Standing on a triangle of grass in East Palo Alto on Sunday, 2004 Nobel Peace Prize winner Wangari Maathai issued a challenge:

Everyone gathered in the park that sunny afternoon needed to plant trees.

Not just one or two trees, she said. Ten trees each. Minimum.

``I want to make sure there is a real campaign here in East Palo Alto,'' she said.

Maathai, the founder of a movement responsible for planting 30 million trees in Kenya and throughout Africa, spoke at the intersection of Newbridge Street and Bay Road at a new park named in her honor. Six trees, each chosen to honor a different culture, were recently planted on the grassy strip, and Maathai grabbed a shovel Sunday to finish planting the last of them, an African olive tree.

Maathai, 66, the first African woman to win the Nobel Peace Prize, founded the Green Belt Movement in 1977 to address problems caused by deforestation in Kenya and to create a source of income for the women who planted and cared for the trees. The movement has been credited with raising awareness of environmental conservation worldwide, providing income through the sale of firewood and fruit, and improving the productivity of Kenya's farming soil.

She spoke in East Palo Alto at the invitation of Canopy, a Palo Alto-based environmental organization that recently received a $142,000 grant from the California Department of Forestry and Fire Protection to purchase, plant and care for more than 600 trees in East Palo Alto.

``As soon as I heard she had received the Nobel Peace Prize, I thought, `This is outstanding,' '' Canopy Executive Director Catherine Martineau said. ``It's such an honor to be bestowed on someone who plants trees. It elevates what we do to something universal.''

Funds raised at a Sunday evening benefit dinner in honor of Canopy's 10th anniversary, which featured Maathai as the keynote speaker, will go toward buying additional trees for East Palo Alto. The goal is to plant 1,000 trees by 2010, program director Jana Dilley said.

``It's a cooperation between Palo Alto and East Palo Alto, between the city and Canopy, neighbors across San Francisquito Creek,'' East Palo Alto Mayor Ruben Abrica said.

The Canopy initiative is at least the second concentrated tree planting effort in East Palo Alto's history. A decade ago, the East Palo Alto Historical and Agricultural Society planted about 700 trees, three quarters of which are still thriving, board chairwoman Maisha Mouton said.

In her speech to the approximately 300 people gathered at the new Wangari Maathai Grove, Maathai advocated doing even more. She urged each person to plant 10 trees, both to reduce the environmental impact of their own carbon dioxide and to create more gathering spaces and ties within and between communities.

``The reason we picked a tree in our campaign is it's a very visible symbol of what can happen in the environment, what can happen to our resources, if we take care of them,'' Maathai said.

Ajayi Lawrence, who grew up in East Palo Alto and is now a junior at Amherst College, said it was inspiring for city residents to hear how one woman's vision came to change her home country.

``It's so important for our city to have someone that powerful and that well known give us the nod,'' Lawrence said.

Maathai asked people to take the initiative for planting their own trees, rather than waiting for the government or someone else to take charge. Many people left the gathering with tiny red maple saplings and directions on how to care for the young trees. Others vowed to plant a tree soon.

``I think that resonated,'' said Meda Okelo, East Palo Alto's director of community services. ``We think the East Palo Alto trees initiative, with the goal of planting 1,000 trees, is significant. But hopefully what comes out of it is that people say 1,000 trees is not sufficient.''