What is the author's tone in Last Chance to See by Douglas Adams?

Last Chance to See deals with a subject of deadly seriousness—the extinction of animal and plant species. Co-author Mark Carwardine, a trained zoologist with the World Wildlife Fund, writes in his Epilogue that every species matters because each is an integral part of its environment; one extinction can cause a series of others. Humans are affected as their sources of food, life-saving drugs, and industrial processes disappear. Nature has considerable resilience but no one knows what the limits are. Without these species, "the world would be a poorer, darker, and lonelier place."