Human Activities cause changes in water and carbon stores

Question 1

What human activities have caused changes in water and carbon stores and rates of transfer?

Answer 1

Rapid population and economic growth, deforestation, and urbanization in the past 100 years have modified the size of water and carbon stores and rates of transfer between stores in the water and carbon cycles.

Question 2

Where is the human impact on the water cycle most evident?

Answer 2

The human impact on the water cycle is most evident in rivers and aquifers.

Question 3

What are some consequences of rising water demand in arid and semi-arid environments?

Answer 3

Rising demand for water for irrigation, agriculture, and public supply in arid and semi-arid environments has led to acute water shortages.

Question 4

How has water availability changed in the Colorado Basin in the southwest USA?

Answer 4

In the Colorado Basin, surface water supplies have diminished as more water is abstracted from rivers, and significant amounts are evaporated from reservoirs like Lake Mead and Lake Powell.

Question 5

How has overpumping of aquifers affected coastal regions of Bangladesh?

Answer 5

Overpumping of aquifers in the coastal regions of Bangladesh has led to incursions of saltwater, making the water unfit for irrigation and drinking.

Question 6

How do human activities such as deforestation and urbanization affect the water cycle?

Answer 6

Human activities such as deforestation and urbanization reduce evapotranspiration, which leads to a decrease in precipitation; increase surface runoff; decrease throughflow or interflow; and lower water tables. These activities disrupt natural ecosystems and their role in transferring water to the atmosphere through evapotranspiration, resulting in drier climates and inhibiting forest regeneration.

Question 7

How is the carbon cycle being altered by human activity?

Answer 7

Human activity is altering the carbon cycle by depleting some carbon stores and increasing others.

Question 8

What is the primary source of carbon emissions to the atmosphere?

Answer 8

Fossil fuel exploitation, including coal, oil, and natural gas, is the primary source of carbon emissions to the atmosphere.

Question 9

What has been the effect of rapid industrialization on carbon emissions?

Answer 9

Rapid industrialization, especially in the Chinese and Indian economies, has led to the significant removal of carbon from geological stores through the exploitation of coal, oil, and natural gas.

Question 10

How much carbon is transferred to the atmosphere annually through burning fossil fuels?

Answer 10

Currently, around 8 billion tonnes of carbon are transferred to the atmosphere each year through the burning of fossil fuels.

Question 11

What is the impact of land use change on atmospheric carbon levels?

Answer 11

Land use change, primarily deforestation, transfers approximately 1 billion tonnes of carbon to the atmosphere annually.

Question 12

How has deforestation affected the biosphere’s carbon storage?

Answer 12

Massive deforestation has led to a nearly 50% reduction in the planet’s forest cover, resulting in a significant decline in the amount of carbon stored in the biosphere and fixed through photosynthesis.

Question 13

What role do phytoplankton play in the carbon cycle?

Answer 13

Phytoplankton in the oceans play a crucial role in the carbon cycle by absorbing more than half of the CO₂ emissions from burning fossil fuels, significantly more than tropical forests.

Question 14

How does deforestation and agricultural mismanagement affect soil as a carbon store?

Answer 14

Deforestation and agricultural mismanagement lead to soil degradation through erosion, which reduces soil’s capacity to store carbon.

Question 15

How are the water and carbon cycles interlinked?

Answer 15

The water and carbon cycles are interlinked in several ways.

Question 16

How does atmospheric CO₂ affect the water cycle?

Answer 16

Atmospheric CO₂ plays a vital role in photosynthesis by terrestrial plants and phytoplankton, which are important carbon stores. These plants extract water from the soil and transpire it as part of the water cycle. The exchange of water between the atmosphere and the biosphere is influenced by atmospheric CO₂ levels.

Question 17

How does ocean acidity relate to the carbon cycle?

Answer 17

Ocean acidity increases when there is an imbalance in the exchange of CO₂ between the atmosphere and the oceans, with inputs exceeding outputs. The solubility of CO₂ in the oceans is influenced by lower sea surface temperatures (SSTs). Changes in atmospheric CO₂ levels affect SSTs, ocean temperatures, the melting of ice sheets and glaciers, and sea level rise.

Question 18

How do vegetation and soil interact with the water and carbon cycles?

Answer 18

Water availability influences rates of photosynthesis, primary productivity (PP), inputs of organic litter to soils, and transpiration. The water-storage capacity of soils increases with organic content. Temperatures and rainfall patterns affect decomposition rates and the release of CO₂ to the atmosphere. Vegetation and soil processes are closely linked in the transfer of water and carbon between the atmosphere and terrestrial ecosystems.

Question 19

How does the cryosphere interact with the carbon cycle and water cycle?

Answer 19

The cryosphere, which includes ice sheets, glaciers, sea ice, and permafrost, interacts with both the carbon cycle and water cycle. CO₂ levels in the atmosphere influence the intensity of the greenhouse effect and the melting of ice sheets, glaciers, sea ice, and permafrost. Melting of these frozen surfaces exposes land and sea, which absorb more solar radiation and contribute to further temperature rise. Additionally, permafrost melting exposes organic material to oxidation and decomposition, releasing CO₂ and CH₄. Changes in temperature also impact run-off, river flow, and evaporation rates in the water cycle.

Question 20

How do the interlinkages between the atmosphere, oceans, vegetation/soil, and the cryosphere affect water and carbon cycles?

Answer 20

The interlinkages between the atmosphere, oceans, vegetation/soil, and the cryosphere have significant impacts on both the water and carbon cycles. Changes in atmospheric CO₂ levels influence photosynthesis, evapotranspiration, and precipitation patterns. Ocean acidification affects CO₂ exchanges, sea surface temperatures, and sea-level rise. Vegetation and soil processes control water availability, organic carbon storage, and decomposition rates. The cryosphere affects carbon storage, ice melt, and water flow. Overall, these interlinkages create complex feedback loops and dynamics within the Earth’s systems.