I left home and drove through the Flint Hills of Kansas on my way to the airport to catch my flight to Panama City. It was a frigid morning, and the tallgrass prairie was starkly beautiful. The sun was rising and the light gave a slight orange/pink hue the wind-burnished patches of snow clinging to the northern slopes of the rolling hills. The old big bluestem grass stalks were buffeted by the winds. This was the kind of morning that made me glad not to be living as the indigenous people did during this inhospitable time of year. This was the type of morning where the Native Americans, and later the European settlers that invaded the area, would have stayed inside till the sun took the bite off the bitter windy cold. The icy landscape was stark contrast to the tropical mountain rainforest that I was headed to.
As I drove through these prairie hills, my mind started worrying on the idea of extinction, ecological loss, and the modern world. Only a fiftieth of tallgrass prairie remains in the North America, much of it in the Flint Hills of Kansas and Oklahoma. As I drove to the east, and out of the Flint Hills, the land was taken over by croplands. In a few minutes I was witnessing the transition that altered the vast North American prairies when Europeans broke the sod in the 1800’s. Much of the Midwest’s productive cropland was once a sea of grass.
The Flint Hills only retain grassland by lucky accident. The shallow rocky soils make them better for raising cattle than cropland. The ranchers burn yearly to keep the trees at bay and the cattle simulate the herds of grazing bison that historically roamed the prairie. Where fire has been suppressed, the trees invade. Prairie is becoming more imperiled in the Flint Hills because of the human influence changing the natural fire frequency that occurred. This effect is particularly pronounced in areas with higher population densities where people have built their houses out in the country… an effect that we will see has parallels in Panama.
Bison (popularly referred to as buffalo) are a “keystone” species that shaped prairie ecology, and their loss from the prairies could be considered analogous to the loss of the frogs in the jungle streams. The researchers I work with in Kansas have found that bison are key in maintaining the very high diversity of plants found in tallgrass prairies. There are literally hundreds of species of plants in a healthy prairie. The bison stimulate this productivity by grazing the main grasses that would outcompete the forbs (leafy plants). They also leave fertilizer packets (dung and urine) that stimulate plants that require higher nitrogen conditions. Bison disturb areas with their hoof-prints, their wallows where they take dust baths, and the trails they cut through areas as the herd moves across the landscape. The tadpoles, in the streams, do analogous things. They graze selectively, they disturb some areas more than others, and they excrete and enrich areas with their fecal pellets.
As impressive as the accounts were of massive bison herds on the prairies, there were once much more impressive herds of large mammals that roamed the prairies. Humans were responsible for even move extensive alteration of the natural ecosystems of North America. Before the end of the last ice-age approximately 10,000 years ago, the plains and forests of North America once were home to an astounding diversity of large animals. When tribes of hunter-gatherers that ultimately became the Indians of North America crossed the land bridge and spread across North America, they found a land of plenty.
The diversity of North America rivaled that of the plains of Africa. Camels, horses, huge bison, ground sloths, saber-tooth cats, giant beavers, giant armadillos, mammoths and mastodons were here. These large animals had no evolutionary experience with humans, and within a few human generations they were hunted to extinction.
Similar extinctions of large animals occurred in Central and South America as people swept in from Siberia, through North America and to the south. The America’s are not unique. In Australia, New Zealand, Madagascar and many other smaller islands the archeological and fossil record is unequivocal. When humans arrive, the large animals disappear. Marsupials disappeared from Australia, giant flightless birds were slaughtered in New Zealand, giant birds and lemurs were hunted to extinction in Madagascar. People are consistent in their heavy-handed environmental presence. We are the most successful species because we shape each environment we enter to meet our own needs.
The ecological effects of the extinction of the large herbivorous mammals and their predators are not well understood, but they were probably significant. Some species of plants remain that have large fruits with seeds that are only dispersed successfully over any distance when they pass thought the guts of large animals. The animals ingest the large fruits and carry the seeds within them substantially away before depositing the seeds with a packet of fertilizer. But, animals large enough to pull down tree limbs and graze the crowns of trees no longer range across the landscape.
One difference between historic extinctions and the ongoing disappearance of the frogs of high-elevation Central American habitats is that we can study the ecosystem effects of the removal of an entire taxonomic group in Panama. Perhaps these studies will help us understand the unintended ways that humanity is influencing global ecology and aid in mitigating or minimizing future impacts. At least it could help document some of the negative consequences that could come about from extinctions or extirpations of species.
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