New York City is a world capital in every sense of the word—it's a cultural and economic powerhouse, and arguably the most influential city on the planet. But it wasn't always this way, as the following cities once dominated the world around them.
In the flood lands of the Niger delta people have been building houses and other structures with clay for centuries. The town of DjenneDjenno is made entirely out of clay. It was inhabited as far back as 250 BC, and became an important link in the transSaharan gold trade(跨撒哈拉黄金交易). Constructed on hills called " toguere", the city managed to escape the marshy(沼泽 ) landscape and annual floods produced by the rainy season. DjenneDjenno is believed to be one of the earliest settlements in the subSaharan region, and is considered by some to be "the typical African City".
Archeological evidence shows us a continuous human presence in the area up until the 14th century AD, when people moved to the nearby town of Djenne, founded in the 11th century. Further evidence points out that even before the city's construction, the Bozo people were growing wild rice in the region. In the 13th century AD, with King Koumboro's conversion to Islam, its palace transformed into a mosque.
Legend has it that Carthage was founded by Queen Dido of the Phoenicians. She fled the city of Tyre located in presentday Lebanon in order to escape the hatred of her brother Pygmalion, who was her rival to the throne. Along with a group of settlers, she traveled a great distance by sea and landed in North Africa, where she met King Iarbas. He offered to give them land in order to build a settlement, but no bigger than the surface covered by the hide(牛皮) of an ox. They cleverly cut the hide into thin strips and were able to enclose a fairly large area of land. On this land, the mighty city of Carthage was built.
These stories are most likely just that, but the fact that the Phoenicians built the city around 760 BC is true. Located in such a good position—in the middle of the Mediterranean, close to Sicily, Sardinia and Corsica, and a pretty good distance from Egypt—helped make Carthage a leading trade center and military power. The population soon reached half a million citizens and, in order to house them all, buildings were all built five or six stories tall. Carthage was the first city in ancient times to have a centralized sewage system, linking all buildings within the city walls. The most notable of structures among the ruins was the " Thophet", which is believed to be an altar(圣坛) for child sacrifice.
Tenochtitlan was the capital city of the Aztec Empire. It was built on an island surrounded by Lake Texcoco deep inside the jungles of Central America. By the time the Spanish conquerors were aware of its existence, the population was around 200，000. This was a city very different from what the Europeans were used to. Founded in 1325 AD, the Aztec capital was joined to the mainland by three causeways(堤道). It was laid out in straight street grids and had enormous pyramids at its center, which were surrounded by the skulls of the dead and ceremonial sculptures.
You know those nutrition guidelines the government issues every few years? It turns out that following them isn't just good for your health. It's good for the planet, too.
" What we found is that impacts vary across nations, but in the highimpact nations, in general, you can see that, if you follow a nationally recommended diet, despite the fact that these diets don't mention explicitly—or most of them don't explicitly mention—environmental impacts, that you are going to have lower environmental impacts due to that. So that's sort of fairly clear across all the highincome nations." said Paul Behrens, an environmental scientist at Leiden University in the Netherlands.
The food we eat takes a big toll on the environment. A third of the icefree land on Earth is used for agriculture, and according to some estimates, producing food accounts for roughly a fifth of all humancaused greenhouse gas emissions. Fertilizer runoff also leads to other problems, like the algae blooms in Lake Eerie and the Dead Zone in the Gulf of Mexico.
However, following dietary guidelines would reduce those impacts, especially in wealthy countries like the US. "Most of the reductions come from meat and dairy," which have an outsized impact on land use and pollution, and are a major source of greenhouse gases.(That's partly due to cow farts. Seriously.) Following the suggestions would also mean eating fewer calories, since many people here eat more than they need.
Overall, in highincome countries, Behren's team estimates that following the rules could result in as much as a 17 percent reduction in land use, a 21 percent reduction in nutrient pollution, and a 25 percent drop in agricultural greenhouse gas emissions. Cutting down on how much food we waste—which is roughly a third in the US—could help even more. The results are in the Proceedings of the National Academy of Sciences.
Of course, people are notoriously bad at following diets. But: "These nationally recommended guidelines do actually have a knockon effect on other areas of policy making. So if I'm developing a new healthyeatingforschools program then that's going to be based off a lot of detail that I get from the nationally recommended guidelines. So while it might not necessarily be the case that people follow directly …they actually are quite influential on the preparation of other advice."
It seems that a smaller environmental footprint and a healthier lifestyle could go hand in hand.