Population and diversity

Population and population growth have a lot to do with biodiversity — especially agricultural biodiversity.

Why? For one simple reason: The more people there are on Earth, the more they eat. They will need to stay alive and healthy. They’ll need more food, medicine, clean water, breathable air, space for recreation, and places just to contemplate beauty and get away from the crowd. But as Earth’s population increases (and it has been increasing greatly), the space for producing all those necessities and benefits shrinks. At the same time, our trash, waste, and polluted soil, water, and air are becoming ever-greater problems.

Many people = much trash (FP)

More people equals a need for more food growing on more land, for clean water, for space in which to live. But the amount of land, water, and space is limited by Earth’s size. So we have been pushing deeper into what in the past have been storehouses of diversity. Far too often, biodiversity suffers when forest is cleared to create land for crops, or when clean river water is diverted to irrigate crops that may be treated with poisons to kill bugs.

One big reason that the globe’s population has been increasing is that farmers and scientists have made so many improvements in food production in past years. At the same time, there have been great improvements in health and medicine. More babies survive through infancy, and people live longer. The result? More hungry people, sharing a planet whose size is fixed.

So population growth is related to biodiversity in two major ways. One, more people means smaller areas where diversity can thrive. Two, the crops we eat need a constant supply of genes from their wild relatives and farmers’ varieties so that they may continue to evolve — to develop characteristics that can fight off insects and diseases, or allow the crops to be grown on soils of lower quality. Less land means less diversity, and that means a reduced supply of genes.

A crowded globe..
Population growth has been rapid in recent years. If you draw a graph of Earth’s population growth, you’ll see a very flat line — representing very little increase — from the year 1 AD, when there were an estimated 200 million people, to the year 1500, when there were 500 million. After that, the line curves sharply upward. By mid-1994, there were an estimated 5.6 billion people sharing the planet. By summer 2000, the estimate was 6.1 billion.

The United Nations, which keeps track of population data and makes estimates about future growth, says that by the year 2050, a “medium projection” is for 9.3 billion Earthlings. The statisticians, who realize that their figures are only highly educated guesses, have made two other projections, one lower and one higher. After about mid-century, the rate of births (“fertility rate” is the term used by the experts) is expected to decline. Better health and educational opportunities have already begun to motivate couples to have smaller families.

The UN offers several population scenarios, which it frequently updates. (You can see the latest at http://www.un.org/ecosocdev/geninfo/populatin/dpi1519e.htm, if you're lucky. The UN changes Web addresses about as frequently as most people change their socks. A better bet is to use a search engine to look for "UN population projections".) The scenarios range from a low of 7.9 billion to a high of 10.9 billion. Any way you look at it, Earth is going to have to feed a lot more people. There will be plenty of need for biodiversity in agriculture.

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