Today marks the 40th anniversary of Earth Day. Approximately 1 billion people will participate in Earth Day celebrations this month, and today alone countless people will plant trees, clean up rivers, pledge not to use plastic bags and decide to walk rather than drive. All of this helps, of course, but it's not going to save the planet. To be truly "green", we've got to make our diets more environmentally friendly by kicking the meat habit and going vegan. An apple a day can help keep environmental destruction away.

Our most serious environmental problems – climate change, overexploited natural resources, deforestation, wasted land, water and air pollution – as well as today's most serious health problems, including heart disease and cancer, are all directly linked to the consumption of meat, eggs and dairy products.

A 2006 United Nations report revealed that the livestock sector generates more greenhouse gases than all the cars, trucks, trains, planes and ships in the world combined. The report attributed 18% of annual worldwide greenhouse-gas emissions to farmed animals, but new research indicates that the figure actually could be much higher. In Livestock and Climate Change, the Worldwatch Institute estimates that raising animals for food actually accounts for 51% of all greenhouse-gas emissions.

The Food and Agriculture Organisation of the United Nations estimates that 30% of the Earth's ice-free land is now involved – either directly or indirectly – in livestock production. Huge swaths of forests are being bulldozed to make more room for animals and the crops that feed them. According to Greenpeace, all the wild animals and trees in more than 2.9m acres of rain forest were destroyed in one year's crop season in order to grow crops that are used to feed chickens and other animals on factory farms.

Some activists will be showering in the street today behind a curtain that reads, "1kg of meat = 1 year of showers. Clean your conscience: go vegan". That's because between watering the crops that farmed animals eat, providing drinking water for billions of animals each year and cleaning away the filth on factory farms and in trucks and slaughterhouses, the farmed-animal industry places a serious strain on our water supply. A totally vegetarian diet can be produced with only 1,100 litres of water per day, while producing a diet that includes meat requires more than 15,000 litres of water per day.

Then there's the energy required to operate factory farms, feedlots, slaughterhouses and trucks that transport animals. The respected environmental magazine E noted in 2002 that more than one-third of all fossil fuels produced in the US are used to raise animals for food.

That's not all. Our meat-based diet is partly to blame for world hunger, because land, water and other resources that could be used to grow food for human beings are used to grow crops for farmed animals instead. It takes up to 16 pounds of grain to produce just one pound of meat.

It's time to face what some may consider an inconvenient truth: our meat, egg and dairy habits are destroying the planet. Let's not forget about being environmentalists the moment we sit down to eat.

If we are to halt climate change and environmental destruction while stopping animal suffering and improving our health, we must celebrate Earth Day every day – at every meal.