I grew up in the Great Lakes State, and for many years now, during my annual summer, visit back to Michigan, I’m always happy about what I don’t see. I don’t see crowds of Californians rushing lovely lakeside towns like Petoskey or Glen Arbor. I don’t see hundreds of New Yorkers playing about Lake Michigan or coming down the steep white sands of Sleeping Bear Dunes.

No offense to the masses on both coasts, but I’ve always been glad the original charms of northwest Michigan felt like my secret-or at least a secret held by a smaller group of people, largely from the Midwest.

Lately, however, I’ve been thinking about the downside of being out of sight and out of mind.

Most people seldom think about Lakes Michigan, Huron, Superior, Erie, and Ontario. Many can’t even name all five. But they should care about them because, as Tim Folger writes in this month’s cover story, the Great Lakes are “arguably the continent’s most precious resource, unmeasurably more valuable than oil, gas, or coal.”

Together the lakes hold more than 20 percent of the surface freshwater on Earth and 84 percent of the surface freshwater in North America. Almost 40 million Americans and Canadians “drink from the lakes, fish on them, transport goods over them, farm their shores, and work in cities that wouldn’t exist” without them, Folger writes.

And yet we abuse them terribly: polluting them, introducing invasive species, allowing fertilizer runoff(径流) to create algal(藻类) blooms large enough that they can be seen from space. Climate change means the lakes don’t freeze as much as they used to, and severe storms have become more frequent.

So read Folger’s story. Appreciate the beauty of the landscape in the amazing photos by Keith Ladzinski. Become an advocate to protect our Great Lakes.

Wheat and corn are used to make bread, pizza and other delicious foods, but in a few years they could also power your car. Renewable biofuels could soon replace the harmful fossil fuels that we’re used to using. It’s now well established that fossil fuels are incredibly harmful to our health and the environment and they’re not renewable, either. When so many people rely on petrol and diesel (柴油) to power vehicles, it makes sense to develop a renewable alternative that’s easy to use.

That’s where biofuel comes in. The most common biofuel produced globally is ethanol (乙醇), and it’s used frequently in Brazil and the US, while biodiesel is more popular in Europe. However, first-generation biofuels like ethanol have got issues that need fixing before they can go mainstream. It curently takes more ethanol than gasoline to produce the same amount of energy, for instance. Production is expensive, and several parts of the process sometimes use fossil fuels, which means that some biofuels aren’t actually carbon-free.

Some environmental campaigners also say that it would be more useful to grow crops for food rather than biofuel, and that growing crops for biofuel can cause problems with soil loss and deforestation. Using land for fuel rather than food can lead to an increase in food prices, too, and can affect natural habitats.

Crop and fat-based biofunels may not be perfect, but those aren’t the only biofuels available. Some organisations are creating biofuels with algae (海藻) instead. This process uses water and land that often isn’t suitable for many other situations, so it doesn’t take up space that’s useful for food production, and it often has better yields (产量) than other types of biofuel components.

There’s plenty of development beyond algae, too. Some companies even use seaweed. Scientists are also working on plans that will be able to abstract biofuels from household waste, wood chips and other junk — a move that could massively increase the material that’s viable for biofuel production. These second-generation biofuels could make biofuel far cheaper and more accessible, and help cut emissions down.

Despite growing concerns over tiny bits of plastic filling the world’s waterways, the long-term environmental effects of that waste remain unclear. Now an experiment on freshwater sediment (沉积物) communities exposed to microplastics for over a year helps clarify how harmful this pollution can be.

Researchers put trays (托盘) of sediment littered with different amounts of polystyrene (a very light soft plastic) particles (颗粒) — ranging from 0 to 5 percent plastic — in the bottom of an outdoor waterway where bugs, snails and other little creatures colonized the mud. After 15 months, fewer organisms were found living in the trays with 5 percent polystyrene than in trays with less plastic, largely because fewer Naididae worms lived in the most polluted mud. The trays with 0 to 0.5 percent microplastic averaged between about 500 and 800 worms per tray, while mud with 5 percent plastic averaged fewer than 300, researchers reported January 31 in Science Advances.

That reduction in Naididae worms suggests that severe microplastic pollution can throw freshwater ecosystems out of balance. The 5 percent plastic concentration where researchers saw a major drop in the Naididae worm population has more pollution than what is typically found in freshwater sediment, says study coauthor Bart Koelmans, who studies aquatic ecology at Wageningen University & Research in the Netherlands.

“It’s a really important piece of work,” says Richard Thompson, who studies environmental effects of plastic pollution at the University of Plymouth in England but was not involved in the study. “Most of our understanding about the impacts of small pieces of plastic comes from laboratory studies over several weeks. The new experiment gets closer to assessing microplastic’s long-term, real-world effects,” he says.

Just because the researchers didn’t observe a significant effect on these freshwater communities at lower plastic concentrations “doesn’t mean that there are no effects,” says Ana Luísa Patrfcio Silva, an ecotoxicologist at the University of Aveiro in Portugal not involved in the work. Simply keeping a count of the organisms living in mud with a certain amount of pollution doesn’t rule out the possibility that microplastics weaken the creatures’ ability to function normally, she says.