DW: What is the relationship between population size and climate change?

Daniel Schensul: In general we have about 7.2 billion people in the world right now and we are projecting to grow to 9.6 billion by 2050. Over the last 100 years our impact on emissions and our consumption has grown in leaps and bounds – multiplied in some sense by the number of people but also by significant growth in consumption at the high end and in extractive industries, industries based on fossil fuels, production and consumption. So when I think about the link between population and climate change, I always want to think about not just the number of people but how they consume, how they produce and also the distribution of consumption and production across the population.

As the world's population increases, so too does the pressure on resources and on the environment. Does that mean that curbing population growth would help alleviate pressure on resources and food security?

I think it's undeniable that over the long term slowing the trajectory of population growth would have an influence on the way that we use resources and the amount of resources that we use. But – and this is a big but – the trajectory of consumption and the trajectory of our environmental impact has really moved much faster than population growth and it is in some ways not limitless but each individual person can actually consume quite a lot. One of the common mistakes that's made in thinking about the link between population and climate change is to confuse a person with a unit of consumption. Not every person contributes in the same way and some people contribute massively. So, let's say right now there are probably about 2.5 billion people in the world and that their income is above 10 dollars a day – that equates to consumption that has some kind of significant impact on environment. That's actually not that many people relative to the total number of people in the world and actually even within that 2.5 billion, it's far fewer who really consume the most and drive a lot of the changes that we are seeing.

When looking at the population/climate change discussion – what sorts of complexities or population features need to be considered?

We never want to look at just population alone, we want to look at population, consumption and production, our technology and our energy base altogether. That's what we want to stabilize and reduce. I think sometimes it's easy for people to ignore some of those other pieces and say that stuff is too hard and say hey, it's much easier to try to change the population trajectory. For that matter, it allows some of us who consume a lot to continue consuming a lot and still find a way to sustainability. So that's the biggest complexity.

I would say the second is inequality. We really need to look at how we distribute our environmental resources around the world. With the rise in inequality that we've seen, finite resources that we have are being used to enrich those at the top and that undermines our resources for future poverty reduction and undermines our ability to continue to develop without creating and continuing processes like climate change and other environmental degradation.

Should conversations about how to tackle climate change focus more on population?

It's interesting; the climate negotiations per se have really never taken up the issue of population. It has been a controversial issue. It also has many complex political dynamics between north and south in terms of where the location of population growth is. I think there are major political concerns here.

At the same time, I think we need to be much more cognizant of the importance of population issues for climate change. That includes population growth and in some places population decline. It includes issues like urbanization. We're expecting to have upwards of 3 billion more urban residents by 2050. The nature of our transition to a more urban society will really shape how we are able to combat climate change and how we are able to be protected from climate change.

Why is the issue of population so controversial?

I think there are three reasons. The first is that there's a difference between where population is growing rapidly and where emissions are happening. The highest levels and per capita rates of emissions are in rich countries that are experiencing slow population growth and the fastest rates of population growth are in very poor countries that are emitting almost nothing and historically have contributed little to nothing to climate change. So as a solution it's sort of putting the onus on those who have not created the problem and are not creating the problem now.

The second is that a lot of population growth is driven by momentum which is that a lot of women around the world are entering their reproductive years and they are just going to have children even if they have just two children. And that is going to cause some built up population growth. That momentum limits what you can do in terms of policy to change the trajectory of population.

The third is that there is a very long history of human rights violations when we have population or fertility targets whether it is forced sterilizations or severe limits on the number of children people can have. The world really got together 20 years ago at the International Conference on Population and Development to shift the idea of population away from these kinds of targets and away from these human rights violations and towards women's rights, women's health and women's ability and empowerment to choose their fertility and choose their reproductive life decisions.

A recent study done by ecologists at the University of Adelaide in Australia found that reducing the population would not achieve much in the short term (this century) to solve issues of global sustainability. Does that line up with the view of the UNFPA?

It's a very captivating, interesting study. It's got a lot of premises that I'm not sure UNFPA would agree with necessarily in terms of the relationship between the population and the impact on the environment. But in the end it makes an undeniable point that we have enough people already to have an enormous impact on the environment. Even if we had fewer people that would be plenty to have an enormous impact on the environment. Just 2.5 billion people consume enough to have a significant impact on climate change and here we see climate change unfolding.

Daniel Schensul works for the United Nations Population Fund (UNFPA) as a technical specialist in population and development.

The interview was conducted by Charlotta Lomas