You should look up the UK Green Film Festival which has been running for some years now, i am currently working with the organisation in adding Coventry to the list of screening venues. They used to show dramas with environmental themes but now their focus is on the pick of the best documentaries from around the world.
https://www.ukgreenfilmfestival.org/
I gave a talk with Friends of the Earth at the premiere of the magnificant film 'More than Honey' at the magnificent independent cinema the Hackney Picturehouse.
https://m.youtube.com/watch?v=2NT05qEJxUk
It was a full house and right at the time when we were campaigning against the use of neonicotinoids. The film contrasted different approaches one worked with bees the other just used them with scant regard for their worth other than to pollinate crops that year. That film got to the heart of what is wrong with our capitalist uncaring society well worth a watch.
I would also look at the lists on Letterboxd here is one list which focused on films and documentaries with an environmental theme.
https://letterboxd.com/cinematiccritic/list/cinematiccritics-candidates-for-an-environmental/
Hope that is of interest. I would love to know what films you come up with in the end...