We have spent our careers campaigning for our fragile environment. We are also vegans – we have chosen not to use any product which derives from the use of animals.

You may think this puts us fairly high up the chart of smug, self-satisfied do-gooders. But, as The Vegan Society launches the latest phase of its Plate Up For the Planet  campaign, we are not writing to lecture or hector you.

We are not wagging our fingers, or tutting loudly while you order your lunch. Instead, we are asking for your understanding, your patience, and ultimately your respect.

Good conscience

Food unites and divides us. It brings us together to share meals and special occasions, but causes upset when we can’t agree on what food is best, or ethically correct for us to eat.

We know that vegans get a bad press – we’re awkward, we’re stubborn, why can’t we just have the cheese sandwich like everyone else?

We can’t just have the cheese sandwich because we know the devastating effect that animal agriculture has. Animal farming is a greater contributor to climate change than transport, it's destroying precious habitats, both here and in the Amazon.

It's a hugely inefficient food choice, giving us only 12 calories back for every 100 we feed to animals. With a vegan diet, we're cutting our food emissions by up to 50 percent, halving our land use, and if we all opted for vegan we could feed 3 billion more people.

It's pretty clear that veganism is the best 'off the shelf' diet for the environment. We can’t in good conscience, just go with the flow. This is too important.

Never look back
So, forgive us for our inconvenient statistics. Humour our persistent attempts to get you to try our home-made houmous.

And please respect that the choice we have made comes not from a desire to be difficult, or a need to be noticed, but from a deep-seated belief that veganism is the only way forward for future generations.

It's time that those who care about our planet positioned veganism as an aspiration, not as an extreme. We need to be far more bolder than ‘eating less meat’ if we are to protect our precious planet.

Please join us by taking part in the seven-day Plate Up for the Planet challenge. You may find you never look back.

For more information on the Plate Up For the Planet campaign, visit: www.vegansociety.com/take-action/campaigns/plate-planet

Authors: George Monbiot is the country's leading environmental journalist and author. Kerry McCarthy is the MP for Bristol East. Dale Vince is the founder of Ecotricity. Jonathan Bartley is Green Party co-leader. This is an open letter to environmentalists first published with the Vegan Society to support its Plate Up for the Planet challenge.