Africa is on the rise. GDP is expected to grow at over 5% up to 2015 and inflation is coming down. It's attracting investors: in 2012 foreign investment grew to $50 billion and exports to $641 billion.

The continent's urbanizing fast and a consumer class is being created. One of the biggest challenges is feeding this population; it is therefore necessary not just to attract investment for urban areas but for rural infrastructure as well: roads, irrigation, electricity, storage, conservation systems and supply networks. Cities need their hinterlands.

And all of this must be done in a sustainable fashion, bearing in mind that Africa will receive the brunt of the increasing climate changes.

It's hard to get your head around how big Africa is. It's physical size is large than China, India, the USA, Japan, most of your and the UK combined. It will soon contain the world's largest workforce.

The African Development Bank sits at the heart of many major investment negotiations and decisions and its latest report provides a snapshot of the state of the continent.

It contains just over 1 billion people, half of whom are under the age of 20 and will need jobs. By 2050 this population will have increased by a factor of 2.4 and will continue to grow to 4 times its current size in the next 100 years.

Where will these people live? How will they be fed and nurtured? Increasingly, in cities. The bank has logged the urbanization trend and ranks the fastest-growing cities. They are:

City, Country: Projected population in 2025 (thousands) %change from 2005

• Dar es Salaam, Tanzania: (6,202) 85.2%
• Nairobi, Kenya: (6,246) 77.3%
• Kinshasa: (15,041) 71.8%
• Luanda, Angola: (8,077) 69.3%
• Addis Ababa, Ethiopia: (4,757) 62.4%
• Abidjan, Côte d'Ivoire: (6,321) 53.2%
• Dakar, Senegal: (4,338) 51.5%
• Lagos, Nigeria: (15,810) 49.5%
• Ibadan, Nigeria: (4,237) 49.3%
• Accra, Ghana: (3,497) 49.3%
• Kano, Nigeria: (5,060) 49%
• Douala, Cameroon: (3,131) 47.3%
• Alexandria, Egypt: (5,648) 28.7%
• Algiers, Algeria: (3,595) 28.4%
• Casablanca, Morocco: (4,065) 23.8%
• Cairo, Egypt: (13,531) 23%
• Ekurhuleni, South Africa: (3,614) 12.9%
• Durban, South Africa: (3,241) 126%
• Johannesburg, South Africa: (4,127) 12.5%
• Cape Town, South Africa: (3,824) 12.3

Source: United Nations Human Settlements Programme (UN-Habitat)

Africa has 52 cities with populations of 1 million or higher, the same number as Europe. Several of these, such as Dar es Salaam and Kinshasa are now and will continue to be amongst the fastest-growing in the world.

The urban share of Africa's population has doubled from 19% to 39% over the last 50 years, meaning more than 360 million new citydwellers. By 2030 this population will have increased by 350 million more.

The percentage of people living in cities is higher than in India and will reach 58% by 2030.

If all goes well, the 22nd century could belong to Africa, just as the newly elected Prime Minister of India Narendra Modi has claimed that the 21st-century belongs to that country, as a powerhouse of innovation, growth and activity.

But it is in dire need of good governance and responsible urban investment. Good governance means that planning is done in a way which learns from the mistakes made in developed countries and does not repeat them.

These cities do not need to be built to rely upon the car when most people do not have cars. They need to be compact and prioritise sanitation, resource efficiency and health and safety. They need to utilise sustainable urban mobility and regenerative infrastructure, incorporating - not banning - nature from cities, and the use of abundant renewable energy resources in particular solar power.

But outside investors, who, perforce, are increasingly besieging Africa like a second wave of colonialism, often do not care about this. They require short-term profit, and city managers can be seduced by the prospects simulated in glossy presentations of status-ridden skyscrapers blazing with lights that look like Hong Kong, Singapore, or São Paulo.

Who will provide the counter-force to these slick and slimy salesmen? Will it be the African Development Bank?

The problem with African cities now is that half the population lives in slums, the worst being in Nigeria, the second richest country in the continent. The reason is quite simple: corruption.

If all a developer's sales force has to do is to provide backhanders to the municipal negotiators to receive permission to pour concrete onto land once occupied by slum dwellers who are meanwhile banished to places nobody cares about, and if there is no legal way to stop them, then such things will continue to be inevitable as they are at present.

The Bank's Chief Economist & Vice President, Prof Mthuli Ncube, in his foreword to this report, promises a strategy to support "the transformation of Africa into a stable, competitive, integrated and greener continent, built on a foundation of inclusive and sustainable growth". Note that this word 'sustainable' does not at all mean the same thing as it does when used as an adjective to the word 'development'.

Growth cannot be continuously sustainable because there are limits and in Africa these limits are all too obvious.

The Bank's report's conclusion confidently states that "stronger institutions of governance will reinforce the rule of law, facilitate transparency and accountability and peacefully resolve conflicts".

Further, it adds: "by incorporating green principles in development plans African countries will extend access to water, energy and transport, boost agricultural productivity and create new jobs. They will build sustainable cities and develop their natural resources while reducing waste."

The source of such optimism is not at all apparent. But it is clear that if Africa does not succeed in developing in this manner, then its population is condemned to untold further misery.