For animals in Mozambique's Gorongosa National Park, the normal balance of competition and predation was upended when a war wiped out the top predators. The remaining animals didn't simply grow in numbers—they began behaving in unusual ways, veering outside their typical territories and feeding patterns. Could it be that it's not just predators' kills that keep other populations in check, but also the fear they inspire? NOVA joins a team of scientists as they reintroduce wild dogs to Gorongosa to find out if restoring the park's "landscape of fear" can restore balance to an entire ecosystem.

As global temperatures continue to rise, scientists are wondering if we need solutions beyond reducing emissions. Enter geoengineering. From sucking carbon straight out of the air to physically blocking out sunlight, the options may seem far-fetched. But as time runs out on conventional solutions to climate change, scientists are asking the hard questions: Can geoengineering really work? How much would it cost? And what are the risks of engineering Earth's climate?