A new report by a British-based plant protection group says almost 30 percent of the world's tree species are at risk of extinction. The State of the World’s Trees report warns that 17,500 tree species are at risk of dying out. And 440 species have fewer than 50 individual trees left in the wild. The report was recently published by Botanic Gardens Conservation International (BGCI). The number of threatened tree species is double the number of threatened mammals, birds, amphibians and reptiles combined, the report said. In a statement, BGCI Secretary General Paul Smith said, "This report is a wake-up call to everyone around the world that trees need help." Among the most at-risk trees are species including magnolias and dipterocarps. These trees are commonly found in Southeast Asian rainforests. Oak trees, maple trees and ebonies also face threats, the report said. Trees help support the natural environment and are considered important for fighting global warming and climate change. The extinction of a single tree species could mean the loss of many others. Every tree species matters to the millions of other species that depend on trees, and to people all over the world, Smith said. The report found that thousands of kinds of trees in the world's top six countries for tree-species diversity are at risk of extinction. The greatest single number is in Brazil, where 1,788 species are at risk. The other five countries are Indonesia, Malaysia, China, Colombia and Venezuela. The report said the top three threats facing tree species are crop production, logging and livestock farming. Climate change and extreme weather are also growing threats. At least 180 tree species are directly threatened by rising seas and severe weather, the report added. It noted that island tree species are more at risk than other trees. This is particularly concerning because many islands have species of trees that can be found nowhere else, the report said.