SCIENCE · INVESTIGATE AND EXPLAIN

Defend a resource portfolio across explicit stress scenarios

Energy, agriculture and water choices supply multiple services under uncertain conditions. A portfolio mixes alternatives; a tradeoff compares outcomes without pretending all values have one natural unit. Before optimizing, declare minimum service needs, relevant environmental limits, affected groups and the scenarios being considered.

Learning outcome: Compare A shares 0,0.5 and 1 at both stress endpoints. Identify which portfolio can meet an explicitly proposed yield threshold while using less water, and state when no supported option meets the threshold.

Starting recap

Fix the useful service, lifecycle boundary and scenario; distinguish a conditional model result from an observed causal improvement.

All lessons are open directly. Your saved experiments remain when you leave and return.

Try

At half area in A and stress 0.5, A yield 6 and B4.75 give portfolio 5.375 tonnes/ha. Water 3000 m³/ha and climate 1500 kg CO₂e/ha. At severe endpoint its yield is 4.25, not the normal-state average 6.5.

Open the experiment

Predict

Without probabilities, the stress index supports:

Your prediction and reason

Experiment

Compare A shares 0,0.5 and 1 at both stress endpoints. Identify which portfolio can meet an explicitly proposed yield threshold while using less water, and state when no supported option meets the threshold.

Compare a resource portfolio across a declared stress scenario

Worked teaching model · synthetic values · Original one-hectare portfolio. A yield=8−4s tonnes/ha, water 5000 m³/ha, lifecycle emissions 2000 kg CO₂e/ha. B yield=5−0.5s, water 1000, emissions 1000. Linear area mixing and independent yields; stress index is not probability or a climate projection. No universal social objective or optimal allocation is assumed.

Area share of system A: 0.5 fraction Climate stress index: 0.5 index

Reset keeps your prediction, captures and practice history.

Original synthetic system; units differ by row
Quantity	Value	Unit
System A yield under supplied stress	6	tonnes/ha
System B yield under supplied stress	4.75	tonnes/ha
Portfolio yield	5.375	tonnes/ha
Portfolio water use	3000	m³/ha
Portfolio lifecycle climate burden	1500	kg CO₂e/ha
Portfolio worst-endpoint yield	4.25	tonnes/ha

A portfolio comparison requires service thresholds and declared scenarios, not a single universal score.

Stress has no probability attached. Expected performance needs probabilities; robustness examines performance across stipulated scenarios. Equity, ecosystem requirements, correlated failures and uncertainty remain separate decision criteria.

Predict, change one control, and save contrasting captures. Reconstruct the balance with units; then explain a process the ledger deliberately leaves out. Display precision is not measurement precision.

A portfolio comparison requires service thresholds and declared scenarios, not a single universal score.

Observation to attach to a capture

Captures preserve recipes and replay their calculated results. They are synthetic model evidence, not physical measurements.

Understand

Define the useful service

Construct the comparable ledger

The fictional one-hectare portfolio mixes system A and B. Under stress index s, A yield is 8−4 s tonnes/ha and B yield 5−0.5 s. A uses 5000 m³ water and 2000 kg CO₂e per hectare; B uses 1000 m³ and 1000 kg CO₂e. Area weighting gives the portfolio totals. Coefficients are original scenario assumptions, not crop forecasts.

Interpret the competing metrics

A has higher yield at low stress, while B retains more yield at the severe endpoint. Their yields cross when 8−4 s=5−0.5 s, so s=6/7. Mixing changes water and climate burdens as well as output. A favorable normal-state yield cannot alone establish robust food supply.

Challenge the boundary and scenario

The stress index is not a probability. Expected yield requires justified probabilities, whereas a worst-endpoint comparison asks what happens across the stipulated range. Robustness still depends on which scenarios were included; correlated failures, ecological thresholds, distributional effects and costs are omitted. The model supports a defended conditional choice, not a universal optimal allocation.

Worked original packet

Investigation

Changed-case transfer

A share 0.25 at stress 1: compute yield, water and climate burden. Is a 4.4-tonne minimum met across the endpoints?

Feedback

Yield 0.25×4+0.75×4.5=4.375 tonnes/ha, water 2000 m³/ha, climate 1250 kg CO₂e/ha. It misses 4.4 at the severe endpoint; averaging with the normal endpoint would not satisfy an all-scenarios requirement.

Sources and evidence boundary

Original prose, numerical packets and exercises. Primary method/mechanism source, checked 30 October 2026. Supplied values are not measured operating data, universal coefficients or recommendations. No physical equipment work, chemical application, organism manipulation or water extraction is requested. Retain first reasoning and critique in the course workspace; public feedback is practice, not independent assessment.

Apply

Public practice checks a specific claim. It does not establish independent mastery.

A share 0.25 at stress 1: compute yield, water and climate burden. Is a 4.4-tonne minimum met across the endpoints?

Your explanation and limitations

Continue

Completion requires a saved prediction, at least one capture and a reflection. Presence checks do not grade your reasoning.

Skipping retains experiments and awards no mastery.

Previous: Count production needed for a consumed-food service Next: Audit measurement continuity before interpreting a trend

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