Yemen is a country in the south-western tip of the Arabian Peninsula. The country is mainly mountainous and typically arid, but there are wide areas where rainfall is sufficient for agriculture to be successful. Yemen's history, culture, people and economy have been shaped by its strategic position at the southern gateway to the Red Sea, at the crossroads of ancient and newer trade and communication paths. During ancient times, the states which ruled the area now known as Yemen, controlled the supply of essential goods such as frankincense and myrrh, and also dominated the market for many other valuable commodities like Asian spices and aromatics. Yemen has been home to many ancient kingdoms thanks to its fertility and commercial wealth. Later on, Yemen was where coffee was first grown commercially, and before coffee plants were introduced to other parts of the world, it was the only source of this valuable bean for a long time. The current Republic of Yemen was created in May 1990 when the Yemen Arab Republic was united with the People's Democratic Republic of Yemen. Under the terms of the merger agreement, the political capital of the country is Sana'a, the former capital of northern Yemen, and the economic center is Aden, the former capital of southern Yemen. There are six terrestrial ecoregions in Yemen: the coastal misty desert of the Arabian Peninsula, the dry heathlands of Socotra Island, the foothill savannah of Southwest Arabia, the montane forests of Southwest Arabia, the Arabian Desert and the Nubo-Sindian tropical desert and semi-desert of the Red Sea.