Pros
At UNEP-WCMC there is a legal split between the WCMC part and the UNEP part. The former is becoming well run with some innovative ideas. I'll cover the latter UNEP side of things in the cons as there really are no pros other than the name recognition. The WCMC CEO is good, trying to make changes but running against the current.
Cons
The UNEP component to the organisation is risk adverse, hyper-hierarchical and filled with nonsensical platitudes. Everything takes 10 times longer than it should and puts more junior staff under a lot of pressure having to chase down senior management to get sign-off. Cambridge is an expensive place to live. Even more so with inflation where its at. There is a chasm between the salaries of senior management and the employees who actually do the work. Leaders drive Teslas, and diesel guzzling SUVs (for an organisation which prides itself on trying to stem biodiversity loss and climate change) to work. While their minions cycle and walk. The average salary is substantially below the UK national average. I think people would be okay with the low salary if they really felt that what they were doing was making a real difference but because of the organisational lethargy driven by its association with UNEP this 'feel good' element isn't even there. In short a number of different factors come together in perfect alignment, resulting in an intrenched, unbending, toxic culture which permeates throughout the organisation.