It is predicted that the world population will reach 7 billion on Monday.  At want time the 7 billionth human will be born and to which lucky mother, I do not know.  But it is a time to reflect on what it means for us and the other millions of species on which we share this planet.

Population growth is a contentious, complex (and occasionally a taboo) subject given its links to reproductive health rights, migration, religious beliefs, and past ineffective coercive means to reduce it.

Our view is that the absolute size, growth rate and distribution of the human population, are important drivers of environmental change but no simple relationship exists between population size and environmental change.

In fact, the impact of humans on nature is a function of how many people there are on the planet, what they consume and the availability of technology.  Consumption patterns of the world’s peoples are critical to the resulting environmental impacts. 

It is also a fact that environmental impacts of population growth vary significantly across the planet.  Direct human impacts are particularly severe in biodiversity-rich developing countries where there are populations that are directly reliant on local natural resources. 

On a global scale, the size and composition of an economy together with income inequality, are better predictors of biodiversity loss than population density. The greatest impact of human population on the environment largely takes place in developed countries where population growth is actually lowest and this is down to our comsumption patterns.

In the UK, while national income has more than doubled in the last forty years, population has grown by only 10%.  Our environmental impacts stem mainly from our increased affluence which translates into a much larger environmental impacts than those of previous generations. The UK’s ‘ecological footprint’ extends well beyond our borders as we import many of the resources we consume, some of which are environmentally damaging e.g. feedstocks, such as soya from South America or oil palm from Indonesia.

The UK’s population profile adds an additional level of complexity to the issue.  We are an ageing population with dependency ratios declining dramatically.  From an economic perspective, this change will create a vast financial burden on those of working age and will clearly have ramifications when assessing our economic potential against large, dynamic economies with young populations (like Brasil, India or China).  It is conceivable that future population debates will focus more on the optimal distribution of population rather than its absolute size.

So what is the solution?

The first priority must be to try to fix the system in developed nations so that economic growth is decoupled from environmental damage.

Second, it is important to work with others to advocate more sustainable development in the emerging economies. Rio+20 provides an opportune platform to advance this.

Third, we need to support effective, non coercive, approaches to reduce fertility levels.  This involves improving living standards of the poor, improving women's rights and education, and providing access to reproductive health services.
The challenge we face today is to provide a vision of how a growing population can live within environmental limits.  Living within our means.  That surely is something we can all buy in to.