There's a revolution underway. When the store where you buy cereal plans a major initiative to work with grain growers to reduce fertilizer impacts, you can feel the ground shift beneath your feet. When buyers routinely move their conversations with suppliers from price and shelf space to product recyclability, we're definitely in a new millennium. Retailers are dramatically broadening their scopes to take responsibility for the impacts of the products they sell – even if those impacts are far back in their supply chains. When one of the retailers leading the charge is the global retail giant Walmart, the transformative potential of this mind shift hits you with the force of a combine.

Why do retailers care?

For many retailers, about 80 percent of the impacts from their businesses come from their supply chains. Walmart estimates the figure is closer to 90 percent. It's impossible to be a sustainable business - to speak of the environment and preserving the earth for your grandchildren - and ignore the elephant upstream. Replacing a few inefficient light bulbs in stores will not cut it anymore.

Food sellers have an additional interest in improving resource efficiencies to ensure that we can safely, affordably and nutritiously feed two billion more mouths in 2050. As the largest grocery retailer in the U.S., Walmart is looking to safeguard its supply chain from resource constraints and price volatility.

Walmart recently showcased some of the successes of its supplier collaborations at its latest Milestone Meeting (highly recommended viewing, 1.5 hours). The clever pairing of buyers and suppliers to present most of the nine case stories emphasized a key feature of Walmart's approach: partnership. No retailer can go it alone on product sustainability. This was particularly evident in the story about fertilizer presented by Walmart buyer Tim Robinson and Diane Holdorf of Kellogg Company.

Fertilizer: from bad guy to success story

Scientists have implicated synthetic nitrogen fertilizer as a major culprit in rising levels of greenhouse gases. In fact, fertilizer has the greatest climate change impact in most agricultural products. Fertilizer is also expensive, providing even more incentive to use it efficiently.

But how can any retailer- regardless of their size - get grain farmers to change their ways? Grains are commodities and the harvest from individual farms is aggregated before being sold. Not only does Walmart not know who grows the grain in its products, its suppliers don't know either. Holdorf noted that just as Walmart had turned to them, Kellogg's had to partner with their grain supplier to understand and influence its supply. Walmart was also able to leverage expertise and support from EDF and the National Corn Growers Association for this project.

The initiative is providing farmers in key U.S. grain growing states with tools and strategies that will encourage adoption of improved application timing, nutrient placement and soil monitoring methods as well as more sophisticated precision farming techniques. As Robinson stated, “We're not farmers… We're a big retailer that has influence. What we're trying to do is connect people with best practices."

That's a reasonable approach, given the supply chain realities, but will it be enough?

Robinson and Holdorf predict it will be plenty effective, achieving the following by 2020:

• Reduce fertilizer application on 14 million acres in the U.S.
• Reduce greenhouse gas emissions by 7 million metric tons
• Reduce fertilizer application by 30 percent.

Influence and partnerships

Walmart has clearly decided to use its vast power and connections for good. Many of its suppliers had already been working on sustainability initiatives but the retailer's influence brought the right experts to the table, sped up the time frame and enabled industry-wide collaborations. Walmart's twice-yearly survey of its suppliers through the Sustainability Index provides the company with a framework for communicating its priorities and for tracking progress. The Index questions are based on scientific research by The Sustainability Consortium (TSC), a multi-stakeholder group developing a measurement and reporting system for the consumer goods industry. The group's work highlighted the opportunity for achieving significant reductions in environmental impacts by optimizing fertilizer use in growing grains.

Walmart's commitment to engaging suppliers (5,000 of them by the end of 2013) through the Index institutionalizes the company's product sustainability priorities and ensures the longevity of the program. We are seeing the results of this in our own work as the Index spurs Walmart suppliers to take action to make improvements. It even goes beyond Walmart's own value chain. Walmart has changed the conversation in a way that makes it acceptable, even expected, for a buyer in any company to ask suppliers about fertilizer use or recycled materials or any of the many attributes relevant to product sustainability.

This revolution is here to stay. That's the real milestone.