It been forecast by 2050 we will not be able to produce sufficient cereal and grain to feed to livestock to maintain the current levels of meat protein in our diet and will have to seek protein from elsewhere.
Certainly the lives of those on diets high in meat protein is going to have to change one that is primarily plant-based. And as you say, rising sea levels are going to be highly problematic, creating many millions of refugees that are going to have to be accommodated on higher ground, leading to further pressure on farmland. But it's important to recognise that the issue is primarily not of resource availability so much as resource distribution, those of us in the 'advanced' societies are consuming a massively disproportionate share of the world's resources.
