NASHVILLE — The gift of springtime is the panoply of new life: gray buds breaking open into bright flowers, gray branches sprouting leaves in a thousand shades of green to make a bower of our common lives. In the treetops, birds throw back their heads to sing their full-throated, body-shuddering songs. An ordinary suburban yard becomes a carpet of wildflowers, each one visited by tiny, iridescent bees which seem to materialize overnight out of nothing but the mild springtime air.

But it’s not all flowers and bird song; springtime is also deadly. All the new mouths must be fed. The bluebirds in my nest box are catching those tiny bees for their four hungry nestlings. Somewhere in this yard a large rat snake is hunting, and I can’t be sure if the baffle I’ve mounted on the nest-box pole is large enough to keep the snake out. Even if it does, a house wren with murder on his mind is scooting around in the underbrush with a dagger of a beak, and he will kill those bluebird nestlings in an instant if their father isn’t vigilant enough to protect them.

I worry. Every year I worry about the bluebird babies, and every year I remind myself that house wrens and snakes have their own purposes for springtime, each as urgent as the bluebird’s. This is just the way the natural world works. Pay attention, and it will break your heart a dozen times before dinner.

Last week, the United Nations released the summary of an enormous report that broke my heart in more ways than any backyard-nature observations ever have. The Times article about the report, “Humans Are Speeding Extinction and Altering the Natural World at an ‘Unprecedented’ Pace,” called it “the most exhaustive look yet at the decline in biodiversity across the globe and the dangers that creates for human civilization.” The story opens with the picture of an olive ridley sea turtle washed up on an Indian beach. The turtle is dead, apparently strangled: Fishing rope is looped around its neck, cutting into its throat.