Ferns have been around for over 360 million years. Giant tree fern forests were common for millions of years but they gave way as flowering plants evolved to take their place. Today most of the nearly 800 species of tree ferns are considered endangered because of climate change. Even in Hawaii we see a fraction of the tree fern forests that existed before the 19th century. The introduction of pigs by early Polynesians and later the introduction of cattle played an important part of forest destruction.