Lecture 5 - Soils and Civilisations Flashcards
What is soil made of?
lots of things: air, living organisms, minerals, water and dead material
Where is soil found?
on the terrestrial surface of the Earth
What distinguishes between soil and unconsolidated rock?
The presence of life distinguishes soil and unconsolidated rocks
What is soil a medium for?
Plant growth
What does soil store and regulate?
Water and carbon
A handful of soil has more biodiversity than the Amazon rainforest - true or false?
True
Soil stores less carbon than all the forests and atmosphere on the planet - true or false?
False
How is soil important for cultural heritage?
Stores fossils or preserved human creations preserved in the soil - e.g. Roman shields
How is soil important for our urban areas and buildings?
Supports the structures
What questions do we need to answer to determine how fast soil forms?
How deep is the soil (tape measure)
How long it has been forming for
How do we determine soil forming rate?
depth/time to calculate a yearly growth rate (although we typically use longer time frames, e.g. mm per 1000 years because the rate is so slow
What is the formation speed of soil like?
Incredibly slow
What type of resource can we treat soil as because of it’s incredibly slow formation rate?
A non-renewable resource
When do we believe agriculture began evolving?
around 8000-10,000 years ago
How do we know agriculture was undertaken in the past?
Ancient farm tools and Egyptian tomb paintings
What does a plough allow us to do?
to till large areas in a short period of time, as opposed to having to plant each crop individually
What was the effect of farming in Greece in the past?
The destruction of trees, and planting of crops unconsolidated the land, resulting in a massively increased rate of erosion, in an area that had seen very little erosion before
What are periods of soil instability in the past associated with?
the expansion of agriculture
Widespread grazing of cattle
What are periods of soil stability associated with?
where people have invested in soil conservation
What is the general trend with periods of soil instability overtime?
the soil erosion events are episodic, but have been more concentrated in more recent times
What is the cycle of soil overuse?
Population growth leads to increasing food production and land use - destabilizes soil
Soil erosion increases, soil fertility decreases and crops fail
Land is abandoned and forests replanted
Allows for a period of stabilization and stability
How many people has soil sustained over 50 million years?
Over 100 billion people
How many people currently live with chronic undernourishment?
About 1 billion
How many extra people is it estimated we will need to feed by 2050?
2.3 billion
How much do we need to increase cereal production by to lift people out of poverty and support the extra people by 2050?
70%
To increase cereal production by 70% what needs to change
Output in developing countries needs to double
What environment do agricultural environments have the same erosion rate as?
Alpine regions
Are agricultural lands at a soil surplus, or deficit
Deficit - more is being washed away than forming
How we lose soil nutrients?
Harvesting (takes away nutrients)
Gaseous emissions
Soil leaching into the ground
How much soil do we estimate is lost every year?
35 thousand million tonnes
How much nitrogen is displaced yearly?
23-42 million tonnes
How much phosphorous is displaced yearly?
13-26 million tonnes
What happens if phosphorous and nitrogen flows into rivers/lakes?
Eutrophication
Where is the biggest issues with soil nutrition?
Africa
What is happening to soil nutrition in Africa?
soils are losing more nutrients than they’re gaining (by far)
Which continent consumes the most fertilizer?
Asia
How much fertilizer does Africa consume yearly?
Essentially 0
How have production of rice field in Libya v China differed since the 1960s?
The rice yields in Liberia have remained essentially static, while in China they have been steadily rising since the 1960s
Soil degradation is a factor in the fall of civilizations - true or false?
True
Is soil erosion outpacing soil formation?
Yes
What is happening to soil fertility in sub-Saharan Africa?
Falling dramatically
What condition are soil resources throughout the world and whats happening to them?
only fair, poor or very poor condition and that conditions are getting worse in far more cases than they are improving
Who reported on the global status of soils?
Intergovernmental Technical Panel on Soils
What % of the Planet’s ice-free surface has been cleared for crops or livestock?
35%
What crop production reduction would there be by 2050 is action is not taken?
10%
Is soil acidity a problem?
Yes, a huge one
What 4 steps can we take to solve soil issues?
Minimize further degradation and restore in most effected areas
Stabilize global stores of soil organic matter
Reduce/stabilize global use of nitrogen and phosphorus fertilizer - increase use in regions of nutrient deficiency
Improve our knowledge about the state and trend of soil conditions
