Imagine you're McDonald's. You're one of the world's largest fast-food chains. Your core customers are families raising kids on tight budgets and people who have to drive long distances for work. Vegan, granola-munching, animal-loving activists really are not part of your customer base. 

So what do you do? You make a big, animal-loving announcement just to improve the world. At least, that's what McDonald's did this week when it announced it would  replace plastic straws in the U.K. with paper ones and that it would begin testing plastic-straw alternatives in the U.S. as well.

As you may know, even though oceans cover more than 70 percent of the Earth, humans have dumped so much plastic into them that animals such as pilot whales are dying from consuming it. By 2050, according to a prediction from the MacArthur Foundation, there will be more plastic than fish in our oceans unless something drastically changes in the meantime. 

And it's not just the oceans. A recent study showed that 83 percent of the world's tap water contains plastic microfibers, and (not surprisingly) water sold in plastic bottles contains even more of them.

Plastic straws may seem like a small part of the problem, but the fact that there are so many of them--McDonald's alone hands out many millions every day--and their form make plastic straws particularly harmful. 

"McDonald's is committed to using our scale for good and working to find sustainable solutions for plastic straws globally," according to a statement by Francesca DeBiase, the company's executive vice president for global supply chain and sustainability. "We hope this work will support industry-wide change."

Whether or not it's because of McDonald's, the industry definitely is changing. SeaWorld says it has already eliminated plastic straws and plastic shopping bags at all 12 of its parks. A&W says it will offer only paper straws throughout Canada by the end of this year.

What's driving all this industry-wide change is public opinion, of course, backed up by the threat of laws, such as one proposed in California that would make plastic straws illegal. Anti-plastic-straw sentiment is particularly strong in the U.K., where the BBC aired the documentary Blue Planet II, which showed birds traveling thousands of miles seeking food for their young, only to wind up feeding them plastic because there was so much of it and so little of anything else. Also, the queen has come out against single-use plastics.

McDonald's, perhaps because of its huge size, is taking its time implementing these changes. Plastic straws won't be completely gone from McDonald's in the U.K. until 2020. As for the U.S., the chain hasn't said what kind of plastic-straw alternatives it's testing or where it's testing them or when tests will begin, other than "later this year." Presumably, unless plastic straws are outlawed, most people in the U.S. will still be drinking their vanilla shakes through them for at least a few more years.

Still, for McDonald's to remove plastic straws from its 1,361 restaurants in Britain is a big step in the right direction. Maybe Blue Planet II should air over here as well.