This is generally what people in major cities and heavily urban areas like California, east coast of China, northern Europe think when they look around them, but then when you actually go look around the world, you suddenly discover that the earth is mostly vast, unpopulated tracts of land. Just traveling around can give a vastly different view of things. Do humans put out toxins and eliminate species? Sure they do, but in terms of consumption, the carrying capacity of the earth has grown dramatically over the last 200 years because of innovation and research driven by population growth, and there is still plenty of room *(https://www.quora.com/If-the-entire-world-had-the-population...). The more people you have, the more minds and resources you can throw at a problem.

There's also the interesting fact that my parents raised 7 children on the same amount of resources that most people raised 2; we were _way_ more efficient per capita than most households. Oddly enough, we were raised to be more resource efficient than most people. We knew resources were scarce, so we tried to be more efficient. Maybe the solution is to have more children, not less, then teach them to find solutions to any problems encountered. Heck, mine the moon if you need more resources, invest in hydroponics for food if you run out of space, don't start getting rid of the poor people. Then you'd just end up with a bunch of rich folk sitting in panda refuges.

EDIT: I only bring up the last sentence because the question always encountered when someone says "There are too many people." is "Who do you think we should get rid of, how and when?"

EDIT 2: I do agree that we should do better with taking care of the environment and avoid catastrophic issues from bad decisions, and I agree with the post below about both being able to be right. :D