Malaria and mass extinction

Photo by Graham Watkins

Where will future cures come from?

Johann Hari (12 August) writes that “If we are going to make the planet tropical, we had better start paying attention to tropical diseases”. Thus he gives a global warming edge to his point that malarial parasites can adapt to our medicinal drugs by quickly evolving resistance to them. He relates how this process made chloroquine, an earlier wonder-drug against malaria, nearly useless in much of the tropical world, and how the same is happening to a newer one, artemisinin.

What is not mentioned is that the active ingredients of both chloroquine and artemisinin were invented not by people but by nature. For chloroquine is a variant of quinine, from the Peruvian shrub Cinchona ledgeriana, and artemisinin comes from the Chinese herb Artemisia annua. There is not the slightest chance that either drug would have been discovered by chemists working without the strong hints offered by the plants and the traditional medical practitioners who had used them for centuries. The same is true for many of the other medicines we use today. It is impossible for us to match the inventiveness with which competing lineages of plants, animals and fungi have created useful chemicals over evolutionary time.

The hidden story here is that we are quickly and catastrophically destroying those lineages, and the species to which they belong. We are committing millions of them to extinction every year, most of them completely unknown to science, as we clear and burn tropical forests and degrade or fragment these and other ecosystems. In doing so we are erasing the very source of new medicines which we need to combat resistant forms of disease, and the illnesses that are spreading to new areas with climate change. Meanwhile, our vulnerable human population continues to surge.

Unless we protect and study our remaining natural ecosystems, especially in the tropics, we’ll be cutting medicine off at the knees just when we need it the most.

Julian Caldecott, published in The Independent, 19 August 2009.  See related article in the British Medical Journal on medicine and the fate of tropical forests.