Planet Earth's nine lives: Our planet's limits
Land: not enough for everyone
Most of our planet is covered by the seas and oceans. Only about one third is land, and much of that is either desert or covered in ice. Think of Greenland and almost the entire continent of Antarctica. That doesn't leave a lot for all the land-living animals – including humans.
Before people started farming about 10,000 years ago, most of the land was either forest or grassland. Today, it's very different. Most of the forests have been cut down or burned to make space for growing crops or raising animals. Roads and cities take up yet more land. The animals that used to live there are now either extinct or in big trouble, because people need ever more land for food as numbers continue to increaseThere are now 7 billion humans and the figure increases by about 80 million every year. More humans want more resources and poor people, not surprisingly, want decent living standards like people already have in richer countries.
There's obviously a limit and the scientists reckon that humans can use at most about 15 per cent of land which isn't covered in iceIcy continentsLarge areas of land are still covered by thick ice sheets. I'm sure you know the two biggest? Antartica, a huge continent and Greenland which is a very large island. If all the ice on Greenland melted, sea levels around the world would rise by a whopping 8 metres; over 26 feet. Right now, people are farming around 12 per cent and this is still going upRainforestsMore tropical rainforests are still being cut down or burned to make way for cattle ranching, biofuel production and farming for food.. But people are clever and are getting better at growing more food on the same amount of land. This is because farmers and scientists have a better understanding of things like how to breedBreedingBreeding can be conventional in which plant breeders select the best crop plant or animal - like evolution speeded up. Or it can employ genetic engineering better food plants and animals (genetics), soil fertility, water needs and so on.