It should be a day to celebrate. It's now five years since the sound of chainsaws in the Amazon went from a roar to a whisper. Some of you will have even helped to make this incredible result possible. But a change to Brazil's forest laws threatens to undermine this fantastic progress.

In 2006, following a concerted Greenpeace campaign against McDonalds' use of soya from deforestation in their chicken feed - think chickens and D locks - an extraordinary and unholy alliance developed. Yes, Greenpeace and McDonalds joined forces to build a coalition of European companies that used soya from Brazil but wanted to be a part of the solution not the problem in the Amazon. This coalition used their buying power to force the Brazilian soya traders to stop buying from farmers that deforested their land. The soya moratorium was born.

And it worked. Deforestation in the Brazilian Amazon has declined year on year and last year it was at its lowest ever level. Brazil's National Institute for Space Research, responsible for mapping deforestation in the Amazon, says that the moratorium "has certainly exerted an inhibitory effect on the soya frontier expansion in the Amazon biome (pdf)" .

But this year the chainsaws can be heard again. The Brazilian government's monitoring system picked up a 37% increase in deforestation this year compared to 2010 in Mato Grosso state, where 90% of the Amazon soya plantations are located . The reason is a move to change the Forest Code, the main law in Brazil that protects the forests. The changes would allow an amnesty for past forest crimes, creating an incentive for illegal activity now and leading to an increase in deforestation before the law has even been changed. This can only get worse if the proposed amendments to the Forest Code go through.

That's why we are not celebrating the moratorium's fifth year. Instead we are using the anniversary as an opportunity to make the moratorium even stronger. The threat to the Forest Code means that the moratorium becomes even more important as a tool to drive the changes needed in Brazil to reach our zero deforestation goal.

Companies supporting the moratorium have also expressed their concerns about changes to the Forest Code publicly for the first time. Their voices have added to those of scientists, campaigning organizations and the majority of the Brazilian public, showing that concerned companies are capable of trading with Brazil while keeping their products free from deforestation.