Software or Websites for Checking Niches

Hey guys, I was wondering whether there are any good websites or programs that allow one to look up how populated or hard a niche is. I want to make an environmental blog in preparation for this company I am starting, and I want to know how to go about it to see where my blog would fit in. Also, I looked this up in search, and I could not find anything very useful. Thank you!

What does an "environmental blog" mean exactly?

How about checking out google keyword planner, google trends, semrush, kwfinder, kwrevealer, etc.
You can also check out the competition by searching on facebook, twitter, and such.

Tools will only show you things to manually dig more deeply into, so don't get too caught up.

https://www.blackhatworld.com/search/15599365/?q=niche+research&o=relevance&c[node]=12
https://www.blackhatworld.com/search/15599563/?q=keyword+research&o=relevance
https://www.blackhatworld.com/seo/keyword-research.987991/
https://www.blackhatworld.com/seo/why-keyword-difficulty-calculators-suck-how-to-make-your-own-calculations-2-087-words.935960/