Head towards Snowdonia, take the beautiful road from Beddgelert towards Capel Curig, and in less than a mile you come to Craflwyn, a National Trust education centre. A little further along, you’ll encounter Hafod y Llan, the largest estate farmed by the National Trust. A combined visit to these two sites delivers stunning scenery and opportunities for learning and discussion, primarily in geography but also in geology and tourism.

The original owner of Craflwyn, Llewellyn Parry, was keen to impress his Victorian friends, so he planted acres of rhododendron ponticum. But in the 20th century the garden was neglected and the rhodies ran wild. Since the National Trust bought the estate in 1994, staff and visitors - including school parties - have fought an unceasing battle to clear the colourful but poisonous infestation.

As we walked around the woodlands surrounding the well-equipped education centre, Keith Jones, chief warden, explains the problems caused by the beautiful but deadly bushes. “The waxy rhododendron leaves are poisonous to most animals, birds and insects and nothing lives or grows beneath the shrubs.”

That very day, a party of American students were hacking away - cutting the shrubs back to the ground with bow saws, breaking up the branches and burning them.

The case of Craflwyn’s rhododendrons is just one of the many conflicts involved in managing land - especially in an area of great natural beauty like Snowdonia. Much more complex issues are raised by a visit to the 4,000 acre National Trust farm, Hafod y Llan, two miles further along the road to Capel Curig. These issues are specially relevant to the study of land use and rural change in the geography syllabus at both GCSE and A-level.

Hafod y Llan is a large segment of Snowdon in the shape of a triangle with its base in the Nantgwynant valley and its apex at the mountain top - almost the whole of the southern side of the mountain. The geology of the area - the outcrops of slate, the tiny, high lakes and the serrated edges of the mountains - is interesting enough in itself to make a visit worthwhile.

But there is much more besides. The estate contains a massive tourist attraction, the Watkin Path - the most difficult marked route to the top of Snowdon, but used by 40,000 walkers a year. It was built by the immensely wealthy engineer, Sir Edward Watkin, and was opened in 1892 by the then prime minister William Gladstone.

The impact of tourism is an important element in the complex balancing act which the National Trust has taken on at Hafod y Llan. (Study days for school parties wishing to look at this aspect of Snowdonia can be tailored to the pupils’ needs). But it is the management of the organic Hafod y Llan farm which provides the richest discussion material for schools.

To understand how it is being run, Keith Jones led me around the grassland section of the farm - only 5 per cent of the total area - but where the key developments are taking place. We began by the gently bubbling Glaslyn River, now becoming an ideal spawning ground for brown and sea trout since the farm began its organic conversion in 2000. Fencing the farm animals off from the river and reducing chemical pollution has done the trick.

Keith explained that the Trust’s intention is for the farm not only to make a profit but also adhere to an environmental programme that seeks to increase the biodiversity of flora and fauna on the farm’s land. Hafod y Llan has a deserved reputation for its Welsh mountain ewes which fetch a high price on the market. But too many sheep can cause problems.

“Sheep graze selectively, but cattle eat a wider variety of vegetation and their dung provides nutrients for the land,” Keith explains. So the numbers of sheep have been reduced from 4,000 to 1,500, and a small number of pedigree Welsh Black cattle have been introduced.

Because there has been a big reduction in the overall numbers of grazing animals, the local feral goats have been breeding more prolifically. These goats are no respecters of stone walls - knocking off the top stones and creating gaps, as well as damaging the oak and ash woodlands which the farm management is trying to regenerate and preserve because of their special capacity for increasing biodiversity.

So the solution to one problem has created another - which is further complicated by the fact that Countryside Council for Wales requires much of the 93 miles of stone walls on the estate to be preserved.

After their visit students debate issues such as these in the comfortable discussion rooms at Craflwyn and try to find solutions. Or they may just want to take in the Welsh mountain air on the arduous but rewarding Watkin path (proper supervision is essential) to Snowdon’s summit.

The Education Officer, Craflwyn, Beddgelert, Caernarfon, Gwynedd LL55 4NG.

Tel: 01766 510120; www.eryri-npa.co.ukwww.nationaltrust.org.uk