heres one; some phenomenon has caused all/most/some organic plant life to rapidly increase the rate at which the cells in the plant walls multiply or alternitively cell division at unpresedented rates, the problem goes relatively unnoticed by the political party's as it is breifly seen as the earth saveing the economy and used as a political standpoint for manny to claim responsibility of the new jobs. As a new massive influx of jobs is required to 'contain' the plantlife the problem quickly becomes out of hand as various territory's become damaged by the plant life penetrateing soil, concrete and causeing sections of wood to come undone. freshly paved streets become cracked with vines, within days they become green potholes, and within weeks grow trees and road blocks. areas that have known little plant life such as the foundations of buildings and roads enriched from the nutrients that havent been used for decades find new use in creating uncontainable weeds that slowly creep into the civilized society humans and their pets once called home. even the small potted plants in islands such as manhatten grow out of hand and cause humans to fight a loseing battle aginst nature before the water systems are damaged or destroyed, people with money manage to find transport for themselves and their pets, the poor however leave theirs to die as america (or whatever nation YOUR island your campaign comes from)quickly becomes aware that backpacking becomes there olny option, transportation becomes impossible with the masses of growth. the islands, forgotton as the govenment fights the plant life elsewhere become slowly evacuated as displaced refugees leave little by little, beginning with the intelligent and adventureus and ending with those whom convinced themselves that help would come.
the island of manhatten quickly becomes the homes and graveyard of the dieing pets of selfish owners and the broken fragile minded left to rot in a forest of green steel and breaking glass.
Elsewhere humanity strugles to feed or even find homes for the displaced of their neibors. those who can secure weapons do and quickly lead to a futile resourse war that ebbs the numbers from billions to a few thousand, with the survivors striveing to relearn the hunting skills of ancestors long, LONG since deceaced. however the survivers are not assured sruvival just yet, with high's of plant life comes the low's. the influx of plant life saps the minerals of most of the planets land masses, createing a varitable world wide dust bowl from the barren remains of our planet. the food chain is thrown into dissaray with the breif boon to animal life, herbivores know olny a mass of new food, predators know olny a larger supply of food, eventually food runs desprately low, entire herds starve to death and predators quickly become lone hunters as food becomes a new conciern as the lifeless land masses become the new hunting ground, in time the phenomenon passes, the world stands green and grey, almost taunting the remainer of humanity of the world they could have been born in if they had not lost to plants.
possible campaign ideas could include a scientist (or scientist player character) attempting to learn the secret of immortality which could turn out to be research into any number of lost knowlage which could even be the secret discovery of keeping humans alive for centuries if not forever. also- wow ivebeen typeing a responce for two hours?