1 . Rainwater in cities causes more troubles than wet feet. It carries away waste from rooftops and streets as it washes through cities. European scientists are now trying to work out how to deal with flooding rainwater.

In the city of Wetteren, Belgium, researchers are experimenting with seashells. Millions of shells from the nearby North Sea are used to collect and treat rainwater from a shopping-mall roof and a parking lot. The shells are laid below a surface drain (下水道) through which dirty water is carried away. With a 70% empty space that allows them to store rainwater, they’re also a natural cleaning station, which is then used to water community gardens.

The experiment is part of a project called StopUP whose goal is to prevent rainwater from carrying pollutants into lakes and rivers. The project’s focus is to make sure that such wastewater, which can include everything from plastics to heavy metals, gets treated.

Thomas Jeffery, head of the College of Environmental Engineering in Germany, said a big knowledge gap can exist between the popular perception of rainwater and its true content. “Rainwater seems to be very clean, but when it washes the streets and roofs, it becomes full of dust and other harmful pollutants,” said Thomas.

In Europe, 38% of surface waterbodies have different forms of pollutants, which run deep in the ground and damage soils, plants and animals, according to Julie Rosalie, director of the European Environment Agency. Human health depends on clean water for drinking, bathing and cooking, and now we arc at risk because plants and animals are affected by chemicals in rivers, lakes and coastal waters.

“StopUP technologies and methods could provide tools to reduce rainwater pollution.” Rosalie said. “It has a positive effect on the quality of our common environment.”

2 . The holiday season is a time for celebrating with friends and family, when people give gifts or decorate their homes. Unfortunately, this can all lead to a lot of waste. However, there are ways to reduce the amount of waste you create.

Gift bags or wrap that can be reused are recommended on the list. You can reuse them the next time you give a gift. You can also wrap gifts in old maps, pages from magazines, and art paper. The person receiving the gift could use the wrap for something else. The Chinese traditional cloth-wrapper is popular wrapping cloth, which is pretty and strong. It can be used for other things, like a colorful scarf or tablecloth, rather than just thrown away.

For many people, sending holiday cards is a tradition. Now people are increasingly accepting electronic holiday cards. “There are so many digital options now, and people get just as much joy out of it,” some people said. These cards offer a range of benefits. With the increasing popularity, electronic cards have become a preferred choice.

For decorating the home, real trees have become first option rather than plastic ones. Some trees are grown for the purpose of being cut, and new ones are typically replanted every year. So, the cycle continues. Buying local trees means that it doesn’t use much fuel. After the holidays, trees are picked and processed into usable products, like small wood pieces for the garden. What’s more, you can’t beat the smell of a fresh-cut tree.

3 . You may not have noticed it, but according to a latest report, about 90 percent of the world’s largest cities lie near the sea. They can possibly be influenced by rising sea levels in the near future. But it doesn’t mean people who live in the city have to head for the hills.

City design companies Seanix and Jolly Group are working together on a possible solution. They said at a United Nations meeting that they are planning to build “Seanix Cities” -floating island structures (结构) that join together to form “land” on the surface of the water.

Unlike land-filling plans that have to pour sand into the ocean and ham ocean life, Seanix Cities are built to “live” together with the ocean. For example, energy used in the cities will be clean-mainly coming from waves, wind and the sun—and instead of chemicals, fish waste will be used to enrich the soil.

As promising as this plan sounds, however, there is still one problem: The plan itself doesn’t aim at global climate change. Instead, it’s a “runaway” plan. Similar to the project of building human settlements on Mars, it’s a way out when Earth becomes unsuitable for human life to live on. It doesn’t stop us from ruining the planet in the first place.

But without doubt, things are changing. “As our climate and water ecosystems (生态系统) are changing, the way our cities relate to water needs to change, too, ” Lucas, a UN official, said at the meeting.

Maybe instead of building eco-friendly floating cities, we should learn to live with nature while we still have land.

5 . The battery pack of an electric vehicle (EV) powers the car hundreds of kilometers, again and again, without letting off gases. But when the battery comes to the end of it’s life, its green benefits fade. If it ends up buried, it can release poisonous materials including heavy metals.

That's just one of the emerging problems challenging researchers: how to recycle millions of EV batteries. Current EV batteries "are really not designed to be recycled" , says Thompson, a researcher at an institution.

It wasn't much of a problem when EVs were rare. But now the technology is taking off. Governments realize this is an issue and are inching toward requiring some level of recycling. In 2018, China drew new rules to promote the reuse of EV battery parts. The European Union is expected to finalize its first laws this year. And in the United States, several states, including California—the nation's largest car market—are exploring their own rules.

Recycling won't be easy. Batteries differ widely in chemistry construction, which makes it difficult to create efficient recycling systems. Scientists, meanwhile, say effective battery recycling will require more than just technological advances. The high cost of transporting used batteries over long distances can discourage recycling. It causes an economic barrier: It's often cheaper for battermakers to buy freshly-mined metals than to use recycled materials.

"The need for progress is becoming pressing," says Linda Gaines, who works on battery recycling. "The sooner we can get everything moving, the better." To jump-start recycling, governments and industry are putting money into research centers. Scientists are working to ensure the EV batteries being sold today can be recycled in 2030 and beyond, when thousands of batteries will reach the end of their lives. "There's little time to waste.” says Linda.

6 . Some of the oldest art in human history is being damaged, scientists say. And climate change may be speeding up its loss. New research reports that ancient rock art in Indonesian caves is degrading over time, as bits of rock slowly break off from the walls. It's a huge loss for human history.

Salt crystals（结晶）building up on the walls are a key part of the problem, the study suggests. These salt crystals go into the cave walls, changing sizes as temperatures rise and fall. This process causes the rock to slowly break down.

Salt crystals may become larger when exposed to repeated changes between wet conditions and periods of drought. These kinds of changes are expected to become more obvious as the climate continues to warm.

In particular, the researchers say, climate change may cause more intense El Nino （厄尔尼诺）events in the future. These events can strengthen the kinds of conditions that help salt crystals form Scientists are still debating the exact influence of climate change on El Nino, a natural climate cycle that drives changing patterns of warming and cooling in the Pacific Ocean.

The new study, led by Jillian Huntley, examined 11 ancient cave art sites in South Sulawesi, Indonesia. The researchers found evidence of salt formation at all 11 sites. It's merely a small part There are more than 300 known eave art sites around the region. The researchers note that salt crystals may indeed be part of the problem, adding that climate change is a growing threat, one that deserves more attention.

7 . An Ontario teen is making waves by turning old fishing gear into new treasures. Since last year, Natalie, 15, has been taking lost or thrown — away fishing nets and rope and transforming them into bracelets, rope art, mats, baskets and necklaces.

Last year, Natalie was working on an assignment for her science, technology, engineering and mathematics (STEM) class. As part of the assignment, she learned about “ghost nets”, which are fishing nets that have been left or lost in the ocean by people who fish.

“They have huge effects on our environment. They can kill coral reefs and many animals,” said Natalie. “46 percent of the Pacific garbage is ghost gear.” The Great Pacific Garbage is a huge collection of trash floating in the Pacific Ocean between Hawaii and California.

Natalie told her mom she wanted to do something to help. She got in touch with a handful of charities, including the Sea Protection Society and Coastal Action.

After getting some shipments of ghost nets and rope from those organizations, Natalie, with the help of her family, started turning the discarded gear into new artworks. “We've made bracelets, rope art, mats, baskets, and we've made necklaces, which also use beach glass in them,” she said. Natalie then started selling the artworks online, the crafty buying and selling website.

She donated all her profits-minus a small sum of change to cover supplies — to the charities that donated fishing supplies to her. She's also been donating all the income from her non-profit business, called Nautical Waters, to charity. Natalie said she hoped to continue her passion for ocean life, with plans to study marine biology in university.