英语流利说 Level 6 Unit 3-1 Depletion
A number of scientists are emphasizing the tremendous challenges that will soon be faced when the depletion of fossil fuel supplies coincides with an alarming increase in the global population. They highlight agriculture which is heavily dependent not only on gasoline to fuel machinery, but also on the petrochemicals necessary to manufacture synthetic fertilizers and pesticides. Without these petrochemicals, crop yields would be only a fraction of what they are today. To assume that an abundant source of renewable energy will address this challenge is to ignore the vital non-fuel uses of petrochemicals.
Then there is the challenge posed to the current levels of mobility. As a fuel, gasoline is unrivalled in its portability. Electricity requires bulky batteries and hydrogen is notoriously difficult to store. Biofuels might seem like an alternative, but the energy consumed when converting corn into bioethanol, for instance, greatly exceeds the output when the fuel is utilized. In any case, once we reach a crisis in the food supply, it will not make sense to divert food crops to other uses.
Although there seems to be a widespread belief that the era of oil dependency is coming to an end due to some technological remedy, this may be mistaken. Relying on such an assumption can lead to complacency and a failure to take precautions. Experts may not be able to come up with the kind of solution that can lead to a pain-free transition. Scientists warn that relying on alternative resources might only support half of the global population. The absence of realistic alternative to fossil fuels will mean that the first priority will be to curb the demand for food.
（The article implies that the general population assumes that things will get better.）
（Petrochemicals are used to manufacture pesticides which are important for agriculture.）
（There is a widespread belief that the era of oil dependency is coming to an end.）
（The aim of the article is to highlight the seriousness of the situation.）
（As fossil fuels become depleted there may not be enough food for the growing population.）
（Curbing the demand for food will require a reduction in the global birth rate.）
