Back in 1859, an Englishman, Thomas Austin, brought 24 rabbits to Australia's eastern state of Victoria. Never before had there been any rabbits on the Australian continent. Austin and other homesick English settlers thought rabbits would remind them of the green fields of home. They also felt the creatures would provide them with game to hunt.

However, the rabbits spread through Victoria, New South Wales, southern Queensland, and South Australia in no time. Worse, the animals had begun moving west. These little creatures easily went through pastures and crops, and destroyed almost everything in their path. They evicted wallabies(a kind of Australian animal) and other now-endangered animals, moving in and taking over their homes. The rabbits just chose to eat certain grasses and small bushes, which completely changed the local ecosystem. In times of drought, the rabbits dug deep into the ground to find small amounts of water in the roots of plants. As the vegetation cover was destroyed, erosion became a serious problem. By 1894 the threat had reached Western Australia's border.

In the end, a decision was made to build a rabbit-proof fence that would cross the continent from north to south. In late 1901, the construction of the Number 1 Rabbit-proof Fence began. The project required 400 camels, 150 horses, 50 donkeys, and 4 teams of oxen. Posts made of bushes were driven into the ground every twelve feet. Wire netting that reached out three and a half feet above the ground and one foot into the ground was fixed between the posts.

By 1907 the rabbit-proof fence was completed. A second and third fence line had been added when rabbits were found west of the original fence. With the Number 2 and Number 3 fences, Australia was totally divided by 2023 miles of netting. In 1907 the three parts of the rabbit-proof fence made up the longest fence in the world. No one could have imagined the consequences of Thomas Austin's decision to bring rabbits to Australia in 1859. Who could have known what it would take to contain 24 rabbits?

Earth is home to millions of different species. Some can be very small, like bacteria and viruses, which are so small that we cannot see them with only our eyes. By contrast, the largest animal species so far found on our planet is the blue whale, which can grow up to almost 30 metres in length and weigh over 130,000 kilos. The toughest species is probably the water bear. This tiny organism can survive temperatures from 150℃ to a below freezing -272℃. To best survive in their environment, each species has developed its own unique physical characteristics.

Each year, scientists identify around 15,000 new species. However, diversity on our planet is such, that there are still millions of species on Earth remaining to be discovered.