evsc week 12 - LAND SYSTEM CHANGE

global distribution of land use

• Land use involves how humans are using land, such as for agriculture or urban areas.

• Global land area is finite, so increasing land use in one category decreases it in another, making systems thinking important to understand interactions.

main drivers/causes of land use change 

1. population growth

2. logging

3. mining

4. small-scale farming

5. ranching (practice of raising livestock)

control variable for land system change (global)

Area of forested land as a percentage of original forest cover.

planetary boundary (global)

75% of original forest cover

biome control variable

Area of forested land as % of potential forest

biome planetary boundary

Tropical 85%

Temperate 50%

Boreal 85%.

Current value of GLOBAL control variable

 62% 

why is forest change the focus of the land system change planetary boundary

Because forests are critical for the global carbon cycle, biodiversity, and climate regulation

• deforestation has cascading effects on other planetary boundaries, making it a key indicator of land system health.

List and describe ecosystem services provided by rainforests 

• Biodiversity

• Photosynthesis

• Oxygen production

• Flood protection and water quality

• Carbon sequestration

Flood protection and water quality

Wetlands in rainforests absorb water and facilitate nitrogen, phosphorus, iron, and sulphur cycles.

Carbon sequestration

Efficiently stores carbon, helping regulate the global carbon cycle.

resilience in relation to forests

• Resilience refers to the ability of forests to recover from disturbances like wildfires

• Example: After a wildfire, if vegetation regrows and climate conditions stabilize, permafrost and forest systems can recover. Persistent climate warming, however, can exceed this resilience, causing long-term degradation.

Impacts of land use change on the earth system

1. Alteration of the global carbon cycle and climate

2. Changes to the regional climate through surface energy and water balance modifications.

3. Transformation of the hydrologic cycle, affecting freshwater supply.

4. Nutrient pollution from fertilizers and atmospheric deposition, degrading water quality.

5. Biodiversity declines due to habitat loss and fragmentation.

Feedback loop 1 – Amazon

Deforestation

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Reduced evapotranspiration

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meteorological changes

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further stress on rainforest ecosystems, potentially amplifying forest loss.

Feedback loop 2 – Boreal/permafrost forests

Wildfire

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permafrost thaw

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vegetation drying

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increased wildfire risk, creating a reinforcing cycle of permafrost degradation and forest loss.

Link land use change to other planetary boundary processes

• Deforestation and land system change influence:

  • Climate change: through carbon emissions and changes in surface energy balance.

  • Biogeochemical flows: nutrient cycling is altered by fertilizer use and land conversion.

  • Freshwater use: land conversion modifies hydrologic cycles.

  • Biodiversity loss: fragmentation and degradation of habitats.

basic science behind the planetary boundary

The boundary is based on how human land use disrupts key Earth-system processes.

• Forests regulate climate, carbon cycling, water balance, and biodiversity, so the control variable is forest cover.

• When forest cover drops too far below its original extent, it destabilizes the climate (less evapotranspiration and carbon storage), alters the hydrologic and nutrient cycles, and causes biodiversity loss