Meet the microscopic worm that can kill forests. It’s called the pinewood nematode (Bursaphelenchus xylophilus) and though each one is barely a millimetre long, they can collectively bring down a towering pine tree.

Once it gets into a tree, the nematode spreads through the trunk, branches, and roots. It feeds on the cells lining the pine’s resin canals, causing resin to leak into other vessels that carry water around the tree. Cut off from their water supply, the pine’s needles turn yellow and brown. The change is dramatic. Within just a few months, the tree wilts and dies. This pine wilt disease has claimed millions of pines, especially in Europe and East Asia, causing huge problems for ecosystems