Of course, an event of this magnitude would require very carefully planned steps to execute properly, and would have even less tolerance for purposes of maintaining sustainability afterwards.

First, a location should be selected in which to place the remaining population- something of a sacrificial continent. North America- especially the United States- is a logical choice for this. First, there is a significant amount of agricultural land and capital. Next, there is a strong infrastructure, and sufficient resources to maintain a small population base for an extended period of time. Third, it is by and large a temperate climate, with long growing seasons, fertile soil, and significant amounts of most renewable natural resources. Also, the United States has almost all of its arable land in use, which would make sense to continue using, in a more sustainable manner, rather than cutting new plots in less damaged areas.

Next, certain societal elements should be preserved. In this case, ecological experts, who also know about sustainable development, agricultural engineers, forestry management professionals, energy source specialists and power engineers, and technicians capable of making use of any resource left behind and deactivating potentially harmful objects (i.e. unattended nuclear plants, etc). These should total approximately 1,000 people, this being a sufficient task force for the needed jobs, but maintaining a less than 0.2% total population segment. This is good because these people will effectively be the government of the reorganized sustainable society, and this ratio provides for their needs without making too large an impact on necessary production by the rest of society. The best way to arrange for these people to be available would be to, before the event, isolate a significant amount of fuel, small aircraft, and other supplies. Then these should be set aside with instructions to use them to gather survivors and make appropriate preventative measures in any hazardous areas. Then abduct all of the people chosen to be a part of this governing body approximately two weeks before the event. Vaccinate them and hold them in isolation until afterwards. It would be prudent to install an automatic release system on the location in which they are secured, to allow for the probability that no one who knows where they are will be among those who are inherently immune.