According to CIWF, to reduce our impact on the environment and climate change, we need to reduce consumption of meat and dairy products in line with government carbon reduction targets: that is, by one-third by 2020, and by 60 per cent by 2050.

That could mean having a couple of meat-free days a week; reducing the amount of meat – for example, eating one lamb chop, not two; or, more likely, increasing the number of meat-free meals. When people do buy animal products, they can then spend a little more for humanely produced meat, eggs and dairy.

Joyce D'Silva, Compassion's Director of Public Affairs, commented: "With 70 per cent of farm animals now raised in industrial factory farms, with their huge capacity for pollution and their insatiable appetite for corn, soy and wheat for animal feed, it's surely time to create dietary change. That land could be growing crops for consumption by some of the world’s one billion hungry people. Add in the crucial factor of animal suffering and the case for reducing meat consumption and changing to more humane and environmentally sustainable systems, such as pasture-reared animals, is overwhelming."

Livestock farming has many adverse effects on the global environment, says CIWF. It is probably the largest source of sectoral water pollution, contributing to the degradation of coastal areas and coral reefs. Seventy per cent of former Amazonian rainforests have been turned over to production of beef cattle or growing soya for animal feed. Twenty per cent of the world’s pasture land has been harmed by over-grazing, with more and more pastures turning into desert. Livestock production already threatens nearly half of the world’s land eco-regions.

That is not all, adds CIWF, as the amount of meat and dairy produce consumed globally is set to roughly double by 2050 – so if there is a problem now, how big will it be by then?

Studies in Europe, the US and Japan have shown that the more meat in your diet the greater the global warming potential and the lower its energy efficiency, according to CIWF. If you eat a portion of pasta with broccoli and peas, it will be twice as energy-efficient as pasta with pork.

To conclude, Compassion believes Earth Day presents the perfect opportunity to consider how cheap meat production affects the whole world. Compassion in World Farming will consequently be asking its supporters to pledge to go meat-free on Earth Day itself and to cut down their meat consumption from then on.