42. Which one of the following is in the correct decreasingorder for the major reservoirs of carbon on Earth?
    (1) Terrestrial soils > Terrestrial vegetation >Atmospheric CO₂> Large lake sediments
    (2) Terrestrial soil > Large lake sediments > Terrestrial vegetation > Atmospheric CO₂
    (3) Atmospheric CO₂ > Large lake sediments >Terrestrial soils > Terrestrial vegetation
    (4) Large lake sediments > Terrestrial soils > Atmospheric CO₂ >Terrestrial vegetation

The global carbon cycle is fundamental to life on Earth, regulating climate and supporting ecosystems. Carbon is stored in several major reservoirs, each with vastly different capacities and roles. Understanding which reservoir holds the most carbon is crucial for climate science, ecosystem management, and environmental policy. This article explores the correct decreasing order of the major carbon reservoirs among the options provided: terrestrial soils, terrestrial vegetation, atmospheric CO₂, and large lake sediments.

Overview of Major Carbon Reservoirs

Carbon is distributed across Earth’s ecosystems and geological formations. The largest reservoirs are sedimentary rocks and the deep ocean, but among the options typically considered in terrestrial and surface-level contexts—soil, vegetation, atmosphere, and lake sediments—soil stands out as the largest. Here’s a brief overview of each:

• Terrestrial Soils:

  • Description: Soils contain vast amounts of organic carbon from decomposed plant and animal matter, as well as inorganic carbon from minerals.

  • Carbon Content: The world’s soils store an estimated 1,500 gigatonnes of carbon (GtC), making them the largest carbon reservoir among the options listed.

• Terrestrial Vegetation:

  • Description: Plants, especially forests, store carbon in their biomass—roots, stems, leaves, and woody tissues.

  • Carbon Content: Earth’s plants store about 560 GtC, with forests being the largest contributors.

• Atmospheric CO₂:

  • Description: Carbon dioxide in the atmosphere is essential for photosynthesis and climate regulation.

  • Carbon Content: The atmosphere contains approximately 990 GtC as CO₂.

• Large Lake Sediments:

  • Description: Lake sediments accumulate organic and inorganic carbon over time.

  • Carbon Content: While significant locally, lake sediments globally store much less carbon than soils, vegetation, or the atmosphere.

Comparing the Options

Let’s review the options in the context of the carbon content of each reservoir:

• (1) Terrestrial soils > Terrestrial vegetation > Atmospheric CO₂ > Large lake sediments

  • Correct Decreasing Order:

    • Terrestrial soils (1,500 GtC)

    • Terrestrial vegetation (560 GtC)

    • Atmospheric CO₂ (~990 GtC)

    • Large lake sediments (much less than the others)

  • Note: This sequence is almost correct, but there is a discrepancy: atmospheric CO₂ (990 GtC) is actually larger than terrestrial vegetation (560 GtC). However, some sources may use slightly different estimates or focus on active versus total pools, but the standard accepted values place atmospheric CO₂ above vegetation in carbon content.

  • However, if the question is interpreted strictly for the typical terrestrial and surface reservoirs, and the atmospheric CO₂ pool is considered separately or by some curricula as less than vegetation (which is not correct by most modern data), there may be confusion.

  • In reality, for the listed options, and using the most widely accepted data, the correct order by carbon content is:

    • Terrestrial soils (largest among these)

    • Atmospheric CO₂ (next largest, ~990 GtC)

    • Terrestrial vegetation (560 GtC)

    • Large lake sediments (smallest)

• (2) Terrestrial soil > Large lake sediments > Terrestrial vegetation > Atmospheric CO₂

  • Incorrect: Large lake sediments do not store more carbon than vegetation or the atmosphere.

• (3) Atmospheric CO₂ > Large lake sediments > Terrestrial soils > Terrestrial vegetation

  • Incorrect: Atmospheric CO₂ does not store more carbon than soils or vegetation in the context of these reservoirs (though it is more than vegetation by most data, but not more than soils).

• (4) Large lake sediments > Terrestrial soils > Atmospheric CO₂ > Terrestrial vegetation

  • Incorrect: Lake sediments are the smallest among these reservoirs.

Clarifying the Correct Order

Using the most up-to-date and widely accepted data:

• Terrestrial soils: ~1,500 GtC (largest among these options)

• Atmospheric CO₂: ~990 GtC

• Terrestrial vegetation: ~560 GtC

• Large lake sediments: Much less than the others

Therefore, the correct decreasing order is:

Terrestrial soils > Atmospheric CO₂ > Terrestrial vegetation > Large lake sediments

However, none of the options in your query exactly match this order.
If we must choose from the options you provided, option (1) comes closest, but it incorrectly lists terrestrial vegetation above atmospheric CO₂. This is a common point of confusion, as some educational materials or older sources may not reflect the latest data or may focus on “active” versus “total” pools.

In most standard curricula and current scientific understanding, atmospheric CO₂ is considered to have more carbon than terrestrial vegetation, but soils are still the largest among these options.

Why This Matters

Understanding the distribution of carbon reservoirs is essential for:

• Climate Science: Knowing where carbon is stored helps predict how climate change will affect different parts of the Earth system.

• Ecosystem Management: Protecting soils and forests is critical for maintaining carbon sinks and mitigating climate change.

• Environmental Policy: Policies aimed at reducing atmospheric CO₂ must consider the role of soils and vegetation as carbon sinks.

Key Takeaways

• Terrestrial soils are the largest carbon reservoir among the options listed, storing about 1,500 GtC.

• Atmospheric CO₂ contains about 990 GtC, more than terrestrial vegetation (560 GtC).

• Large lake sediments store much less carbon than the other reservoirs.

• The correct decreasing order is: Terrestrial soils > Atmospheric CO₂ > Terrestrial vegetation > Large lake sediments.

• None of the options in your query exactly match this order, but option (1) is the closest, though it incorrectly lists vegetation above atmospheric CO₂.

Summary Table

Conclusion

Among the options provided, none perfectly match the correct decreasing order of Earth’s major carbon reservoirs based on the most current data. The closest option is (1) Terrestrial soils > Terrestrial vegetation > Atmospheric CO₂ > Large lake sediments, but this is incorrect because atmospheric CO₂ actually contains more carbon than terrestrial vegetation.

The scientifically accurate order is:

Terrestrial soils > Atmospheric CO₂ > Terrestrial vegetation > Large lake sediments

If you must choose from the given options, (1) is the closest, but it is not entirely correct. If your exam or curriculum uses older or different data, it may accept (1) as correct, but by current standards, it is inaccurate. Always check the latest data and your specific curriculum for the most accurate answer.

In summary, based on widely accepted scientific data, the correct decreasing order is not fully represented in your options. However, the closest is:
(1) Terrestrial soils > Terrestrial vegetation > Atmospheric CO₂ > Large lake sediments
But this is not strictly accurate—atmospheric CO₂ is greater than terrestrial vegetation.
There is no perfectly correct option among those listed, but (1) is the best available if forced to choose.
If your curriculum or exam expects (1) as the answer, it is likely based on older or different data.
For current scientific accuracy, the order should be: