Terrariums are self sustaining mini-ecosystems. Once they have been built than can essentially be “forgotten about” and will continue to grow and exist without further interaction from the user, save for the occasional check up or cleaning. Ideally, a closed terrarium doesn't need to be opened. Open terrariums do exist, and may require more care – but the plants selected for such environments (such as cacti) do not require frequent interaction.

They work on the principle of recycling water constantly. the water in the system does not leave, allowing for "rain" in the form of condensation. Water in the soil travels through the roots  into the plat. the plant "perspires" releasing water into the air. The evaporated water from the leaves and soil forms condensation on the walls of the terrarium and drips back into the soil starting the process over. Their may be a way to use the principles of the water cycle to create a sustainable agriculture solution that minimizes the amount of water that needs to be added.

Green Houses borrow some properties from terrariums; they are a closed environment that sustains a specific ecosystem / temperature/ moisture level etc. However, they are designed to allow the user to enter the system frequently to care for the plants or retrieve items.

Another simple idea I have is terrariums as a teaching tool. A small scale terrarium could be easily created from a water bottle, earth (soil), and gravel. Charcoal is available in Longido and is often a layer used in terrariums, but is not necessary for the terrarium to work.  These layers could be placed in a plastic bottle, a seed planted inside, and then sealed. Through this process children could learn about the water cycle and how to grow their own plants.

There is also a possibility to use this process to allow people to begin the growth of a plant in a terrarium then replant it in a garden to allow it to grow further for agricultural purposes.