Extreme environments futures practice questions.

Thawing permafrost in the West Siberian lowlands releases methane and carbon dioxide, which contribute to warming and so cause further thaw. Which systems concept does this illustrate?

• A positive feedback loop that amplifies the change
• A negative feedback loop that damps down the change
• A steady-state equilibrium maintained by balanced inputs and outputs
• A closed system with no transfers of matter across its boundary

Answer: A positive feedback loop that amplifies the change

The output of the process amplifies the change that started it, which is precisely what positive means in systems language rather than beneficial. A negative loop would instead damp the warming and return the system towards its former state.

As Arctic summer sea ice has retreated, more vessels have used the Northern Sea Route along the Russian Arctic coast. What is the most direct advantage of this route for trade between north-east Asia and northern Europe?

• Ice-strengthened hulls and icebreaker escorts are no longer needed at any time
• Sailing distance is shorter than the route via the Suez Canal
• Cargo capacity per vessel is roughly double that of a Suez-class ship
• Ships can maintain their maximum service speed for the whole voyage

Answer: Sailing distance is shorter than the route via the Suez Canal

The gain is purely geographical: a high-latitude track between these two regions is substantially shorter than the Suez route, which cuts voyage time and fuel use. Ice class requirements, escort fees and speed restrictions remain, so the saving is only partly realised.

The Noor Ouarzazate complex in Morocco uses concentrated solar power with molten-salt heat storage rather than photovoltaic panels alone. What is the main operational advantage of that storage?

• It removes the need for any transmission line to the national grid
• It raises the instantaneous efficiency of converting sunlight to electricity
• It allows electricity to be generated for several hours after sunset
• It removes the plant's demand for cooling water in an arid setting

Answer: It allows electricity to be generated for several hours after sunset

Storing heat rather than electricity lets the turbine keep running into the evening demand peak, so the output is dispatchable instead of tied to daylight. That reliability is why a desert country accepts a higher cost per unit than for plain photovoltaics.

The Great Green Wall initiative across the Sahel began as a plan for a continuous belt of planted trees and has shifted towards a mosaic of restored land, water harvesting and farmer-managed natural regeneration. What does this shift reflect?

• Restoring land use across many sites works better than one planted line
• Tree planting has been shown to have no effect on soil anywhere
• The Sahel has become too wet for degradation to continue
• Regional governments withdrew from the initiative entirely

Answer: Restoring land use across many sites works better than one planted line

Seedlings planted in a line across drylands died in large numbers and did not address why land was degrading; supporting farmers to protect natural regrowth on their own fields spread benefits and survived without irrigation. The lesson is that degradation is a land-use problem, not a gap in the tree cover.

Thawing permafrost is described as a climate feedback rather than only a local hazard. Why?

• It releases carbon dioxide and methane from long-frozen organic matter
• It reflects more sunlight back to space as the ground darkens
• It removes carbon from the atmosphere as new vegetation colonises
• It has no measurable effect beyond the settlements that subside

Answer: It releases carbon dioxide and methane from long-frozen organic matter

Permafrost holds roughly twice as much carbon as the atmosphere, locked in undecomposed plant material; thawing lets microbes break it down and release greenhouse gases, which causes further warming and further thaw. Vegetation growth offsets only a fraction of this.

Reduced Arctic sea ice has increased interest in shipping through the Northern Sea Route. Which factor most limits its use as a reliable trade corridor?

• Seasonal and unpredictable ice conditions requiring escort and insurance
• The route is longer between north-east Asia and northern Europe than the Suez route
• No state claims jurisdiction over any part of the route
• Ports along the route already handle more traffic than they can manage

Answer: Seasonal and unpredictable ice conditions requiring escort and insurance

The distance saving is real, but shipping economics depend on schedule reliability, and a route that may need an icebreaker escort and attracts high insurance premiums cannot support just-in-time supply chains. Search and rescue capacity along the route is also thin.