Interesting (and striking lions!), I've not seen many netted lion exhibits...is there a reason for it in terms of bird problems, or keeping them in, or something else?
Looking at the picture, I would guess that the netting increases the usable area and especially volume for the animals without expanding the footprint. In addition, the natural-looking wall design with wood, rock relief, and wild vines would probably not be possible without netting.
@Cyathea I see. But even if these populations aren't purebred, I believe they are undoubtedly descendants of individuals with strong Barbary lion bloodlines.