'Remember not the former things, nor consider the things of old," says the Old Testament (Isaiah 43:18).

In such a spirit, the archdiocese of Glasgow is urging congregations in the city to consider the current and future needs of the Catholic church, natural though it is to look back wistfully to the past.

It will sadden and dismay individual parishioners to think that their church, perhaps the site of their wedding or first communion, may eventually close but Archbishop Tartaglia and the diocesan management are courageous and right to be prepared to close as many as half of the West of Scotland's parishes. As the Archbishop has said: "Everyone knows that we cannot go on as we are."

The church has a chronic shortage of priests as it is and there are not enough new priests coming through seminary training to replace them. The drop in regular church-going witnessed in most Christian denominations has meant once busy churches have rows of empty pews on Sundays. At the same time, the population of Glasgow has fallen and there has been a demographic shift in the Catholic population so that areas such as the east end, where there was previously a large Catholic community, need fewer churches.

The number of Catholics in Scotland is no longer falling. The 2011 census showed those classing themselves as Catholic had actually increased by 40,000 in 10 years to 841,000. But insufficient numbers are regular churchgoers to make it viable to maintain so many parishes in Glasgow. The figures speak for themselves. There are 12 priests in the Glasgow South deanery, but in 20 years' time it is expected there will be just five.

The number of parishes across the archdiocese has fallen by 13% since 1991, but priest numbers by 57% over the same period. To use dry management speak, human and financial resources have become overstretched and the situation is unsustainable.

Just as some schools in Glasgow and across Scotland have had to consolidate in the face of changing demographics, so too must churches. Parishioners will understandably have an attachment to their church, but they will also want to know that diocesan funds are being used in the most prudent way.

Church closures will reduce the bill for upkeep but also raise the question of what will become of architecturally important buildings. The Catholic Church in Glasgow commissioned a number of internationally renowned modernist churches in the 1950s and 1960s, which now face an uncertain future. If they were bulldozed, it would be a great loss to the city. Perhaps alternative uses might be found for important buildings that cannot continue as churches.

The Scottish church has been through turbulent times of late, with Cardinal Keith O'Brien standing down following allegations of sexual misconduct but, like the Kirk, it is still a very significant body in Scotland, engaging passionately with Scottish affairs. This process will undoubtedly have sad moments, but it should build a church in Glasgow that is better able to meet current and future needs.