I asked a journalist to come and have a rainforest picnic one day. Intrigued, she joined me on a rug in an English woodland. I laid out a selection from a local supermarket. A Scotch egg, cake, apple juice, crisps, delicious biscuits, some Dutch cheese and a tin of corned beef. “You can eat anything you like,” I said, “as long as you can be sure there’s no rainforest in it.”

She reached for the crisps. Checking the packet, she saw that it said they were cooked in vegetable oil. “That could mean palm oil,” I said. “It’s out.” Next came the Scotch egg. “It’s tricky,” I said. “Soya from the Amazon used to be imported through Holland as cheap feedstock for Europe’s cows, pigs and chickens, but today most is going to China.” Since 2005, the soya moratorium in Brazil has virtually ended the expansion of soya ranches into the Amazon, but if it is rescinded, the encroachment could begin again.

In the end, the only item we could be absolutely sure did not contain a rainforest footprint was the apple juice. Palm oil is grown in plantations on land cleared of rainforests. Liquid at room temperature, it has invisibly infiltrated our cakes, cookies, crisps and curries as a replacement for harmful artificial trans fats. The corned beef also lay unopened because beef exports to Russia, Egypt and Europe from Brazil have, over decades, helped to drive the massive expansion of cattle ranching there, the principal cause of Amazon rainforest destruction.

In the last two decades the expansion of agribusiness has become the greatest cause of deforestation in the tropics. ‘Forest risk commodities’ such as beef and leather, soya, palm oil, paper and pulp, and biofuels now drive some 80% of deforestation – not poor families cutting wood for fuel!

In Africa, massive Chinese investment in land is under way to secure food provision, and palm oil is expanding there rapidly too, just as it is in the Peruvian Amazon, as Brazil successfully squeezes illegal deforestation out of its own frontier states.

With 9 billion mouths to feed by 2050, water and land have become the new constraints on global food production, so land prices will rise, the upshot of which will be that land occupied by rainforests will look cheap.

So how can our food become deforestation-free? The recent horsemeat scandal in Europe has demonstrated that we do not sufficiently know what we are supplied to eat through often corrupt and convoluted global supply chains.

Traceability means knowing exactly where your food is coming from, right back to the farm. From supermarket to soya ranch or oil palm plantation, that can be hard, often involving numerous steps in the chain, from buyers to processors to importers and global traders, to big ranches that import their surplus demand from small ones. And it’s these smaller farms that are often at the rainforest frontier – poor, desperate, easily manipulated and eager to clear rainforests for cash and a better life. The law may say they shouldn’t, but who is checking?

So whose responsibility is it to check? The horsemeat scandal pointed the finger at those who sell it to the end users, the retailers. So European supermarkets cleared their shelves, wrung their hands in the media, and jumped on their compliance departments. But the biggest markets for palm oil are in India and China, and for Brazilian beef it’s the Brazilians themselves. In these markets ‘rainforest concern’ does not exist or is in relative infancy. Without consumer pressure to change, how else can change be triggered? The answer is through investors that have a stake in the companies that use ‘forest risk commodities’.

In 2009, I started the Forest Footprint Disclosure Project (which has now merged with the Carbon Disclosure Project as CDP’s Forests Program) to alert FTSE 100 companies in the global forest supply chain to the need to clean up their act and move towards becoming ‘deforestation-free’. We started sending an annual questionnaire to CEOs inviting them to disclose their use of forest risk commodities in their operations and supply chains. Using the data, we scored performance and shared the results with investors. Most companies would bin it were it not for the investors backing our request, whose number has now grown to 184, and who manage assets in excess of US$13 trillion. It’s their authority, as part-owners of these companies, that encourages their hard-pressed compliance departments to respond.

The benefits to companies in engaging with our project, and managing down the risks they are running by being directly or indirectly engaged in deforestation, can be huge. A fashion house espousing quality may not know that the leather in its handbags causes deforestation; a company does not want Greenpeace highlighting that the palm oil in its chocolate bars may have made orphans of orang-utans whose rainforest homes have been destroyed to make it; a toy company might have foreseen that Ken might divorce Barbie because her paper packaging contained rainforest fibres.

So is it all just about reputation? No company wants Greenpeace hanging off the building, but the impacts of such actions are transitory and rarely affect the share price for long. There is, however, a deeper and far more widespread change occurring. Every child in the UK is taught to love rainforests at school, so fewer parents want to work for a company accused of destroying them. The brightest graduates do not want to work for a ‘dirty’ company either.

The UN has made Reducing Emissions from Deforestation and Degradation in Developing Countries (REDD+) a central pillar of its bid to slow climate change. The Prince’s Rainforests Project mandated Prince Charles to badger CEOs and heads of state alike on the issue. Eighteen heads of state signed up to his ‘Emergency Plan’ that eventually led to US$4.5 billion in governmental ‘Fast-start’ funding being earmarked for rainforests at the UN climate meeting in Copenhagen in 2009. In 2010, the board of the Consumer Goods Forum, representing 400 retailers, manufacturers, service providers and other stakeholders in 70 countries, agreed to a ‘no net deforestation’ goal by 2020. Last year, they and the US government announced that they would work together to reduce deforestation by promoting sustainable supply chains.

A sea change in attitudes to consumption and deforestation is happening worldwide, but will it be enough to save rainforests? In my final article, in the next issue, I will explore a largely invisible link in the rainforest supply chain: the role of the financial sector. Ultimately, it is here that the key lies to halting the money supply that has facilitated the 20th-century destruction of rainforests, and to redirecting it towards beneficial forest finance, at scale.

Andrew Mitchell is the Executive Director of the Global Canopy Programme. www.globalcanopy.org