L14 - Resource Use

What is ‘peak oil’?

• The moment in time when people stop discovering new reserves of oil and production begins to decrease

• Oil production and availability will peak in the next ~50 years and decline after.

How has fossil fuel use and discovery changed over time?

• Discovery peaked in 1970 and is expected to decrease soon because there are no new reserves being found

• Availability is peaking now and is expected to decline soon

Why are fossil fuels so finite?

• Fossil fuels have minimal recycling potential

• Coal and oil are still being produced (100,000 tonnes per year)

• The decline of these resources will result in a collapse in society unless society becomes decarbonised

What confirms climate change by hydrocarbons?

• The burning of hydrocarbons puts more carbon dioxide in the atmosphere and results in the reduction of oxygen in the atmosphere.

What is the recent pattern of sea level change?

• Mostly sea level rise around the world

• Largest increase off the southern coast of Africa (3m rise)

• Sea level decline around Greenland and Antarctica (4+m loss) due to glacis-eustasy

What is glacio-eustasy?

• Changes in sea level due to the melting or growth of glaciers and/or ice caps

How does glacio-eustasy work (in Greenland)?

• The amount of gravitational force is proportional to the mass of the body

• Ice sheets can be very large and exert a gravitational pull on the water, pulling water towards it.

• At the edge of the Greenland ice sheet, water gets pulled higher towards the ice sheet, leaving areas where there is less water, resulting in the supposed decreasing sea level.

What is glacio-isostasy?

• The vertical movement of the earth’s crust in response to weight (of ice sheets)

• Happens because the mantle and crust can be deformed over time due to weight.

How does glacis-isostasy work?

• Ice sheets exert a downward force on the crust and mantle. The mantle and lithosphere sag, causing a peripheral bulge to occur in the farfield, causing a relative decrease in sea level.

• In the far field, the pull of water towards the ice sheet removes the weight on the crust, resulting in the upwelling of land.

• Once the ice sheet has melted, pressure is removed from the lithosphere, it moves up as glacial rebound, the peripheral bulge comes down, and sea level rises.

  • At the same time, there is a loss of ice sheet, causing a rise in sea level.

• In the farfield, there is a more water in the basin, sea level rises, putting a downward pressure on the mantle.

How is marshland evidence for sea level change?

• Plant life changes from salt tolerant to freshwater grown plants, and a change in organisms that live in the soil, relative to the distance from the coast.

• As sea level changes, the position of salt marsh will also change.

• Change in location of sea and vegetation is preserved in sedimentary and stratigraphic columns.

• Cores can be taken to track this change.

How does ocean acidification occur?

• It is a major consequence of our use of hydrocarbons

• Carbon dioxide is acidic and will dissolve in oceans to form carbonic acid - although not a very strong acid, it has effects nonetheless.

• The amount of CO2 dissolved in seawater is increasing, resulting in the pH of seawater decreasing between 1990 and 2010.

How does ocean acidification impact marine organisms?

• Marine organisms produce calcium carbonate shells - they have to concentrate the calcium carbonate until it is saturated and precipitated to form their shells.

• As pH drops, it is harder for them to produce their shells

  • This will use up their energy, of which could have been used to reproduce, potentially impacted their population.

• If they cannot make their shells, they could become easy targets to predators, and could result in a collapse of food chains if their population shrinks enough.

How has the availability of minerals and metals changed over time?

• Availability is currently peaking and is expected to decline over the next 20-30 years.

• Metals are easy to recycle.

• Majority of metals needed for green energy production are in china and access is restricted by geopolitics.

What is the impact of mining?

• Mining generally results in a loss of biodiversity

• It can generate lots of dust

  • Impacts human health

  • Can get into streams and impact aquatic life

How has phosphorus supply changed over time?

• Production rates of phosphorus peaked in the 1980s then dropped off, largely due to concerns over pollution and eutrophication.

• At some point in the near-distant future, demand for phosphorus will outstrip supply.

• Over time, we are running our of readily accessible phosphorus supplies; we are dependent on phosphorus for modern day agriculture and food supply.

How does eutrophication work?

• Phosphorus that has been applied to land gets carried off to water sources, causing a growth of aquatic plants and algae, which die and sink to the bottom of the of the water column, where they are oxidised, causing water to become deoxidised, and killing fish.

Why can’t phosphorus be recycled?

• Phosphorus is relatively dilute.

• When it is used up it gets into the water column.

• Not economically feasible to recycle

How can struvite mineral replace phosphorus?

• Phosphorus present in human and farm animal waste is being concentrated to precipitate struvite mineral.

• Struvite = relatively insoluble phosphorus-ammonium compound that ca be applied to the land to replace phosphorus-nitrogen fertilisers.

• This way, the phosphorus is released at a rate that the plants can absorb it, reducing eutrophication.

How has groundwater supply changed?

• Groundwater is being used more rapidly than it can be replenished.

• Groundwater will take a long time ti replenish, but it can replenish itself.

• We need to minimise our usage to preserve supplies.

What is soil salinisation?

• The accumulation of salts in soil: if soil is too salty, plants cannot grow.

• There is evidence that soil salinisation caused collapse of society due to food supplies being destroyed.

• About 10% of the world’s soils are at risk of salinisation. Happens particularly in arid areas where the irrigation of crops evaporates, leaving salt behind.

How can soil salinisation be avoided?

• Irrigation should happen at night

• Soils need to be drained well

• Salts need to be flushed out the system

How was soil eroded in the US dust bowl?

• Mass migration to the great plains following an unusual period of rainfall resulted in the growing of crops.

• When the climate returned to a natural state, soils blew away, causing starvation and poverty.

• Modern plants don’t have very long roots, cannot hold soil together, and will accelerate erosion

  • This area has been revived by adding lots of water to the regions resulting in a depletion of ground water sources.

  • Agriculture in this region is not sustainable and needs to change.

How does soil organic matter prevent soil erosion?

• Organic matter holds soil together

• Arable land has relatively low organic carbon content

• Modern agriculture tends to remove carbon content, which can accelerate erosion.

How does the distribution of global soil lifespans change?

• Soils erode faster (1mm per year) if they are managed badly.

• Soils will be lost if we do not change our agricultural methods - 34% of soils will be gone in 100 years

• By doing regenerative agriculture, we can reduce this to 7% of soils being lost over 100 years.

What is the impact of deforestation on soil and nutrients in the Amazon?

• Fairly regular rate of felling in the Amazon.

• Clearing forest areas is done for agriculture; when forest is cut down, biodiversity declines in that immediate area.

  • Soils there are relatively infertile and most nutrients have been leached out of the soil and nutrients are now largely in the plants.

  • By clearing the area for agriculture, the plants will extort the remaining nutrients from the crops.

  • As grazing animals eat the plants, these nutrients cannot be recycled.

What are the planetary boundaries?

• Defines 9 boundaries - if we live within the central circle, we can live comfortably.

• By moving to orange zone, we increase the likelihood of some catastrophic change which can cause harm to society

• Some boundaries have quantifiable values.

• We have now exceeded 7 of these boundaries