It is mostly high plateau with some hills and mountains. The Zambezi River forms a natural riverine boundary with Zimbabwe which includes the famous Victoria Falls.
Lake Kariba on the Zambia-Zimbabwe border forms the world's largest reservoir by volume (180 cu km; 43 cu mi).
Zambia's major environmental issues include:
- air pollution and resulting acid rain in the mineral extraction and refining region; chemical runoff into watersheds;
- poaching seriously threatens rhinoceros, elephant, antelope, and large cat populations;
- soil erosion;
- desertification; and,
- the lack of adequate water treatment presents human health risks.
It is susceptible to periodic drought, and tropical storms from November to April.
The territory of Northern Rhodesia was administered by the British South Africa Company from 1891 until it was taken over by the United Kingdom in 1923.
During the 1920s and 1930s, advances in mining spurred development and immigration.
The name was changed to Zambia upon independence in 1964.
In the 1980s and 1990s, declining copper prices and a prolonged drought hurt the economy.
Elections in 1991 brought an end to one-party rule, but the subsequent vote in 1996 saw blatant harassment of opposition parties.
The election in 2001 was marked by administrative problems with three parties filing a legal petition challenging the election of ruling party candidate Levy Mwanawasa. The new president launched an anticorruption investigation in 2002 to probe high-level corruption during the previous administration. In 2006-07, this task force successfully prosecuted four cases, including a landmark civil case in the UK in which former President Chiluba and numerous others were found liable for USD 41 million.
Mwanawasa was reelected in 2006 in an election that was deemed free and fair. Upon his abrupt death in August 2008, he was succeeded by his Vice-president Rupiah Banda, who subsequently won a special presidential election in October 2008.
Michael Sata was elected President in September 2011.
Location: Southern Africa, east of Angola
Geographic Coordinates: 15 00 S, 30 00 E
Area: 752,614 km2 (740,724 km2 land and 11,890 km2 water)
Natural Hazards: periodic drought, tropical storms (November to April)
Terrain: Mostly high plateau with some hills and mountains. Its lowest point is the Zambezi River (329 metres) and its highest point is an unnamed location in the Mafinga Hills (2,301 metres).
Climate: Tropical; modified by altitude; rainy season (October to April)
Topography of Zambia. Source: Wikimedia Commons
Ecology and Biodiversity
Source: World Wildlife Fund
- Itigi-Sumbu thicket
- Central Zambezian Miombo woodlands
- Zambezian flooded grasslands
- Zambezian and Mopane woodlands
- Southern Miombo woodlands
- Zambezian Baikiaea woodlands
- Western Zambezian grasslands
- Zambezian Cryptosepalum dry forests
- Southern Rift montane forest-grassland mosaic
People and Society
Population: 14,309,466 (July 2012 est.)
Zambia's population comprises more than 70 Bantu-speaking ethnic groups. Some ethnic groups are small, and only three have enough people to constitute at least 10% of the population. Most Zambians are subsistence farmers. The predominant religion is a blend of traditional beliefs and Christianity; Christianity is the official national religion. Expatriates, a majority of whom are British (about 15,000) and South African, live mainly in Lusaka and in the Copperbelt in northern Zambia, where they are employed in mines and related activities. Zambia also has a small but economically important Asian population, most of whom are Indians. The HIV/AIDS epidemic is ravaging Zambia. Approximately 13.5% of Zambians are infected by HIV. Over 800,000 Zambian children have lost one or both of their parents due to HIV/AIDS.
Ethnic groups: African 99.5% (includes Bemba, Tonga, Chewa, Lozi, Nsenga, Tumbuka, Ngoni, Lala, Kaonde, Lunda, and other African groups), other 0.5% (includes Europeans, Asians, and Americans) (2000 Census)
0-14 years: 46.7% (male 3,253,125/female 3,228,844)
15-64 years: 50.8% (male 3,544,640/female 3,508,344)
65 years and over: 2.5% (male 148,531/female 197,852) (2011 est.)
Population Growth Rate: 3.034% (2011 est.)
Birth Rate: 43.51 births/1,000 population (2011 est.)
Death Rate: 12.42 deaths/1,000 population (July 2011 est.)
Net Migration Rate: -0.76 migrant(s)/1,000 population (2011 est.)
Life Expectancy at Birth: 52.57 years
male: 51.35 years
female: 53.83 years (2011 est.)
Total Fertility Rate: 5.9 children born/woman (2011 est.)
Languages: English (official), major vernaculars - Bemba, Kaonda, Lozi, Lunda, Luvale, Nyanja, Tonga, and about 70 other indigenous languages
Literacy (2003 est.): 80.6% (male: 86.8% - female: 74.8%)
Urbanization: 36% of total population (2010) growing at a 3.2% annual rate of change (2010-15 est.)
The indigenous hunter-gatherer occupants of Zambia began to be displaced or absorbed by more advanced migrating tribes about 2,000 years ago. The major waves of Bantu-speaking immigrants began in the 15th century, with the greatest influx between the late 17th and early 19th centuries. They came primarily from the Luba and Lunda tribes of southern Democratic Republic of Congo and northern Angola but were joined in the 19th century by Ngoni peoples from the south. By the latter part of that century, the various peoples of Zambia were largely established in the areas they currently occupy.
Except for an occasional Portuguese explorer, the area lay untouched by Europeans for centuries. After the mid-19th century, it was penetrated by Western explorers, missionaries, and traders. David Livingstone, in 1855, was the first European to see the magnificent waterfalls on the Zambezi River. He named the falls after Queen Victoria, and the Zambian town near the falls is named after him.
In 1888, Cecil Rhodes, spearheading British commercial and political interests in Central Africa, obtained a mineral rights concession from local chiefs. In the same year, Northern and Southern Rhodesia (now Zambia and Zimbabwe, respectively) were proclaimed a British sphere of influence. Southern Rhodesia was annexed formally and granted self-government in 1923, and the administration of Northern Rhodesia was transferred to the British colonial office in 1924 as a protectorate.
In 1953, both Rhodesias were joined with Nyasaland (now Malawi) to form the Federation of Rhodesia and Nyasaland. Northern Rhodesia was the center of much of the turmoil and crisis that characterized the federation in its last years. At the core of the controversy were insistent African demands for greater participation in government and European fears of losing political control.
A two-stage election held in October and December 1962 resulted in an African majority in the legislative council and an uneasy coalition between the two African nationalist parties. The council passed resolutions calling for Northern Rhodesia's secession from the federation and demanding full internal self-government under a new constitution and a new national assembly based on a broader, more democratic franchise. On December 31, 1963, the federation was dissolved, and Northern Rhodesia became the Republic of Zambia on October 24, 1964.
At independence, despite its considerable mineral wealth, Zambia faced major challenges. Domestically, there were few trained and educated Zambians capable of running the government, and the economy was largely dependent on foreign expertise. Abroad, three of its neighbors--Southern Rhodesia and the Portuguese colonies of Mozambique and Angola--remained under white-dominated rule. Rhodesia's white-ruled government unilaterally declared independence in 1965. In addition, Zambia shared a border with South African-controlled South-West Africa (now Namibia). Zambia's sympathies lay with forces opposing colonial or white-dominated rule, particularly in Southern Rhodesia. During the next decade, it actively supported movements such as the National Union for the Total Independence of Angola (UNITA) and later the Popular Movement for the Liberation of Angola (MPLA), the Zimbabwe African People's Union (ZAPU), the African National Congress of South Africa (ANC), and the South-West Africa People's Organization (SWAPO).
Conflicts with Rhodesia resulted in the closing of Zambia's borders with that country and severe problems with international transport and power supply. However, the Kariba hydroelectric station on the Zambezi River provided sufficient capacity to satisfy the country's requirements for electricity. A railroad to the Tanzanian port of Dar es Salaam, built with Chinese assistance, reduced Zambian dependence on railroad lines south to South Africa and west through an increasingly troubled Angola.
By the late 1970s, Mozambique and Angola had attained independence from Portugal. Zimbabwe achieved independence in accordance with the 1979 Lancaster House agreement, but Zambia's problems were not solved. Civil war in the former Portuguese colonies generated refugees and caused continuing transportation problems. The Benguela Railroad, which extended west through Angola, was essentially closed to traffic from Zambia by the late 1970s. Zambia's strong support for the ANC, which had its external headquarters in Lusaka, created security problems as South Africa raided ANC targets in Zambia.
The major figure in Zambian politics from 1964 to 1991 was Kenneth Kaunda, who led the campaign for independence and successfully bridged the rivalries among the country's various regions and ethnic groups. Kaunda tried to base government on his philosophy of "humanism," which condemned human exploitation and stressed cooperation among people, but not at the expense of the individual. Kaunda's political party--the United National Independence Party (UNIP)--was founded in 1959 and was in power under Kaunda's leadership from 1964 to 1991. Before 1972, Zambia had three significant political parties, but only UNIP had a nationwide following.
In 1973, the Zambian constitution established a one-party state, and all other political parties were banned. Kaunda, the sole candidate, was elected president in the 1973 elections. Elections also were held for the National Assembly. Only UNIP members were permitted to run, but these seats were highly contested. President Kaunda's mandate was renewed in December 1978, October 1983, and October 1988 in a "yes" or "no" vote on his candidacy.
In response to growing popular demand, and after lengthy, difficult negotiations between the government of President Kaunda and opposition groups, Zambia enacted a new constitution in 1991 and shortly thereafter became a multi-party democracy. Growing opposition to UNIP's monopoly on power had led to the rise in 1990 of the Movement for Multiparty Democracy (MMD). The MMD assembled an impressive group of important Zambians, including prominent UNIP defectors and labor leaders. After Kaunda agreed to allow multi-party democracy and end the one-party state, Zambia held multi-party elections for parliament and the presidency on October 31, 1991. MMD candidate Frederick Chiluba resoundingly carried the presidential election over Kaunda with 81% of the vote. To add to the MMD landslide, in the parliamentary elections, the MMD won 125 of the 150 elected seats, and UNIP won the remaining 25.
By the end of Chiluba's first term as President, the MMD's commitment to political reform had faded in the face of re-election aspirations. A number of prominent supporters founded opposing parties. Relying on the MMD's overwhelming majority in parliament, President Chiluba in May 1996 pushed through constitutional amendments that eliminated former President Kaunda and other prominent opposition leaders from the 1996 presidential elections. In the presidential and parliamentary elections, Chiluba was re-elected, and the MMD won 131 of the 150 seats in the National Assembly. Kaunda's UNIP party boycotted the parliamentary polls to protest the exclusion of its leader from the presidential race, alleging in addition that the outcome of the election had been predetermined due to a faulty voter registration exercise. As Chiluba began his second term in 1996, the opposition and civil society challenged the results of the election amid international efforts to encourage the MMD and the opposition to resolve their differences through dialogue.
Allegations of massive corruption characterized the latter part of President Chiluba's administration. Early in 2001, supporters of Chiluba mounted a campaign to amend the constitution to enable him to seek a third term of office. Civil society, opposition parties, and many members of the ruling party exerted sufficient pressure on Chiluba to force him to back away from any attempt at a third term.
Eleven parties contested the presidential, parliamentary, and local government elections held on December 27, 2001. The elections saw numerous administrative problems. Opposition parties alleged that serious irregularities occurred. Nevertheless, MMD presidential candidate Levy Mwanawasa, having garnered a plurality of the vote (29%), was declared the victor by a narrow margin. He was sworn into office on January 2, 2002. His opponent, Anderson Mazoka of the United Party for National Development, who lost to Mwanawasa by less than 2%, sued to have the election results overturned. The Zambian Supreme Court dismissed the case in 2002. Opposition parties won a majority of parliamentary seats in the December 2001 election, but subsequent by-elections gave the ruling MMD a majority in parliament.
During his first months in office, President Mwanawasa encouraged the Zambian Anti-Corruption Commission (ACC) to aggressively pursue its mandate. In July 2002, in a speech before the Zambian National Assembly, Mwanawasa provided details on a number of corruption allegations targeting former President Chiluba, and called for parliament to consider lifting Chiluba's immunity from prosecution. Mwanawasa also established the Task Force on Corruption to investigate and prosecute corruption committed by Chiluba-era public officials.
Mwanawasa was re-elected president on October 2, 2006, with 43% of the vote. Prior to the election, the government in mid-2006 introduced some changes to the electoral process to avoid a repeat of the 2001 election. The changes included the use of transparent ballot boxes, addition of photos on voters’ cards, introduction of an electoral code of conduct, and limits on political campaign donations and handouts. President Mwanawasa suffered a debilitating stroke on June 29, 2008 during an African Union summit in Sharm El-Sheikh, Egypt, and died from complications in a Paris hospital on August 19, 2008. He was succeeded by Rupiah Banda.
On May 4, 2007, the London (U.K.) High Court found former President Chiluba and several others liable in a civil suit for misappropriating as much as $58 million of public resources. In August 2009, after 8 years of investigation by the Task Force on Corruption, a Zambian magistrate acquitted Chiluba of corruption; the government declined to appeal the case. In August 2010, the Zambian High Court refused to register in Zambian court the London High Court's 2007 judgment, arguing that the law did not allow foreign judgments to be registered in domestic courts.
Following President Mwanawasa's August 2008 death and in accordance with the constitution, Vice President Rupiah Banda assumed executive powers as acting president. He was required to hold elections within 90 days of Mwanawasa's death, and elections were held on October 30, 2008. Banda was declared the winner after narrowly defeating Michael Sata of the opposition Patriotic Front party by only 30,000 votes. Although international observers were satisfied overall with the conduct of the election by the Electoral Commission of Zambia, Sata sued to have the election results nullified. He withdrew his petition in March 2009 after losing preliminary decisions. Banda was sworn in on November 2, 2008, and announced his new cabinet on November 14.
Banda vowed to continue the business-friendly and corruption-fighting policies of his predecessor, but corruption scandals in the government and the acquittal of former President Chiluba raised questions about President Banda’s initial commitment to fight corruption and promote transparency and accountability in government. Although the Task Force on Corruption established under the Mwanawasa administration prosecuted several cases of abuse of office and high-level corruption, it was stripped of its responsibilities and placed under the ACC in November 2009 by the Banda administration. The dismissal of important anti-corruption officials, including Task Force on Corruption head Max Nkole, prosecutor Mutembo Nchito, and Attorney General Mumba Malila; the government’s failure to appeal corruption cases to higher courts; and elimination of the abuse of public office clause from the Anti-Corruption Act underscored concerns about the government's commitment. In parliamentary by-elections held between 2009 and 2011, candidates from all parties violated the electoral code of conduct because the government lacked sufficient capacity to enforce it. To reaffirm his government's commitment to fight corruption, Banda launched Zambia’s first national anti-corruption policy and companion action plan with anti-corruption targets through 2015. During a national convention held in April 2011, Banda was nominated as the MMD’s presidential candidate for the 2011 general elections. President Banda entered the election with a slightly weakened party after the defection of several party leaders to the political opposition.
On September 20, 2011, Zambia set a record in the southern Africa region by conducting peaceful and credible elections that brought to power an opposition party for the second time since independence in 1964. The Patriotic Front (PF) defeated the incumbent MMD by over 200,000 votes, with Michael Sata winning the presidency. The PF also gained a strong plurality in the National Assembly, winning 62 seats. President Sata’s election platform was to fight corruption. He has also publicly prioritized job growth, poverty reduction, diversification of agriculture (away from maize production), improved government efficiency, expanded health services, and enhanced quality of education.
Another key initiative of the Sata administration is constitutional reform, which has been proposed and then aborted four times previously. Top reforms under consideration include requiring a majority vote for presidential elections, allowing the president to choose his cabinet members from the general public (currently they must be members of parliament), and abolishing the death penalty. Other reforms supported by civil society organizations would limit the power of the presidency and devolve more power to local governments. Sata has appointed a technical committee to draft a constitution based on the recommendations of previous commissions that will be subjected to two rounds of review by provincial and sectoral conventions. The technical committee plans to have a penultimate draft ready for the President’s review by June 2012.
Government Type: Republic
Zambia became a republic immediately upon attaining independence in October 1964. The elected president is chief of state and head of government. The National Assembly is comprised of 150 directly elected members, up to eight presidentially-appointed members, and a speaker. Zambia is divided into nine provinces, each administered by an appointed deputy minister who essentially performs the duties of a governor. The Supreme Court is the highest court and the court of appeal; below it are the high court, lands tribunal, industrial relations court, subordinate courts, small claims court, and local courts.
The constitution promulgated on August 25, 1973, abrogated the original 1964 constitution. The new constitution and the national elections that followed in December 1973 were the final steps in achieving what was called a "one-party participatory democracy." The 1973 constitution provided for a strong president and a unicameral National Assembly. National policy was formulated by the Central Committee of the United National Independence Party (UNIP), the sole legal party in Zambia. The cabinet executed the central committee's policy. In accordance with the intention to formalize UNIP supremacy in the new system, the constitution stipulated that the sole candidate in elections for the office of president was the person selected to be the president of UNIP by the party's general conference. The second-ranking person in the Zambian hierarchy was UNIP's secretary general.
In December 1990, at the end of a tumultuous year that included riots in the capital and a coup attempt, President Kaunda signed legislation ending UNIP's monopoly on power. Zambia enacted a new constitution in August 1991, which enlarged the National Assembly from 136 members to a maximum of 158 members, introduced two term limits on the presidency, established an electoral commission, and allowed for more than one presidential candidate who no longer had to be a member of UNIP. The constitution was amended again in 1996 to require presidential candidates to have been habitually domiciled in Zambia for 20 years prior to an election and to require that both parents of a candidate be Zambian-born.
In February 2006, the government agreed to allow the formation of a Constituent Assembly to consider and adopt a draft constitution, subject to certain conditions. In August 2007, the Zambian parliament passed a government-sponsored law creating a National Constitutional Conference (NCC) charged with drafting a new constitution. The NCC, comprised of over 500 members drawn from parliament, political parties, civil society, and government, began meeting in late December 2007 and had its mandate extended into 2010. Some members of the political opposition and civil society refused to participate in the NCC, saying that its membership was too heavily stacked in the government's favor and pushing instead for the promised Constituent Assembly. The government presented the final draft of the constitutional bill to parliament in March 2011, but the bill did not receive the necessary two-thirds majority.
Capital: Lusaka - 1.413 million (2009)
Administrative divisions: 9 provinces; Central, Copperbelt, Eastern, Luapula, Lusaka, Northern, North-Western, Southern, Western
Independence Date: 24 October 1964 (from UK)
Legal System: based on English common law and customary law; judicial review of legislative acts in an ad hoc constitutional council. Zambia has not submitted an International Court of Justice (ICJ) jurisdiction declaration; but accepts International criminal court (ICCt) jurisdiction.
Suffrage: 18 years of age; universal
International Environmental Agreements
Zambia is party to international agreements on: Biodiversity, Climate Change, Climate Change-Kyoto Protocol, Desertification, Endangered Species, Hazardous Wastes, Law of the Sea, Ozone Layer Protection, and Wetlands.
Total Renewable Water Resources: 105.2 cu km (2001)
Freshwater Withdrawal: Total: 1.74 cu km/yr (17% domestic, 7% industrial, 76% agricultural).
Per Capita Freshwater Withdrawal: 149 cu m/yr (2000)
Agricultural Products: corn, sorghum, rice, peanuts, sunflower seed, vegetables, flowers, tobacco, cotton, sugarcane, cassava (tapioca), coffee; cattle, goats, pigs, poultry, milk, eggs, hides
Irrigated Land: 1,560 sq km (2003)
arable land: 6.99%
permanent crops: 0.04%
other: 92.97% (2005)
|Energy in Zambia|
9.597 billion kWh
7.614 billion kWh
96 million kWh
279 million kWh
(1 January 2011 est.)
0 cu m
0 cu m
0 cu m
0 cu m
0 cu m
(1 January 2011 est.)
|Source: CIA Factbook|
International Disputes: in 2004, Zimbabwe dropped objections to plans between Botswana and Zambia to construct a bridge over the Zambezi River, thereby de facto recognizing a short, but not clearly delimited, Botswana-Zambia boundary in the river; 42,250 Congolese refugees in Zambia are offered voluntary repatriation in November 2006, most of whom are expected to return in the next two years; Angolan refugees too have been repatriating but 26,450 still remain with 90,000 others from other neighboring states in 2006
Zambia's economy weathered the effects of the global economic crisis and a subsequent fall in world copper prices. In early 2009, high inflation, currency volatility, rising unemployment, and restricted access to capital dampened Zambia’s economic performance. Although poverty continues to be a significant problem in Zambia, its economy has stabilized, attaining single-digit inflation in 2009-2010, real GDP growth, decreasing interest rates, and increasing levels of trade.
Zambia experienced positive economic growth for the 13th consecutive year in 2011, with a real growth rate of 6.7%. The rate of inflation dropped from 30% in 2000 to single-digit inflation of 7.9% by December 2010 due to fiscal and monetary discipline and the growth of the domestic food supply. Much of the economy's growth is due to foreign investment in Zambia's mining sector and higher copper prices on the world market, which have rebounded and returned to more stable, profit-yielding levels. The Zambian Government is pursuing an economic diversification program to reduce the economy's reliance on the copper industry. This initiative seeks to exploit other components of Zambia's rich resource base by promoting agriculture, tourism, gemstone mining, and hydropower. The government is also seeking to create an environment that encourages entrepreneurship and private-sector led growth. Zambia has yet to address effectively issues such as reducing the size of the public sector and improving Zambia's social sector delivery systems.
HIV/AIDS is the nation's greatest challenge, with 13.5% prevalence among the adult population. HIV/AIDS will continue to ravage Zambian economic, political, cultural, and social development for the foreseeable future. About 59% of Zambians live in poverty, of whom 63% live on less then $1.25 per day. The per capita annual income is $1,600, well below the level at independence. Although the 2011 World Bank Report reclassified Zambia as a middle-income nation, social indicators continue to worsen, particularly the maternal mortality rate (470 per 100,000 live births). The country's rate of economic growth cannot support rapid population growth or the strain that HIV/AIDS-related issues (i.e., rising medical costs, decline in worker productivity) place on government resources. Zambia is also one of Sub-Saharan Africa's most highly urbanized countries. Over one-third of the country's 14 million people are concentrated in a few urban zones strung along the major transportation corridors, while rural areas are underpopulated. Unemployment and underemployment are serious problems.
Zambia began to slide into poverty in the 1970s when the price of copper, Zambia's principal export, suffered a severe decline worldwide. The socialist government made up for falling revenue by increasing borrowing, turning to foreign and international lenders for relief. But as copper prices remained depressed, it became increasingly difficult for Zambia to service its growing debt. After democratic multi-party elections, the Chiluba government (1991-2001) came to power in November 1991 committed to an economic reform program to liberalize the economy and privatize industry. The government was successful in some areas, such as privatization of most of the parastatals, maintenance of positive real interest rates, the elimination of exchange controls, and endorsement of free market principles. Corruption grew dramatically under the Chiluba government.
Zambia's copper production had declined steadily for 30 years, from 700,000 metric tons in 1973 to 226,192 metric tons in 2000. The decline was the result of poor management of state-owned mines and lack of investment. With the privatization of the mines in April 2000, the downward trend in production and exports was reversed as a result of investments in plant rehabilitation, expansion, increased exploration, and high copper prices on the international market. Copper production rose to 720,000 metric tons in 2010.
By the mid-1990s, despite some limited debt relief, Zambia's per capita foreign debt remained among the highest in the world. In April 2005, the International Monetary Fund (IMF) and the World Bank's International Development Association (IDA) provided Zambia significant debt service relief and debt forgiveness under the Heavily Indebted Poor Countries (HIPC) initiative. Zambia was the 17th country to reach the HIPC completion point and benefited from approximately U.S. $6 billion in debt relief. In July 2005, the G-8 agreed on a proposal to cancel 100% of outstanding debt of eligible HIPC countries to the IMF, African Development Fund, and IDA. Zambia is among the beneficiaries of this additional multilateral debt relief. Zambia also completed a Poverty Reduction and Growth Facility (PRGF) arrangement with the IMF for the period 2008-2011.
A high birth rate, relatively high HIV/AIDS burden, and market distorting agricultural policies have meant that Zambia's economic growth has not dramatically decreased the stubbornly high poverty rates.
GDP (Purchasing Power Parity): $21.93 billion (2011 est.)
GDP (Official Exchange Rate): $18.4 billion (2011 est.)
GDP- per capita (PPP): $1,600 (2011 est.)
GDP- composition by sector:
services: 43.5% (2011 est.)
Industries: copper mining and processing, construction, foodstuffs, beverages, chemicals, textiles, fertilizer, horticulture
Exports: copper/cobalt 64%, cobalt, electricity; tobacco, flowers, cotton
Imports: machinery, transportation equipment, petroleum products, electricity, fertilizer; foodstuffs, clothing
Economic Aid Recipient: $504 million (2007)
Currency: Zambian kwacha (ZMK)
Ports and Terminals: Mpulungu