DSE Geography | Agriculture and Food Security: A Teacher Prep Guide (6% Self-sufficiency)

2026-11-04

Tutor lesson-prep guides · Secondary Geography

Students happily say Hong Kong has no farming, then start guessing at self-sufficiency. This lesson pins it down with two numbers, output and demand, and then shows why more output is not the same as food security.

Objectives — Students can: (1) draw the input-process-output system for a farm type; (2) compute food self-sufficiency from output and demand; (3) state three Green Revolution gains and two costs.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Units	Kilograms in one tonne	1,000 kg
Percentages	5,400 out of 90,000	6%
Systems	The difference between inputs and outputs	Inputs start the system, outputs end it

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0-10 min	The system	Inputs, processes, outputs	Draw three columns
10-24 min	Output	Area times yield per hectare	5,400 tonnes
24-38 min	Self-sufficiency	Local output over total demand	6%
38-50 min	Green Revolution	Seed, fertiliser, irrigation; costs	Two costs named
50-56 min	Food security	Availability, affordability, safety	One example each
56-60 min	Exit check	Three questions collected and marked	Independent

03 Teaching script (read it out)

Scene 1: The system: three columns before examples

Inputs split into physical (climate, soil, water) and human (labour, capital, technology, market); processes cover ploughing, sowing, fertilising, irrigation and harvesting; outputs are crops, cash income and environmental impact.
Commercial farming is capital-heavy with high output; subsistence farming is labour-heavy with output mostly consumed on the farm.

Ask the class: the biggest input difference between intensive paddy rice and nomadic herding (labour against land).

Scene 2: Self-sufficiency: keep numerator and denominator in one unit

1,200 hectares x 4.5 tonnes per hectare = 5,400 tonnes.
Demand = 1,500,000 people x 60 kg = 90,000 tonnes, so self-sufficiency = 5,400 over 90,000 = 6%.

Ask the class to compute: what fills the other 94% (imports, which is why food prices track world markets).

Scene 3: Green Revolution and security: more output is not more security

Better seed with fertiliser and irrigation lifts yield from 4.5 to 9.0 tonnes per hectare, raising self-sufficiency from 6% to 12%, at the cost of soil degradation, water depletion and smallholder debt.
Food security has three pillars: stable supply, affordable price, safe food. Miss one and the household is not secure.

Warn them: doubling yield does not double security; distribution, price and stocks decide that.

04 Question types and worked steps

Type	Example	Steps	Answer
Diagram	Draw the input-process-output system	Three matching columns	Three items each
Calculation	Total output	Area times yield	5,400 tonnes
Calculation	Self-sufficiency	Output over demand, times 100	6%
Evaluation	Costs of the Green Revolution	Environmental and economic	At least two

Sanity check (teach this): Both figures must use the same unit: convert demand of 90,000,000 kg to 90,000 tonnes before dividing, or the ratio is out by a factor of 1,000. Self-sufficiency can exceed 100% for exporting countries; that is not an error.

05 Independent practice (3 questions)

Question	Answer	What to watch
Total output	5,400 tonnes	1,200 times 4.5
Food self-sufficiency	6%	Output over demand
Self-sufficiency after the Green Revolution	12%	Output rises to 10,800 tonnes

06 Common mistakes and what to say

Mistake	Student writes	Say this
Skipping the unit conversion	Ratio around 0%	“Kilograms become tonnes first; numerator and denominator must match.”
Inverting the ratio	Ratio around 1667%	“Self-sufficiency is local output over total demand, not the reverse.”
Leaving inputs blank	Only processes described	“Inputs explain why yields differ: climate, capital and technology all belong there.”
Assuming output equals security	More food means food secure	“Look at price and distribution; food you cannot afford is not security.”

07 Homework (paper, section and question numbers)

Secondary Geography chapter index — All chapters and practice
DSE Geography practice paper — Section B data response on farming

08 Exit check (last 5 minutes)

Question	Answer	Decision
Total output	5,400 tonnes	All three right: move to industrial location
Food self-sufficiency	6%	One wrong: reteach unit conversion
Three pillars of food security	Supply, price, safety	Two or more wrong: back to the first act

09 Tutor FAQ

Must self-sufficiency be under 100%?

No; exporting countries can exceed it.

Is the Green Revolution purely positive?

Yields rose sharply, but fertiliser, pesticide and water costs must be taught alongside.

Does Hong Kong still farm?

Yes, mostly fresh produce, but the share of total demand is tiny.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.