When food prices rise, children in the poorest parts of the world suffer first and most. Many die quickly because the staples their families rely on – grain, wheat, rice – are no longer affordable. And many more are priced out of a nutritious diet, stunting their development and weakening their bodies and brains. This type of chronic malnutrition is the underlying cause of one-third of all child deaths.

A combination of global trends – climate change, rising food prices, economic uncertainty, and population growth – means this problem will get worse unless something is done. The last global economic crisis, combined with record high food prices, plunged a further 100 million people into poverty, and meant a nutritious diet became unaffordable for many.

Last year in East Africa, early warning systems alerted the world to an impending food crisis, but governments and others failed to act fast enough and thousands of children died who need not have. Now, in Niger, a similar crisis is brewing. Rains have failed, crops have been wiped out and families are struggling to buy the food they need to survive. The main problem here is not lack of food, but high prices. Families are already cutting meals or selling livestock to pay for food, and it's set to get worse.

There is still time to prevent a repeat of last year. Some donors – including the UK and EU – have already stepped up, but others need to follow their lead. Save the Children is already scaling up cash transfer schemes, and health and feeding programmes. But much more money is needed if we are to prevent the crisis becoming a catastrophe. In the longer term, the solution goes beyond emergency responses. It's about investing in agriculture and implementing policies that promote food security and improved nutrition. That will require political will from leaders of the G8 and the G20 this summer. They must put nutrition at the top of the agenda, or we'll once again count the cost in children's lives.

Bernard Aryeetey is head of government relations at Save the Children