The concept of an ecosystem comes from the science of ecology, which studies the underlying principles and interactions of organisms and their environment, including the movement of energy and matter through the system. Analysis and management of the natural environment with an ecosystem perspective should ideally include a basic understanding of the functioning of ecosystems.
The functioning of ecosystems at all scales involves the three core processes of solar energy flow, mineral cycling and water cycling. Almost all ecosystems are powered by energy captured by plants from the Sun via photosynthesis. This energy then flows through food webs to herbivores and on to carnivores or omnivores and to decomposers, with the amount of energy decreasing at each level. Minerals such as carbon and nitrogen are cycled to and from the physical environment by living organisms, with the amounts and rates of cycling depending on the composition and structure of the ecosystem, such as food web complexity. Similarly, water is essential for life and is cycled through living organisms and ecosystems. Change in the functioning of any one of these core ecosystem processes also means change in the functioning of the others, as they are inter-linked aspects of the same system.
A fourth intrinsic ecosystem process could be called ecological succession, as the living organisms and their interactions in ecosystems capture and store the Sun’s energy and increase in structural complexity, diversity and biomass. An example in the UK is the potential for development over a few decades of a woodland on an area of bare soil. Some scientists call this process the self-organising capacity of ecosystems.
As humans are part of ecosystems we depend on the capture and conversion of the Sun’s energy by plants into food, as well as for useful products such as timber, fibres and medicines. We of course also harvest and manage animals for food and other benefits. In some ways, human activities such as farming, forestry and aquaculture can be seen as alteration of ecosystem structure and functioning to maximise the ecosystem processes of solar energy flow and local mineral and water cycles for desired human benefits.