Justin Long believes that 'engaging these places is incredibly important to the remaining task' of world evangelization. I agree and here are a few thoughts on this list for those who think strategically or are considering their role in bringing the Good News here.
Nearly all of the places on the top 40 list are located within tropical or sub-tropical climate zones. Because they are in low latitudes more than one staple crop can be grown, enabling a relatively small area to support a large population, with major consequences for the rise of civilization (see below). These places are hot. Anyone seriously considering relocating to one of these places from more temperate climes must count the cost. Perhaps air-conditioning will be available if your budget can handle that. But how is the creation of artificial climates in our homes (with the doors and windows closed all the time) going to enable you to build relationships with you neighbours, especially those for whom such luxuries are unimaginable? Missionary lifestyle has always been a hot issue (excuse the pun): our rights as the Lord's servants are not to be held on to at all costs. Rather, we have the opportunity to give up our rights in order not to be a stumbling block to others.
2. Rivers and mountains
Nearly all of the top 40 are dependent on the Asian monsoons, the annual rainy season, during which nearly all of the year's precipitation is dropped, and around which the agricultural cycle revolves. Furthermore, the majority are located on or near a major river system, such as the Ganges/Brahmaputra complex (Uttar Pradesh, Bihar, West Bengal, Dhaka, Haryana, Rajshahi, Delhi, Rangpur, Khulna, Uttarakhand), the Indus and its tributaries (Punjab - in both India and Pakistan, Sindh, Khyber Pakhtunkhwa, Chhattisgarh, Jammu and Kashmir), the Yellow (Shandong, Gansu), and the Yangtze (Sichuan, Hunan, Hubei). The mighty Himalayan mountain range stores up much of the precipitation in the form of snow to be released slowly over the course of the year as it melts. All the above rivers (and several others that are nearly as important, such as the Irrawaddy, Mekong, Salween) flow from the Tibetan Plateau.
The Himalayas themselves do not constitute a watershed so major tributaries of the Ganges, for instance, arise on the north side of the mountains, swing south and cut through the range creating the deepest gorges on Earth. The significance of this is that, given the monsoon climate, crops have to be irrigated. Without these rivers agricultural production would be much lower than it is. Historically, then, these regions could not have supported such a dense population and would not have developed the rich civilizations that they have. What effect will climate change have on these places? It seems incontrovertible to me that anthropogenic global warming is already having drastic effects on these provinces. Photos of the Himalayas taken decades apart dramatically demonstrate that the waters flooding down off the 'roof of the world' are not just fed by last year's snow. Mission in these provinces must be forward looking and consider how to respond to possible great upheaval.
3. The Eurasian continent
All the provinces in the top 40 list are located in the great Eurasian landmass. (Only one is not wholly in Asia - Istanbul which is mostly located on the European side of the Bosphorus waterway - but I don't think this is significant. Eurasia is not usually seen as a single continent because the Ancient Greeks decided that Europe should be delimited by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas and the waterways connecting the Black and Aegean Seas, but in fact Europe is really the westernmost peninsula of Eurasia.) The great significance of this is that Eurasia is the only continent on the globe that enjoys a predominant east-west axis. That, as Jared Diamond points out in Guns, Germs and Steel: A Short History of Everybody for the Last 13,000 Years meant that innovations, such as the domestication of grains and livestock, could diffuse easily across the wide landmass, in spite of desert and mountains barriers. The people of Eurasia, then, were in the right place to develop complex civilizations.
I have been aghast on occasion at the wanton ignorance of some missionaries toward their host country's history. Anyone who seeks to engage the peoples of these top 40 provinces must place a high priority on learning the history of their host community. Only such people will deserve and receive a careful hearing as they share the message of Christ. I am reminded of the western missionary whom Narayan Vaman Tilak met on a train who was able to engage him deeply on his own turf and the tremendous impression it had on him. That ability doesn't come overnight but is the result of time-consuming and costly learning. Anything less than this is to short change our hosts. Not all are able to study in depth but those who can must make it a priority and all must do what they can. Ignorance does not adorn the gospel.
More thoughts here.