Forest canopies not only support high terrestrial biodiversity but also represent a critical interface between the atmosphere and the earth. They provide goods and services to support diverse human communities and offer opportunities to explore sustainable use of resources for many generations of local livelihoods. Forest canopies are important carbon sequestration units and serve as climate control for the planet. Canopies are important energy production centers for the planet and serve as the basis for many food chains. The canopy can also act as a hook for education outreach and conservation, inspiring ecotourism through recreation and other sustainable uses such as treetop walks, zip lines, and birding. Despite these critical services provided by forest canopies, almost no dedicated research in the treetops was initiated until the late 1970s, when single rope techniques were developed by mountaineering professionals and adapted for use in the canopy. An array of canopy access tools was designed in the 1980s and early 1990s that have opened up this "8th continent" for global exploration and discovery. This volume uses the major findings of the 5th international Canopy Conference as a platform for organization, but does not mimic the sessions and presentations of the conference. Instead, it builds on important themes that emerged from the conference and solicits articles that represent future priorities and advancements for canopy science in the next decade. Despite conservation efforts over the past 3 decades, forests are degrading at an accelerated rate, and biodiversity is increasingly threatened by human activities. This volume summarizes the issue of "treetops at risk" and assembles a global authorship to examine past accomplishments and future initiatives critical in forest conservation.