URBAN GROWTH, FARM EXPORTS DRIVE TROPICAL DEFORESTATION (ENVIRONMENTAL SCIENCE PROJECT TOPICS AND MATERIALS) CHAPTER ONE INTRODUCTION A big but so far unspecified chunk of the cash will go on programmes to prevent loss of tropical forests, which is a major source of greenhouse gases. Beyond 2012, tens of billions of dollars per year could be primed if a planned UN pact on curbing climate change comes to fruition. But environmental scientists publishing in the journal Nature Geoscience on Sunday cautioned