how can eating meat have a negative effect on the environmen

how can eating meat have a negative effect on the environment这里的eating是动名词作主语吗？
英语语法问题
how can eating meat have a negative effect on the environment？这里的eating是动名词作主语吗？
For a start,all animals,such as cows,pig and sheep,release a gas named methane,which is.....这里的主谓用逗号隔开是因为all animals这个插入语吗？
Today many people have come to realize that to help the environment and for the human race to survive,most of....这里的宾语从句后面的to help the environment 是因为逻辑主语是
people而用to还是不定式作状语？那 for the human race to survive呢，两个并列状语从句？为什么这么用。
Today many people have come to realize that to help the environment and for the human race to survive,most of us will need to become vegetarian这个是原句还有个版本to help the
environment 没有to
另外还有个问题It lacks the vitamins and minerals essential for health.这里是be essential for吗？而lack代替了be动词。