Everyone alive today is witnessing a mass extinction event caused by the more than eight billion humans who share this planet. At times, it seems there is little hope. Climate change, resource exploitation, agrochemicals, overfishing, plastics, dead zones in our oceans, drought and desertification, conversion of habitat to housing, farming, and industrial infrastructure—the list of impacts and insults goes on and on. We are, it seems, on an unalterable path that will continue to decimate biodiversity.

A feeling of hopeless, while not unwarranted, is part of the problem. Without hope, without some belief in the possibility of positive outcomes, the fight for nature is over. Why even try if the battle is already lost?

While staring the problems squarely in the face, A Sea Full of Turtles offers hope for those who care about our living world. Delivered as a travel narrative set in Mexico's Gulf of California (Sea of Cortez), at one level the book focuses on dramatically underfunded but highly successful efforts to protect sea turtles. But the book goes beyond Mexico and beyond sea turtles to look at how some humans have changed their relationship with nature—and how that change can one day end the extinction crisis.

Enchanting, galvanizing, and brimming with joy and wonder, A Sea Full of Turtles will inspire immediate action to face the great challenges that lie ahead. Pessimism is the lazy way out. Optimism, it turns out, is both a reasonable and an essential attitude for us all as we fight for the beautiful diversity of life on our Earth.