当一个叫做世界农林中心的农业调查机构发现有一种树可以帮助非洲农民扩大粮食产量，它们介绍了一种全新且有价值的方法以克服长期困扰非洲的粮食危机。
When an agricultural research unit called the World Agroforestry Center discovered that a certain tree could help African farmers grow more food, they introduced a new and valuable approach to overcoming Africa's chronic food crisis.