Water and Carbon Cycles CASE STUDIES Flashcards
Case Study of a Tropical Rainforest illustrating carbon and water cycle and their relationship with environmental change and human activity.
Amazon Rainforest
What is the location of the Amazon Rainforest?
- South America.
- Borders 9 countries, majoritycovering 68% of Brazil.
- 8.4 million sq km.
- From West Andes Mountains to the Atlantic Ocean.
What does the water cycle in the Amazon Rainforest affect?
- Climate
- Freshwater Sources
- Biodiversity
How does the Amazon Rainforest affect the climate? (WATER)
Receives >2000mm of rainfall annually and 1/2 may never reach the ground as it is intercepted by 40,000+ plant species. Half of those regulate the local climate, keeping 50-80% moisture within the biome. 40-50% of water is evapotranspirated into the atmosphere and releasing convectional rainfall. Releases 20 billion tons of moisture per day, some controlling global climate patterns such as rainfall in the Great Plains, USA.
How does the Amazon Rainforest affect Freshwater Sources? (WATER)
Only a 1/3 of rainfall in the Amazon Basin ends up in the Atlantic Ocean. This accounts for 15% of the global freshwater supply, entering the ocean through the second largest river in the world: Amazon River. Contains up to 1/5 of global river discharge in the world at 175,000 cumecs.
How does the Amazon Rainforest affect biodiversity? (WATER)
Most biologically diverse ecosystem in the world. Here are short-term transfers of water including respiration, photosynthesis, interception, infiltration (20-30%), evapotranspiration (40-50%), surface run-off (<1%). Maintains hot and humid conditions which are optimum for decomposition on forest floors however topsoil remains infertile (too many plants).
What does the carbon cycle in the Amazon Rainforest affect?
Effectiveness as a carbon sink.
How does the carbon cycle affect climate in the Amazon Rainforest?
Carbon sinks so takes in more CO2 than they release, decreasing atmospheric greenhouse gas levels. Mitigates climate change through carbon sequestration and an albedo effect. Stores 100 PgC of carbon in majority 182 tree species (out of 16,000) or 1% of trees in rainforest store 1/2 of all carbon sequestered in biome. Both long-term (sequestration) and short-term transfers of carbon (photosynthesis, respiration, decomposition).
How is human activity affecting the Amazon Rainforest?
- Deforestation
- Agriculture
- Energy Development
- Illegal trading
How does deforestation affect the Amazon Rainforest?
For logging, illegal trade of timbers or mostly clearling land for agricultural use. Decreases number of trees, reducing effectiveness of biome in carbon sequestration. Can boost local economy through sales however short-term income if not selectively logged. Opens up more areas of rainforest for development such as the Trans-Amazonian Highway.
How does deforestation affect the water and carbon cycle as well as environmental change in the Amazon Rainforest?
Water: Decreases vegetation and therefore, interception and infiltration, significantly increasing surface run-off. Impacts local wet and humid climate to be drier and reduces global rainfall patterns since no moisture is released.
Carbon: Decreases short-term transfers of carbon between atmosphere and biosphere, less is stored in trunks and more stays in atmosphere, contributing to enhanced greenhouse effect and global warming.
How does agriculture affect the Amazon Rainforest?
Cattle ranching accounts for 95% of total deforestation in Amazon Rainforest. ‘Slash and burn’ farming increases frequency of wildfires and commercial farming clears land for soybean and palm oil which reduces habitat space for the fragile ecosystem.
How does agriculture affect the water and carbon cycle as well as environmental change in the Amazon Rainforest?
Water: Agriculture includes same impacts of deforestattion. May apply water abstraction which depletes long-term storage of aquifers or water table may be off-balance.
Carbon: Some crops may be used for biomass which is considered a carbon neutral fuel however rotting organic matter may transfer some carbon back into the soil through nutrient recycling whilst simultaneously releasing methane into the atmosphere, contributing to enhanced greenhouse effect and global warming.
How does Energy Development affect the Amazon Rainforest?
In Peru and Colombia, oil extraction and drilling has contaminated freshwater sources and large areas of the biome, reducing biodiversity by poisoning and killing it. In Brazil, 150 dams are planned to be built in the Amazon with hydroelectric power such as the Belo Monte Dam.
How does energy development affect the water and carbon cycles as well as environmental change in the Amazon Rainforest?
Water: Hydroelectric dams tend to flood valleys and restrict water movement downstream, directly impacting aquatic ecosystems and the river discharge (of Amazon River). Higher evaporation rates possibly, increasing local rainfall and soil surpluses annually. Oil extraction just contaminates and decreases the low 3% of freshwater sources making up the hydrosphere.
Carbon: Same impacts of deforestation. Oil drilling for fuel use will release more greenhouse gases into the atmosphere, contributing to the enhanced greenhouse effect and global warming.
How does illegal trading affect the Amazon Rainforest?
Illegal animal trade makes millions abroad so the local economy doesn’t benefit and instead encourages further trade. Decreases competition within biome which is not ideal and seed dispersion by certain animal species
How does illegal trading affect the water and carbon cycle as well as environmental change in the Amazon Rainforest?
Water: decreases transfers of water within biosphere.
Carbon: Decrease in animal species means less die and are decomposed on forest floor, returning carbon and nutrients back into infertile soil. Respiration still occurs where carbon enters atmosphere just not in the rainforest. Overall, decreases short-term transfers of carbon within biosphere.
Give an example of a positive feedback cycle in the Amazon Rainforest.
- Increase in deforestation.
- Soil and climate is drier.
- Increases frequency of wildfires.
- Increased pollutiopn and greenhouse gases entering atmosphere.
- Leads to heatwaves or dry seasons.
- Cycle repeats (can exclude step 1 now).
More of a local impact cycle!
Give an example of a negative feedback cycle in the Amazon Rainforest.
- Global Temperatures increase.
- Stimulates more plant growth.
- Due to carbon fertilisation, more plants sequester more carbon from atmosphere.
- Global temperatures decrease.
More of a global impact cycle!
Case study of a river catchment(s) at a local scale to illustrate and analyse the key themes above,
engage with field data and consider the impact of precipitation upon drainage basin stores and
transfers and implications for sustainable water supply and/or flooding.
The Hogsmill River
What is the location of the Hogsmill River?
- Tributary of the River Thames
- Source is in Ewell, Surrey
- Mouth is in Kingston-Upon-Thames
What are factors affecting the source of the Hogsmill?
- Surrounded by low-lying land, unusual for sources.
- In a vegetated area - more infiltration and interception.
- Surrounded by very permeable ground, clay and silt.
- Many flood defences including brick river walls, flood relief channel and sandbags.
- Extremely low river discharge, normal below 0.2m.
What are factors affecting the middle course of the Hogsmill?
- Less meanders so quicker river discharge.
- Less vegetation, more urbanised surfaces with impermeable ground.
- Continued flood defences such as sluice gate and storm tank.
What are factors affecting the mouth of the Hogsmill?
- Even quicker river discharge
- Majority urban surroundings with impermeable ground
- Flood defences continued such as concrete embankments and artificially redirecting the river (away from main urban area).
