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More than 75% of river flows are withdrawn for agriculture, industry and domestic purposes - approaching or exceeding sustainable limits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
What is bottom trawling
Dragging a net over the ocean floor to catch fish
Very effective, but cause issues for entire ocean ecosystems
Non-discriminative (captures everything in its path; many organisms are injured or die)
Major issue with trawling, or fisheries in general
Bycatch: catch or non-target fish and ocean wildlife, including what is brought to port and what is thrown overboard at sea, dead or dying. One of the largest threats to maintaining healthy fish populations and marine ecosystems
What is ‘fishing down the food web’
Catch top predators, deplete them. Then catch lower level predators, moving to lower and lower levels as we overfish the higher ones
What is the precautionary principles
Where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation
Possible solution to overfishing
Aquaculture
What is high impact aquaculture?
Setting up nets in the ocean and growing fish inside
Introduces non-native species, drugs (antibiotics, hormones), herbicides (control algae growth), fish sewage (possibly pathogens), new diseases and parasites
What is lower impact aquaculture
Recirculating aquaculture systems
Having containers of water on land
