Massive investment is needed in education (many prisoners can barely read), mental health services (the rate of mental illness amongst prisoners is very high), drug dealing prevention (the bulk of prisoners are addicted or become so in prison), drug rehabilitation, early years support to struggling parents, youth services, decent housing etc. etc.
Prison populations rise when society is failing its most vulnerable members and failing to provide even the most basic services.
Investment in preventive services is a brave step for governments to take as results are slow in appearing and the electorate want quick fixes.
There always will be a small number of people who absolutely must be detained in prison, but it helps none of us for there to be vast numbers of prisoners detained when other alternatives would serve better to steer them away from offending and keep them away from the drug infested prisons.
Building new prisons is not the answer - the capital expenditure could be better spent on all those services outlined above; and, even when a new prison is built, it has to be staffed, and prison staffing is already a problem.
There are no simple answers; but good solutions need investment and commitment. Every one of us would benefit from this.
This will all take time - lots of it. Investment in proper services takes time to show results, and in the interim the existing prisons need to be managed better while lower demand filters through. We are talking decades - but unless this process is started now things will get no better - ever.