As people move they take their beliefs with them. For many, religion is one of the few aspects of their previous life, a key to their sense of identity - stronger than the citizenship of their adopted country or the nation they left behind.
The world's religious landscape is changing dramatically, thanks to differences in population structure such as age and sex, demographic processes such as fertility, mortality and, of course, religious conversions between different groups. Increasing migration has meant that most countries are becoming more religiously diverse. This is most evident in major cities, often the first port of call for new arrivals. Christianity covers most of Europe, the Americas and large swathes of Central and Southern Africa, while Islam is mainly centred in North Africa, the Middle East and Asia. How these different faiths co-exist will have a profound effect on society in the coming decade.
Why is this important? Over eight out of ten people around the world identify with a religion and are, to a greater or lesser extent, influenced by it. For many it provides a sense of belonging and definition in society, both in terms of behaviour and orientation, and can influence trade patterns, female employment levels, legal systems and societal structures. On a personal level it can affect marriage and fertility choices and even health-related behaviour.
Recent research projects that, over the next four decades, Christians will remain the largest religious group, but Islam will almost equal their number around the world by 2050. If current demographic trends continue, the world’s population is expected to increase by 35% by 2050; over the same period the Muslim population is projected to increase by 73% (Christians rise by about 34%), simply because of its comparative youth and high fertility rates. Young religious people of the developing world are in sharp contrast to ageing and increasingly secular westerners (content to keep their families small), so expect the number of religious people in developing countries where there is a high birth rate and declining infant mortality to grow more quickly.
The Yearbook of International Religious Demography describes the Religious Diversity Index as the inter-religious diversity of a particular country or region's population. Among the six regions analysed in this study, the Asia-Pacific region has the highest level of religious diversity followed by sub-Saharan Africa. Europe and North America in comparison have moderate religious diversity, while the Latin America-Caribbean and Middle East-North Africa regions have low religious diversity.
Unsurprisingly perhaps non-religious people tend to live in religiously diverse places, as do Christians whose number living in religiously diverse countries has increased by approximately 50% over the past century. The opposite is true for the Muslim faith; a century ago 20% of all Muslims lived in countries with low religious diversity but by 2010 this had increased to more than 30%.
Although still a key aspect of many western societies, there has been a gradual separation of religion and state in many Christian nations, however this is not the case for Islam - some more extreme than others. Saudi Arabia does not tolerate any form of overt religious practice other than the officially approved interpretation of Sunni Islam, whereas Indonesia and Malaysia, countries with Muslim majorities, have a tradition of syncretic Islam that is more tolerant. There is growing concern across the globe that the stricter forms of Islam imported from the Middle East, seen as more modern and correct, are gaining popularity. At its most extreme these are the ultra-conservative views of Wahhabis, which form the basis for Daesh (ISIS).
Increasingly the concept of religious freedom, a human right, is being challenged. The latest US State Department report on the matter points to terrible violations of basic freedoms in dozens of countries. It says that this is due not to cruel governments, but more to the kind of forces which step in to a vacuum when legitimate authority collapses; warlords, racketeers and terrorist groups. On the Syrian-Iraqi border, Daesh is reported to have “forcibly displaced hundreds of thousands of people, conducted mass executions, and kidnapped, sold, enslaved, raped and or forcibly converted thousands of women and children...” Daesh is not the only fanatical organization. In its quest for religious domination, Boko Haram has been similarly barbaric in Nigeria, Niger, Chad and Cameroon.
Some expect that the rise of Islam in Europe, boosted as it is by immigrants from North Africa, Turkey and South Asia Islam, will challenge the secular nature of state governance - and may well re-shape the balance between religion and state. Some consider that Western democracies lack the mechanisms for dealing with the powerful transnational ideological forces of extreme Islam and may well struggle to maintain a balance between the desire to maintain a society which upholds the right to religious freedom, and adherence to a common set of values which all can agree. There are also fears that countries such as Indonesia and Malaysia will retreat from diversity and cede greater control over beliefs, customs and freedom of expression to a dominant orthodoxy.
The next decade will see different countries approaching the matter in different ways. France, much like the United States, has a clear constitution with a specific set of founding principles, and it expects all citizens to accept them, including the idea that universal education should help to reinforce the messages. Britain, though, lacks a specifically written constitution, and has taken a different approach, allowing immigrant sub-cultures to develop and accepting faith-based schools, including ultra-conservative ones. Germany, keen to avoid any fanatically professed ideology, religious or secular, has always supported religious education and is now making room for Islam through its classrooms.
Clearly migration and population growth amongst Muslims in Europe is re-shaping society. Governments will have to tread carefully to manage this and in particular their response to radicalization amongst the young. Rather than mete out harsh penalties, in the future, community-based programmes designed to divert young people from extremism may well be the solution. Against this backdrop, Christianity drifts south. There are 277m adherent Christians in sub-Saharan Africa and 250m in Latin America. That has moved the centre of Christianity to Niamey, the capital of Niger (calculated by taking the Christian-adherence weighted-average latitude and longitude of countries' capital cities). Should the Vatican follow?