Like the history of gardens as places of pleasure and relaxation, sculpture in the open air reveals a happy interaction with the natural world, weather, an acceptance of varied light, and the processes of change.

It ideally suggests the proud harmony of man and nature we find in the great baroque palace gardens of Europe, or the brooding bronze goddesses of Henry Moore as they focus misty vistas in Yorkshire.

On a sudden sunny Sunday, it didn't take much to tempt me to visit a recently installed group of sculptures at the Hunter Region Botanic Gardens, curated by the University Gallery, on view until August 4 and set up among the rain forest species near the southern wetlands.

Recent rain had created drifts of fallen leaves and some instant weathering for the 12 works sited along a triangular circuit of paths. I was disappointed that the area was so open, hoping rather that the individual works might appear suddenly and more mysteriously among the leaves and tree trunks, with occasional vistas opening up to reveal more distant works. I wonder why this area was selected? How much more exciting it could have been to find man-made objects set among the bizarre forms of cactuses and other ancient plants in the succulent garden further along the track.

That said, many of the artists represented here are less concerned with interacting with the natural world as visual excitement than with investing their work with strongly expressed political and personal messages.

Andrew Styan has created the most elaborate installation, as we might anticipate from earlier ambitious environmental assemblages. Here he contrasts a plastic solar bandage spiralling up a pale tree trunk with recorded bird song, including the ominous squawking of crows, interspersed with disembodied human voices invoking climate change. Simple man made materials set up confronting tensions with the natural environment.

Louisa Magrics, well known for her crocheted space-filling installations, has recycled here a successful piece shown last year in the Royal Botanic Gardens in Sydney. It drifts between the trees, suspended and tensioned, a great white fairy-tale web. Stela Brix also suspends a web from a tree, a delicate structure incorporating red glass beads, echoing the seepings of translucent gumtree sap. As an exchange student from Europe she brings new eyes to the life of the bush.

Gavin Vitullo and Kris Smith each animate a perspective. Peter Tilley and Megan McCarthy each use a life-sized female figure; Peter Tilley's white cocoon shimmering in the distance, while Megan McCarthy's dark ruffled ball gown is a surreal spectre among the trunks. Braddon Snape's inflated steel graft is also a surreal intervention. Andy Devine's carefully lettered texts have the power of palaeography. Michael Garth's assertive brass axe suggests our white alien presence gradually fading into the environment.

Other artists who create real surprises are student Annika Thurbon and master of landscape reinterpretation Brett McMahon. Annika's coven of predatory spiders only gradually reveal themselves, while it is almost possible to walk past Brett's piled blocks and hanging tapes before the realisation occurs that this apparently casual work is a complex fusion of the real and the recreated. Putting much of this work in thicker undergrowth would have set up greater dramatic tensions.

Viewing this exhibition calls to mind a work on the Callaghan campus of the University of Newcastle. Outside the Chancellery, between its main entrance and the roadway, Vlase Nikoleski carried out a commission to create a sculptural environment, incorporating a monolithic structure and a series of watercourses and pools.

The well-maintained work now sits between large trees, hillocks and bushes, obviously a human intervention, but happy in the natural environment, large enough to explore, and sufficiently concealed so there are surprises. It must provide ongoing pleasure to visitors and resident staff of the institution where Vlase Nikoleski taught for so many years.

It is well worth a visit. Indeed, much of the campus is enlivened by sculptural pieces animating vistas and emphasising visual perspective to lawns and wooded areas.