Earth Lakes Are Under Threat Reading Answers Review

Report: "Earth's Lakes Are Under Threat" — Summary and Key Findings

Question 4: Define the “peak water” phenomenon as described in the text.

Answer: A temporary increase in lake water from glacial melt, followed by a permanent decline as glaciers retreat.

Explanation: Paragraph 2 explains that lakes fed by glaciers reach a maximum inflow (peak water) before inflows drop permanently. This concept is critical for understanding future water security in regions like the Himalayas and Andes. earth lakes are under threat reading answers

Main threats

• Climate change: Warming alters thermal stratification, increases evaporation, reduces ice cover, shifts species ranges, and exacerbates harmful algal blooms.
• Water extraction & flow alteration: Irrigation, dams, groundwater pumping, and diversions shrink lake area and change residence time, concentrating pollutants.
• Nutrient pollution (eutrophication): Agricultural runoff and untreated sewage increase nitrogen and phosphorus, causing algal blooms, oxygen depletion, and fish kills.
• Pollution & contaminants: Heavy metals, plastics, persistent organic pollutants, and emerging contaminants (pharmaceuticals, microplastics) degrade ecosystem and human health.
• Invasive species: Non-native fish, plants, and invertebrates outcompete natives, alter food webs, and change water clarity and nutrient cycling.
• Land-use change & habitat loss: Urbanization, deforestation, and shoreline development destroy wetlands and buffer zones that protect lakes.
• Overfishing & resource exploitation: Unsustainable harvests reduce populations and disrupt trophic structure.
• Salinization and mineralization: Reduced inflows and irrigation return flows raise salinity in terminal lakes (e.g., Aral Sea, some inland lakes), harming biota.
• Sedimentation: Soil erosion increases turbidity, buries spawning grounds, and fills basins, reducing storage.

Question 1: What percentage of the Earth’s liquid surface freshwater is stored in lakes?

Answer: Nearly 90%.

Explanation: The passage explicitly states in the introduction that lakes contain “nearly 90% of the planet’s liquid surface freshwater.” This statistic highlights the disproportionate importance of lakes relative to their small surface area. Report: "Earth's Lakes Are Under Threat" — Summary

Earth Lakes Are Under Threat: Reading Answers & Comprehensive Analysis

5. Summary Completion (Example)

Gap-fill text:
Lakes are threatened by _______, which causes oxygen depletion, and by rising _______ due to climate change. In addition, _______ species can outcompete native wildlife. Question 1: What percentage of the Earth’s liquid

Answers:

1. eutrophication
2. temperatures
3. invasive