Europe is facing one of the greatest human tragedies for a generation. The arrival of a million refugees in 2015 is roughly four times the number who arrived the year before. They do not represent an existential threat ­– yet. But a million is just the start. What the continent cannot withstand is an unfettered influx, driven by an exodus from North Africa and beyond.

Europe’s leaders have so far responded chaotically, as well as anarchically. At an acrimonious meeting of EU interior ministers in Amsterdam last week, a decision was announced to trigger “Article 26” of the Schengen rules allowing border controls to be extended for up to two years and suspending Europe’s passport-free travel zone.

Despite Greek protests, Brussels officials have been instructed to work on plans to lock Greece out of the travel area because the country has failed to stop hundreds of thousands of migrants at its borders.

The Commission is now working on a new system of frontier controls to prevent migrants getting from Greece to Germany through the Balkans. Discussions with Turkey to return every migrant entering Greece across the Aegean Sea in exchange for the EU accepting 250,000 documented asylum-seekers a year from Turkish camps are also in hand.

Like the near-collapse of the eurozone, the EU’s immigration crisis has exposed long-suppressed tensions throughout Europe. Some east European nations, with little history of multiculturalism and a long-standing flirtation with the far right, cannot be reconciled with the more liberal west. And the poorer south cannot share common interests with the richer north.

The Schengen agreement, designed to permit the free movement of labour, in practice permits the free movement of almost everybody. It may well be that Schengen – now likely to be “suspended” for two years – cannot survive and will never be revived.

The migrant problem is greater than Syria alone. Dealing with it is the greatest challenge to Europe’s future. The search for long-term solutions grows more urgent by the day. At the heart of the problem lie the demographic pressures, economic and political instability in North Africa and sub-Saharan Africa, and the caravan of humanity heading north.

The demographic time bomb on Europe’s doorstep, in Egypt, Libya, Tunisia, Algeria and Morocco, is the real threat to Europe’s long-term ability to manage migration flows. The pressure from these countries can only grow. Some have also been used for transit by migrants originating from countries south of the Sahara.

Egypt, Libya and Tunisia have experienced acute political unrest and change. They share a number of characteristics with high unemployment and mostly authoritarian, undemocratic and corrupt regimes.

The refugee crisis risks distorting the gender balance across Europe

The demographic pressures on all five countries are massive. These are the key factors driving political and social unrest. Their populations grew fourfold between 1950 and 2010 to over 170 million today. The population growth in these countries over the next 15 years is projected to reach 215 million. The total number of people aged 15 to 24 has increased by over 25 million to 34 million today, constituting one fifth of their populations with the highest unemployment rate in this group in the world.

In truth, Europe’s great migration crisis is only just beginning. The sticking plasters being applied in Amsterdam and Brussels will not provide the long-term answer. Europe’s liberal ideals are at risk if it fails to control the numbers of young men who dominate the flow of refugees and migrants from Africa.

On New Year’s Eve, in Cologne and at least three other German cities, scores of women were assaulted by men of Arab or North African appearance. More than a third of the refugees reaching Greece and southern Italy are male. A fifth are under 18.

The refugee crisis risks distorting the gender balance across Europe. One year into the crisis, Sweden’s sex ratio among people aged 16-17 years already favours males – at an astonishing 123 boys for every 100 girls – more heavily than China’s. Studies have established a correlation between gender imbalance and a rise in violence and radicalisation.

As the EU flails around for a coherent policy on immigration, it should consider controlling the numbers of single young men entering their countries. If this balance is not managed carefully by countries bearing the brunt of the influx, they may find they are unable to manage it at all.

The challenges to Europe are massive. Attempts to find a solution have repeatedly been thwarted by the inability of member states to find common cause or a common strategy. The lack of a coherent immigration policy will continue to haunt the EU and could bring it down.

It is a race that Europe is doomed to lose as long as it remains unwilling, or unable, to confront the true scale of the crisis. These upheavals present the EU with an unprecedented challenge to its identity, its administrative muscle and its ability to adopt hard-headed solutions.

It faces a crisis of political leadership and morale the likes of which it has not witnessed before. The odds on an acrimonious break-up have shortened. The threats of Brexit and Grexit have not gone away and in the former case appears likely.

The crisis is fuelling anti-immigrant extremism and defying the EU’s efforts to devise a coherent response, let alone an effective one. There is an urgent need for EU countries to rally round one policy if it is not to continue unravelling.

There are two vital strands to the policy which must be brought together. First, nations should be reminded that it was Europe (with American leadership) that in the ensuing chaos after 1945 was able to create the 1951 Geneva Convention on Refugees which successfully resettled millions of stateless persons throughout the continent.

Short of overturning international and European law, nation states have an obligation to live up to that noble vision and to absorb refugees and to share the burden across Europe by distributing the load equitably.

It is not just altruism which should drive EU policy. Europe is a rapidly ageing continent. It is essential to its continued economic development to have regular injections of young migrant workers.

The trick lies in ensuring the numbers are controlled.

Moreover, this should not be an open-ended European commitment. Migration and the effects of the demographic time bomb on Europe’s door-step are a global problem requiring global solutions. The United Nations plenary summit on immigration in September offers an opportunity for Europe to press for a global response.

Second, border controls on land and at sea and the processing of asylum-seekers at Europe’s external borders should be strengthened. There are plans to beef up Frontex, the EU’s external border agency. They are long overdue.

An enlarged European border and coast guard urgently needs to be created with the power to intervene in a country whether the member state likes it or not.

While this would impinge on frontline nations’ sovereignty, there is now a need to balance this against the greater good – not least in the battle against terrorism – which can only be achieved by re-establishing European control over the continent’s borders.

If European nations refuse to hang together on this issue, they will assuredly all hang separately.