"...just as planning for response to an industrial accident doesn’t make an industrial accident more likely, so too planning for relocations should not make them more likely... It is .... likely that the slow-onset effects of climate change will lead many to voluntarily migrate in anticipation that conditions will worsen. Those who are left behind – and who will need government assistance to relocate – thus may be particularly vulnerable." — Brookings Institute
The pressure to start preparing for inevitable relocations due to global warming and the resultant rise in sea levels is growing for many communities around the world. For some, the time for preparation is already running out and the time for action is now. In the United States, the first "climate refugees" are in the largely-native communities along Alaska's coastline. Many of the small island nations of Oceania are beginning to ask their neighbors for asylum preemptively. This will certainly present one of the most challenging realities facing architects in the future as the global refugee population begins to increase. An important strategy will be to learn from existing "refugee cities" such as Zaatari in Lebanon, currently the country's fourth largest city. Populated by people fleeing the violence in neighboring Syria, a current water shortage crisis proves that, today, nearly every situation is in some ways affected by environmental conditions.
For places without as drastic a deadline, urban planning and (landscape) architecture have been increasingly put under pressure to go beyond "greening" and LEED certification and to start strategizing ways that urban infrastructure could become fundamentally more adaptive and resilient to worsening environmental conditions, thereby preempting massive human migrations when it's possible. Perhaps one of the most interesting invitations for architects to consider global warming in an American city was the recent "Rebuild by Design" RFP for the greater New York area (you can see the finalists' proposals here). Some cities are even being sued by insurance companies, for not being well enough prepared for the known, imminent repercussions of climate change.
It is the onus of architects and urban designers, as well as government officials, to preempt population shifts brought on by global warming -- not solely as a sustainability issue, but as one of human rights.