Someone poisoned our trees. Not all of them. Just the ones along the boundary of our native garden. We came back from holiday and found the trees on the edge covered with browning leaves — while everything around them was healthy and untouched. Two had already been struggling: one died back and resprouted from the roots, the other started growing an entirely new form, as if trying to find a different way of living. We had been watching them with a kind of cautious attention f

The first whisper came in 1974. Two chemists warned that a group of everyday chemicals was destroying the ozone layer. More than a decade later, the world finally acted. Nearly fifty years after that first warning, the hole in the sky is healing. Credit: “NASA Ozone Watch” At the time, though, nobody knew that was where the story was heading. Mario Molina and Sherwood Rowland had done the mathematics on what happens when chlorofluorocarbons — the chemicals in aerosol cans, re