A handful of companies have the power to save the oceans. Here’s why we’re urging them to reinvent our land

The health of the oceans starts on land. We’re both lovers of the ocean who are working to make change here on solid ground. Ellen is an accomplished sailor who set a world record for the fastest solo nonstop voyage around the world, and Wendy recently became the first American and the first woman to win the Barcolana, the world's largest sailing race.

Together, we’ve devoted our energy and resources to advance a circular economy–one where we design out waste–because we know that human-generated material, particularly plastics and greenhouse gas emissions, are acidifying the ocean, raising sea levels, warming the planet, and harming human and marine health in ways we still don't fully understand.

Now, we’re bringing the circular economy to a place where it's sorely needed: the food system. Food production and distribution creates one-third of all greenhouse gas emissions. Nearly two-thirds of American coastal waters have been degraded by agricultural runoff, as have marine areas worldwide, leading to toxic, algae-infested waters that hurt ocean biodiversity and harm humans.

Our food system has evolved to take advantage of technologies developed in the last century, many of them the products of wartime development, such as chemical fertilizers and plastics. Convenience and consumer choice were the guiding values: We like summer fruit in winter, dozens of varieties of corn-based cereal, and pre-cut pineapples in plastic containers. Industrial crops were grown year-round with the help of pesticides, plastic packaging made food last longer and travel further, and single-serving options flew off grocery store shelves. The technologies that initially benefited us, when used at scale, turned out to be deeply damaging.

Our current food system is estimated to generate about $12 trillion a year in hidden health, economic and environmental costs, far exceeding the market value of food systems. The environmental costs could run even deeper than this estimate suggests: Animals, plants, our soil, and ocean life are suffering the impact of what we eat and how, as farmland encroaches on habitat, chemicals rob soils of nutrients and contaminate our waters, along with the alarming residue of our plastic use, much of which is food packaging.

Existing government policies and entrepreneurial efforts in both of our countries generally address food waste at the end of the cycle–think composting requirements, businesses that deliver slightly imperfect produce, or encouragements to go meatless on Mondays and shop at local farmers markets. These efforts are certainly laudable, but they forget the outsize impact major supermarkets and food brands can have in remaking the food system.

In the United Kingdom and the European Union, the top 10 food brands and retailers directly influence 40% of agricultural land use and what we eat. In the United States, four companies control 85% of the meat market, and worldwide, another four dominate grains.

A study from the Ellen MacArthur Foundation found that applying circular principles to the use of three staple ingredients–wheat, dairy, and potatoes–can reduce greenhouse gas emissions by 70% and biodiversity loss by 50%. Food output for the same land area could increase by 50%, and cash flow would increase by $3,100 per hectare on average following a few years’ transition. It's a win for climate, consumers, farmers, and companies.

This represents an enormous opportunity for businesses to act at scale and start to change the system.

Consumers are increasingly aware of the need to eat less and better-quality animal protein. The global vegan market is estimated to reach $61.35 billion in 2028, and a recent U.S. study showed that consumers would be swayed by climate impact labels on food.

Companies can stay ahead of these trends by collaborating closely with farmers, creating climate-friendly packaging, and designing products that use lower impact, upcycled, and/or regeneratively produced ingredients.

Building on our longstanding transatlantic partnership in pursuit of a circular economy, and recognizing the deep interconnections between ocean and land, we recently announced the Big Food Redesign Challenge to invite food growers, manufacturers, and distributors to design food products using circular design principles–and earn prized grocery store shelf space.

Many leading brands are already setting climate and biodiversity targets alongside economic ones through efforts like Race to Zero. Businesses are also improving the way they source ingredients. These are laudable steps–but circularity requires deeper and more comprehensive efforts.

While 75% of food and agriculture businesses have made public commitments to sustainability, only a handful have concrete plans, and many of the commitments are based on a single issue or problem, not the systemic challenges we face. That's where the principles of the circular economy come in: the food sector can focus on eliminating waste and pollution, circulating products and materials, and regenerating–rather than just sustaining–nature.

We’ve spent a hundred years thinking we can control and harness natural systems for the benefit of humanity. Now, our man-made systems are wreaking havoc on the planet–and we have no time to waste in trying to undo the damage. The food industry has no choice but to lead the way.

After a professional sailing career, Dame Ellen MacArthur launched her namesake foundation in 2010 to accelerate the transition to a circular economy and help tackle some of the biggest challenges of our time, such as climate change and biodiversity loss. Wendy Schmidt is president of the Schmidt Family Foundation, which she founded with her husband Eric in 2006 to work with communities around the world to advance clean, renewable energy, resilient food systems, healthy oceans and the protection of human rights. The two philanthropists have partnered together on circular economy initiatives since 2013.

The opinions expressed in Fortune.com commentary pieces are solely the views of their authors and do not necessarily reflect the opinions and beliefs of Fortune.