Ecosystems

The origin of tropical forests

Until last century, tropical forests were larger than they are today. Fossil finds prove that forests developed in the Tertiary period (between 65 and 2 million years ago) in south-eastern Asia and their flora was not different from today's. Some aspects of their structure in the late Pleistocene (after the last glaciations, 10,000 years ago) have been explored by palaeontology (the science that deals with ancient living beings through fossils) and bio-geography (the science that deals with the geographical distribution of living beings on the earth's surface and its causes). The past of this ecosystem is now being investigated through fossil pollens and phytolytes (mineral inclusions in leaves, stems and fruits). The largest tropical forests probably extended in the post-glacial area. The study of the past and current diversification and distribution of the living species suggests that in the Amazonian area there must have been stretches of forests running through the prairies; when these "strips" of forest joined together, their species spread to other areas and the forests achieved today's biological diversity. In distant ages, the tropical forests covered northern countries as well, including the Thames valley in the UK, which was rich in tropical flora and fauna. The succession of climatic changes made it disappear, while at the tropics the tropical forests survived and extended.