The City of Paris, in partnership with ONFI (the International wing of the National Forestry Office) and AIMF (the Association Internationale des Mairies Francophones) is putting in place a project called "One Parisian, One Tree". The objective is to fight against climate change, to help preserve biodiversity, and to help in the economic and social well-being of French-speaking developing countries by planting 2000 hectares of trees.
With the adoption of a Plan Climat in 2007 and a vast program to decrease and control energy consumption in public equipment, the City of Paris set up a voluntary policy to reduce greenhouse gases. At the same time they wanted to give responsibility to and mobilise Parisians round a project which will reduce greenhouse gases for the whole planet.
People are invited to donate money to finance the first two projects in Cameroon and Madagascar. A third phase will take place in Haiti. Each tree is expected to cost between 3 and 6 euros, depending on the species, and the date and place of planting.
There is a great deal of information on the project website, all in French. You have to scroll through the text by hovering over the little green arrows on the seedling towards the right hand side. The design is a little odd (it took me a moment or two to spot the seedling scrollbar) but there is a great deal of interesting information.