Life

World plants

The main factors that affect the spreading of a vegetal species are climatic conditions (especially sun exposure, temperature and availability of water) and the characteristics of the soil. The impact of the other living organisms that inhabit the same ecosystem (herbivores, insects, other vegetal species, etc.) should not be underestimated either. But an analysis of the factors above is not sufficient to account for all the reasons why a species inhabits a given place and not another, similar one. A species can actually spread in a given place just because of an occasional event: for instance, many Arctic species that grow in the Alps arrived there during the glaciations, when all Europe offered them favourable climatic conditions. As the glaciers withdrew, they disappeared everywhere but on the mountain tops, where they still found favourable living conditions. In other cases, the chance factor is man, who, through migrations and trade, has promoted the spreading of numerous species away from their places of origin.