Population is the third rail issue for environmentalists. Even the founder of Earth Day, Gaylord Nelson, was concerned that it was being ignored. A guest writer on MNN wrote:

Nelson had become deeply disappointed with the wholesale retreat of the environmental establishment from advocating limits to population growth. Rather, a new generation of more pragmatic (expedient?) campaigners preferred to prattle on about safer and sexier topics.

Perhaps sexier is the wrong adjective, but population is definitely an issue we tend to avoid because it's so intertwined with the hot-button issues of abortion, birth control and immigration.

The problem is that in many countries, the fertility rate is declining below the replacement rate. Japan has been going through this for years; the Russian population is crashing; and now Europe, according to the Guardian, needs many more babies to avert a population disaster. “The net effect is a ‘perfect demographic storm’ that will imperil economic growth across the continent.”

Spain is in crisis, with its population shrinking rapidly, as is Portugal. The problem isn’t just that the numbers are shrinking, but that everyone who is left skews old.

In Italy the retired population is soaring, with the proportion of over-65s set to rise from 2.7% last year to 18.8% in 2050. Germany has the lowest birthrate in the world: 8.2 per 1,000 population between 2008 and 2013, according to a recent study.

In Portugal, it's beginning to look like a scene from "Children of Men":

The EU’s Eurostat agency estimates that by 2050, Portugal will be the country in Europe that is home to the smallest proportion of children, with just 11.5% of the population expected to be under the age of 15. Toy shops and hundreds of schools are closing while petrol stations and motels are being converted into nursing homes.

In Italy, they have started a baby bonus; In Quebec, Canada, they provide cheap day care and long paternity and maternity leaves; In Sweden, the social support network is extensive, including subsidized childcare and the promotion of gender equity.

In North America, the situation is not really that different. The fertility rate in the U.S. is 1.9 children per woman and in Canada 1.6. The replacement rate in industrialized countries is 2.1. After World War II during the baby boom, the American rate was 3.8.

refugees in GreeceRefugees from Afghanistan and Syria reach Lesbos, Greece. (Photo: Soeren Bidstrup/AFP/Getty Images)

Yet all over the world, fences and walls are being built to keep immigrants out. Thousands are dying in boats in the Mediterranean, and American politicians are proposing walls right out of "Game of Thrones" to keep out Mexicans. The problem is not one of population, as they note in the Guardian,

Record numbers of economic migrants and asylum-seekers are seeking to enter the European Union this summer and are risking their lives in the attempt. The paradox is that as police and security forces battle to keep them at bay, a demographic crisis is unfolding across the continent. Europe desperately needs more young people to run its health services, populate its rural areas and look after its elderly because, increasingly, its societies are no longer self-sustaining.

In xenophobic Japan, they are solving the problem with robots that do the work of dealing with the elderly and filling service jobs in hotels. Everywhere else, the answer — no matter how much people hate it — is immigration. My mom and many other Canadian seniors couldn’t survive without their network of Filipino caregivers. But that’s a tough sell in many countries.

The answer to the problem isn’t higher fences. It's education and equity. Carl Sagan said it best in 1998:

There is a well-documented correlation between poverty and high birthrates. In little countries and big countries, capitalist countries and communist countries, Catholic countries and Moslem countries, Western countries and Eastern countries — in almost all these cases, exponential population growth slows down or stops when grinding poverty disappears. This is called demographic transition…

Our job is to bring about a worldwide demographic transition and flatten out that exponential curve — by eliminating grinding poverty, making safe and effective birth control methods widely available, and extending real political power (executive, legislative, judicial, military, and in institutions influencing public opinion) to women. If we fail, some other process, less under our control, will do it for us.

That makes a whole lot more sense than a big wall.

Lloyd Alter ( @lloydalter ) writes about smart (and dumb) tech with a side of design and a dash of boomer angst.