Millions of live animals and plants are shipped around the world each year to supply the pet trade and to meet the demand for ornamental plants. Fur skins, leather, timber, and articles manufactured from these materials are all traded in large quantities. In 1973 the scale of trade aroused such concern for the survival of species that an international treaty was drawn up in Washington to protect wildlife against overexploitation and to prevent international trade from threatening species with extinction. These countries have joined together to ban trade in an agreed list of currently endangered species and to regulate and monitor trade in others that might become endangered. There are over 13,000 known species of mammals and birds, as well as thousands of reptiles, amphibians and fish, millions of invertebrates and some 250,000 species of flowering plants.
Extinction is a natural part of the evolution of life on Earth.
But in recent times humans have been responsible for the loss of most of the animals and plants that have disappeared. The last dodo, a large flightless bird, was killed on Mauritius in 1681, while the passenger pigeon, whose huge flocks darkened the skies of North America barely a hundred years ago, was also wiped out by demand for food early this century. Many species are declining in numbers because of loss of habitat and increased exploitation as the human population grows. Trade has now also become a major factor in the decline as improvement in transport has made it possible to ship live animals and pl ants and their products anywhere in the world. A dramatic example is the vicuna, a gazelle like relative of the camels, which lives in the high Andes.