Separate rivalry from exclusion
In a common-pool resource, excluding users is difficult and use subtracts from what remains. A fish caught today cannot be caught by another fisher. A public good is non-rival: another listener can hear a warning broadcast without using it up. These are economic characteristics, not judgements about public ownership.
Individual incentives can conflict
An open-access user may gain from taking more while part of the depletion cost falls on others. The conflict does not prove collapse is inevitable. Access rules, collective institutions, monitoring and enforcement can change incentives and outcomes.
Ask how the system works
Who can enter? Who monitors use? What happens when limits are exceeded? Rules that work in one place may not transfer unchanged elsewhere. Ecological regeneration and enforcement costs matter alongside prices.
Connect economics with evidence
A resource policy should be assessed against a credible alternative, not just an improvement after its introduction. Environmental economics identifies the incentive problem; econometrics helps examine the evidence. Both are needed to avoid treating either pessimism or a success story as universal proof.