UK supermarket giant Tesco is partnering with WWF with the aim of halving the environmental impact of the average UK shopping basket, producing a weighting metric for various environmental issues and applying it to 20 of its grocery products.

Alongside staples such as bread, rice, eggs and milk, farmed salmon and canned tuna have been chosen as representative products for UK consumption.

The model seeks to weight products by their environmental impact across a range of issues, which in themselves have been weighted in terms of their urgency, scope, direct impact and governance.

Climate change has a 25 percent weighting, deforestation 20 percent, sustainable diets 15 percent, sustainable agriculture 12 percent, marine sustainability 10 percent, food waste 10 percent and packaging waster 8 percent.

Each criteria will include a number of sub-metrics that mark progress and take into account sourcing criteria and certifications already in place for that particular product.

For farmed salmon, feed is the main concern, with Tesco and WWF categorizing its environmental impact under marine and forests, with attention being paid to the percentage of South American soy from verified zero-deforestation areas and the percentage reduction in the forage fish dependency ratio (FFDR) in fish feed among key suppliers.

Canned tuna's impact is categorized purely as marine, with its key issue identified as bycatch and the drive for change as the percentage of Marine Stewardship Council and WWF green-rated fisheries that its product is sourced from.

You can see the full basket of products and their environmental considerations here.