
Genetic consequences: Droughts can create genetic bottlenecks by drastically reducing population sizes.
Predator-prey imbalances: Changes in population sizes can disrupt established ecological relationships.
Drought significantly impacts soil health and water bodies, which form the foundation of ecosystem function.
Soil undergoes several changes during prolonged dry periods:
Aquatic ecosystems face severe challenges during drought:
Different ecosystem types respond to drought in unique ways based on their natural characteristics and adaptations.
Forests experience increased tree mortality, heightened fire risk and pest outbreaks during drought. Even drought-resistant trees can die after prolonged water stress. The loss of canopy trees creates gaps that change forest structure and composition for decades.
Wetlands may dry completely, causing massive die-offs of aquatic plants and animals. Peat in dried wetlands can decompose or burn, releasing stored carbon. Many wetland species lack drought adaptations and may be locally extirpated.
Grasslands often have better drought tolerance but still experience reduced productivity and shifts in species composition. Drought can accelerate the invasion of non-native species that are better adapted to dry conditions.
Australia's Millennium Drought was one of the worst recorded droughts in the country's history, lasting over a decade. The ecological impacts were severe and wide-ranging:
This case demonstrates how prolonged drought can fundamentally alter ecosystems and push them beyond their ability to recover to their previous state.
Despite the severe impacts of drought, many ecosystems have evolved mechanisms to survive periodic water scarcity.
Ecosystems in drought-prone regions often display these adaptations:
When drought ends, ecosystems begin recovery processes that vary in speed and completeness:
Climate change is altering drought patterns globally, with significant implications for ecosystem resilience.
Increased frequency: Many regions are experiencing more frequent drought events.
Greater intensity: Droughts are becoming more severe due to higher temperatures.
Longer duration: Extended drought periods give ecosystems less recovery time.
New locations: Areas previously unaffected by drought are becoming vulnerable.
Ecosystem-based adaptation: Working with natural processes to increase resilience.
Protected area networks: Ensuring connected habitats allow species migration.
Restoration efforts: Rebuilding degraded ecosystems with drought-tolerant species.
Monitoring programs: Early detection of drought impacts to guide interventions.
Drought creates a cascade of effects throughout ecosystems:
Understanding these interconnected impacts is crucial for predicting ecosystem responses to drought and developing effective management strategies in a changing climate.
Log in to track your progress and mark lessons as complete!
Login NowDon't have an account? Sign up here.