I've wondered about a shortage of urban burial space for a long time, and it looks like the UK is facing just that.
The disturbance of human remains in burial grounds is to be allowed for the first time since the early Victorian era to deal with a shortage of graves, The Times has learnt.Under a test scheme to begin in the new year, local authorities across the country will be allowed to exhume remains and rebury them deeper to create space for further burials on top. In some cases, new inscriptions will be added to the existing headstone to ensure that the heritage of the grave is not destroyed. Damaged or insignificant headstones would be removed and replaced with only the new name.
There are a few other options listed, but not the most obvious: vertical burial! Why must bodies be buried horizontally and stacked, when they could be easily buried vertically? Much less land required, and no one has to suffer the indignity of being buried beneath a rotting corpse.
Of course, as a commenter points out:
Nearly 1.2 million people can be buried per square mile (640 acres). Only about 200,000 of each year's crop of 600,000 dead Britons are buried. Thus, the UK needs only 106 acres per year of new graves out of 60,000,000 acres in the UK. There's simply no problem for millennia to come.