 I'm Salvatore Bobonis and today's lecture is the ecological footprint. The ecological footprint or carbon footprint is a clever way to evaluate things or actions on the basis of their impact on the environment. The fundamental principle of the ecological footprint is that the cost of a thing or action should be attributed to the purchaser or doer, not to the producer. For example, the ecological impact of driving a car is calculated as the total environmental impact of producing the car, plus the impact of producing the gasoline, burning the gasoline, maintaining the road you drive on, etc. If oil is produced in the Middle East but used in North America, it is charged against North America's ecological footprint because that is where the product is consumed. The ecological footprint is a summary evaluation of a thing or action's impact on the environment. Ecological footprints are usually expressed in terms of units called planet Earths, or sometimes hectares of average planetary surface consumed. The idea is that the ability of the Earth to generate clean air, clean water, etc. is limited and thus the total can be estimated with the impact of everything we do charged against that total. If you drink a glass of water, that's charged against the amount of fresh water that the Earth is able to regenerate every year. By most estimates, we are using the services of between 1.5 and 2 planet Earths per year. This means that we are constantly degrading the capacity of the Earth to provide ecological services. For example, take fresh water. We use more fresh water every year than the Earth regenerates. As a result, we are degrading the Earth's capacity to produce fresh water because we are draining out the lakes. We are pulling water out of the aquifers. We are making it more difficult for the Earth to give us the ecological resources we need. We're thus in a quandary that as consumption continues to rise, the capacity of the Earth to service our consumption continues to fall. You can see this in domain after domain. The oceans have been fished out, so it's getting more and more difficult to find wild fish in the oceans. Rivers have been fished out. There is less and less land available for agricultural exploitation. Soils are being depleted, so they need increasing amounts of fertilizer in order to grow food on them. In domain after domain, we are simply drawing down the Earth's capacity to provide services for us. An alternative to ecological footprint is the carbon footprint. Instead of using the planetary regeneration capacity as a basic unit, carbon footprints are simply expressed in tons of carbon dioxide emitted for a given activity. The two measures produce broadly similar results. Something that uses up a lot of carbon dioxide, that emits a lot of carbon dioxide or creates a lot of pollution, is almost something that is a high ecological footprint. There are some examples where that's not true. For example, using fresh water might have very little carbon footprint, but a very high ecological footprint. But most of the sorts of things we do are complex activities, whether it's consuming food or driving or living in a building, going to work, using space on the planet Earth. Pretty much all of the things that we do have such a long chain of activities behind them, that ultimately if you add up the ecological services involved or if you add up the amount of carbon emitted, you get the same sort of answer. Estimates of ecological footprints vary widely, but a typical result is that food consumption makes up a surprisingly large proportion over one quarter. And food housing, housing including energy use, that is heating and lighting your house, and transportation usually account for more than half of the total ecological footprint. Food is relatively less important when it comes to carbon footprints, because obviously food has a, raising food has a direct impact on the environment and only an indirect impact on carbon emissions. But again, estimates vary widely. A lot of this depends on how much, how you include the ultimate carbon impact of food in terms of carbon released from the soil or methane farted out by farm animals. So it can be very difficult to estimate these things. When you put it all together, whether you're looking at ecological footprints or carbon footprints, either way food, housing, and transportation usually make up a little over half of the total. Consistent with overall environmental performance on a range of indicators, it's the Anglo-Saxon colonial countries, Australia, New Zealand, United States, Canada, that tend to have the highest ecological footprints. Europe usually does a little better and the best countries of all are the very poorest countries of sub-Saharan Africa and Southeast Asia. An interesting outlier on this graph, Sweden has one of the highest ecological footprints in the world and that's because of a high level of logging in forestry industry in Sweden and also because of high levels of meat consumption. But in general it's the usual suspects, North America and Australasia, that have very high ecological footprints. Ecological footprints and carbon footprints are used in academic research and policy research to estimate the overall impact of policy and lifestyle choices. Now, obviously high consumption lifestyles perform worse than low consumption lifestyles on these metrics but surprisingly the amount of things a person consumes isn't really the biggest lever for determining the ecological footprint. Food, housing, and transportation tend to matter much more than the sorts of things you purchase and the reason is that food, housing, and transportation are things that we use every day, day in and day out all the time. Your refrigerator is running continuously all day every day and so the ecological footprint of your refrigerator tends to be very high whereas the ecological footprint of buying a new pair of shoes may be large on the day you buy it but since you only buy shoes a few times a year the cumulative or over time average ecological footprint of buying things like shoes or even television sets can be relatively low. Of course, using the television set uses electricity and also has a footprint of its own. That would go into the housing footprint. Population averages however mask potentially massive class differences and individual differences. So look at it in an individual sense. For food, vegetarians have roughly half the ecological footprint of meat eaters. Raising meat is ecologically very destructive eating vegetables much less so. Apartment dwellers have roughly half of the ecological footprint of house dwellers. That's because it is much, much cheaper to heat and cool apartments in buildings where people live on top of each other than it is to heat and cool and climate control individual houses that are highly exposed to the environment around them. Transportation footprints also very widely. People who use mass transit have roughly half the impact of people who drive. Of course people who walk everywhere have virtually no ecological footprint for transportation whatsoever. Only the very tiny ecological footprint of the paving of the sidewalks that they walk on which is relatively inconsequential. So choice of lifestyle within a country can have an enormous impact on the kind of ecological footprint people have. That's not just a choice issue, it's also a wealth and class issue. People who live in smaller houses and drive smaller cars have much smaller ecological footprints than people who live in big houses and drive big cars. Also within each category, massive efficiency gains are possible with only minor changes in consumption or behavior. So a lot of people think that we all have to go back to living a very, very primitive pre-industrial lifestyle in order to bring down our ecological footprint. In fact we don't have to do very much at all to have a dramatic impact on our ecological footprints. Some very simple things like driving cars that have very small 0.8 liter engines instead of very large 1.5 or 2 liter engines has an enormous impact on our ecological footprints. Using television sets that are half the size of one of the enormous modern flat screen TV sets, a television set of half the size will have electricity use of one third or one quarter as much as the larger television set. Having smaller refrigerators and keeping less food stocked at home again has a big impact on people's ecological footprints. So there are easy efficiency gains to be had from very small lifestyle changes. People can still drive to work as long as they drive smaller cars and live closer to their workplaces. That wouldn't be ideal and that won't save the earth but it would give us a lot more time before the earth is totally destroyed. In other words a lot more time to find a permanent solution to the sorts of problems we face. Key takeaways. Humanity collectively uses at least 150% of the absorptive capacity of the earth. Some estimates are 160 or 180 or even 200% but I haven't seen any estimate that's under 150% of the absorptive capacity of the earth. Resulting in a continuous degradation of the earth's capacity to generate ecological services. As a result the percentage of the earth's absorptive capacity being used is going to be rising and rising every year because the absorptive capacity itself is constantly degrading. Second, daily lifestyle components like food, housing and transportation make up more than half of the average person's ecological footprint. And finally within each recurring lifestyle component massive efficiency gains are possible with minor changes in consumption or behavior. We don't have to all live like hermits to have a big impact on our utilization of the earth's ecological capacity. Thank you for listening. I'm Salvatore Bobonis. 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