Striding the last kilometres of his 644 km walk from north-west Uganda, Gerima Mustafa emerged out of the rain like a dream. The ex-teacher now campaigning to save the shea tree was greeted by ululations at the gates of World Agroforestry and Karura Forest in Gigiri. Senior staff of the UN Environment Programme also joined in.

He was greeted by Tony Simons, Director General of the World Agroforestry Centre, and Dr Musonda Mumba, head of the Global Decade on Ecosystem Restoration.

Gerima describes himself as an environmental walker, using walking to raise awareness. The shea tree is a vital source of cooking, skin cream, medicine and fruit in northern Uganda. Despite many attempts including bye-laws to protect it, the indigenous tree is dense, burns slowly, and so is being aggressively cut for charcoal.

In Kenya, shea is best known under its Sudanese name ‘lulu’ and is sold in supermarkets. Its butter is used for traditional cooking, can be blended into a mosquito repellent, or made into a sunscreen for albinos. It has become popular in beauty products across the world over the last ten years.

The shea tree, vitellaria paradoxa, starts bearing fruit after it is 10 years old and then produces nuts for up to 200 years. It grows in the dry belt across Africa from Somalia to Senegal.

Women tend to harvest the shea nuts but it is young men who burn it for charcoal. Gerima wants to raise US$650,000 for a massive shea tree planting campaign in Uganda and Sudan.

"Shea is very important. I am worried about its extinction," said Gerima as he greeted the crowd. "We had white rhino in our place. But people did not pay attention to it and now white rhinos are not there anymore. We do not need to lose these things."

Gerima relied on the kindness of strangers on his epic march. He was never mugged. While in Nairobi, he attended Wangari Maathai Day on and will meet teams at the UN.

"I am just a message," said the environmental activist as he called for action on the tree. "It will be an ecological disaster if it goes extinct."