Despite growing political support for the use of nature-based solutions in climate change mitigation, a number of concerns have been raised. These include: uncertainties about the scale of the contribution, especially given challenges with implementation and financing; doubts about whether the necessary safeguards will be put in place; and worries about the use of offsets by the private sector. This report will assess the current state of knowledge on the size of the contribution that nature-based solutions can make and the types of action they will involve. It will discuss the importance of social and environmental safeguards, how nature-based solutions can be financed and the role of offsets. Most importantly, it will consider the potential of nature-based solutions for mitigation to also contribute to climate adaptation and other pressing challenges.