school energy&environment

The agricultural ecosystem

A typical example of artificial ecosystem is a cultivated field or agro-ecosystem. This is a natural system altered by men through agricultural activity.

It’s different from a natural ecosystem for four main characteristics:

• simplification: a farmer favours a plant species removing all other animal or plant species which could damage it
• the energy intake employed by men in the form of machinery, fertilizers, pesticides, selected seeds, processings
• the biomass (harvest) which is removed when ripe. This makes the ecosystem an open system, which means it depends from external processes to reintroduce fertilizing substances suitable to nourish a new growth and development process of organic material (plants). A natural ecosystem, instead, self-fertilizes as the biomass remains in its original setting
• the introduction of pollutant substances which, in the case of intensive agriculture, are chemical fertilizers, antiparasitics and other chemical non biodegradable substances which accumulate in the ecosystem or which seep in the subsoil, in some cases getting to the point of seriously polluting groundwaters, seas and rivers.

A home is also a small artifical ecosystem. Objects, food, solar energy, water, etc. are introduced inside houses from outdoor and solid and liquid waste generated by human activities is removed outdoor. The city functions in the same way. A city, in fact, depends from external areas for water and food supplies as well as building materials and other resources necessary for its development and waste generated in a city is unloaded outside the urban area (in landfills and incinerators), which means everything which doesn’t contribute to the survival of the urban ecosystem is deposited in these areas.