UNEP Billion Tree Campaign, at www.unep.org/billiontreecampaign, viewed 12 October 2007; «Mexico Celebrates Día del
Arbol with a Commitment to Plant 250 Million Trees,» at www.unep.org/billiontreecampaign/CampaignNews, viewed 26 October 2007; Ethiopia pledge from Daniel Wallis, «
UN Wins Pledges to Plant a Billion Trees,» Reuters, 22 May 2007; Senegal pledge from «Global Tree Planting Campaign Puts Down a Billion Roots on International Biological Diversity Day,» at www.unep.org/Documents.Multilingual, viewed 12 October 2007.