4 - Renewable resources Flashcards
What are renewable resources
Can be replenished over short periods of time:
- sunlight, wind, organic matter, soil, groundwater
What is renewable?
- capable of regeneration after harvest
- to be truly renewable, must be harvested at a rate less than or equal to regeneration
- cab be sustainably harvested
How much freshwater is available to us?
0.024% of water supply
97.5% of water is saltwater
Two categories of fresh water
- surface water: lakes, ponds, streams, rivers
- groundwater: underground reservoirs that accumulate in so-called aquifers
Renewable vs non-renewable water
Groundwater (surface water) = renewable
Aquifers = non-renewable
What determines water scarcity? What is physical water scarcity?
Determined by amount and quality of water
More than 75% of river flows are withdrawn for agriculture, industry and domestic purposes - approaching or exceeding sustainable limits
Reasons for water scarcity
Physical shortage, institutional failures or lack of adequate infrastructure to ensure regular supply
Causes of water scarcity
- irrigation (crops with high water demand e.g. corn)
- hydroelectric dams (producing electricity/energy using water)
- bad planning (e.g. las vegas; in middle of desert, one water supply (river delta))
- too many people (esp in dry places)
Agriculture impact on water scarcity
- 70% of all freshwater on the planet is used for growing food
- cotton, rice, sugarcane and wheat = 58% of irrigated farmland
Slide 23
Reducing water footprint
Roles of soil
- fertility (nutrient content) cycles
- organic matter cycles
Problems with soil resource
- erosion (loss of nutrients)
- nutrient and organic matter cycles are unbalanced
- it is drying up (tied to water usage)
- it is getting salty
What is erosion?
Process of removal and transport of the topsoil by action of water, wind and mass movement that causes its deterioration in time
Causes of erosion
- over-cultivation (reusing soil over and over without giving it time to recover)
- over-grazing (remove grass/plants = loss of stability)
- poor forestry practices
- mining
Best practices for good nutrient and organic matter cycling in soil
- cycle fields + fallow years
- plant cover cropping
- leaving crop residuals (dead plants/crops can resupply lost nutrients)
- no till farming
- crop rotation (diff types of nutrients available to soil)
Salinization of soil
Accumulation of salts in soils due to excessive irrigation and/or excessive fertilizer use
Problems with timber use
- we are cutting for the wrong reasons
- deforestation (can happen naturally e.g. wildfire) and clear-cutting (technique used to cut trees)
Problems caused by deforestation
- soil loss
- nutrient leaching
- loss of biodiversity
- decreased CO2 sequestration
- hydrological disruptions
What is clear cutting?
- deliberate removal of all trees in an area by humans
- usually for harvesting and trees are allowed to regrow
- problems can be similar to those for deforestation if not done properly
What is a nutrient sink? Affect of timber
Reservoir that provides storage for a nutrient
Young, rapidly growing understory vegetation can act as a nutrient sink after a disturbance (e.g. logging or forest fire)
What is silviculture
Planting back some harvested trees
Problems and solutions for silviculture
- whole-tree harvest depletes nutrients: stem-only harvest, leave residues
- short rotation (50 years) depletes soils: implement longer rotations (100 years)
- big cuts can lead to mass leeching of nutrients: harvest smaller areas mixed with untouched areas (buffers)
- logging roads disrupt streams, cause erosion: plan roads around streams
Old growth forests
- very high biodiversity and number of endemic species
- most are in Western Canada
- rare, limit harvest
Fish as a renewable resource
- we eat too much fish
- almost all global fish stocks are over-harvested
- also, huge increase in aquaculture, cultivation of fish in semi-domestication
