As is shown by the two graphs,the U.S. population soared from 2 million to 250 million from 1800 to 1990.

如图所示，从1800年到1990年，美国人口从200万猛增到2.5亿。

In contrast, the number of wildlife species no longer existing shot up,adding up to 70 over the same period of time.

与此相反，灭绝的野生物种数也直线上升，在同期增加到70种

It is obvious that the extinction of wildlife resulted from the population explosion.

显而易见，野生动物的灭绝源于人口剧增。

We may cite a variety of reasons for this situation.

我们可以引用很多原因解释次现象。

First of all, the destruction of ecological balance plays a pushing role.

首先，生态平衡的破坏发挥了主导作用。

Due to population problems,pollution and desertification are becoming increasingly serious.

由于人口问题，污染和沙漠化日渐严重。

Furthermore, a great number of species were killed for food.for money and even for fun.

其次，很多物种由于捕食、赢利甚至娱乐而被猎杀。

Even worse, with the rapid growth of human population,

更糟糕的是，由于人口急剧增长，

inhabitable areas were expanding so fast that few areas were left for wild animals.

人类居住地扩张如此迅速，以至于野生动物无家可归。

To sum up, it is imperative for us to take effective measures to protect wildlife.

总而言之，我们很有必要采取有效措施保护野生动物。

Firstly, the U.S. government should pour more investment into wildlife protection in a bid to create a better environment.

首先，美国政府应向野生动物保护投入更多资金以便改善环境。

Secondly, the birth rate in the U.S. must be put under control as the dramatically expending population gives rise to serious environmental problems.

其次，由于人口激增导致了严重的环境问题，美国人口出生率必须得到控制。