1 . Meat is crucial for feeding the planet, leading scientists have said, as they warned it is not more environmentally-friendly to go vegan (素食).

Prof. Geoff Simm, Director of Global Academy Agriculture and Food Security at the University of Edinburgh, said, “I think livestock (家畜) farmers do feel they are being demonized (妖魔化).” Often the argument is made that going vegan would minimize land use, but the modelling studies that have been done demonstrate that’s not the case. We feel that while livestock production has a range of economic, social and environmental costs and benefits, the costs have perhaps been receiving far more attention recently than some of the benefits. Meat has massive social benefits. It’s an important source of dietary protein, energy, highly bioavailable micronutrients (微量营养素), even small amounts of animal-sourced food have a really important effect on the development of children, in the developing world on their cognitive and physical development and they are really important.

Prof. Mike Coffey, from Scotland’s Rural College, added, “It’s completely unnecessary to go vegan. If everybody went vegan it would be devastating for the UK environment. Animals bred for food help boost biodiversity.”

Researchers are currently attempting to breed more environmentally friendly cattle, which grow faster and eat less, which could further reduce the sector’s carbon footprint by reducing the amount of methane (甲烷) released by cows.

Prof. Coffey said that the difference in methane emissions from best and worst cattle was about 30 percent and that if all UK farmers used the most efficient animals this could reduce carbon emissions by nearly a third. But Prof. Coffey said the next stage will be trying to measure the methane given off by different breeds of cattle to find which are the lowest emitters. Prof. Coffey said that soon shoppers could be able to check meat labels to find out how much environmental impact their food has had. He added, “My expectation is that at some point in the near future there will be product labels that relates to the efficiency or carbon impact of the food.”

Professor Andrea Wilson, also of Edinburgh University, said more research was needed into the impact of veganism (绝对素食主义). She added, “We know a lot about the livestock sector because people have looked at it. We actually know very little about the vegan sector. The danger is we demonize one and jump too quickly to the other.”

2 . Our carbon footprint is the estimated amount of carbon dioxide given off as we go about our daily lives. While the global average carbon footprint is about 4 tons per person each year, Americans contribute approximately 20 tons of greenhouse gas per person each year. Compared to other countries, even those who use the least amount of energy in the US still contribute double the carbon emissions than the global average per person. And, not surprisingly, a person's carbon footprint increases in size as his or her income increases.

How is it possible that people in the US who live simple lifestyles, e.g., children or the homeless, make such large contributions to greenhouse gas emissions? The answer is simple: Each US citizen has access to various basic government services such as firefighting and police departments, road and bridge repair, libraries, prisons, the military, etc. When these public services are divided equally among the entire US population, it significantly raises the carbon footprint per person.

While it is admirable to make changes in lifestyle to reduce a carbon footprint, in reality, it is very difficult to do. The MIT study revealed that a "rebound effect" occurred when someone made an effort to reduce his carbon footprint. Take the example of a person who made the deliberate choice to buy a hybrid(混合动力的)car instead of a large SUV to save money on gas costs. Very often that person would use the money he saved to do something else, e.g., take a long airplane trip. In this case, just one long airplane trip produces more CO₂ emissions than driving the large SUV for a year. This ends up having a negative impact on a person's carbon footprint by making it bigger!

Can Americans reduce their carbon footprints? According to the study, it is possible, but it would require lifestyle changes such as giving up long distance travel and buying fewer smartphones and tablets that have large energy cost to produce and deliver. Another way is to add a CO₂ tax on food, housing, and transportation. Unless we can find a way to reduce our carbon footprints, the price we may ultimately have to pay is much higher than the amount Americans will ever have to pay in taxes.