Researchers and environmentalists have been pushing for clean energy, as well, contending with the rising threat of climate change. An increasingly researched renewable resource is called Ocean Thermal Energy Conversion (OTEC), in which the sea’s temperature variations are used to produce power. On the surface of the ocean, the temperatures are much warmer compared to the seafloor. It gets considerably colder the deeper you go because the sunlight cannot reach the bottom. These temperature differences are most noticeable in the summer when the sun is present for a majority of the hours of the day. To put it simply, OTEC uses a series of pipes that take the cooler water out in the depths of the ocean. The warm water on the ocean’s surface helps heat the cool water, which then vaporizes (蒸发) a fluid, and as a result, turns a turbine (涡轮机) to produce electricity.

Three types of ocean heat renewable energy systems are being developed and researched. An OTEC closed-cycle is perhaps the most common and well-researched, consisting of a condenser (冷凝器), evaporator, pumps, turbine and generator. There are also open systems and hybrid systems.

Systems work by pumping the warmer surface water through an evaporator containing a working fluid with a low boiling point, such as ammonia. Once the fluid vaporizes, it is used to drive a turbine and generator. From there, the vaporized fluid turns back into a liquid through a condenser, cooled by the cold, deep ocean water that pumps up from the depths. The OTEC systems that use seawater can use condensation to make water without salt.

OTEC systems need to place technology about 1 kilometer below the surface of the water. The cold water intake pipe is in the deepest area, and the piping where warm water enters is above sea level. The pumps are needed to move warm water into the system, and a heat exchanger is required to evaporate the fluid. Condensers condense the steam produced in the system, and a marker keeps the entire system afloat.

Energy is essential for almost all human activities. If the world wants to avoid an energy crisis, people need to begin relying on renewable energy. Fortunately, the three types of OTEC can provide energy for large populations.

Alaska's Arctic is experiencing surprising changes with the effects of climate change occurring at twice the rate of the rest of the world. Significant loss of sea ice from a warming climate is one example of this change. Polar bears rely on sea ice — their primary habitat — to hunt seals, which are their primary food source. In certain regions of the Arctic, loss of sea ice has sharply reduced the ability of polar bears to hunt for seals, and it has resulted in polar bears coming to shore to look for food and den in greater numbers.

There are 19 polar bear populations throughout the circumpolar Arctic, two of which include the Chukchi and Southern Beaufort Sea Populations. The Southern Beaufort Sea population is considered the most endangered on the planet, and Defenders has prioritized our polar bear work to focus on this population.

Defenders has a multi-pronged approach to protecting the Southern Beaufort Sea population of polar bears. We are working to protect its critical habitat, minimize climate change effects and reduce human-polar bear conflicts. To reduce human-polar bear conflicts, we promote and support a variety of coexistence measures, including the use of polar bear-proof food storage lockers and polar bear patrols in Arctic communities that use non-lethal hazing   and deterrence measures as a first line of defense.

The Southern Beaufort Sea population of polar bears has experienced such a dramatic rate of decline in the past few decades that it's possible that this population could be extinct within our lifetime. Clearly strong measures are needed to limit greenhouse gas emissions to lessen the effects of climate change and slow the loss of sea ice.

In the case of the Southern Beaufort Sea population of polar bears, in addition to reducing climate impacts, we need to continue to work to reduce human-polar bear conflicts so that community residents remain safe and fewer of these polar bears are lost to “defense of life and property” kills. Defenders is grateful to be able to work with Arctic communities, families and residents to do what we can't to ensure community safety and preserve and ultimately recover this polar bear population.

In 2016, the world’s population cast aside 49 million tons of electronic waste, known as e-waste.

It has been calculated that this number will grow to more than 60 million tons by 2021.

What is causing the upsurge ( 激增 ) in e-waste? Technology is becoming more and more widespread, covering almost every aspect of our lives. Meanwhile, the lifespan of devices is getting shorter---many products will be thrown away once their batteries die, to be replaced by new devices. Companies intentionally plan the obsolescence ( 过时 ) of their goods by updating the design or software and discontinuing support for older models, so that now it is usually cheaper and easier to buy a new product than to repair an old one. Since prices are falling, electronic devices are in demand around the world.

As more people buy electronic equipment, manufacturers ( 制造商 ) are beginning to face shortages of the raw materials needed to make their products, so recycling and reusing materials from discarded products and waste makes economic and environmental sense.

Recycling e-waste is practiced both formally and informally. Proper or formal e-waste recycling usually involves taking apart the electronics, separating and sorting through the materials and cleaning them. Companies must obey health and safety rules to reduce the health and environmental hazards of handling e-waste by using pollution-control technologies. All this makes formal recycling expensive. Informal recycling is typically unlicensed and uncontrolled. At informal recycling workshops, men and women recover valuable materials by burning devices to melt away non-valuable materials. Usually they do not wear protective equipment and lack any awareness that they are handling dangerous materials.

With the amount of e-waste growing around the world, recycling alone will not be enough to solve the problem. In order to reduce e-waste, manufacturers need to design electronics that are safer, and more durable, repairable and recyclable. The best thing you can do is resist buying a new device until you really need it. Try to get your old product repaired if possible and, if it can’t be fixed, resell or recycle it responsibly. Before you recycle your device, put any broken parts in separate containers and close these tightly to prevent chemicals from leaking. Wear latex gloves and a mask if you’re handling something that’s broken.