Gisele Bundchen dressed up for a good cause in NYC last night in order to attend the United Nations For the Environment Programme’s Champions of the Earth Awards at the American Museum of Natural History. She's a goodwill ambassador for the organization and shared the stage with luminaries like Mexican President Felipe Calderón. It was the supermodel's third night of philanthropy in less than a week, after she attended Friday's Global Environmental Citizen Awards and Monday's Robin Hood Gala. She had her husband, Tom Brady, and his hair on hand for the latter event, which raised $47 million to fight poverty. Gisele's latest evening of charity was to kick off a UN-sponsored challenge for World Environment Day, which is on June 5. She and actor Don Cheadle are challenging fans to see which star can get more people to help plant a new forest — check out the World Environment Day page to get involved.