school energy&environment

Biomes

Ecosystems are everywhere: a wood, a lake, a river, a lawn, a beach, the sea, even the green areas of our towns. Briefly, every centimetre of our planet is or belongs to an ecosystem. Ecosystems can markedly vary in size. The temperate forest that covers most of North America, Europe and Northern Asia, and the cavity filled with water and life of a beech from the same forest are both considered as ecosystems (in this case, a “micro-ecosystem”).
The Earth itself may be regarded as one big ecosystem. The division into smaller and more neatly defined ecosystems is necessary for target studies, but in fact the limits of ecosystems normally blur into each other and many organisms may be part of different ecosystems at different times. For instance, freshwater becomes brackish water near the coast, so the sea ecosystem and the freshwater ecosystem are connected to each other by energy and food flows. The boundaries of an ecosystem may also vary in time, due to a number of disrupting factors, such as the disappearance of a species, man’s work, the introduction of exotic species in an ecosystem and others. In ideal conditions, areas having consistent physical and chemical characteristics should have well-defined and easily recognisable ecosystems. But such consistent conditions cannot be found in nature. Especially in the case of terrestrial ecosystems, it is easier to identify associations of ecosystems. In particular, closely related ecosystems that share the same biogeochemical cycles and have similar abiotic components are called “biomes”. Terrestrial ecosystems can therefore be grouped into many biomes.