I think it would be both (man-made or natural disaster)
I believe, from a population that is uniformly distributed through its habitat a biologist can infer that it has reached it's carrying capacity. Population distribution describes how the individuals are distributed, or spread through out their habitat. Population size and population measure are important measures of the population. When the population is uniformly distributed, it means that they are evenly spaced over the area they occupy, thus the individuals compete for a scarce environmental resources, such as water in a desert.
A stream rounds and smooths rocks into pebbles
They move to the opposite sides of the cell during anaphase
I'd say agriculture, though in more recent years you could argue for mining.