1,000,000,000. That’s the approximate weight, in pounds, of the bananas we sell to our customers each year – and one of the insights I shared in a speech this week before a large gathering of scientists and sustainability experts at the National Conference and Global Forum on Science, Policy and the Environment in Washington, D.C.

Organized by the National Council on Science and the Environment, this year’s forum was focused on building solutions to climate change.

So why should we talk about bananas at a climate change meeting? Because it’s the lens through which we at Walmart view sustainability. For Walmart’s grocery division, sustainability is about solving the conundrum of making more food with fewer resources, sustainably sourcing key agricultural products, and creating less waste, while keeping food affordable and supporting farmers and their communities.

In keeping with our mission to save people money so they can live better, sustainability at Walmart must be rooted in the practical.  Whether it’s spreading best practices across our food supply chain, reducing food waste in our stores, DCs and from the suppliers we source from , or deploying solar panels. Our ambition is to make sustainability not only a practical and cost-effective solution for our customers and our business, but for all business by using our scale and size to impact the marketplace.

At the same time, we must have one foot in the future. We aspire to grow and serve more customers around the world. Yet, given the challenges facing our planet and earth’s resources, we must identify practical solutions that enable our growth while reducing our impact on the environment. We’ve found that these solutions are within reach. For example, we are forecasting that the greenhouse gas emissions from our buildings’ energy use will decrease by 2020, despite significant business growth plans in that same time period.

We’ve learned a lot since we began our sustainability journey eight years ago. Here are some of those lessons I shared with the gathering in Washington.

First, when designing practical solutions, we must begin with the customer – a merchant’s first rule. Our local-sourcing initiative is one example. Customers love the fact that they can have a positive impact on their environment by reducing the miles that food is travelled. But what they especially like is being able to support farmers in their communities, and even create more jobs in their communities, and without paying more.

Two, engaging our suppliers is critical. The vast majority of our carbon footprint is created in the production, distribution, use and disposal of the products we sell. By setting goals, we can incentivize progress across the supply chain. Our role is to catalyze continuous improvement. We’re demonstrating this through our work on Fertilizer, where we’re working with 16 suppliers to increase the use of fertilizer optimization technologies and practices on 2 million acres across 18 states. Not only is fertilizer optimization one of the most material ways we can reduce greenhouse gases in food, but it has also proven to save farmers money and help their operations become more profitable.

Three, we cannot do this alone. The major challenges facing society today are too big and too complex for any one country, sector or company to solve. We are big believers in the power of working together: with NGOs, academia, our competitors and even our critics. We are not going to solve the climate challenge, lower GHGs, or feed a growing planet by working alone, but rather by sharing knowledge and moving the marketplace as a whole. Which is, in fact, the very point of my participating at the Global Forum today – to share our story, but to learn from the experts I had the honor to stand before today.