30 Some people believe that the Earth is being harmed (damaged) by humanactivity. Others believe that human activity makes the Earth a better place to live. What is your opinion? Use specific reasons and examples to support your answer.

Nobody can deny the fact the environment has become much worse than beforealthough we may live a more comfortable live than our ancestors, and, if we keep over-exploiting the Earth, we would meet our ends some day.

我总是很喜欢你的开头的风格，很活泼。

Looking around, you may find out easily what we have done to the planet,which once was a blue sky with forests covering the whole lands as home toa diversity of creatures. The result of the examination may give you asurprise and force you to admit that the situation is not good for us.Waste is being dumpedsintosrivers, landfills are everywhere and you mayhave noticed that there may well be several reports in today's newspapersabout the leakage of the sunken oil tankers that pollute the sea seriously.

The ecosystem of our world is at the edge of breakdown.

这一段用蓝色的线标出的是你的topic sentence.你用黑体写的词很好，很生动。例子也举得很好！

Our planet gives us everything we need, but her greedy son, our humanbeings, is killing the self-giving mother. We are too avaricious in takingwhat we want without giving anything back. What's more, we always want toget more than we actually need--more clothes, more food, more furniture, more factories, more cars--the more the better, and maybe the more the faster to bury ourselves by our own hands. You may argue that I am too pessimistic but such things are facts as the sand storm happened in Beijing, the dead elephants without their beautiful ivories, the barrenground caused by over grazing, the sunken city made because of excessiveexploration of groundwater, the tendency of global warming as a result ofexcessive emission of carbon-dioxide and many other environment problems.这一段的例子排比地列出来，也写得很精彩！句子也很生动！不过，我认为这一段的主题句可以写得更明显一些，以便从意思上和上面一段区别开来，因为上面一段着重于人类对地球的破坏，这一端是写的人类索取无度，其中的意思可能会有重叠，比如你的environmental problems实际上就包含了上面一段很多的例子，不妨试着分开。

And the natural resources that are used as the main energy are notlimitless as we once thought. Such energy as fuel, coal is become perilousand will be used up one day, and what can we do then?

这一段似乎和上面一段提到的索取无度又有意义上的重叠，不是作为转折放在这里，因此应该归入上面一段，并且正好可以代替上面的环境问题，避免意义混淆。同时，这一段可以这样转：其实，人类还是正在越来越注意保护环境的，我们会尽可能在提高生活水平的情况下，让地球变得更美好。

We can't wait to that day; we must do something to prevent things frombecoming worse and worse. Maybe I am a little pessimistic but to makethings more serious than they really are can draw more attention. So as you see, people need to respect the Earth and try every means to preserve it.If we don't, what kind of future will we have? (Maybe none at all)

结尾的风格也是你的，比较活泼的那种，当然也不妨加上对前面几段观点的简要重述。