I just got pointed to this by a friend.
Why has aquaponics not been considered?
It seems that the impediments to agriculture on said island is restricted by soil conditions (fertility, erosion, availability), potable water availability, and low available space.
Aquaponics is capable of producing steady streams of fish (aquaculture) coupled with year-round, high-yield, produce, using (about) 90% less water, with no fertilizers.
The main input is fish food, which done commercially is not cost effective, nor sustainable. The key would be closing the cycle. You need to take agricultural inputs such as human/animal waste, biomass, and food waste. WIth these you can use vermiculture to create an enrichening compost, as well as very beneficial worms which can be used as fish food (and soil enrichment).
So vermiculture on a large scale (worms, black soldier fly, etc), duckweed (a small, water-based, nutritional plant for animals), and maybe a few odd inputs I haven't conceived of, and you have a sustainable system.
Additionally, on the subject of plant life, sewage processing can be done using specialized batteries of plants that can filter black water. Considering that we can partially close the water stream, all that's left is to implement a desalination facility. This is a lot more dependent on energy than plant life, however. Just thought I should mention it.
Total loses from a well made aquaponics system are variable, but somewhere in the range of 1-5% of total water volume.
18.104.22.168 01:10, September 8, 2014 (UTC) Vince