Most of our planet's freshwater is stored as snow on mountain tops or in glaciers. However, with global warming most of this precious water is melting into the ocean.

This means that we may have more saltwater available to us than freshwater.

One such use of seawater besides desalinisation for drinking purposes is to use it as it is for seawater agriculture. The concept of seawater agriculture is best defined as growing salt-tolerant crops on land using sea water. In this week's article I will look more into this concept of farming and the pros and cons of implementing it.

Basically, seawater agriculture works by cutting channels, which allows the seawater to flow inland which reduces the rising sea level due to global warming.

This water is then used for aquaculture purposes like to grow fish, shrimp and shellfish. The waste water from these farms which are now rich in animal excrement containing nitrogen which in turn is good for plant growth is used to irrigate salt-tolerant crops. Containing this excrement is beneficial to marine ecosystems, because if allowed to flow back into the sea, the excrement rich water from coastal shrimp farms can cause algal blooms and diseases.

Usually plants are irrigated by freshwater in one form or another, for instance, using water from rivers, streams, lakes or by rainfall. In order to be taken seriously, seawater agriculture must fulfil two main criteria to be regarded as cost effective.

The first, being that pumping seawater inland is quite expensive, so that this type of agriculture must produce useful crops with quite a high yield. Secondly, the environment must not be harmed in the process.

The top five crops in the world; corn, wheat, rice soybeans and potatoes are all freshwater tolerant crops.

Therefore, this agriculture can take place via two routes, with some scientists trying to breed conventional crops like wheat and barley to tolerate salt rather than the other route, where crops that can naturally tolerate high levels of salinity, called halophytes, are selected. However, the first method has been met with very little success.

Some benefits of seawater agriculture include freeing up freshwater for human consumption and it does not need specialized equipment. The planting of crops also introduces more vegetation into the area, thereby aiding in the absorption of carbon dioxide.

Also, it will additionally increase the biodiversity of the area both in terms of plants and animals.

This is because as the varieties of plants increase so will the variety of animals, as there are more microhabitats and food sources available to them.

The increase in biodiversity will in turn also make the area more appealing for recreational purposes. Finally, seawater agriculture like other forms of agriculture will also provide jobs to persons in the area.

A disadvantage of seawater agriculture is that it requires frequent and regular irrigation to prevent salt build-up.

However, if the farm is located near to sea level it will require less energy than conventional farms where water needs to be pumped from wells up to 100 metres deep. Also by locating it in an area with sandy soil drainage back to the sea is not hindered.

However, like everything there is concern about how this type of agriculture will affect the environment. But what must be kept in mind is that the soils in this area are almost barren so that less biodiversity is affected as in a conventional agriculture system. Also, coastal and salt desert aquifers already contain elevated concentrations of salt so that entry of saltwater should not affect them further.

The tropics and sub-tropical regions present a particular problem. There is an approximately combined area of approximately 93 million hectares which are available for farming and housing.

However, most of it is also forest which contains biodiversity that needs to be preserved. So by using land – such as coastal and inland salt deserts, this type of farming can be used to feed the population and generate necessary income.

Some salt-tolerant plants that have been grown as crops include Salicornia sp (glass wort), Atriplex sp. (salt bush) and Suaeda sp (sea blite). In order to support these plants as crops, efforts have been made to determine if they can be used to support livestock.

Halophytes or salt-tolerant plants make good feed as they are high in protein and digestible carbohydrates.

Unfortunately they contain a large amount of salt which is their way of adjusting to a saline environment.

As a solution, halophytes are mixed in with the hay and fed to livestock which has worked and not affected the quality of the meat. Another promising halophyte species is the saltmarsh plant Salicornia biglovii which grows on mud flats. This species produces many seeds which are high in oil and protein but has a low salt content. After oil extraction, the seed meal can be used as chicken feed.

Therefore it can be seen that seawater agriculture is another alternative to help alleviate one of our approaching environmental problems – global warming. However, it requires more years of research in order to make it viable and applicable to suit our needs.