At Marine Mammal Laboratory, laboratory director Herman put a dolphin through its paces. Using hand signals, Herman asked, “Is the ball in the pool?” The dolphin correctly pressed a lever for “YES”. Herman asked it to push the ball to a basket. It did. Then he signaled his pupil to do it again, but he removed the basket. Herman expected the dolphin to be confused. Instead, it carried the ball to the NO lever and stopped there. Herman was astonished. “This is a totally untrained, invented response,” he said, “We never dreamed the animal would ‘think’ the problem through like that.”

To get a closer look at these amazing creatures, Herman and his team spent a week on board the Jennifer Marie. Whenever they heard the cry “Dolphins!” they slipped into the water. The dolphins approached, curious about them, observing them with dark, liquid eyes. Dolphins love to imitate. If they swam on their backs, Dolphins did too. If they dived, Dolphins followed. This talent can be carried to extraordinary lengths. In one instance, a trainer blew a puff of cigarette smoke against the window of an observation tank. A young dolphin rushed to its mother, nursed briefly, and spat out a cloud of milk against the glass.

Herman said “We’re still in the early stages of learning about the intelligence of these animals and our ability to communicate with them.” Scientists are amazed at dolphins’ intelligence, but fear for the future of these trusting ocean creatures.

Dolphins’ trouble could be sharks, killer whales or, worse yet, a fishing vessel. Indeed, in the past three decades, commercial fishing, especially the biggest threat—the drift net fishing, has greatly decreased the world’s dolphin population. Every night in the North Pacific, hundreds of Asian fishing vessels put out these “curtains of death,” each up to 50 miles long. Floating with the currents, they sweep up all sea life in their path. People wonder what the world would be without dolphins.

In the past 50 years, the amount of water in the open ocean with zero oxygen has gone up more than fourfold. In coastal water bodies, including river mouths and seas, low-oxygen sites have increased more than tenfold since 1950. Scientists expect oxygen levels to continue dropping even outside these zones as the Earth warms.

“Oxygen is fundamental to life in the oceans,” said Denise Breitburg, marine ecologist with the Smithsonian Environmental Research Centre. “The decline in ocean oxygen ranks among the most serious effects of human activities on the Earth’s environment.” “Actually, it’s a great loss to all the services that rely on recreation and tourism, including hotels, restaurants and everything else. The severe impact of unhealthy ecosystems in the ocean can be extensive,” said Lisa Levin, scientist at the University of California San Diego.

In areas traditionally called “dead zones”, like those in Chesapeake Bay and the Gulf of Mexico, oxygen plummets (暴跌) to so low levels that many animals die. As fish avoid these zones, their habitats become smaller and they’re easier to be attacked or caught. But the problem goes far beyond “dead zones”. Even smaller oxygen decline can prevent growth in animals, get in the way of reproduction and lead to disease or even death. It can also cause the release of dangerous chemicals such as nitrous oxide, a greenhouse gas up to 300 times more powerful than carbon dioxide. While some animals can thrive(茁壮成长) in “dead zones”, overall biodiversity falls.

Climate change is the key culprit (问题的起因) in the open ocean. Warming surface waters make it harder for oxygen to reach the inside of the ocean. Furthermore, as the ocean as a whole gets warmer, it holds less oxygen. In coastal waters, too much nutrient pollution from land creates algal(海藻的) blooms, which use up oxygen as algae die and break down.

People’s livelihoods are also on the line, the scientists reported, especially in developing nations. Smaller fisheries may be unable to relocate when low oxygen destroys their harvests or forces fish to move elsewhere. So we humans have to carry on a war against climate change now and win the war.

Lithium (锂) is called “white gold” for good reason. The metal value has been growing rapidly over the last several years, mainly because it is an essential material of lithium-ion batteries, which play an important part in several key sustainable technologies, for example, electric cars.

As ocean waves, wind and solar power have grown into major players in the energy industry, lithium has also become key to building a future free of petrol. But getting lithium comes at a huge cost. As with most meals, its mining is damaging. It often works like this: Briny water, containing lithium and other meal, is pumped to the surface from underground. Then it sits in pools to allow the water to evaporate, leaving the rest behind as poisonous matter. Workers use chemical reactions to remove the lithium from that, making it into powder which is then packaged and shipped to the buyers around the world. Any accident that releases mine matter into surrounding communities or the groundwater supply could have damaging long-term impacts.

Indigenous (当地的) communities often bear the result of the damage, and political leaders have paid little attention to their concerns. In Arizona, for example, an expanding lithium mine is threatening the Hualapai Tribe’s historical sites. And for politicians who have promised to work with native peoples to deal with it, mining lithium and other precious metals is putting them into a dilemma: How do you ensure the availability of materials which are essential to the future while protecting indigenous people’s rights?

Mining of the metal is expected to increase greatly in coming years. Overtime, that will make electric cars inexpensive and, therefore, more popular.

As environmentally conscious consumers buy electric cars in ever-greater numbers, it’s important to be aware of the dirty process that powers those clean air vehicles.