Unstoppable crawl of giant land snail
One of the world's largest species of snail has descended on Florida.
The giant African land snail is considered one of the most destructive invasive species, feeding on more than 500 types of plant.
They can also eat through plaster walls, providing the calcium content needed for their shells.
Jon Ablett, curator of Mollusca at the Natural History Museum, says there is "no clear answer" on how to stop their expansion.
- From the section Science & Environment