By Mark Doyle BBC world affairs correspondent

The desolate, dusty town of Pibor on South Sudan's border with Ethiopia has no running water, no electricity and little but mud huts for the population to live in.

You would be hard put to find a poorer place anywhere on earth.

I went there as part of a journey across Africa to ask the question "Why is Africa poor?" for a BBC radio documentary series.

We have oil and many other minerals - go name it Barnaba Benjamin, South Sudan regional co-operation minister

I was asked to investigate why it is that the vast majority of African countries are clustered at or near the bottom of the United Nations Human Development Index - in other words they have a pretty appalling standard of living.

In Pibor, the answer to why the place is poor seems fairly obvious.

The people - most of whom are from the Murle ethnic group - are crippled by tribal conflicts related to disputes over cattle, the traditional store of wealth in South Sudan.

The Murle have recently had fights with the Lol Nuer group to the north of Pibor and with ethnic Bor Dinkas to the west.

In a spate of fighting with the Lol Nuer earlier this year several hundred people, many of them women and children, were killed in deliberate attacks on villages.

There has been a rash of similar clashes across South Sudan in the past year (although most were on a smaller scale than the fights between the Lol Nuer and the Murle).

And so the answer to why South Sudan is poor is surely a no-brainer: War makes you destitute.

Why is there so much war?

And yet South Sudan is potentially rich.

"It's bigger than Kenya, Uganda, Rwanda and Burundi combined," the South Sudan Regional Co-operation Minister Barnaba Benjamin, enthused.

"Tremendous land! Very fertile, enormous rainfall, tremendous agricultural resources. Minerals! We have oil and many other minerals - go name it!"

Our leaders, they just want to keep on being rich. And they don't want to pay taxes Fisherman on Lake Victoria Blog: Why is Africa poor?

The paradox of rich resources and poor people hints at another layer of explanation about why Africa is poor.

It is not just that there is war. The question should, perhaps be: "Why is there so much war?"

And the headline question is in fact misleading; Africans as a people may be poor, but Africa as a place is fantastically rich - in minerals, land, labour and sunshine.

That is why outsiders have been coming here for hundreds of years - to invade, occupy, convert, plunder and trade.

The spectres of slavery and colonialism hover in the background of almost every serious conversation with Africans about why most of them are poor.

It almost goes without saying that, of course, slavery impoverished parts of Africa and that colonialism set up trading patterns which were aimed at benefitting the coloniser, not the colonised.

But there is a psychological impact too.

Hajia Amina Az-Zubair, the Nigerian president's senior adviser on poverty issues, told me that colonialism "was all about take, not build", and that this attitude "transferred itself into a lot of mindsets".

Even today, Ms Zubair said it was sometimes difficult to design poverty-reduction programmes that were inclusive:

"You sit round a table and ask 'What are your needs?' and you get an absolute blank. Because for years, they've been told what they're going to have. So even the ability to engage has been difficult for us."

The resources of South Sudan have never been properly developed.

During colonial rule South Sudan was used as little more than a reservoir of labour and raw materials.

Then independence was followed by 50 years of on-off war between the south and north - with northerners in Khartoum continuing the British tactic of divide and rule among the southern groups.

Some southerners believe this is still happening today.

Corruption

On my journey across the poorest, sub-Saharan swathe of the continent - that took in Liberia and Nigeria in the west, Sudan in the centre, and Kenya in the east - people explored the impact that both non-Africans and Africans had had on why Africa is poor.

Ellen Johnson-Sirleaf says she underestimated the problem of graft

Almost every African I met, who was not actually in government, blamed corrupt African leaders for their plight.

"The gap between the rich and the poor in Africa is still growing," said a fisherman on the shores of Lake Victoria.

"Our leaders, they just want to keep on being rich. And they don't want to pay taxes."

Even President Ellen Johnson-Sirleaf of Liberia came close to this when she told me she had underestimated the level of corruption in her country when she took office.

"Maybe I should have sacked the whole government when I came to power," she said.

"Africa is not poor," President Johnson-Sirleaf added, "it is poorly managed."

This theme was echoed by an architect in Kenya and a senior government official in Nigeria.

Both pointed out that the informal sector of most African economies is huge and almost completely unharnessed.

Eastleigh has the most expensive real estate in Nairobi

Marketplaces, and a million little lean-to repair shops and small-scale factories are what most urban Africans rely upon for a living.

But such is their distrust of government officials that most businesspeople in the informal sector avoid all contact with the authorities.

Kenyan architect and town planner Mumo Museva took me to the bustling Eastleigh area of Nairobi, where traders have created a booming economy despite the place being almost completely abandoned by the government.

Eastleigh is a filthy part of the city where rubbish lies uncollected, the potholes in the roads are the size of swimming pools, and the drains have collapsed.

Africa is not poor. Africa is just poorly managed Architect Mumo Museva

But one indication of the success of the traders, Mr Museva said, was the high per-square-foot rents there.

"You'll be surprised to note that Eastleigh is the most expensive real estate in Nairobi."

He added that if Eastleigh traders trusted the government they might pay some taxes in return for decent services, so creating a "virtuous circle".

"It would lift people out of poverty," he said.

"Remember, poverty is related to quality of life, and the quality of life here is appalling, despite the huge amount of wealth flowing through these areas."

Then the young Kenyan architect echoed the Liberian president, some 5,000km (3,000 miles) away on the other side of the continent.

"Africa is not poor," he also said.

"Africa is just poorly managed."

You can hear the first of Mark Doyle's programmes Why is Africa poor? on the BBC World Service on Monday 24 August 2009 at 0906 GMT, 1406 GMT and 1906 GMT. It will also be available on the website.