There are an estimated 84,000 dams in the United States which impound 600,000 miles of river, or about 17% of the rivers in the country. Within the next 15 years, more than 90% of the world’s rivers will be fragmented by at least one dam.
Spider silk – the protein fiber spun by spiders to make webs, nests, cocoons, and wrapping for prey that they stash away – is a remarkable substance. Its mechanical properties combine high tensile strength and high extensibility or ductility. This allows spider silk to absorb a lot of energy before breaking. It is stronger than steel, but not as strong as Kevlar, for example. On the other hand, it is tougher than either.
Poor air quality is a serious problem. Exposure to air pollution is linked to the premature deaths of an estimated 6.5 million people every year. This makes air pollution the fourth largest threat to human health. Only high blood pressure, dietary risks, and smoking are a bigger danger.