Gehan de Silva Wijeyeratne's efforts to popularize natural history and create livelihoods through wildlife tourism have made him a wildlife celebrity in Sri Lanka. He has published over 15 books and 380 articles. In the words of British TV wildlife personality Bill Oddie, 'no single individual has done so much to publicise a country for its wildlife as Gehan has done for Sri Lanka'.

Gehan popularized the Elephant Gathering and his 'Sri Lanka is Best for Blue Whale' campaign was pivotal in developing whale watching in Sri Lanka. He also explained why Kalpitiya is a hot spot for whale watching and pelagics and brought to public attention the fact that the largest gatherings of Sperm Whales takes place in Sri Lanka. He has championed Sri Lanka as being 'Best for Big Game' outside Africa and introduced the concept of Leopard Safaris in Sri Lanka.

In his many books, Gehan has also popularized birds, mammals, butterflies and dragonflies and authored the first ever complete photographic field guide to the birds of Sri Lanka, as well as the first portable and affordable photographic field guide to the country's mammals. He is one of a small handful of natural history personalities in the world who have both written and photographed field guides to multiple taxonomic groups spanning birds, land and marine mammals, dragonflies, butterflies, wild flowers and trees, as well as books on where to watch wildlife and general overviews of the natural history of a country. Through his articles and talks, he continues to support the branding and commercial development of Sri Lankan wildlife tourism.