Overpopulation for the environment is a huge problem in Asia. The Chinese actually have addressed the problem by urging their own citizens not to reproduce. Diseases are keeping the african population down, which is a good thing.

But I do get your point. The environmental groups have been silent on this although I do think protecting the environment is a white and right thing to do.... to a point....

There is one HUGE argument missing from the immigration debate.

It is a non-partisan argument.

Destruction of our enviroment by overpopulation.

Who can argue that increased immigration will not increase pollution, and increase destruction of the enviroment?

Why dont I see this argument being used?

Where is GREENPEACE?

Where is the SIERRA CLUB?

The people at this website have always stressed the environmental angle: http://www.numbersusa.com/index

I know nothing about Greenpeace.

What I've heard about the Sierra Club is that over the past few years, perhaps over the past couple of decades, the rank and file membership have wanted the immigration issue to be on the club's platform. That is, they want some kind of immigration restriction.
However, the club's elitist leadership has always nixed that sentiment. As a result, it's my understanding that a good number of it's members have become somewhat dissillusioned and the organization as a whole much less influential.
This much has been in the news during the past few years.

I get the impression that the Sierra Club is deliberately being destroyed from the top down.
I would suggest you do some Google searches as I'm not really up on the issue.