Situation: Vintners now use plastic corks in more than 5 percent of their bottles, which may be a surprising impact of wildlife. Cork oaks are grown on more than three million acres in Spain and Portugal. For centuries the trees have been tended by cork farmers, who harvest the bark about every nine years. Many different species of wildlife have flouished among the trees. Now conservationsists worry that more use of plastic may depress the cork market, forcing cork farmers to turn to other crops that are more distruptive to wildlife.