阅读材料：
In the past century, the steady growth of the human population and the corresponding increasing in agriculture and pesticide use have caused much harm to wildlife in the United States – birds in particular. Unfortunately for birds, these trends are likely to continue, with the result that the number of birds in the United States will necessarily decline.
在过去的一个世界，人类数量的增加以及随之而来的农业生产的发展和杀虫剂的增加使得很多美国的野生动物受到了影响，而这种问题在鸟类上表现得更为明显。更加不幸的是，由于人口数量、农业生产和杀虫剂使用的趋势不会改变，美国的鸟类数量将会必然地随之下降。
First, as human populations and settlements continue to expand, birds’ natural habitats will continue to disappear. Forests, wetlands, and grasslands will give way to ever more homes, malls, and offices. As the traditional areas suitable for birds keep decreasing, so will the size of the birds’ populations that depend on those vanishing habitats.
首先，随着人口数量和居住面积的不断扩张，鸟类天然的栖息地持续地减少。森林、湿地和草原都变成的住宅、商场和写字楼。随着那些传统的适宜鸟类栖息的地方持续减少，失去赖以生存栖息地的鸟类，数量自然是减少的。
Second, agricultural activities must increase to keep pace with the growing human population. The growth of agriculture will also result in the further destruction of bird habitats as more and more wilderness areas are converted to agricultural use. As a result, bird populations in rural areas will continue to decline.
第二，为了能够满足增长的人口数量，农业活动也必须随之增加。农业的增加的代价是进一步破坏鸟类的栖息地，越来越多的荒地变成了农业用地。因而，鸟类在乡村的数量也随之持续减少。
Third, as human settlements expand and agriculture increases, the use of chemical pesticides will also increase. Pesticides are poisons designed to kill agricultural and home garden pests, such as insects, but inevitable, pesticides get into the water and into the food chain for birds where they can harm birds. Birds that eat the poisoned insects or drink contaminated water can die as a result, and even if pesticides do not kill birds outright, they can prevent them from reproducing successfully. So, pesticides have significantly contributed to declines in bird population, and because there will continue to be a need to control agricultural pests in the future, this decline will continue.
第三，随着人类居住地的扩展和农业的发展，化学农药的使用也增加了。农药是用来杀死诸如昆虫之类的生长在农田或者菜园的害虫的有毒物质。不可避免的是，这些农药会进入水系和食物链，进而伤害鸟类。鸟类会吃被毒死的昆虫或者喝污染了的水。这样会导致鸟类的死亡，即便不会不会导致鸟类的立刻死亡，也会影响鸟类的繁殖。所以，杀虫剂会对鸟类的数量有非常严重的影响。同时，因为即便是在将来，还是需要杀虫剂来控制农业害虫，所以，鸟类数量减少的趋势难以改变。
阅读部分需要提取的观点是：
- Main point: 三个原因导致鸟类数量减少
- Sub point 1: 人类居住地的增加
- Sub point 2: 农业用地的增加
- Sub point 3: 杀虫剂的使用
