Social collapse Worse-case scenario

Social collapse Worse-case scenario
A hypothesis for the end of the world

Back

Chapters

Basics

Intro
Social Effects

Lifestyle
Social Life

Population

Food

introduction
Effect after event
Production

Water

Supply
The Population
Measureable Effect
Pollution and Stagnation

Health

Hospitals
Sanitation
Disease’s Spread
Death Rates

Migration of Population

Suburbs
Exodus
Destination

The Countryside

Devastation
Use
Reason
After-effects

Urban areas post-event

Degradation
Looting
Fire!
Reclamation

Social structure shift

Communities
Factionisation
Agriculturalism

The Next Phase

What Next?

Growth of new communities
Establishment of new culture
Geographic isolation and its effect

Stability
Rebirth
Fork in the road

Differing paths, i.e. rebuilding modern civilization, or turning to more traditional life

The End

Introduction

Cause: EMP event derived from a large scale solar emission event.
Initial effect: Total destruction of unprotected electronic devices within hours of radiation contact on Earth.

Initial event causes almost all electronic equipment to be rendered useless due to static overload. This in turn causes a failure of all electronic communications systems which delays the reaction time, but eventually it will be realized as to the magnitude of the ensuing situation, which will cause mass panic:

A rush for food stocks will occur
A rush for essential medical supplies will occur
Crime rates will exponentially increase over the first weeks after the event
Law enforcement and military intervention will be over run and will collapse internally.
Mass exodus will occur out of major cities causing a clogging of transport routes.
Government systems will collapse entirely
Small scale localized wars will take place over essential territories (Food production, power production, water sources)

Short Lived due to lack of resources

Massive spread of contagious pathogens due to collapse of sanitary and health systems.

Extremely rapid spread causing large scale fatality rates on a global scale

After a period of between 5 weeks and around 3 months there will have been a large scale evacuation out of major cities and urban centers into the outskirts and country side. As a result urban environments will have totally collapsed due to looting and the spread of fires, as well as the failure of water systems causing flooding in tunnels and subways networks. Criminal activities will follow the moving populations centrifugally away from urban centers, as well as be created in population conglomerations due to competition of resources. Small communities will develop in the country side in national parks or on farmsteads and after several months will become relatively self sufficient, however will be repeatedly attacked by bandit groups or other communities over resources or equipment, such as livestock or farming tools.

Lifestyle:

Immediate removal of electronic devices from households causing fast civil unrest on a local scale
Loss of food preservation devices (i.e. Fridge/Freezes) causes food to spoil over a number of days, depending on climate.
Communication devices will become in-operational; as a result transfer of information regarding events becomes impossible aside from direct person-to-person conversation.

Unlike conventional “natural disasters “ where a perspective of the actual scale of the event can be ascertained, if communication devices were to be disabled there would be a significant delay in the large scale reaction to the event.
There would be no effective effort to control civilian populations and to provide effective aid.

All forms of transportation apart from manually operated or diesel powered vehicles will cease to function, however due to a combination of social factors, mainly being the largely petrol operated motor vehicles on the roads which will stop on roads, causing them to be un-traversable in convention motor vehicles. Also since production of all fuels will stop, any remaining vehicles will be unusable.

Social Life

Food production and transportation will permanently cease.
Food outlets will no longer be stocked with food, and existing stocks that require constant maintaining of environment (i.e. Freezers, refrigeration, heating) will spoil within 48 hours.
Any durable food stocks (Canned, freeze-dried etc.) only make up a third to a half of all stocks at any one time.
Any food stocks in an outlet are limited due to the reliance of constant restocking of goods.

Existing stocks will be removed within hours, to a maximum time span of a day

Large scale starvation causes massive death rates
Loss of medical services and supplies causes increased death rates due to disease
Loss of sanitation and running water supplies causes fast spread of disease and increase of pests
Food will be almost non-existent in large cities, and perhaps smaller ones to large towns.
Any operating electrical system i.e. wind turbine or solar panel will be fought over and ultimately destroyed in the attempt to do so
Mass exodus out of urban areas will occur, as a result the surrounding hinterlands and countryside will be devastated along with any food production or agricultural systems still in operation.
Crime rates will rise exponentially as the remaining populations fight over very limited resources, mainly food but also, depending on the climate and region: water, clothing and shelter as well as transportation such as bicycles or horses
Small communities will settle around major urban areas, and will expand continually outwards when available resources are depleted.
Populations will continue to fall dramatically as mass famine, epi-/pandemics, violence in the form of wars or otherwise, exposure to extreme climate, lack of water and so on.
The remains of urban centers will be most likely torn apart by a number of things; the most prevalent one would be fire which would consume, without opposition, large portions of a city, most substantially suburban areas.
Movement of populations in and amongst urban regions, most notably suburban areas in the case of conurbation or other extensive, interlocking metropolitan regions.

Areas that are moderately still intact will attract settlers back or directly into suburban regions where, given appropriate conditions and population densities, small communities will occur in the ruins.
Scavenging and looting will be wide spread and will create a form of trade or for support for small communities.

Areas with extensive rural regions (i.e. Canada, the American North-West and Lake Region, as well as largely unoccupied areas of Eastern Russia, North West China and many parts of Africa and Australia) will better be able to support the large amount of migrants from urban centers. Regions such as Western Europe and the American East Coast will suffer severely due to the high density conurbations and “Megalopolises” that span the entire area.

Population

Globally populations will suffer substantially in all areas and forms of society (with the exception on those with absolutely no connection with modern civilization, both politically and physically) due to the globalised nature of modern society. Any community dependant on external sources for food, water or supplies of any kind will be affected, depending on their reliance on such imports.
Clearly the most effected will be the high-density, technologically advanced modern cities that make up all of the western world, as well as the up-and-coming cities, such as Beijing in China as well as many Indian cities that are becoming more advanced. Their high density will be the major factor in their outcome, coupled with the high expanse of the metropolitan area which will make evacuation a major issue after the event. In the United States in particular where the common ideology of “suburbia” where one lives 40-50 miles from their place of work will cause significant issues depending on the time of the event. I.e. during typical working hours, a very large proportion of the population will be in the downtown area, about 50-60 miles inside the urban zone where there is little access to significant food or other supplies present in supermarkets or other vendors, most of which are located in or around the suburbs.
It is logical to assume that high-density areas of population would be worst affected closer to the initial event, where a steep population decline will occur do to the large volume of people as well as the layout of the urban center, being access to food outlets mainly, however water will be a significant issue, especially in cities not situated along a river or other fresh water source.
Death rates will initially rise at an exponential rate as food immediately runs out, and any lack of water is emphasized, and forms of conflict or other violence arise from both prior issues. As time progresses disease will become prevalent as sewerage lines stagnate and the continual creation of human waste is added to the immediate environment, be it sewerage or carrion.
Hygiene will become the major factor in the spread of disease, which will be attached to the availability of fresh clean water in the immediate area.
It may be the case where many new strains of a particular virus of pathogen will play a major part in the effect of disease on the population, such is the result of large scale antibiotic use causing both a loss in natural immunity, as well as very potent pathogens which will overpower any existing immunities.

Hospitals will play a major role in the spread of such super diseases as hygiene within them breaks down accompanying the influx of patients and the lack of any or all services, as well as any pre-existing pathogen that may have remained dormant (i.e. golden staph infection etc.).
Antibiotics will soon become one of the highest valued commodities alongside food and water (depending on the climate and geographic location) and will quickly attract many instances of extreme violence.
Any person with dependencies on artificial drugs (Insulin or others treating chronic disorders, such as immune suppressants for transplant patients) will most likely not survive more than a few weeks depending on their requirements. Those on life support, in open surgery or with pacemakers will die almost immediately.

Food

Introduction

Initial food stocks located in outlets such as supermarkets and delicatessens, mostly in suburban areas or inter-mixed zones.
Available stocks are replenished via constant delivery from a distribution warehouse, whereby multiple outlets are restocked from the same central facility.
Approximately 50% of stocks have a constantly maintained local environment (i.e. refrigerators, freezers or heaters.)
25% of stocks are non-perishable goods, such as toiletries or household utensils as well as other hard goods.
25% are sealed, tinned, freeze-dried or dehydrated, are fruits or vegetables or otherwise long life goods that do not need to be maintained.
Smaller outlets, such as private deli counters or green grocers will sell a more specific range of goods, however usually they are either green foods or confectionaries with limited selection of long lasting or sealed foods.
Cafés, kiosks or other small outlets, usually located more so in the downtown or central business districts will contain a very limited selection of all goods, and will not in most circumstances stock long life storable goods.
A large food outlet will usually cater for >5000 individuals at any one time, however this is spread out over time and counts for all those within a particular radius.

Smaller, privately owned outlets will be located within the radius of the larger ones but will serve a substantially lower base population, and will be more specific in the range of available goods

Event occurs:

Initially, once a perception of the present situation occurs, there will be a significant rush for food stocks.
All persons within an outlets attractive radius will, at once, attempt to gather food.

Depending on the climatic conditions, season or other weather variables, food kept under maintained conditions will turn within 1-2 days, depending on its type of maintenance (i.e. whether it’s refrigerated or frozen, heated etc.)
Priority choices will be canned foods, followed by sealed, freeze-dried and dehydrated as well as fruits and vegetables. Depending on the outlet, alcohol will also be of preference, particularly spirits or wine

Due to the nature of the methods of stock maintenance employed by all large scale outlets, food or other stocks will quickly deplete

Food Production

Production and/or cultivation of foods stuffs on a large scale will cease altogether in all parts of the world that use it.
Transportation of produced stuffs will be impossible on a large scale.
Maintaining of produced stocks, which require it, will cease, causing them to deteriorate and turn.
Any agricultural activity that is still in operation (through traditional means, nonetheless) will have no impact on urban areas, and will mostly be used for private sustenance or for that of local, small communities.

Food availability and actual amount

Within a month of the event, depending on local variables, all food stocks that were either salvaged, looted or otherwise acquired will deplete, any large stores acquired pre-event will hold out perhaps a year at the most depending on the means of its preservation and actual properties. (an example of the later is the typical “nuclear fallout shelter” emergency supply, although only a very limited number of persons will have this, in any form)
Within the first month, food related death, will be harsh but not immense, as large stocks will exist and will somehow make their way to a majority of a population; however, after a month any existing stocks, of all varieties will begin to, or would be depleted.
If it hasn’t already due to other factors, panic will quickly spread, or worsen substantially as food of all varieties are depleted.

Violence over food will escalate exponentially and will involve all members of a population
Death due to starvation will exponentially rise
Exodus will occur on a massive scale, if it hasn’t already, out of major urban centers and metropolitan areas, into the countryside

Water

Supply

Water mains supply most of an urban center’s infrastructure with fresh water, sourced from aquifers, local reservoirs or river systems.
Pumped, actively, though a network of pipes.
Depending on the geographic location there may be freshwater rivers, lakes or other water sources in the metropolitan area
Water towers on top of high-rise buildings will store a large quantity of fresh water, and are located on almost all buildings higher that 6-10 floors
Climate is an important factor, both In relation to temperature, humidity and the actual precipitation.

Largely dependent on season as well as geography.

Personal stores of water, particularly in the suburbs will account for a minute fraction of total reserves, and if left standing will become undrinkable
Stored bottled water will make up a fair portion of water located within the suburbs, however its quantity is limited and is non renewable if no natural source is available

The Population

In a large urban center with a population of 1 million or more, immediate access to water will be largely restricted aside from that sourced from water mains. This is rivers, lakes etc.
A large migration may occur to a water source, depending on its location, or existence. It depends, however, on the climate as to how water is prioritized. Food will almost always take priority.

Measureable Effect

After a moderate period of time (4-7 days) water requirements will become very pronounced, and if they haven’t already, a large amount of population will move to readily available water sources. These include rivers, lakes and so on but also could include water towers on buildings (which use gravity to give flow, rather than actively pumping it) or natural springs. Again, it depends on the climate, where a wet climate would allow for rain water collecting.
A lack of water in the suburban regions will cause a lack of general hygiene, as well as a general deterioration in health through dehydration (climate dependant).
Accompanied with hunger, deteriorating health and any number of social factors related to the situation as a whole, a lack of clean drinking water will almost certainly spark more violence for control over any sources of it.
Any storm drain system will clog and become ineffective as solid waste will block entrances, or drains. As a result the streets will become water logged potentially causing flooding
Underground tunnels such as subways, sub-surface roads, service tunnels or canals will flood as pumping equiptment will have ceased to function. This will likely cause a measurable amount of fatalities depending on climatic and environmental variables as well as the location of any persons in the tunnels at the time of the event

Pollution and Stagnation

Any large human presence at the vicinity of a water source will ultimately lead to the addition of pollutants. Be it solid, inorganic waste such as plastics, inorganic liquids such as runoff from streets via storm drains, or any chemicals that get introduced if a storage facility were to fail or otherwise leak its cargo into the environment; however the most potent pollutant will almost certainly be organic waste.

Human waste will get flushed, dumped or otherwise drained into a water source either in a passive (i.e. sewers utilizing gravity, waste on the streets getting washed away) or actively, which entails manual dumping of wastes into a water source one way or another.
There is also the case of corpses ending up in a water source, which would allow for it to become a grounds for pathogens to congregate and spread, especially if it is a still source such as a pond or small lake

Any standing source such as a barrel or bucket left outside for extended periods of time will cause it to stagnate rendering it undrinkable, and potentially a source for the spread of disease
Intact sewer lines will stagnate and eventually overflow, most likely onto the streets above. This is caused by any continual usage, in some form, or by introduction of excessive fluids (i.e. if it gets filled with rain water)
Any event of flooding, waste will be washed through the streets and will provide a means for the spread of any waste throughout the area.

Health

Hospitals

All medical equipment will become useless
All hospitals will draw many people in from all parts of the urban area, causing over-crowding and an almost immediate collapse in all medical systems
Chronic patients requiring regular drugs (i.e. insulin for diabetes, immune suppressants for transplant patients etc.) will die within a month, if not by other means, depending on their own supply. Any individual with a pacemaker will die almost immediately after the event occurs.
Any pharmacy, be it part of the hospital complex or not, will be a major target of many varieties of individual, from junkies to opportunists to families seeking antibiotics or drugs for people with chronic illness (see above)
Drugs themselves will become a major cause of crime for many reasons (again see above), especially antibiotics, or in some cases prescription drugs such as strong pain killers or sedatives
The hospitals themselves will become a major center for crime or other violence in all varieties, partly due to the high populations that would accumulate at them, yet also due to a combination of all of the above to a large extent.

Sanitation

Overall an almost complete loss of sanitation at all levels, due to a variety of factors.

Availability of clean drinking water, and its prioritizing of being used for drinking
The condition of any available water source will compromise hygiene significantly
Build up of sewerage on surface streets

As deaths occur over time a buildup of corpses, human or otherwise, will be evident throughout urban areas, allowing further spread of disease.

Spread of Disease

Death Rates

Food will be the primary factor in the mortality rates over time, or at least it will be if you count for its consistency. It will however be closely followed by violence related deaths, lack of water (depending on the climate), disease will build up over time to be a key player also and perhaps in more localized regions it can be overall the single largest cause of death.
Deaths related to pre-existing health issues will be a short, but significant, peak on the graph occurring very soon after the event. However its total number of collective deaths will not number high overall.
Depending on the location and climate, environment related death will be an issue, particularly later on after a month or more. Death from exposure will be significant as most will not be able to prepare for any severe weather effectively, that coupled with the situation at hand that existing residence will be more than likely in a state of deterioration. Any extreme weather will more than likely kill many thousands (heavy rain storms, ice storms, heat waves etc.). This will be particularly pronounced at higher latitudes.
If an outbreak of a virus were to occur (influenza for instance), it would kill in the millions, especially if it were to occur late after the event when there has been time to allow considerable deterioration to take hold.
Eventual death rates are impossible to calculate in the long term, but a combined total of starvation, victims of violence or conflict, disease or exposure will top over 3 billion quite easily, depending on how things progress (which more than likely will not be in the positive direction) it could easily climb further. At the worst there could be a mortality rate in the region of 95 – 97% of all human life (as of today), which will reduce the human population to about 3-6 hundred million, or less.

The Migration of Populations

The Suburbs

Due to lower density, as compared to the areas closer to the urban center’s central business district, the suburbs will attract a large portion of the population from the interior of a metropolitan area.
The availability of many resources, such as distribution of perishable goods, in suburban areas will make them an attractive residence for the displaced population, that was once living in the down town regions.
Due to the suburbs usually being a border between the higher density, core regions and the rural countryside, suburbia will be at least a stop off region for those migrating out of the metropolitan area.
Due to the makeup of the suburban regions, as in their single family houses, the effect of degradation will be far more pronounced than in areas of high-rise apartment buildings, and, since most houses have a wooden framework, fire will be a major issue that can arise particularly in lower socio-economic regions where that are of poor maintenance and with residences of high proximity to one another.
An increase in the overall population in suburban regions will cause a competition for residence, or otherwise a significant appearance of homelessness. It is likely that ramshackle communities will develop by refugees from the inner metro areas.
Resources, that were used by existing suburban residents i.e. food, will be of high demand by refugees. Crime rates will escalate exponentially in all regions and by all parties involved.
Due to the failure of all essential utilities the suburban regions will quickly stagnate and become a cesspool of all manner of waste produce be it organic or otherwise. Disease will spread rampantly.
Climbing death rates, due to a combination of factors (food, water(maybe), disease and crime) will cause, firstly, greater competition of resources or residence, and secondly an increasing act of migration out of the metropolitan area altogether. This will be a trend that increases over time rather than a spontaneous event as the exodus out of the central metro areas (downtown). This could be a period spanning up to several years, starting immediately after the event has occurred.

Exodus

Upon the event first occurring, a migration out of metropolitan areas will occur into various surrounding areas, most notably the rural countryside.
It will occur in various amounts over time but it is certain that overall a trend to migrate in a centrifugal fashion away from the central core of a metropolitan area will exist in some form.
Exodus of large, highly populated urban regions, such as the conurbations and megalopolises of the North American East Coast, will cause a major population shift almost at once which will create havoc along major transport routes, which will be the primary routes of refugees.
Groups numbering in the millions will travel in an almost swarm like fashion, which will ravage the regions they pass through for resources, be it natural or artificial produce. Towns will be looted and wiped clean of food and other supplies.
Criminal activity will further escalate as resources will get ever scarcer within groups. Deaths over very trivial things such as blankets, cutlery, plastic water bottles (be they filled or not) and most importantly: food, in any form.
Death due to exposure, disease, starvation or violence will wipe out huge portions of the population causing panic, and an ever increasing presence of what would be called primal instinct, that is the unquestionable will to survive regardless of consequence.
If the climate is not in favour of the general population (i.e. if it is winter in the northern USA or Canada, Northern Europe, Russia and Northern Asia) there will be a significant increase in the amount of deaths in all counts, as well as exposure being one of the top causes of death alongside starvation and its related effects.
It is likely that some groups will stop to create rudimentary campsites or “Tent cities” in various locations along migration routes.

Destination

Most refugees will follow the person in front of them, with no real idea where they are headed, apart from perhaps the knowledge of moving into the “country”. However they could attempt to move to other cities or urban centers, as a widespread knowledge of the extent of the event will not be known. Many would think of it to be a localized event, something attributable to a nuclear exchange, which would not be a scarcely mentioned theory
Most with any idea of a destination will inevitably head to the country in hope of a supply of food, with the assumption that all agricultural activities are located there, and can support large populations with a continuous supply. However, millions will either make the same assumption, or will learn of this idea from others and follow.
Of cause, there will be the fraction of a percent that will have somehow prepared for a crisis such as this, in one way or another and as such, may have predetermined destinations complete with preservations and other supplies, however the limiting factor in getting to it may lie in the routes taken by refugees, as well as its distance away from the urban area.
If any group of people were to arrive at particular area, a national park for example, there would be a creation of a small community, which could perhaps take up an initiative and become self sufficient for a time. However, subsequent waves of refugees will arrive in some form or another at the same location, and as this happens the partially established community will break down, after consuming most of the natural resources in the area.
Farms will be a universal destination in some form or another, due to the idea of massive quantities of renewable food supplies and large open space
National parks will be a universal destination also, depending on the resources available (a river with fish, for example)
Rural communities, at least for a short while, will become a destination for many, until they become completely drained of any resources, at which point the migration will continue, along with the community’s original inhabitants.

The Countryside

Devastation

Rural communities, in particular, will be destroyed as migratory groups pass through. Any and all resources will be taken and when there is nothing left, the group will move on.
Any farmland that has been come across will be devastated as thousands of people attempt to settle on its land, and in the process render the once fertile land useless. Existing crops as well as livestock will be eradicated and the introduction of disease and crime will wipe out any previous inhabitants.
National parks will be stripped of their trees as millions cut them down for firewood, rivers are cleaned of fish and all wild life is either removed by action of the two prior effects, or are hunted for food.
By combination of pollution, over-exploitation and mismanagement of resources, loss of ability to maintain land (agriculture) and an overall overpopulation of previously sparsely occupied regions, the means in which to live sustainable lives on the agricultural countryside are lost resulting in the combined deaths of most of those that made it this far.

Use

Usage of rural areas is mostly agricultural, or light industrial and as a result is generally sparsely populated.
Agricultural activities are aimed at providing for the urban regions either domestically or internationally and are operated by means of very complex and hi-tech techniques in order to utilize vast areas of land at any one time.
Natural wilderness reserves serve no purpose to the general public, at least not actively; however they may be utilized for recreational hunting or fishing.
Climate will in all cases dictate the usage of rural regions, in colder climates, agriculture is limited, or at least differentiated to that of temperate or warm/sub-tropical regions. Colder climates will usually raise livestock, while temperate climates grow grains and other crops and tropical climates will produce fruits, rice and sugar as well as material crop such as cotton, rubber and tobacco.
The climate will deduce the usage of the land as refugees migrate onto it, for instance there could be larger instances of animal hunting to sustain a population in colder climates, as opposed to varying levels of agriculture in temperate to tropical climates and communities will develop accordingly.

Reason

As previously explained, the countryside is the primary location for all agriculture, and as is known in the general population that means growing food products, be they livestock or flora.
It is also known that it is generally lacking in large population, and therefore an individual or small group could support themselves with what is at hand, which in most cases is plenty.
It would be deduced that the countryside and its food production will provide a far more sustainable lifestyle than if one were to remain in the metropolitan areas, which would be polluted, infested with disease, probably in the process of burning down or otherwise degrading, or just that any form of life is impractical in such areas. The open country will give a better chance of survival overall.

After Effects

After the refugee migrations have either passed through, or have settled in/on rural regions, there would be a major deterioration in conditions in that area, and subsequently the whole countryside of any given region.
Actual effects depend on the expanse of rural regions, the United States , Canada and Western Russia , for example contain large tracts of un occupied land that can be exploited one way or another and therefore can allow populations to spread over it more, whilst in the United Kingdom or Western Europe it is the exact opposite as there is far less open country, the same sized population will be forced into a smaller area increasing the density, which will over populate the region, and most likely stripping it bare or resources within a short space of time.

Urban Areas Post-Event

Degradation

Immediately after the event has occurred, the urban areas of the world will begin to degrade as there are no more services to maintain them.
The effect of the population exodus out of the central areas of a metropolitan area to the suburbs, and subsequently into the countryside will accelerate any degradation as the areas are torn apart by conflict, or other means of destruction, be they passive or otherwise.
The failure of safeguards such as water pumps, sewerage systems or levies will cause localized degradation as areas are eroded or washed away or are generally overrun by previously maintained forces.
Un-maintained exposure to natural forces (Weather, flooding or even age and decay) will cause widespread degradation and dilapidation of urban regions as a whole. Most significantly, however, at least initially, the suburbs of metropolitan areas will be the most severely affected as most of the houses constructed there use a wooden frame, and use a clay brick construction which (opposed to high-rise, concrete structures) will dilapidate or otherwise decay quite rapidly.
Concrete constructions will withstand most natural forces inflicted upon them and, apart from losing their façade, will remain in place for many years.
Overgrowth by plant life will become a major factor present within a few years being unmaintained. In suburbia in particular where grass lawns and back gardens are common, overgrowth of flora will take hold extremely rapidly and will invade all homes in some form or another.

Looting

From the moment of the initial event to many years after, looting will be very common in and amongst urban areas.
Scavengers will occupy large portions of most of the metropolitan areas, looking for anything of possible use in some form or another.
They will be either independent individuals, or small groups meaning to sustain themselves by living in the abandoned urban regions, or they could come from established communities from outside the metropolitan areas looking for anything of use to return with. The latter would occur more so later after the population has stabilized, and will serve as more of acting on curiosity than anything else, as in “you never know what could be useful”
In the first days and perhaps weeks after the event looting will be rampant, as it has been in the case of any major social collapse and will be mostly opportunistic individuals taking advantage of a situation of chaos rather than people looking to sustain themselves.

Fire!

Due to a combined effect of degradation, the destructive migration of refugees through the suburbs and natural forces, fire will be a definite major force that will move through all regions of a metropolitan area.
Large office buildings, tower block as well as single family homes in the suburbs will be significantly affected.
Fire will not be contested, aside from natural elements, such as rain, in all major modern cities where they will spread through the metropolitan regions with devastating effect and no body to put them out
If the conditions are suitable, a large fire or fires will continue to burn through a city for months and could consume an entire metropolitan area.
Fire would inevitably drive out many millions of refugees who are still within the boundaries of the metro area, depending on the time it occurs after the event.

If it occurs early, within the first few weeks to a month then it could cause accelerated effects mentioned prior, starvation, exposure, de-hydration (maybe) and a new factor is introduced which is a reduction in the atmosphere quality, as large volumes of smoke and ash are expelled into the atmosphere, which can cause respiratory related deaths such as smoke inhalation, chemical poisoning or asthmatic responses.
If it occurs later, a couple of months or a year after the event, the amount of human effect will be far less, however, fire will drive large amounts of fauna out of the cities and into the surrounding countryside which could be a further catalyst in the spread of disease.

The introduction of smoke, chemical fumes, ash and other debris into the atmosphere will cause large scale degradation in the atmosphere of large regions.
Depending on the density of urban development in a particular region, and the extent of the spread of fire, a national or even global effect related to massive introduction of solid matter particles into the atmosphere.

The good example of the North American East Coast, which is almost entirely a large conurbation (or megalopolis), which will almost certainly be subjected to large extents of fire damage in some form or another and will, first of all, create an almost inhospitable region surrounding it extending inland where ash and soot will fall as rain or snow, and with it will be toxic materials introduced by the industrial elements of the region, as well as the combined effect of that of burning artificial substances such as plastics and the rubber of vehicle tires as well as the general infrastructure within buildings be it chemical or solid material.

Global climate could possibly be altered to the extent that a form of nuclear winter could occur, at least localized to nation regions. Such an effect can be compared to a volcanic eruption where, if large enough, such a large volume of material is expelled into the atmosphere that global climate shifts to an extent that an ice age can occur. The theorized nuclear winter works in much the same way, the only differing factor will be the fallout related to the radioactive material that is added to the equation
Vegetation and animal life in the areas downwind of a major fire, in a large city or conurbation, will be severely affected due to the harsh atmospheric conditions, actual effects will vary, however, the introduction of chemical or toxic aerosols will ultimately cause a noticeable decline in the densities of flora and fauna

Human settlement or just human populations in general will be affected in much the same way. Deaths will occur directly (chemical poisoning, respiratory issues etc.) as well as indirectly (disease from animal life fleeing the burning cities, the loss of plant and wild animal life could cause further loss of food and other material sources causing starvation

The consummation of much of the suburban regions, as well as the central high-density areas of a metropolis will remove much of the contaminants that were built-up due to a combined effect of the migration of population out of the urban areas, as well as the degradation and overall decay of infrastructure as well as remove almost all feral animal populations, that carried disease.

Wood-frame construction, which makes up much of the suburban development, when burnt will release nutrients into the local environment, most notably nitrogen into the ground which can support larger varieties of vegetation.

Reclamation

After human populations have migrated out of the urban areas, or even before hand in limited amounts, vegetation will begin its course in reclaiming the land that was built up on. The most obvious example of this is the overgrowing of household gardens and lawns which is an occurrence which can be observed in any form of human civilization today.
The extent of vegetative overgrowing will depend on the environment that is present, for instance if fire has swept through an urban area, then vegetation will expand in large varieties and in greater volumes that if it hasn’t due to the amounts of toxic material in varying forms present after utility infrastructure has stopped functioning. Also, as stated before, if fire has had an effect, nutrients will be expelled into the ground in various forms (the most important, at least initially, is nitrogen) allowing for increased amounts of growth.
In the event of a widespread reclaiming of land by vegetation, fauna will ultimately move to graze upon it. This will be a rather slow process however as there will only be isolated growth, in any sizable volume, spread around the region so large open grazing will not be possible.

Social Structure Shift

Communities

Most certainly, given some time after the event has occurred, communities will begin to develop amongst groups of persons that have, at the least, survived up to the point where the population of an area does not surpass the availability of resources grossly

At least initially, communities will be formed from groups of persons that have traveled in a group. If a group of refugees moved in a certain direction to a certain place then eventually, for no reason other than that they are in the same place together, they will cooperate for the conscious benefit of the rest of the group.
Groups formed from like ideas will not be present, and in most circumstances will not occur at all. Therefore there will be a marked difference in the formation of such communities, compared to that observable throughout history. The basis for this is the multi-cultural societies that occur throughout the western world where many different racial, cultural or political ideologies and beliefs will converge and in most cases, be forced to interact with varying outcomes.

An important note regarding inter-racial/cultural mixing in these kinds of communities is that there may be a marked difference in the proportion of ethnicities, cultures or political views. This stems from the segregated nature of western society, where different cultures and/or races will conglomerate in particular areas in an urban centre, which when the event occurs, will migrate as one. That is a largely Korean populated suburb will move in the same direction, following their cultural peers so the eventual community formed from that migratory group will be largely Korean in terms of culture and race, therefore Caucasians will be a minority.
It is not that communities will develop depending on the major cultural or racial (or political, if it is still relevant) beliefs, rather that the resulting community will develop according to the present circumstances, over time.

The extent of community development will occur at the end of a migratory route, rather than along it. For instance if a group were to head to a farm, or area of largely agricultural land use, in search of a food source, then once they have found or arrived at it then they will most likely settle there in some form or another, as there will be no, at least no better, place to go to and they would make the best of what they have there.
Communities will perhaps also form along the route, for varying reasons, however such a community will be originally formed from a small group of individuals that can be sustained on any source of food available locally, or that is brought with them. Such communities will likely acquire further sustenance from the ruins of the urban areas, which will be in easily reachable proximity.

If a community must scavenge for its sustenance then in all likelihood it will eventually end up scavenging on other communities as well. As a result “criminal” or bandit communities will develop

Communities in reachable distance from an urban center or outer metropolitan area could return to form a community within it after any fires have been or extinguished or the area becomes livable.