Rare crops found in the Pacific islands and former British colonies should be grown in much larger quantities to help the world avoid food shortages, a leading expert on plants has warned.

Professor Stephen Hopper, director of the Royal Botanical Gardens at Kew in London, said people needed to start eating rare crops like breadfruit, cowpea and Bambara groundnut.

He said cultivating species such as breadfruit, grown on trees native to the South Pacific islands, and bulrush, whose roots were a popular carbohydrate among indigenous Australian aborigines, could also help preserve biodiversity.

He argued that the world was too reliant on a handful of key species of edible plants for food, warning that the combined threat of disease, climate change and lack of diversity in commercial crops had left the dozen staple species that provide the bulk of the global food supply - such as wheat, maize and barley - increasingly vulnerable.

Professor Hopper predicted that crops such as breadfruit, a fruit grown in British colonies in the 18th century as a cheap foodstuff for slaves, Barbados cherries, Bambara groundnuts, cowpeas and pigeon peas were among the crops that had potential to become future staples.

"Famine has become an ever more frequent condition facing the world, particularly in heavily populated but marginal desertifying lands most susceptible to global warming.

"Food shortages are inevitable in such circumstances and will be exacerbated as the human population increases globally.

"The world is currently fed primarily from just a dozen species - around 80 per cent of the world's food comes from those few plants used in commercial agriculture. Yet there are more than 30,000 edible plants known on the planet, so it is baffling we are so reliant on so few species.

"Diversifying the range of crop species is a sensible approach and could ensure food is available from alternative crops should staples fail in any given season."

Professor Hopper spoke out after giving a speech about biodiversity to business and government officials at the 2009 Sustainability Summit organised by the Economist magazine in London in February.

He said industrialised agriculture mass produced crops such as wheat, rice, maize, barley, oats and potatoes, which were the main staple forms of food around the world, at the expense of other types of plants that were cleared to make way for these crops.

As global temperatures increase, many areas that grow these crops will become unable to sustain them. Low genetic diversity in these staple food crops through generations of breeding has left them vulnerable to disease and pests.

The International Panel on Climate Change has warned food shortages will become far more common over the next 20 years.

Breadfruit: starch-rich, grapefruit-sized fruit that grows on South Pacific islands. Can be roasted, baked, fried or boiled and when cooked, tastes similar to fresh baked bread.

Bambara groundnut: Pulse from West Africa with seeds rich in protein and the essential amino acid methionine at levels higher than most other legumes. A traditional food source in parts of Africa which can be eaten fresh or boiled after drying.

Barbados cherry: Also known as wild crapemyrtle. The fruit from a thorny shrub is bright red, contains up to three hard seeds and has a sweet and sour flavour. High in vitamin C.

Amaranth: Another traditional food in Africa. It contains up to 30 per cent more protein than other cereals plus other nutrients such as vitamin A and C.

Pigeon peas: Small bean that can be eaten as a fresh vegetable or dried and used to produce flour.

Cowpea: A nutty pulse and excellent source of protein which is related to the black-eyed pea.

Tamarind: A multipurpose tropical fruit tree well known as a spice. The hard green pulp of young fruit can be eaten as a savoury or as a snack when ripe.