Prairie Wanderings: Biodiversity matters
By PAUL G. JANTZEN
Contributing writer
Hiking in relatively undisturbed areas is so fascinating because of the great variety of creatures we encounter.
We may hear the howl of a coyote, the mournful bass strumming of a bullfrog, or the chirp of a cricket. We might see the majestic forms of bison grazing on a prairie hillside, the golden breast of a meadowlark, or the brilliant blossom of prickly pear cactus. We may smell the sweet blossoms of wild plum or the leaves of fragrant sumac.
And we can imagine the myriad microbes in the soil under us and in the nearby prairie stream, each with a role to play in the drama of life.
One way ecologists measure the health of a biological community is to note the variety of species in it, called biological diversity, or biodiversity. They are concerned when they see a reduction in biodiversity.
There are five factors which frequently threaten the biodiversity of an ecosystem. Habitat destruction is a major factor.
Certain grassland bird species in the Great Plains have experienced a marked decline in numbers in the last 30 years due to our converting much of the grassland to agriculture. Without their native food and nesting areas, where are they to go?
Reduction of native grassland has also caused the greater-than-usual decrease in the population of black-tailed jack rabbits in recent decades. (And during this drought year, the sparseness of plants in western Kansas has allowed an increase in their numbers.)
And there are marked declines in amphibians, especially frogs, in much of North America and Europe due to various causes but especially habitat destruction.
A second factor causing a decline in native species is the competition of invasive species. Their natural predators that kept their numbers in control may not be present in their new habitat and, like cancer cells, they multiply out of control.
House sparrows were introduced into Kansas in 1865 to control insects. In one community, five were introduced in the spring of 1874. That fall there were 12 birds, the next fall 60, the third fall about 300 birds.
Cheatgrass, or downy brome, is native to Eurasia and was probably imported with wheat seeds. When it competes with wheat, it cheats the farmer of his desired crop yield.
Other invasive plants include bindweed, musk thistle, crown vetch, and sercea lespedeza. Crown vetch was introduced from the Mediterranean area and used primarily as a bank stabilizer along roadways. However, it now aggressively invades surrounding fields.
Sericea lespedeza is an Asian legume introduced into the U.S. in 1896 to control erosion and proved forage for cattle. It came to Kansas in the 1930s, and by 1987 it was spreading out of control, partly because cattle wouldn't eat it.
Pollution is third factor that threatens various species and biodiversity. During the dust bowl days of 1935, 170,000 tons of dust were suspended over each square mile of Wichita — dust from 250 miles west. Water erosion has washed silt from the land, choking streams already polluted by run-off from feedlots, over-fertilized fields, and pesticide-treated croplands.
Wide use of DDT seriously threatened populations of many bird species including our national symbol, the bald eagle. As this effective insecticide entered the food chain, it interfered with the construction of strong egg shells, jeopardizing reproduction. The decline in amphibian populations is attributed not only to habitat destruction but also to chemical pollutants in air and water.
In 1999 on about Oct. 12, Earth's human population reached six billion. It continues to increase by 200,000 each day. And more people means an increase in the other factors that endanger biodiversity.
The fifth factor is overharvesting. In the early 1800s, the bison population in Kansas numbered in the millions. By 1879, bison were exterminated in the state. They had been slaughtered by meat hunters, robe collectors, bone gatherers, and those who wished to destroy an important food source of Native Americans. Some paleontologists believe that the extinction of large mammals at the end of the Ice Age was caused by human hunting.
It is widely believed among ecologists that the more species in an ecosystem, the more stable it is. By stability we mean the absence of wide variation in the total abundance of all species through time, and a fairly quick recovery form stresses such as drought, flood, and fire.
If a species disappears from an ecosystem, its niche (function) is more likely to be filled by another species if there are five candidates for the role instead of just one.
The International Union for the Conservation of Nature and Natural Resources reported recently that "today, two of every three species worldwide are thought to be in decline."
Whether we care for our planet for personal aesthetic reasons or for Earth's survival, biodiversity matters.
