Why is the Chinese government so concerned about food security?

China has the unenviable task of  feeding one-fifth of the world’s population with less than 10 per cent of the world’s arable land. In recent years, the country’s leadership has regarded food security as one of the key components of national security. So what has been done to fulfil President Xi Jinping’s order that  “the rice bowl of Chinese people should firmly be held in their own hands”?