An ecosystem has been defined by the Convention of Biodiversity as a "dynamic complex of plant, animal and micro-organism communities and their non-living environment interacting as a functional unit". A variety of ecosystems have been identified, including aquatic, chaparral, coral reef, desert, marine, rainforest, savanna, and tundra, to name a few.
Agriculture, population growth and development of urban areas take many acres of land out of natural ecosystems. These human activities are referred to as anthropogenic effects. Anthropogenic activities place many different stresses on the ecosystem. For example, land is graded or regraded before an area is developed for a neighborhood; topsoil may be removed, or non-native soil brought in; soil is disturbed through digging for foundations, and heavy equipment is used throughout the construction process. Roads are developed, thus changing water run-off patterns that existed prior to development, causing disturbed and compacted soil. Paved areas for driveways, sidewalks and patios contribute further alterations to natural drainage patterns. The urban heat island effect occurs when a city is warmer than the surrounding countryside. Concrete and asphalt are major contributors, as they radiate a great deal of heat received during the day. A further factor is the lack of plants that would normally lose water through evapotranspiration and thus cool the air around them. This cooling effect of plants can be experienced by walking on grass barefoot in the summertime. The ground and grass are noticeably cooler than surrounding surfaces, including bare ground. Furthermore, breezes are hampered in areas with a lot of buildings, or even in backyards where plant screens, fences and walls exist.
For the homeowner, replacing the native ecosystem that existed prior to development, is impossible. It is probably safe to say that most homeowners are not aware of the natural ecosystem that existed before their area was developed. In many cases, immediately prior to home construction, the land was used for agricultural purposes. Of course, agricultural land use has already altered the land from its native state. Therefore, it is an unattainable goal for the homeowner to create an ecosystem. However, it is feasible for the homeowner to learn about the native system that existed before their land was developed, and to take steps to encourage as many components of an ecosystem as is feasible. The components include the living components: plants, animals, and micro-organisms as well as the non-living components: sun and shade, physical and chemical aspects of soil, precipitation and water. Temperature is another component of the ecosystem. Together, all the components form an interconnected web of life that, while impossible to replace in an urban setting, can be used as a model from which to pattern landscaping practices.
The homeowner has the most control over the types of plants to use, as well as encouraging wildlife through the use of plants and design. Micro-organisms can be encouraged through practices which contribute to healthy soil, including composting yard waste and using natural mulches such as wood bark or chips. If there is a natural water feature, such as a pond, lake, river, or stream, homeowners can use native plants that have evolved in these environments, and work to remove weedy or invasive plants.