The south of the country is desert. The terrain in the north is mountainous, which, moving south, gives way to a hot, dry central plain. The south is semiarid, and merges into the Sahara. A series of salt lakes, known as chotts or shatts, lie in an east–west line at the northern edge of the Sahara, extending from the Gulf of Gabes into Algeria. The lowest point is Chott el Djerid at below sea level and the highest is Jebel ech Chambi at . Biodiversity Tunisia is home to five terrestrial ecoregions: Mediterranean conifer and mixed forests, Saharan halophytics, Mediterranean dry woodlands and steppe, Mediterranean woodlands and forests, and North Saharan steppe and woodlands. Government and politics Tunisia is a representative democracy and a republic with a president serving as head of state, a prime minister as head of government, a unicameral parliament, and a civil law court system. The Constitution of Tunisia, adopted 26 January 2014, guarantees rights for women and states that the President's religion "shall be Islam". In October 2014 Tunisia held its first elections under the new constitution following the Arab Spring. Tunisia was the only democracy in North Africa until 2021. The country now classifies as "hybrid regime" in the Democracy Index. The number of legalized political parties in Tunisia has grown considerably since the revolution. There are now over 100 legal parties, including several that existed under the former regime. During the rule of Ben Ali, only three functioned as independent opposition parties: the PDP, FDTL, and Tajdid. While some older parties are well-established and can draw on previous party structures, many of the 100-plus parties extant as of February 2012 are small. Rare for the Arab world, women held more than 20% of seats in the country's pre-revolution bicameral parliament. In the 2011 constituent assembly, women held between 24% and 31% of all seats. Tunisia is included in the European Union's European Neighbourhood Policy (ENP), which aims at bringing the EU and its neighbours closer. On 23 November 2014 Tunisia held its first presidential election following the Arab Spring in 2011. The Tunisian legal system is heavily influenced by French civil law, while the law of personal status is based on Islamic law. Sharia courts were abolished in 1956. A Code of Personal Status was adopted shortly after independence in 1956, which, among other things, gave women full legal status (allowing them to