Caribbean islands are marketing themselves as places for learning with geology, biology and history among the subjects on offer in an eco-tourism boom.

In Dominica, children as young as six are led through rainforests and river valleys, learning about complex ecosystems on the way.

In St Lucia, summer programmes for nine to 12-year-olds explore the island, with local children, through field trips and project work. Teen Tours has designed a four-week, multi-racial programme for 13 to 18-year-olds focusing on the environment and themes in Caribbean culture, culminating in a performance and exhibition of the children’s work.

The oldest town in St Lucia, Soufriere, is a good starting point for a course in Caribbean history. The Diamond Falls and Mineral Baths were built in 1713 by Louis XIII for his troops - the Empress Josephine bathed there as a young girl.

Plants and trees are labelled with detailed descriptions of their evolution and culinary or medicinal uses. The Sulphur Springs offer a unique lesson in geology with the world’s only drive-in volcano. The putrid smell of hydrogen sulphide greets visitors from a platform perched above the boiling grey mud. Carib Indians called it Qualibou, the place of death.

The Maria Islands are easily reached from Soufriere and have been a nature reserve since 1982. As they have never been inhabited by humans, frigate birds feel safe to nest on the cliffs carpeted with towering cacti, and leatherbacks and other turtles meander through living coral reef. Access to the islands is permitted only in the company of trained guides and the islands are closed to human visitors from May 15 to July 31.

Dominica is for the more intrepid eco-tourist. Rainforests, reefs and volcanic craters combine to make a luscious learning environment. Guides are essential and one of the toughest trails is through rainforest and the Valley of Desolation to the Boiling Lake: the largest active fumarole or volcanic hole in the world.

The route winds through tangled thicket. Mosses and epiphytes run riot, while the trees are bent double under the weight of their hospitality and the region’s strong trade winds.

As visitors climb the peaks of extinct volcanoes, wade through streams and tiptoe along narrow ridges, guides give informal lectures on botany and the forest food chain, identifying various strains of orchids and bromeliads.

The Valley of Desolation was once part of the rainforest that covers this region. In 1880 a volcanic eruption left it a seething mass of sulphuric vents and molten lava. Fumaroles bubble and burp up their gases and the sun, denied access to the rest of the forest floor, scorches the land.

The 63-metre-wide Boiling Lake lies in a basin just beyond the valley. The volcanic heat of the crater keeps the water bubbling at a constant 920C. One moment it simmers gently, the next it is exuding huge clouds of steam and gases.

Children as young as six can enjoy these walks which, because they carry less weight, they find less arduous than adults. Waterfalls and hot mineral pools provide cooling-off points and picnics of fresh fruit take place in forest clearings.