Mature or overgrown? semantics, and not mutually exclusive. If not properly maintained and left to grow wild, there will be no point in visiting islands in the future. You might just as well visit any public park, and imagine that there are exotic wild animals behind the thick foliage. The new Islands squirrel enclosure illustrates the current problem well, and yes, it really is a 'growing' problem, just ask general members of the public if you don't believe me. Look at the plants that have been put in the border right in front of that exhibit. Tall, dense and thick growing species have been chosen, in addition to similar plant species inside the exhibit. Within a year the squirrels will not be visible, I guarantee.
Enclosures can still be naturalistic without obscuring public view. The trick is to keep the foreground clearer.
Chester has already done a fabulous job of making it difficult to view elephants indoors. However they've failed with the outside enclosure thus far, the elephants are still far too easy to see and to photograph outside. It's high time that the outside viewing area was made more 'naturalistic', I'd suggest a 6ft wooden fence along the elephant / bear bridge (like the one successfully used for the lions), and at ground level any fast growing thick tall foliage would suffice. If there are any unfortunate gaps through which public could glimpse the elephants, might I suggest breezeblocks made to look like old trees or termite mounds to complete the naturalistic theme? After all, it's not reasonable to expect to see elephants every time you visit the zoo is it? You'd have no guarantee of seeing them in the wild.
