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Over the years, many attempts have been made to estimate Earth's "carrying capacity" - that is, how many humans the planet can take, and consuming at what level. The conclusions as to a sustainable population level have varied wildly, from Ehrlich's 1968 estimate of 1.5 billion to tens of billions. This year, the UK's Royal Society tried its hand. In a report entitled People and the Planet, it concluded that there is no one right answer: it all depends on technology. And it is here, in the third of Ehrlich's metrics, that there might be a glimmer of hope for peak stuff.

Urban sustainability is among the most critically important global issues of the 21st century. Over half the world’s population live in urban areas - from small cities like York, to megacities like New York - and by 2050 that proportion will rise to 70% of all humanity.

It comes as the UN confirmed this week that global fish prices had hit a record high. Supply constraints, fuelled by China’s growing appetite for seafood, will push prices higher in coming months, says the UN. With wild fish stocks dwindling due to overfishing, many see farming as the best way to feed the world’s population.

In much the same way, China's urbanisation will continue to unfold in the major centres where the jobs are. Today, only about 15 per cent of China's population lives in its top three urban regions: the Yangtze River Delta, Pearl River Delta and greater Beijing

But since the turn of the millennium, the world has a different take on Africa thanks to an economic boom that refuses to fit into the usual distorted picture. The same voices that once proclaimed the continent dead are now predicting a rebirth for Africa, the awakened giant with nearly incalculable natural resources (around 40 percent of the world's raw materials and 60 percent of its uncultivated arable land), fast-growing markets and a young, highly motivated population.

Developing countries such as China, India and Brazil have large populations and are modernizing quickly, but closing the gap with the developed world will require a large amount of electric power. HVDC is the most environmentally friendly and economical way of transmitting large amounts of electric power. Compared with AC, DC transmission needs much narrower right-of-ways, while higher voltages reduce both electricity losses and the cost of building large-scale power lines. As generation takes place further and further away, higher and higher transmission voltages are required. The highest DC transmission voltage has almost doubled during the last decade

Power demand in Saudi Arabia, the world’s largest oil supplier, is set to increase 8 percent a year as the population expands and the government invests to spur economic growth. The utility plans to invest 205 billion riyals in capacity expansion by 2018.

Power transmission capacity between Finland and Sweden will increase by 40 percent from 2011 as aresult of a 800 MW electricity cable to be built with European Investment Bank(EIB) support. The project is a significant contribution to an integrated Baltic Sea Region power market. Under an agreement signed today, the EIB will provide a EUR150 m loan for the project to Fingrid Oyj, the Finnish grid operating company.The Fenno-Skan 2 cable across the Gulfof Botnia is a Trans European EnergyNetwork (TEN-E) priority project and is to connect densely populated areas incentral Sweden and Southern Finland. It will allow grid operators to betteroptimise production in power plants in the region. Fenno-Skan 2 will also in coming years, by enabling betterlinks to major areas of consumption in the region, permit more efficient use ofhigher capacity in Finnish power generation and in power transmission linksconnecting Russia and Estonia to the Nordic area.

Three types of risk The expert group put together by the Commission has already identified three types of risks: Import risk, where raw materials are imported from a politically instable region or from a country where the market economy does not work. "That is relatively easy to do as the World Bank has put together governance indexes which measure the political and economic stability index of countries," the EU official explained.    Production risk within the EU, with potential problems such as land access. "If we are in a country for example where the population density is very high, where urbanisation is very high, obviously access will be weak," the EU official explained. Environmental risk, based on indicators such as air or soil pollution, where the impact of raw materials use is measured from an environmental point of view. "This is innovative compared to other studies," the EU official said. "We have just launched a life-cycle analysis to determine what the environmental impact is for each raw material in terms of exploitation, use, treatment, recycling etc., for air or soil pollution as well as emissions of greenhouse gases."

According to a study by the Metatech Corporation, commissioned under Executive Order 13407 for assessment of vulnerability to geomagnetic storms, manufacturers presently have a backlog of nearly three years for all extra highvoltage transformers (230 kilovolts and above). Only one plant exists in the U.S.A. capable of manufacturing a transformer up to 345 kV. There is no manufacturing capability in the U.S.A. for 500 kV and 765 kV transformers, which represent the largest group of at-risk transformers in the U.S. power grid. The 500 and 765 kV transformers are the backbone of the grid that extends into regions that contain nearly 80 percent of the U.S. population, according to John Kappenman of Storm Analysis Consultants and Metatech Corp.

For many decades, the transformers that populate our power grids have led a fairly one-sided existence. Now, however, their world is being shaken up and a lot more is expected of them: They should cater for the plethora of renewable power sources appearing on the grid; they are required to help maintain grid power quality; they are expected to do their bit in reducing greenhouse gas emissions; and they have to fit in with smart grids. Of course, the traditional commercial pressures to decrease all-round costs, extend asset life, improve monitoring and optimize maintenance still remain.

So what has made this outbreak so big? The overriding factor could be urbanisation. In the past, village outbreaks remained small, unless people went to hospitals. "Population size and high mobility make it hard to do contact tracing," says Peter Walsh at the University of Cambridge. Cities provide more chances to spread the virus, something that may also have enabled the spread of HIV. According to the African Development Bank, the continent has had the world's highest urban growth rate for 20 years, and the proportion of Africans living in cities will rise from 36 per cent to 60 per cent by 2050.