The link from OSM to Wikidata does not cause any problem (the only license it carries is OSM’s own license). The problem is that if you remove the text version of the information from OSM (e.g. species=*) in favor of the Wikidata link (e.g. species:wikidata=*) you are forcing any user (like a map that needs to show the species) to take that information from Wikidata, which carries another license.
By including both the text version and the link to other sources you are
- technically simplifying the usage of the data (not forcing users to combine data from other sources), which is good
- legally simplifying the usage of the data (not forcing users to combine data with other licenses), which is good
- still allowing users that need extra info and are ok with the extra technical and legal overhead to use it, which is good
- introducing redundancy, which is bad (because it allows to include inconsistent data and forces to do extra work to keep them consistent over time)
IMO there is no perfect choice about which fields to keep, but keeping both is still the best one