i want to write a research proposal on "Climatic stress on Forest Ecosystem Services affect GDP" The questions of the research are as follows: 1. What are the climatic stress that has effect on Forest Ecosystem Services? 2. What are the estimated tangible impacts (monetary value) of Climatic Stress on Forest Ecosystem Services? 3. How the GDP is affected (figuring out the fluctuations) by Climatic Stress on Forest Ecosystem Services? what economic method and tool i need use?