Syria’s conflict is dragging down its neighbours, none more perilously than Lebanon. Beirut’s official policy of “dissociation” – seeking, by refraining from taking sides, to keep the war at arm’s length – is right in theory but increasingly dubious in practice. Porous boundaries, weapons smuggling, deepening involvement by anti-Syrian-regime Sunni Islamists on one side and the pro-regime Hizbollah on the other, and cross-border skirmishes, all atop a massive refugee inflow, implicate Lebanon ever more deeply in the conflict next door. It probably is unrealistic to expect Lebanese actors to take a step back; Syria’s fate, they feel, is their own, and stakes are too high for them to keep to the sidelines. But it ought not be unrealistic to expect them – and their international partners – to adopt a more forward-looking approach to a refugee crisis that risks tearing apart their own country’s economic, social and political fabric, igniting a new domestic conflict that a weak Lebanese state and volatile region can ill afford.

This is a story numbers tell best. Over one million Syrians are in Lebanon – registered and unregistered refugees, as well as migrant workers and others. That figure – more than 25 per cent as great as the approximately four-million citizen population million– is rising and likely will soar if and when the battle for Damascus is fully joined. It would be staggering anywhere but is truly frightening when one considers the state’s institutional frailty, meagre resources and, perhaps above all, highly sensitive sectarian balance. Unsurprisingly, the government – divided and polarised, on this issue as on most others – was slow off the mark.

The day-to-day impact is palpable. The demographic change can be felt in virtually all aspects of life, from the omnipresent Syrian dialect, to worsening traffic congestion, mounting housing prices and rising delinquency. Yet, the refugees do not pose a humanitarian problem alone. Their presence also has been politically deeply polarising. The vast majority are Sunnis who back the uprising. Most Lebanese view the conflict through a sectarian prism, and thus their attitude toward refugees from the outset has largely been informed by confessional considerations, as well as by their potential security impact and implications for future domestic politics.

Refugees generally have moved to hospitable, predominantly Sunni areas. Even there, however, patience is beginning to wear thin. Hatred for the Syrian regime remains acute and tends to dominate other feelings. Still, there is growing anger at the fact that they are attracting Syrian fire by providing succour and cover to anti-regime rebels. Besides, a history of stereotypes is at play: as many Lebanese see them, Syrians fall into broad categories: low-income, poorly uneducated, menial workers, criminals or abusive security officers and soldiers. Complaints go both ways: from Lebanese who fault their guests for introducing greater insecurity, to Syrians who accuse Lebanese of disrespecting, exploiting or even assaulting them. Street fights and criminality have trended upwards.

Hostility and suspicion are far more discernible among Shiites and Christians. In predominantly Shiite areas now witnessing refugee arrivals, many local residents express concern that the numbers could grow, while Hizbollah fears that refugees’ anti-regime sentiment could be a prelude to activism against the movement itself. Many Christians feel even more vulnerable, alarmed at a demographic balance that continuously tilts against them. The current human wave harkens back to the community’s experience with Palestinian refugees whose initial, theoretically short-term resettlement turned into a massive, largely Sunni, long-lasting, militarised presence. And it feeds into a more general belief that Lebanon’s Sunni community – more specifically, Islamists in its midst – are being empowered, riding an irresistible regional tide.

The refugee issue is only one aspect of a far broader challenge Lebanon faces as a result of the Syrian conflict. The political demography of the area that includes the two countries is shifting as borders become ever more permeable. Lebanese Islamic organisations set up to assist Syrian refugees also are instruments of socialisation; they threaten to radicalise a generation of Syrians, inculcating militant anti-Shiite and anti-Alawite outlooks. Sunni Islamist militants in Lebanon smuggle weapons and join their Syrian brethren’s struggle in what has become jihadis’ destination of choice. There is risk of blowback: once their work in Syria is done, they might well turn their sights back home.

If anything, Hizbollah’s involvement is more intense. What began as relatively modest help to the regime over time has mushroomed into what now appears to be direct, comprehensive, full-fledged and less and less concealed military support. Israel’s recent (officially unconfirmed) air attacks against targets in Syria – supposedly Iranian arms shipments destined to the Shiite movement – and heightened Hizbollah rhetoric reflect growing possibilities of regional entanglement involving Lebanon. All in all, even as the government in Beirut hangs on to its policy of dissociation, non-state actors hardly feel so constrained. Lebanon’s hopes of being immune to the conflict have been brushed aside by domestic parties for whom its outcome is quasi-existential.

Historically, and to a far greater extent than any other neighbour, Lebanon’s fate has been deeply intertwined with Syria’s. As Syria heads even more steadily toward catastrophe, there is every reason for Lebanese of all persuasions to worry about their own country – and to do something about it. Regrettably, it is likely too late for them to wind back the clock and revert to a policy of non-interference in the Syrian war. But if the country’s various political forces cannot agree on what to do in Syria, at least they might agree on a sensible approach toward the refugee tragedy. A population influx of such magnitude would be a huge problem anywhere. In Lebanon – with fragile institutions and infrastructure; a delicate political and sectarian balance; tense social fabric; and declining economy, all of which the refugee crisis worsens – it is a nightmare.

Beirut/Brussels, 13 May 2013