In his regular column, BBC environment analyst Roger Harrabin looks at whether our planet's looming population growth challenge can be tackled with engineering solutions.

POPULATION OVERLOAD?

Image caption Can politics and economics change tack on population growth?

The world is hurtling towards population overload, placing billions of people at risk of hunger, thirst, lack of energy and slum housing.

But the problems can all be overcome through existing engineering solutions, if politics and economics can only change tack.

This is the message from a group of 70 engineers worldwide whose views have been collated by the Institution of Mechanical Engineers in the UK.

What is more, their report says the challenges of a population of 9.5 billion can mostly be overcome by re-directing existing spending.

Unfashionable issues

The report calls for more emphasis on engineering solutions to problems caused by rapid population growth, particularly in sub-Saharan Africa.

It says governments must prioritise unfashionable issues. One is to build ponds to capture rainwater so it filters down to replenish underground water stores - aquifers.

Another is to ensure that farmers can get their food unspoiled to markets (the report says 50% of African produce is damaged before it gets to market).

Another is to allow local people to be able to choose low-carbon local energy sources, rather than being obliged to rely on large-scale electricity grids run on polluting coal.

The report says engineers can help serve a growing population by improving food output through biotechnology, mechanisation, food processing and irrigation.

Slum areas will need community-centred infrastructure for water, sanitation and energy. Governments should encourage the capture of rainwater for use in washing and lavatory flushing, without the need for all water to achieve drinking water purity.

Buildings will need to be better insulated as part of a drive to reduce energy consumption. Money should be invested to bring down the cost of de-salination for people's water supplies as population grows.

Defining challenge

When asked if population had overtaken climate change as the key global issue, Tim Fox from IMechE said: "Population is in our view the defining challenge of the 21st Century. Climate change is a stress [amplifier] on top of that."

Asked if climate change had been over-emphasised in comparison with population growth, Mr Fox agreed.

The report will be welcomed by some who consider that climate change has assumed too dominant a role in international policy circles.

But others will criticise the institution for allowing climate change and population to be set against each other in the public debate.

This looks like a re-run of the discussion leading up to the Rio Earth Summit in 1992, in which development groups angrily rejected any intellectual framing in which population growth in developing countries was identified as the core global problem.

They pointed out that rich nations like the UK and US had already experienced their own periods of rapid population growth during industrialisation - and blamed Western consumers for appropriating too many of the planet's resources.

Opening salvo in debate

The marketing of the IMechE document will be seen by some as inflammatory. The report's headlines ask: "Population Growth - Can the Planet Cope?" and "Population: One Planet, Too Many People?"

Yet the report itself makes no proposal to stem the absolute growth in human numbers, and no mention of population policy or contraception. It simply assumes current projections of population growth then sets out policies to cope with the extra numbers.

The IMechE says this is the opening salvo in the debate about re-defining the UN's Millennium Development goals, which are up for review in 2015.

But it is likely to be criticised for asserting that problems mostly can be overcome with current levels of spending, without setting out any figures to prove its case, or to explain how policies would be afforded.

At the news launch, for instance, the speakers criticised the system in which Europe imposed standards to clean up diesel cars then exported the dirty cars to prolong their lives in Africa. But they did not say how African taxi drivers would afford new clean cars.

They said existing cash needed to be diverted from the "wrong places" to the "right places". But they were reluctant to identify any of the "wrong places".

Hierarchy of problems

When pressed, Stephen Tetlow, chief executive of IMechE, offered the example of coal-fired power stations. There must be no Western help to build coal-fired power stations in Africa without carbon capture and storage, he said.

He did not say who would pay for a technology which increases the cost of power generation so much that it has still not been adopted in rich nations which have caused the climate problem.

Development groups are nervous about attempts to define a hierarchy of global problems with population at the peak.

Oxfam's head of policy, Duncan Green, told BBC News: "Population is a very important issue in terms of natural resources and in terms of women's rights.

"But it's not the main issue on climate change for the simple fact that countries with the fastest growing rates of greenhouse gas emissions are the ones with the lowest rates of population growth. The problem with climate change is excessive consumption by rich people, not procreation by poor people."

'Wrong target'

Christian Aid spokeswoman Rachel Baird said: "Of course the world needs engineers to help people cope with the impacts of climate change and to minimise future emissions. However - as the new report recognises - some global problems such as hunger are due to poverty, the solutions to which are political."

Dr Joe Smith, from the Open University and co-author of a report 'The Consumption Explosion', said: "IMechE could be taken for naïve… dangerously so. There is plenty to agree with in their report, but in focussing so bluntly on population and on techie 'solutions' they are pointing a weapon at the wrong target.

"For forty years there has been scaremongering about 'the population explosion'. The best available knowledge about why people decide to have smaller families shows that people need security: food, health, education, clean water. Good policy and determined politics will deliver those things more reliably than any amount of technology."