(Mustangs has a negative influence on rangeland.)

1. 因为野马会吃掉很多的草overgraze，破坏土壤和整个牧场的动植物生态圈

(The Mustangs will overgraze grass, thus making it expose to rain. Wind would carry the topsoil.)

2. 因为还有其他的farm animal，cattle 和 sheep等，野马太多会破坏整个牧场的carrying capacity

(The land has carrying capacity. Horses hunt sheep, so the sheep’s population will be reduced.)

3. 野马喝水会破坏水质并且阻碍juvenile fish的生长

(Mustangs will degrade the water quality. Therefore, the juvenile fish can not survive.)

听力一一反驳：

1. 野马只是吃掉表层的草，不会破坏root，还能继续生长，另外野马的粪便粪便可以当做fertilizer，反而对草是有益的

(Indeed the Mustangs would graze grass, but they only eat top of plant, so grass will grow again. Besides, fertilizer provided by Mustangs would aid plants’ growth.)

2. 野马的存在可以保护sheep的数量，因为捕猎会同时捕这些动物，野马数量减少的话，就会捕更多羊

(It will not exceed carrying capacity.)

3. 野马的存在并不一定是对young fish有害。举了beaver的例子，之前这里有海狸，它们筑起了dams，减缓了water flow，更适合小鱼生长。后来海狸消失后，小鱼的数量反而下降

(It is not caused by Mustangs. There were beavers once. Building dam is good for young fish. However, people think that beavers will damage environment, thus killing them. Without beavers, young fish can not survive.)

Task 2

暂缺，待补充

TASK 3

讲了一种研究方法（普通人一起参与研究） 例子是鸟类观察，很多鸟类爱好者提供了帮助

Task 4