Sir David says humans are threatening their own existence and that of other species by exhausting the world’s resources.
He told the Radio Times: “We are a plague on the Earth. It’s coming home to roost over the next 50 years or so. It’s not just climate change; it’s sheer space, places to grow food for this enormous horde. Either we limit our population growth or the natural world will do it for us, and the natural world is doing it for us right now.”
Hi remarks come as latest projections show the world’s population rising to nine billion by 2050
The broadcaster is patron of the group Population Matters, which calls for “everyone to have a smaller family size”.
Simon Ross is its chief executive. “There’s going to be increased competition over limited resources. Rich countries are buying up land in Africa and food prices are going to start rising,” he said.
“In the worst case we’re going to go back to the situation where famine becomes more common because with rising food prices and competition over land there won’t be enough for everyone."
The UN projects that the global population will peak at between 10 and 11 billion at the end of the century.
But a small increase in fertility could mean a global population of as much as 15.8 billion by 2100, while a small decrease could result in an overall decline to 6.2 billion.
But Population Matters says the target should be between just one and two billion.
“We do need to get to that at some point otherwise we will be running out of resources and the fact that we are going from seven up to 10 is a challenge,” said Ross. “What makes it particularly sad is that when I was born in 1960 there were only three billion people and if we’d stopped then we’d be all right.”
To achieve this, Ross wants governments in countries with high birth rates to encourage parents to have fewer children.
“Particularly in sub-Saharan Africa and the Middle East, there are countries with very high birth rates and there really needs to be a big effort in those countries in terms of providing family planning,” he said.
Rob Bailey is a senior energy, environment and resources research fellow at the Chatham House think tank.
He says the world actually produces enough food to feed everyone.
“We produce twice the calories we need on a per capita basis to feed everyone in the planet,” he said.
“The issue is of course that that food doesn’t get to everybody who needs it, so at the end of the day people do end up going hungry, but it’s not actually an issue of the size of the global population, it’s about power and politics and other factors.”
Bailey says even a global population of 10 billion humans could be fed – but only if mankind changes its current behaviour.
“It’s dependent on us tackling climate change and reducing emissions because by the end of the century we could be looking at up to six degrees of warming if we carry on as we are going and that would have catastrophic implications for global agricultural production,” he said.
He says poor country governments can help bring about lower fertility rates, largely by promoting women’s rights.
“As countries develop and access to healthcare and education for women improves, birthrates fall naturally,” he said.
“That’s because women become more empowered, they start to take on roles in the economy and jobs and in order to pursue these opportunities, they want to have smaller families.”
But although Bailey doesn’t share Sir David Attenborough’s view that overpopulation is responsible for today’s famines, he does not disagree with the broadcaster’s description of mankind as a plague on the planet.
“We are now in a period where the earth’s environment, climate, biodiversity and water resources are changing with unprecedented rapidity,” he said.
“That is all the result of man’s activities on the planet and it’s going to have profound implications for us. So I think there’s a lot of truth in that statement, unfortunately.”
Meanwhile, the UN predicts the average life expectancy for humans will rise from 68 years today to 81 years by the end of the century.