The International Organization for Migration estimates that at least 3.6 million Africans have left Africa since the end of World War Two and now live scattered around the world.  African migrants contribute to their home countries in many ways, but because African communities abroad are often fragmented, it is difficult to assess the full impact of their contribution. Now, the African Union is appealing to African expatriates to tackle some of the root causes of why they left and help shape Africa's future. Nina-Maria Potts reports.

A group of high-profile African expatriates recently attended a conference in Paris hosted by the African Union and the South African government to consider a single question: how can they best help Africa?

Delegates agreed there are many ways in which the diaspora is already supporting the continent -- through remittance money sent home, development projects, private investment and knowledge sharing.

They asked, too, if their combined political weight could help solve some of Africa's political and economic problems.

But some delegates, such Amsterdam University professor Kwame Nimako, said the diaspora is not always a force for good. "Some of them support factions in Africa itself. Some of them are also refugees as a result of conflicts which they participated in, therefore the African diaspora may have, or have contributed to political violence in Africa, which is why I also think it's necessary for them to be part of the solution."

Nigerian professor Olusola Ojo-Some said energy would be better spent working for voting rights. "In the case of Eritrea, they helped in writing the constitution in 1993, so there are a lot of good things they can do to help stop conflicts, to help reconciliation."

But some Eritreans living in exile say their country is a poor example of how the diaspora can participate, since a totalitarian regime controls the country.

Domenico Amha-Tsion is a democracy activist living in Belgium. He says even though the diaspora helped draft the constitution, it was never actually implemented.  "That part of the Eritrean diaspora which stands for the respect of human rights, that stands for democracy, is completely shut out.

Conference delegates say Africans abroad who feel isolated from politics back home should work together to maximize their political strength.

They agreed on several recommendations, including the pooling of resources and training programs to be presented at the next African ministerial conference in South Africa in November.

Pledging a tighter relationship with the African Union, diaspora representatives said the time has come for African governments to listen to the reasons they left, and help shape Africa's future.