Zac boosts his immune system in the Amazon rainforest before climbing a tree, exploring ayahuasca tourism and watching his dinner wriggle on a plate.

After a beekeeping stop on a New York City rooftop, Zac checks out London's pollution-reduction efforts, from wall gardening to trash collecting.

In the devastating wake of Hurricane Maria, Zac explores sustainability in the region, where he meets chef José Andrés, milks a goat and eats ceviche.

Following a crash course in apple growing, Zac and Darin head to Peru to delve into potato cryopreservation, biopiracy and the sport of sandboarding.

On an island that boasts a notable number of centenarians, Zac rethinks his view on nutrition as he ponders how the locals live such long, healthy lives.

Zac and Darin try out life at a swanky eco-village committed to a small environmental footprint, visit a wildlife refuge and enjoy a zip lining trip.

Before heading to Paris to learn about its tap water system, Zac joins pal Anna Kendrick for a lesson in H20, courtesy of a water sommelier in LA.

In between getting an up-close look at Iceland's renewable energy efforts, Zac soaks in a spa with Darin, samples reindeer and views natural wonders.