This is an optional lecture and not a requirement of the course. In this unit, you learned that scarce resources underlie every economic decision that is made in society. You also learned that because of these scarce resources, there are trade-offs between alternate choices. In this guest lecture, Bjorn Lomborg advances this idea by discussing some pressing issues that need to be addressed. This talk should help you to identify the economic way of thinking, which will be elaborated upon in the next subunit.