IB ESS HL 2.1.22 Human Impacts on Stability Question Bank

Analyse how human activities alter ecosystem stability, feedbacks and resilience.

Exam points

identify the population or ecosystem process in the evidence
apply the correct interaction, growth or sampling model
justify the conclusion using limiting factors, assumptions and uncertainty

[Maximum number: 2]

Years	Average sediment flow / tons yr^{-1}
1921-1960	67.5
1971-1980	41.3
1981-1990	29.2

Table:Changes to sediment flow into the delta

Table: Changes to sediment flow into the delta: Sediment-flow and Danube-delta maintenance context

Table: Changes to sediment flow into the delta data
• 1921–1960 — average sediment flow: 67.5 tons yr⁻¹.
• 1971–1980 — average sediment flow: 41.3 tons yr⁻¹.
• 1981–1990 — average sediment flow: 29.2 tons yr⁻¹.

The Danube River delta is where the Danube flows into the Black Sea and includes UNESCO Biosphere Reserves and a World Natural Heritage site.
A delta is formed by continuous deposition of sediment carried by the river; sediment adds height and helps it extend into the sea.
The delta is a wetland ecosystem rich in plants, birds and fish, including over 1000 plant species, 300 bird species and endangered sturgeon.
Moldova takes nearly 20% of its water supply requirements from a branch of the Danube.

Suggest what effect this change in the sediment flow would have on the maintenance of the Danube River delta.

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2.1.22—Human impacts on stability question 1