We have reported on the African migration crisis, where millions of Africans intend to migrate to the West, whether the West likes it or not, in a Camp of the Saints scenario:
  https://www.euractiv.com/section/future-eu/opinion/tens-of-millions-of-africans-will-try-to-come-to-europe-whats-the-eu-policy/ 
  https://www.amazon.com/Camp-Saints-Jean-Raspail/dp/1881780074 

     There are many reasons for the mass migration, including the fallout effects of big dams in the Sahel region, which have dried out wetlands, endangering the livelihoods of thousands. Consequently, many decided to take the royal road as refugees, environmental refugees in fact:
  https://notalotofpeopleknowthat.wordpress.com/2018/04/01/how-big-water-projects-helped-trigger-africas-migrant-crisis/ 

     Nevertheless, for multiculters seeking easy answers, this alone does not account for the sheer numbers, tens of millions of Africans seeking to flood Europe in the next migration crisis. They seek the lifestyle that Europe offers, and have seen how easy it is, thanks to the New Class elites, to get on the migrant train. With Africa’s population exploding, Europe, and the rest of the West does indeed face Camp of the Saints style swamping, for chain migration will lead to all of Africa entering Europe. By 2050, on the medium growth projection, Africa’s population will be 2.5 billion, and by 2100, 4 billion, one third of all people on Earth:
  https://qz.com/1099546/population-growth-africans-will-be-a-third-of-all-people-on-earth-by-2100/

     The consequences, once the West collapses from its own pathological altruism, will be catastrophic.
  https://news.sky.com/story/just-10-rivers-carry-90-of-plastic-polluting-the-oceans-11167581 

“Just 10 rivers are carrying 90% of the plastic entering the oceans, a study has found. Two of them are in Africa - the Nile and the Niger - while the others are in Asia: the Indus, Ganges, Amur, Mekong, Pearl, Hai he, Yellow and Yangtze. As well as being some of the world’s longest rivers, they have big populations alongside them. The Helmholtz Centre for Environmental Research in Leipzig, Germany, also said they tend to be in countries where waste control could be better.”

     There is also the problem of European nuclear weapons, as well as nuclear power stations going into meltdown and poisoning all life on Earth, when or if, Europe collapses.