OAXACA, Mexico, March 31 - Starbucks, the world's largest specialty coffee company, is deluged with requests for coffee that tastes good but is also good for the cause. Thousands of customers emand shade-grown coffee, cultivated in forests that are sanctuary to threatened wildlife. Some want organic coffee, grown without chemical. Others request fair-trade coffee, produced witout exploiting peasants on coffee plantations. Satisfying such consumers is lucrative business. Sales at Starbucks and other gourmet coffee merchadisers have been exploding and represent a fifth of the $10-billion-a-year American coffee market. But there are challenges. Who will certify that coffee is really bird-friendly or fair to farmers? And how do coffee sellers avoid a dizzying array of environmental labels? At a meeting in this provincial Mexican coffee capital this week, industry experts for the first time decided to impose order in the chaotic world of concerned coffee. Convened by the three-nation environmental agency set up under the North American Free Trade Agreement, 100 representatives of coffee roasters and importers, environmental and other groups agreed to work toward harmonizing criteria to certify specialty coffee producers. The effort could eventually bring a single label, perhaps "sustainable coffee", that would assure the consumer the beans have been produced under conditions good for health, the environment and workers. "There can be label fatigue," said Sue Mecklenburg, the Starbucks environmental affairs director, who was at the meeting. "If you pop up with a new cause each month, it's difficult for the consumer to absorb." The meeting here focused on shade-grown coffee, an environmental favorite in recent years as scientists have realized the ecological role played by the forest canopy that blankets many coffee farms. In Mexico, where most coffee is shade-grown, forests associated with coffee plantations shelter nearly 500 species of birds and mammals. Sweeping ecological devastation has been cause by farmers who have cleared vast forests to plant higher-producing hybrid coffee plants that flourish in the open sun. Environmental organizations expressed alarm about this during the 1990's, after scientists reported that the number of birds crossing the Gulf of Mexico had decreased by half in two decades. Those concerns created a market for shade-grown coffee, but how to define it, and how to certify it? Managers of Green Mountain Coffee Roasters, a company based in Waterbury, VT, with sales of $65 million in 1999, faced these questions a few years back when they offered environmentally friendly coffee to convenience stores and supermarkets. Green Mountain found there was no international system to certify whether coffees were produced under shade or with fair labor. Organic producers, by contrast, have developed broadly recognized criteria, including nonchemical production and natural pest control, that allow several international organizations to certify their coffee. So Green Mountain bought organic, and several of its brands are now big hits. In October, more than 300 Exxon Mobile convenience stores featured Green Mountain's Organic Peruvian Select coffee, and it became Exxon Mobile's most successful nationwide "Coffee of the Month" promotion to date, said Rick Peyser, a Green Mountain executive who attended the Oaxaca conference. Starbucks adopted a different strategy after a conference sponsored by the Smithsonian Migratory Bird Center prompted thousands of customers to request shade-grown coffee. After finding that no organization could certify shade-grown status, Starbucks joined with Conservation International in 1998 to help coffee growers in Mexico's southern state of Chiapas market their crop. The project produced only two shipping container of "Shade-Grown Mexico" coffee. But it was so popular the company hopes to offer a larger batch this summer. If coffee merchants face a marketing challenge, many other American companies face similar confusion with environmental labeling; at least 25 labels, covering 310 products, are competing for consumers' attention. Canada, by contrast, has developed one green label, Environmental Choice. The government has contracted its operation to an Ottawa company, TerraChoice Inc. Last year, Merchants of Green Coffee, a small Canadian company, asked TerraChoice to certify its brands with the widely recognized Environmental Choice label. Studying the competing claims made for shade-grown, organic, bird-friendly, sustainable, and fair-trade coffee, John Polak, TerraChoice's president, found that it took five typewritten pages just to list all the criteria. Nonetheless, he was able to devise a simplified list that harmonizes them, and now Merchants of Green Coffee can label its product Environmental Choice. Mr. Polak's presentation was loudly applauded at the Oaxaca meeting, an indication that participants will aim for similar results.