Energy is and will remain an important factor in U. S. ’s economic growth. While for much the 20th century, America has enjoyed

Now listen to part of a lecture on the topic you just read about.
Professor
You know, the price of wind generated energy fell more steeply than any other energy source over the past 30 years. Indeed, the cost of wind power fell from approximately 25 cents per kilowatt hour in the early 1980s to between 5 cents and 7 cents in prime wind farm areas a decade later. Wind advocates argue that a new generation of turbines will bring the cost down below 5 cents per kilowatt hour—which is competitive with conventional fossil fuel sources for electricity generation.
    Wind power, currently less than 1 percent of the U. S. power supply, could double its share within 10 years. The American Wind Energy Association has optimistically projected that wind power could provide as much as 6 percent of the nation’s energy by 2020.
    Wind power’s environmental benefits are usually overstated, while its significant environmental harms are often ignored. Promised air pollution improvements have failed to materialize. Wind farms generate power only when the wind is blowing within a certain range of speed. When there is too little wind, wind towers don’t generate power; but when the wind is too strong, they must be shut down for fear of being blown down. Even when they function properly, wind farms average output is less than 30 percent of their theoretical capacity compared to 85 to 95 percent for combined-cycle gas fired plants.
    Because of intermittency problems, wind farms need conventional power plants to supplement the power they do supply. Bringing a conventional power plant on line to supply power is not as simple as turning on a switch; therefore most "redundant" fossil fuel power stations must run, even if at reduced levels, continuously. Accordingly, very little fossil-fired electricity will be displaced and few emissions will be avoided because fossil-fueled units must be kept immediately available to supply electricity when the output from wind turbines drop, because wind speed slows or falls below minimums required to power the turbines. Kilowatt-hours produced by wind turbines cannot be assumed to displace the emissions associated with an equal number of kilowatt-hours from fossil-fueled generating units. Combined with the pollutants emitted and CO₂ released in the manufacturing and maintenance of wind towers and their associated infrastructure, substituting wind power for fossil fuels does not improve air quality very much.
    What is more, wind farms could damage the populations of some bird species if they are not carefully sited. We are not saying we should stop building wind farms. Birds would suffer much more from climate change if we don’t. But the data shows we have to be much more careful about where we site them. Wind farms built in deeper water further from the shore might prove better for birds.
    Compared with past assaults, such as organ chlorine pesticides, loss of hedgerows, illegal persecution of birds of prey and intensive agriculture, wind farms should be low down the scale of threats. However, if we put them in all the wrong places then that picture would be very different. Yet when it comes to offshore wind farms, we do not even know where the wrong places are, because so few impact studies have been done.
Question:
Summarize the points made in the lecture you just heard, explaining how they cast doubt on points made in the reading.