Sir: Your articles describe the planet's symptoms while ignoring the disease. Earth's cancer is humanity, breeding out of control and invading areas to the detriment of their inhabitants. The symptoms are death, famine, pestilence, and war. Not until we control our numbers will the apocalyptic horsemen rest. The Biosphere is fighting back with Aids, BSE, cancer, TB, malaria and other diseases. Are we going to be culled, or control ourselves?