Bees are in big trouble. Their populations are declining rapidly all over the world and if they vanish entirely agriculture is going to suffer. The reason is down to pollination. Many plants depend upon bees to carry pollen from one plant to another. This allows the plants to sexually reproduce and is essential to maintaining genetic diversity. If bees perish, plant sexual reproduction will grind to a halt. For this reason, ecologists are working very hard at keeping bees around but, just in case they fail, engineers have their backs with drones that can pollinate plants in the absence of insects. You can listen to the full story on The Economist's science podcast Babbage here.