Shrinking species, shrinking planet

Our credit card for the planet is maxed out, and making the minimum payment is no longer an option. The only source for a bailout is ourselves.

by Don Gordon

In nature most all predators survive by taking the old, the weak, the sick and the very young. Why waste all that energy when there is easy “pickings.”

In contrast, humans which are the world’s most destructive predators, do just the opposite. We seem to hunt the biggest and the healthiest species. A synthesis of research from around the world indicates that our actions are having pronounced effects on the rate of evolutionary change in both plants and animals that may alter their chances for long term survival.

Let’s look at some examples. Hunters take great pride in bringing home big “ trophy” species. They seek out bigger adults and let younger immature organ isms escape. Commercial cod fisherman net the biggest fish and throw the smallest ones back. Ginseng hunters seek the plants with the biggest roots and leave the smaller immature plants. When picking wild flowers, we almost always go for the showiest and the healthiest. Even many of our conservation laws dic tate that we harvest only big mature adults.

So what if we harvest the biggest of the species? In a recent issue of the Proceedings of the National Academy of Sciences, researchers reported that plants and animals harvested aggressively have shrunk in about the last 30 years by about 20 percent, and these organisms are reaching reproductive age about 25 percent sooner. In fish, researchers found that earlier maturing species also produced fewer eggs. In ginseng populations, overall vigor and size of plants is declining.

Some conservation officials are suggesting that we may need to change laws to protect the bigger individuals, but there is a “catch 22” to this idea. If we afford protection to the biggest and best, then the overall harvest may need to be increased to meet the demand. If we want to preserve genetic diversity, we may need to establish more no hunting and no fishing zones, and to impose both minimum and maximum size limits.

The 1989 film, “Honey I Shrunk the Kids,” was fantasy, but shrinking the size of species is not. Nor is the fact that we are also shrinking the planet despite the fact that our population continues to increase.

The current human population now numbers 6.7 billion and the United Nations estimates it will be 9.2 billion by 2050.

On the plus side, some 43 nations now have populations that are basically stabile or are in decline. The United States, in contrast, continues to grow, and the Population Reference Bureau estimates we will have as many as 450 million before stabilizing. Also in this category are Iraq with a predicted 114 percent increase and the Africa continent is expected to increase 107 percent by 2050. This increased population will further deplete our already strained resources. According to environmentalist Lester Brown, our current demand for resources exceeds sustainability by 25 percent, and 15 of the Earth’s primary ecosystems are being downgraded or pushed beyond their limits.

Shrinking species and a shrinking planet are indicators that we are living beyond our means. Our credit card for the planet is maxed out, and paying just the minimum payment is no longer acceptable. The only source for a bailout is ourselves.

Don Gordon is professor emeritus of botany at Minnesota State University Mankato.