为什么我们需要大米?

Rice is low-fat and high in energy, and you can mix it with just about anything to make a wide variety of tasty nutritious dishes. Ask anyone from any country in the world to tell you their favourite rice recipe and you will get a wide selection, ranging from sushi in Japan to risottos in northern Italy.

Rice is closely connected to the culture of many societies. Hindu and Buddhist religions use rice as a religious offering. Burmese folklore uses rice as a central part of their creation story; the gods gave the first people of Burma rice seeds and directed them to Burma, where the rice would grow well. A Chinese proverb says that 'precious things are not pearls and jade but the five grains, of which rice is the finest.' Chinese myth tells how, after severe floods, there was nothing to eat and the people were starving. One day they saw a dog coming across the fields, and hanging onto the dog's tail were bunches of long yellow seeds. The seeds grew into rice and the people survived.

The origins of rice are uncertain, because rice has been grown for so many thousands of years. In several Asian languages, the words for food and rice, or for rice and agriculture, are the same, one of the facts that points to Asia as the origin of rice. It is certain, however, that rice cultivation is one of the most important developments in history, for rice has fed more people over a longer period of time than any other crop.

The demand for rice is growing steadily, with consumption stretching beyond the traditional rice growing areas in Asia. You can find rice fields in Europe, Latin America and Australia. However, Asia is still the biggest rice producer, accounting for 90% of the world's production and consumption of rice.

Rice is a staple food for many countries. In parts of Africa and Asia, many poorer urban families get over half their daily calories from rice. As the world population increases, can rice keep up? To meet growing demands, rice production has to be raised by at least 70% over the next three decades. The area devoted to rice cultivation cannot grow, so much international research is being done to find ways of growing rice on less land.

Rice needs a good water supply to grow. Water is wasted daily all over the world and estimates suggest that most Asian countries will have severe water problems by 2025. It takes 5000 litres of water to grow a kilo of rice, yet many rice growing areas in Asia and Africa are drought-prone. Scientists need to develop varieties of rice that can withstand sudden heavy rains and compete with weeds.

Worryingly, rice production is affected by global climate changes. Global warming is caused by toxic gas emissions in developed countries. The rise in global temperature cuts rice-growing time, and ultra violet light radiation from the sun reduces tolerance to disease. Methane gas, one of the culprits of global warming, is, ironically, a by-product of wet lowland rice cultivation. Methane-producing bacteria thrive in wet rice fields and the plants themselves send the gas into the atmosphere. Water management could reduce methane emissions, but practical methods that do not reduce rice yields still have to be found.

小编：大米脂肪含量低却具有高能量，而且它几乎可以和任意食材搭配制成多种营养美味的食物——从日本的寿司到意大利北部的意式菜饭。种植大米是人类历史上最重要的进步之一，比起其他任何一种庄稼，大米种植的时间更长，填饱了更多人的肚子。

如今，人类对于大米的需求也是日益增长。想要满足这一需求，在接下来的30年中，大米的产量必须提高至少七成。然而，想要提高大米的产量会遇到很多问题：①用于种植大米的土地不会增加；②种植大米需要足够的供水量，但是许多种植大米的国家都面临干旱；③全球变暖现状会影响到大米的产量。

有一天我们会不会无法再吃到喷香的米饭，那个时候我们又该吃什么呢？