A pretty ultramarine blue flower which changes colour in response to temperature, a flying frog and the world's oldest mushroom preserved in amber are among the 350 new species discovered in the Eastern Himalayas over the past 10 years. But experts warn the new discoveries are under pressure from demand for land and climate change.

A report published today by the WWF, The Eastern Himalayas – Where Worlds Collide, lists 242 new types of plants, 16 amphibians, 16 reptiles, 14 fish, two birds and two mammals and 61 new invertebrates. The cache, quality and diversity of species newly discovered between 1998 and 2008 make the mountainous region one of the world's most important biological hotspots.

The WWF is asking the governments of Bhutan, India and Nepal to commit to cooperate on conservation efforts in the geographic region that transcends the borders of the three countries to protect the landscape and the livelihoods of people living in the Eastern Himalayas.

Population growth, deforestation, overgrazing, poaching, the wildlife trade, mining, pollution, and hydropower development have all contributed to the pressures on the fragile ecosystems in the region, the report says. Only 25% of the original habitats in the region remain intact and 163 species that live in the Eastern Himalayas are considered globally threatened.

Because the region sits at the biogeographical crossroads of two continental plates, it contains a wide range of biodiversity and landscapes from both worlds. The Indo-Malayan lowlands are home to Asian elephants, clouded leopards, wild water buffalo, gaur, hornbills, cobras and geckos. The elevated Palearctic to the north is home to snow leopards, red pandas, black bears, and wolves.

The world's highest mountains sit in close proximity to some of the world's deepest gorges in a region that also contains the world's most northerly tropical jungles, temperate forests, tall grasslands, savannas and rich alpine meadows. A great deal of the rugged region, which also includes small areas of China and Burma, is difficult to access and has made biological surveys extremely difficult and left large areas biologically unexplored. But the intrepid are richly rewarded with new discoveries.

Impatiens namchabarwensis, or the blue diamond impatiens, is one of the 242 new plant species to have been discovered in the past 10 years. The highly endemic ultramarine blue flower was discovered during an epic expedition undertaken by Chinese botanists who trekked 60 miles from the nearest road and descended into the Namcha Barwa canyon, a gorge measuring almost 402 miles long and, in places, twice as deep as the Grand Canyon, which can reach depths of up to 6,000 feet. The rare plant can grow as tall as 60cm and flowers all year round.

The flower is perhaps the best symbol of the effects of climate change in the region as its colour changes according to temperature and exposure. In a cool climate, its appears pure blue, but darkens to a purple when the temperature rises.

A bright green, red-footed tree frog was described in 2007, and called a "flying frog" because its long, webbed feet allow it to glide when falling.

An amber mine in far north Burma has also thrown up some important new discoveries: a 100m-year-old gecko, the oldest-known mushroom and fern have all been unearthed preserved in amber.

Mark Wright, WWF's conservation science adviser said: "These exciting finds reinforce just how little we now about the world around us. In the Eastern Himalayas we have a region of extraordinary beauty and with some of the most biologically rich areas on the planet. Ironically, it is also one of the regions most at risk from climate change, as evidenced by the rapid retreat of the glaciers, and only time will tell how well species will be able to adapt – if at all."