Since Burundi's independence in 1962, ethnically based political parties have vied for control of the country, resulting in decades of violent conflict. Families have been forced to flee successive waves of conflict, and tens of thousands have been internally displaced or temporarily resettled in neighboring countries. Lands left by refugees and displaced persons have since been occupied by other families. As a result, rights for returnees are uncertain, and disputes are common. Continued risk of violent conflict in rural areas impedes development and hinders a reduction of government spending on security measures, to the detriment of pro-poor programs. Since the 2005 elections and a 2006 ceasefire, a fragile peace has existed in Burundi. Some incidents of violence occur, such as in April 2008 when rebels fired on the capital, but sustained conflict has not resumed. In mid-2010, the national elections held in the country were marred by pre-election violence and resulting low turnout. The ruling party retained control of the country and despite allegations by opposition parties of election abuses, international election observers concluded that the election procedures were transparent and conducted peacefully. Burundi remains one of the poorest countries in the world, constrained by the productivity of its agricultural sector. Although its tea and coffee sectors have traditionally fueled Burundi's exports, high - and growing - rural population densities have led to increased land scarcity, fragmentation and degradation, and these in turn have contributed to low levels of productivity in many parts of the sector that supports as much as 95% of the country's population. Much of Burundi's forestland has been lost to the demand for fuel wood, and expansion of agricultural lands and plantations has replaced most natural forest. The country has had little experience with community forest management, although local communities have been engaged in plantation development. One of the largest remaining expanses of forestland is Kibira National Park which, together with Rwanda's adjacent Nyungwe National Park, forms one of the greatest remaining tracts of mountain forest in East Africa and the most wildlife-rich ecosystem in the Albertine Rift. Prior conflicts and lack of investment have damaged the country's water supply facilities and reduced the government's ability to provide safe drinking water to the population. In one study, 50% of respondents indicated that they have to pay bribes to obtain access to safe drinking water. The government recognizes the sector's need for reform, and is working with USAID, the German Agency for Technical Cooperation (GTZ) and other donors on a new legal framework and restructuring plans. Although historically Burundi has not been a globally significant source of minerals, it has substantial nickel reserves as well as stocks of other metals, and a British company has begun exploration of petroleum reserves under Lake Tanganyika.