When I worked in Borneo, I was fascinated by the immense diversity of trees in the jungles where I worked, even though I could only identify a few species. I did not even know how many different trees I was seeing. They look so much alike, with some exceptions, that I could walk by a rare, unrecognized tree without knowing it. And that raises the question that has long puzzled biologists: how many kinds of trees are there?
We know that in North America there are about 1,000 tree species, and similar numbers in temperate Asia. Europe has a more limited tree flora, with 250-500 species. The number of tropical trees has never been known with any accuracy.
Now, a worldwide study lead by Prof. Ferry Slik of Universiti Brunei Durussalam, along with 170 colleagues from all over the world, has come up with the most accurate estimate to date, and it is quite astonishing. The problem is that most tropical species are rare, and easily missed in species counts. Instead of analyzing species lists or herbarium specimens, the researchers analyzed a database of over 200 intensively studied forest plots worldwide.
Their conclusion is that there are 40,000-53,000 species of tropical forest trees in the world. This is much higher than any previous estimate or calculation, which typically miss rare trees.
This number, and the high frequency of rare trees, has important implications for conservation. If we are to prevent extinction of large numbers of tropical tree species as the world warms up, we need to change our conservation approach. Instead of focusing on conservation of individual species, as is commonly done with wildlife species, tree species conservation will only succeed if we can set aside very large areas of tropical forest. This could allow rare species to maintain self-sustaining populations. Climate change may result in the loss of large amounts of tropical moist forest, and this will inevitably cause extinction of many rare tree species. Addressing climate change and tropical forest conservation are critical if we are to avoid the loss of a large percentage of tropical tree species.Similar principles can apply to temperate forests. Conservation of large tracts of forest land could help prevent the loss of species as the world warms.