Water And Carbon: Land Use Change Flashcards
Farming practices
Modern farming practices (e.g removing ecosystems for one crop type, which removes specific nutrients. This bleeds the soil dry of particular nutrients. Fertilisers are then made which is horrific for the environment.) Some fertilisers increase the growth rate of algae (eutrophication.)
Pesticides: destroys the micro ions of the soil: in one teaspoon of soil there are more microbes than people on the planet.
Knepp estate and the abandonment of old agricultural land
Knepp estate: Old farm has given land to a rewilding project: one of the most biodiverse ecosystems in the UK
Soil Draining
Drainage pipes remove excess water from the soil and carry it through a network of perforated clay tubes called ‘tiles’. Water would seep into the small spaces within the tiles and drain away. Modern tiles are made of plastic.
When the water table is higher than the tile, water flows into the tubing, lowering the water table over several days as the water drains away from the field, preventing excessive water levels and aiding poorly drained soils.
Disadvantages of draining marginal farmland
- Drains artificially increase the speed of through flow in the soil. This can increase the likelihood of flooding
- Dry topsoil can be subject to wind erosion if not properly protected
- Nitrate loss: this can lead to Eutrophication (as farmers will attempt to replace the nitrate with fertilisers) and pollution of water ways
These problems can be overcome using controlled discharge: this increases the rate of denitrification (converting nitrate into harmless nitrogen gas as soon as the saturated soils warm up in spring , reducing the risk of eutrophication.)
What is shifting cultivation?
A form of agriculture, used especially in tropical locations, in which an area of ground is cleared of vegetation and then abandoned for a new area until its fertility has been naturally restored. This can occur due to the laterite soil composition of tropical locations
What is a bourne?
Groundwater streams which feed into rivers in chalk environments. The London basin is a syncline made up of layered chalk.
Short term effects of deforestation
Less water evaporates from the land surface and through evapotranspiration and is returned to the atmosphere, so more water runs off of the land and stream flow is increased (lag time decreased)
What is water abstraction?
The process of removing water from natural sources like rivers, lakes, or groundwater for human use.
What are the advantages of draining marginal farmland?
- Improves soil structure, allowing for greater root penetration
- Improved aeration, more favourable for microorganisms to thrive as well as increasing the ease at which soils can be warmed (seeds can be sown and are more likely to germinate)
Effects of tree plantations
Taking in carbon BUT reduces diversity: monoculture destroys the soil quality e.g palm oil plantations
Management of the water table (GARDIT)
The reduction of abstraction in London in the early 1990s led to an increase in the water table levels, thus increasing the rising groundwater posed to underground structures e.g the tube. The General Aquifer Research Development and Investigation Team (GARDIT) was created to manage levels.
Groundwater in Milan and Greece
Milan: 25-40m decrease in groundwater in the last 80 years
Greece: 400m deep boreholes contaminated by seawater intrusion (very common)
Effects of water abstraction
Sinking water tables, empty wells and the intrusion of saltwater from the sea. Saline intrusion in rife along the Mediterranean coastlines
Long term effects of deforestation
After the initial rise in discharge, river levels will fall to new lows. Once the water has left the system (and with less vegetation —> evapotranspiration) there will be less atmospheric moisture to condense into rainfall: system inputs will decrease and so will river levels. Can lead to desertification, soil erosion and increased emissions through plant death.
South America’s importance in terms of environment
Environmentally important due to: high biodiversity; generation of over 1/4 of the world’s river discharge
In the last 50 years 10% of the Amazon has permanently disappeared as a result of demand for cattle feed; beef; sugar cane; ethanol
