How does ethanol effect forests?

I'm writing a speech on ethanol and I know that it has resulted in the clear cutting of forests because they need to make more room to grow corn but can anyone give me a statistic saying what percent of our world's forest will be destroyed if we continue making ethanol at this rate and I can only use it if there is a source so could you tell me a credible website, person, organization, or book that says so. thanks