Wildfires are natural and often a necessary event of the ecosystem.
It helps in improving the quality of the soil in various ways:
It helps in clearing the thick underbrush growth and thus enables the sunlight to reach the forest floor which encourages the growth of native species.
It increases the fertility of the soil by increasing the mineral and nutrient contents of the soil. It does so by converting the dead plants and animals chemically into more available forms.
You take any of the "signs of change in populations of organisms and their environments". For imagine, Australopithecus (early man) turning to Homo sapiens. In that way they could tell that you took this journey.
