Economic Tensions Fuel Flare-up. SENEGAL-MAURITANIA CLASHES

A SEMBLANCE of normalcy is returning to this capital city after nearly two weeks of ethnic violence and looting. Aircraft from at least four nations are shuttling between Senegal and Mauritania, carrying to safety thousands of refugees fleeing communal riots in both countries. The Senegalese Army has been called out to protect more than 20,000 Mauritanians that have fled to the International Fairgrounds of Dakar after their shops were systematically looted and destroyed in cities and towns throughout Senegal last week.

In Mauritania, people retaliated by attacking the Senegalese living there, leaving more than 200 dead and hundreds wounded. The government of Senegal declared a state of emergency on Friday, and both countries have imposed curfews.

The immediate cause of the violence was an incident in which animals belonging to Mauritanian herdsmen trampled the gardens of Senegalese farmers near the border town of Diawara on the Senegal River. Two Senegalese were killed; 13 were taken hostage, but later freed.

The incident at Diawara follows a history of tension between Mauritanian herders and Senegalese farmers. There has also been tension in the area between fair-skinned Mauritanians and blacks over land-tenure issues. But these rural disputes do not fully explain the violence in Dakar and Nouakchott.

An official newspaper here blames bands of thieves for taking advantage of the Diawara incident as an excuse to steal, and Senegalese citizens who were swept up in a free-for-all.

But observers here point to a number of other factors, particularly tension caused by a combination of lengthy strikes at the university in Dakar, protests by the main opposition party, and unemployment among youth, as well as mounting racial tension in Mauritania.

In Senegal, a country that has prided itself on its democratic political system and the harmony of its many ethnic groups, the violence has come as a shock.

In Mauritania, ethnic harmony has been less common. The largely desert country is governed by people of Arab-Berber descent, and only officially abolished slavery in 1980. Today the descendants of the slaves, other African ethnic groups, and those of mixed race form a majority of two-thirds in Mauritania, but the Arabs dominate politics.

Tension along the border has also been heightened by a controversial development project to improve the lands of the Senegal River Valley by building dams that would regulate the flow of water, stop salt intrusion, and create hydro-power.

With better possibilities for irrigation and improved land values, northern Mauritanians have been claiming ownership of lands traditionally cultivated by local black residents.

Senegal's own political and economic woes contributed to last week's flare-up, observers say.

Since the presidential election of February 1988 and the subsequent arrest of the leading opposition candidate, Senegal has been wracked by demonstrations pitting dissatisfied youths against government forces in a contest for control of the streets. Students and teachers have staged long strikes; the banking system is in a cash-flow crisis; world prices for peanuts, the main agricultural export, are down; and the social effects of structural adjustments in the economy are just beginning to be felt.

In Dakar, the pillaging of stores appeared to be carried out more by professional thieves than by politically-motivated protesters.

Some 350,000 Mauritanians live in Senegal, and many of them are traders and shopkeepers. In Dakar, for instance, Mauritanians ran 80 percent of the small dry-goods shops that sold everything from hardware to cold sodas and fresh eggs.

For their regular clients, Mauritanian shopkeepers sold food on credit at the end of the month when Senegalese paychecks had run out.

``They were really nice to us,'' said Rachelle Coly, a Senegalese woman who works as a maid in Dakar. ``I don't know what we're going to do at the end of the month now that they're gone.''

Many Mauritanians, however, are bitter about their experience.

``I saw uniformed Senegalese taking part in the looting,'' says Mohamed Vall Ould Ainina, a gray-bearded Islamic judge. ``I had to pay 10,000 francs ($30) to them to ensure my protection and safe passage to the Embassy, as did many of my friends. Now the Senegalese are fighting over how to split up the merchandise they stole.''

The question remains whether the Senegalese - there are 30,000 in Mauritania - will all return to Senegal and the Mauritanians to Mauritania. Some have never seen their titular homelands.

Before Mauritanians began to be killed in numbers in Dakar on Friday, the Mauritanian Embassy was encouraging them to stay. ``It serves nothing for the Mauritanians to run away,'' said an Embassy official on Thursday. ``What are they going to do in Mauritania? And the same is true of the Senegalese. We are economically interdependent.''

On the other hand, for those who have lost everything, the choice is between starting over in a land that has made them feel very unwelcome, or starting over in their homeland.