Dar Es Salaam - The President of Tanzania, Mr Benjamin Mkapa, yesterday declared a national food emergency, banned food exports and appealed to western donors for 916,000 tonnes of food aid. In an appeal for help to western ambassadors, Mr Mkapa said the food aid would cost an estimated $14.5 million, excluding transport costs. He said transport and distribution would push up food aid costs by 40 per cent. "I cannot overstate the seriousness of the food shortage, indeed famine, facing a large part of the country."