There's also the option of migration within the country. If we take an elevation map of Bangladesh and compare it to a climate map, there are areas that are hig

There's also the option of migration within the country. If we take an elevation map of Bangladesh and compare it to a climate map, there are areas that are higher and still have good climates for crops. https://www.researchgate.net/profile/Karar-Ahsan/publication/283621958/figure/fig9/AS:669502031278107@1536633131684/Elevation-map-of-Bangladesh.ppm https://www.researchgate.net/profile/Karar-Ahsan/publication... https://www.researchgate.net/profile/Nicolas-Guilpart-2/publication/314304326/figure/fig3/AS:469673536954373@1488990305674/Climate-zones-in-Bangladesh-and-the-four-selected-locations-Bogra-Dhaka-Rajshahi-and.png https://www.researchgate.net/profile/Nicolas-Guilpart-2/publ... People aren't going to migrate unless there is infrastructure and job opportunities there, so if we want to help these people we should be helping these countries to build new cities that are outside the risk of flood zones. We could even take the opportunity to provide more western standards of living - Dhaka only treats around 1/4 of its waste water - and build more environmentally friendly buildings - Dhaka is within a climate where houses could be heated passively.