6. Read the paper “The Value of the World’s Ecosystem Services and Natural Capital” by Robert Costanza and his colleagues at www.uvm.edu/giee/

publications/Nature_Paper.pdf. Write a half-page summary of what Costanza et al. (1997) mean by natural capital, and describe several real-world examples of how the stock of natural capital generates an economically valuable flow of ecological goods and/or services to people.