Hi, Rachel,
You're right to be disappointed that the change has been made without consulting you, however it is the right action to take as there is a strong likelihood that the data you've added it the map is subject to copyright and therefore doesn't meet OSM terms of use for contributors.
You're right that data added which does meet those terms is then subsequently available for OSM users (i.e anyone who uses OSM to analyse the FWMC catchment in this case). If you want to continue to use OSM to hold the catchment boundary you'll need to get in touch with the copyright holder and request permission from them to release the licence so that it's compatible with the OSM licence.
A template letter of such a request can be found here: https://osmfoundation.org/wiki/Licence/Waiver_and_Permission_Templates
In the future, best practice is to list the source of the data you add to OSM within the changeset comments using the tag osm.wiki/Tag:'source='
I hope that clears things up for you

Hi, and welcome to the OSM community. Can you share where this boundary data is from and clarify whether it is subject to any copyright?
Thanks

OK, it's the first time I've looked at names, and I felt, similarly to you, that it was backwards.

As for the boundaries themselves, the first link shows land ownership, so it would only be appropriate to import that data into OSM if you've got evidence that access is directly linked to ownership. Is that the case?
What seems to be clear though, is that it's not a `leisure=nature_reserve`, and would likely be best represented by updating the existing `natural=forest` polygons into an MP with the appropriate access and operator tags added. Much as:
relation/3155570 or relation/1849496

Hi,
What exactly are you trying to map here? The land ownership, or everything that is publicly accessible? If it's the former, I don't know that it has a place on the OSM database, unless you wanted to highlight natural areas managed by 'operator=Natural Resources Wales': https://datamap.gov.wales/layers/inspire-nrw:NRW_FOREST_LEGAL_BOUND.

If it's the latter then an mp-relation with suitable access tags might be more appropriate.
Either way, I can't see any evidence that it's a nature reserve:
https://datamap.gov.wales/layers/inspire-nrw:NRW_LNR or
https://datamap.gov.wales/layers/geonode:nrw_nnr_declarations
and it'd be worth following the local language, i.e: 'name=Parc Coedwig Afan' , 'name:en=Afan Forest Park'