We've long been aware of many of the simple steps that we can take to make our lives greener, such as recycling and switching to energy-saving light bulbs. Indeed, when it comes to the environment, many activists advocate the three Rs - recycling, reusing and reducing. But while these actions are important and worthwhile, we would be better off at this late stage in the game focusing on a different letter: V for vegan.
According to a UN report, the meat industry is "one of the top two or three most significant contributors to the most serious environmental problems, at every scale from local to global". Just take greenhouse gases, for example: the livestock sector is one of the largest sources of carbon dioxide and the single largest source of both methane and nitrous oxide, which are, respectively, 25 and 300 times more potent than carbon dioxide. A study released last month by Chalmers University of Technology in Sweden warned that cutting greenhouse-gas emissions from energy use and transport will not be enough on its own to hold down global temperature increases. The study's lead author, Dr Fredrik Hedenus, said, "We have shown that reducing meat and dairy consumption is key to bringing agricultural climate pollution down to safe levels". Of course, it would also reduce the terrible suffering inflicted on billions of sensitive animals every year at the hands of these inherently inhumane industries.
The UN has called the livestock industry "a key player in increasing water use" and "probably the largest sectoral source of water pollution". On average, it takes one-third more water and land to produce animal-based foods than plant-based ones - in part because of the extra crops needed to feed farmed animals. By simply going vegan, we can each save nearly 1 million litres of water a year - enough to fill an Olympic swimming pool two and a half times.
The latest Intergovernmental Panel on Climate Change report urging governments to abandon all dirty fossil fuels in coming decades was greeted with open arms by many environmental groups. Here's a fact: it takes roughly 11 times fewer fossil fuels to produce a gram of plant protein than it does to produce a gram of animal protein.
Farming animals for their flesh as well as their skin takes a terrible toll on the world's rain forests. Livestock production is a key factor in deforestation, especially in Latin America, where vast swaths of rain-forest land have been cleared for cattle grazing. Today, approximately 30 per cent of the Earth's land mass is used to graze animals or grow feed crops for them. It takes 20 pounds of grain to make a single pound of beef, 4.5 pounds of grain to make 1 pound of chicken meat and 7.3 pounds of grain to produce 1 pound of pork.
That grain could instead be used to feed hungry people. Vegfam, a UK-based hunger-relief charity, estimates that a 10-acre farm could support 60 people by growing soya beans and 24 by growing wheat but only two by raising cattle.
Earth Day has to be about more than just turning off lights. We need to reflect seriously on the impact that our individual choices are having on the planet and its inhabitants and start to make better ones.
UN officials say that a global shift towards a vegan diet is necessary to alleviate hunger, fuel poverty and the worst effects of climate change. So what are we waiting for? If we care about protecting the planet - and the people and animals we share it with - then what better time than Earth Day is there to try vegan?