sight-seeing boats are threatening the coastal mangrove trees on Iriomotejima island in Japan. Large waves from high-speed boats are washing away the mud around their roots.

With ecotourism booming in Japan, a growing numbers of people are making trips to visit the ancient forests in Iriomotejima, about 440 km southwest of the Okinawa's main island. The most serious damage has occurred around the island's Nakamagawa river.

The mangrove trees grow thickly over a stretch of about 300 hectares on shores and the trees roots spread on to the surface of the water.

For decades, many high-speed boats have been carrying tourists on short trips around the island. They cause strong waves to break on the shores which damage the fragile mangroves.