No position is default?
I'm pretty sure that "i don't know" occurs before both affirmation and negation.
Let's take it further back: absence of knowledge and understanding, is the default. Any scientist worthy of his title, knows not to leap to any premature conclusion. It's possible that lots of "trained scientists" (not all, and probably not the majority) are actually flawed human beings like most of us, and can possibly mistake, misunderstand or misinterpret legitimate facts, and arrive at an incorrect conclusion as a result... whereas the "proper" conclusion in any given scenario, may indeed be "no conclusion," due to insufficient data or tests. Some people conclude prematurely... but the interesting thing is how not all premature conclusions are incorrect, despite the flaw in the process of reaching them. A correct conclusion can still be scientifically invalid. Science can correctly refuse to "scientifically conclude," even when the correct answer seems apparent and/or obvious, due to inadequate understanding of How or Why that answer is correct, or the process of arriving at the correct conclusion, having been incomplete, or somehow flawed or compromised.
We can say "gravity exists, and is X" because we can observe a phenomenon that clearly shows that something is happening, and that something has been named "gravity." But from what i've seen, gravity isn't yet sufficiently understood, despite the fact that we have named it and must agree that it exists, regardless of our incomplete and possibly errant interpretation of how it works, and what it actually is.
But, i don't think any sane, competent person will honestly insist that gravity is a myth, and doesn't actually exist.
Similarly, i don't think anyone sane and/or competent will suggest that pollution doesn't exist, or that it has zero relevant impact on the earth and its habitats and inhabitants, or that humans, whose nature it is, to deliberately and purposefully modify their surroundings to better suit themselves, are not doing Anything detrimental that will have any significant long-term repercussions.
But "how much of a problem is this, Really? And who/what is Actually causing it?" Are very important questions, IMO. I think we can reasonably assume several particular culprits... even in the absence of absolutely conclusive scientific consensus.
In the end... does it really matter? Lots of people think it matters, and in many ways it surely must... but perhaps what the earth really needs, is for humanity to become extinct? Maybe if that happens, the earth will eventually self-correct, and after another few hundred million years or so, perhaps another type or types of life forms will evolve and advance to achieve similar or better than what we currently have? And if that is "nature's way," should we intervene and try to preserve ourselves at the cost of preventing yet-untold species from ever existing?
I will still agree that i think we should minimize our detriments anyway, whether it "matters" or not.