In January 2013, the Jordanian armed forces prevented a smuggling attempt across the Syrian border, claiming that they had stopped a “major shipment of arms, ammunition, explosives and drugs.” It was no isolated event. In 2013 alone, smuggling activity across Jordan’s border with Syria, which is over 230 miles long, increased by more than 300 percent.

The impact of Syria’s crisis on Jordan, its smaller southern neighbor, has been most clearly seen in the form of a massive influx of Syrian refugees, now numbering some 600,000 people. But there are other, less visible, consequences that also contribute to the erosion of Jordan’s internal stability.

Smuggling and Arms Trafficking

The Jordanian border is difficult to police. There are more than 40 crossing points, and they are used by both refugees fleeing Syria’s civil war and smugglers. Although border guards receive Syrians seeking refuge in Jordan on a daily basis, they must increasingly watch for infiltrators from both sides.

Whether those behind the trafficking are simply criminals in search of quick profits or political groups backing the uprising against Syrian President Bashar al-Assad is uncertain. While most of the supplies to Syria’s rebels come through Turkey and Iraq, the insurgency in southern Syria is partly fueled from Jordan. Several border towns, such as Tell Shihab, Khirbet Ghazaleh, and Saham al-Jawlan, have developed into rebel strongholds that serve both as hubs for displaced persons and as key transit points on the smuggling routes between Syria and Jordan.

There is a risk that the flow of weapons and fighters into Syria will contribute to lawlessness and insecurity in Jordan, and the issue is politically sensitive. In October 2013, Jordan tried three Syrians for allegedly attempting to smuggle 36 detonators into Syria on behalf of antigovernment rebels, thereby exposing the kingdom to the danger of Syrian government reprisal.

Tribal Tensions

In the past, Syrian rebels could count on tribal support in the border areas, where relatives on the Jordanian side would aid them with money and weapons. This has particularly been the case in Deraa, a town with strong tribal and family ties across the border. But the efficiency of tribal support from Jordan now seems to be decreasing, as the Jordanian government is tightening its porous border controls.

In addition to this, attitudes among Jordanians are changing. Previously, a sense of tribal loyalty drove many northern Jordanians to support Syria’s uprising and shelter tribal kinsmen from over the border. However, the increased strain on jobs and resources, as well as the sheer number of refugees, has reversed this trend. In the northern Mafraq district, residents even erected a mock “Jordanian refugee camp” to protest escalating rents and the rising prices of basic goods, both sparked by the influx of Syrians.

More than 200 refugees were forcibly returned to Syria after protests broke out at the Zaatari refugee camp in 2012, and hundreds more Syrians have been forcibly returned this year. Authorities worry that as tensions between Syrian refugees and Jordanians increase because of strains on local resources, the presence of arms will increase the risk of civilian violence.

The Black September Complex

Following the hundreds of thousands of Palestinians who arrived in the country in previous decades, the prospect of another wave of refugees from Syria is daunting for many Jordanians, particularly from the indigenous East Bank tribes. Members of Syria’s Palestinian community are particularly exposed to Jordanian resentment against the refugees, and the government has been accused of denying entry to Syrians of Palestinian origin.

Memories of the 1970 Black September civil war between the Jordanian government and Palestinian refugee militias weigh heavily on many East Bankers’ minds, and they make Jordanian authorities wary of any political activity among the Syrian refugees. But there is no sign of the hundreds of thousands of Syrians returning to their homeland anytime soon—and for Jordan, the spillover from Syria is likely to continue.

Nikita Malik is a researcher from the universities of Oxford and Cambridge. She is currently conducting fieldwork in Jordan. Follow her work on www.nikitamalik.com, or @nixmalik on Twitter.