The food world is buzzing: Plant-based burgers just took a whopping leap forward.

Impossible Foods, maker of the meatless Impossible Burger, is teaming up with Burger King to offer the Impossible Whopper.

The move is exciting, but not surprising. Burger King has had a vegetarian patty burger for years while much of its competition has lagged behind in offering plant-based options for customers who want something healthier for themselves, animals or the environment.

And the furthest back are the golden arches. McDonald’s, the biggest name in fast food, doesn’t have a single meat-free entrée in the United States. Instead the company continues to campaign on so-called “sustainable beef” rather than investing in the growing market of plant-based foods.

While McDonald’s is clowning around, other chains are also starting to make big changes. Carl’s Jr. and White Castle now have plant-based menu items that aren’t iceberg lettuce and a crouton. Carl’s Jr. sells a Beyond Meat-based burger, and White Castle offers two options: Impossible sliders and veggie sliders.

But McDonald’s is still dragging its feet. Last year the company introduced the McVegan in Sweden and Finland, and its restaurants in India have offered the McAloo Tikki for years. But U.S. diners looking for a veggie sandwich are still out of luck.

McDonald’s is one of the world’s largest purchasers of beef, and scientists have determined that unless we eat less meat—beef, in particular—we won’t meet the greenhouse pollution reductions necessary to avoid catastrophic climate change.

Put plainly, all of McDonald’s Big Macs, Quarter Pounders and Happy Meals aren’t making the planet so happy.

Americans eat an average of three burgers each a week. All that meat between all those buns requires 682 million acres of land, creates 489 billion pounds of toxic manure and guzzles up more than 21 trillion gallons of water. Producing that many burgers also releases 337 billion pounds of greenhouse gases, which is roughly the same as the emissions from 32 million cars.

Plant-based alternatives have just a fraction of the carbon footprint of meat-heavy options. According to Impossible Food’s sustainability report, a single Impossible Burger saves the greenhouse gas equivalent of driving 18 fewer miles to the drive-thru compared to a regular beef patty. It also saves about 25 days worth of drinking water and 75 square feet of land.

McDonald’s, with its supersized influence over the food industry, could help address this problem. But instead it relies on greenwashing.

The company boasts about its role in the Global Roundtable for Sustainable Beef, whose vague criteria provide little motivation for change, and has been slow to even craft its own definition of “sustainable beef.” And despite proclaiming a commitment to curbing greenhouse pollution, McDonald’s continues to push burger sales.

As a market leader, it has the ability to influence change across the fast-food industry. When McDonald’s removed soda as a default for children, other restaurants like Burger King, Wendy's, Dairy Queen and Jack in the Box did so too.

It’s big news that Burger King has the chance to sell the Impossible Burger at its 7,200 national stores. But, for comparison, McDonald’s has about 14,000 locations across the country. Imagine what would happen if the golden arches began serving plant-based burgers in the United States.

We need to focus on what’s between those sesame-seeded buns. Plant-based options should be available in every restaurant to reduce the carbon footprint of menus and give customers better choices.

It’s time to launch the McVegan in the United States. We’re ready for the Big Impossible.

Jennifer Molidor is senior food campaigner at the Center for Biological Diversity, based in Tucson, Ariz.