Reconstructing the Past

Many modern conservation efforts are focused on returning the landscape back to its original state before the settlement of pioneers, yet even the rolling prairie that once covered most of Iowa shows only a sliver of the land’s biological history. The contemporary flora and fauna communities of prairie and cropland look very different from those of nearly 20,000 ago. The Late Wisconsinan glacial period lasted roughly from 21,000 to 15,000 years ago and drastically changed Iowa’s landscape through complete ice cover for thousands of years. While plants and animals exist and evolve together in certain locations, Baker et al.’s 1986 article from the Journal of Quaternary Science contends that these communities shift over time. Richard Baker and his colleagues at the University of Iowa worked together with researchers from Washington, North Dakota, and Minnesota to study the biological history of the Conklin Quarry in southeast Iowa to shed light on the ancient Iowan landscape. Their work compares ancient flora and fauna communities to those of the modern day in a study which may suggest a new way of approaching conservation. 

Conklin Quarry: a Picture of the Past

Conklin Quarry in Johnson Co., Iowa, contains a large collection of fossils from 18,000-16,000 year ago of a diverse array of organisms. These fossils include pollen, plants, insects, and small-mammals that were preserved in the deposits. While most sites that had been covered in ice, or full-glacial sites, have some of these fossil types, very few locations match the sheer breadth of samples from each group that Conklin Quarry has. This site’s rich selection of fossils represents the environmental spectrum during the Late Wisconsinan glacial period, a range of dates which is normally rare in fossils sites. In addition to the date range, the quarry has arctic plant remains found 1000km south of the nearest reported Wisconsinan arctic floras. This unique site provides important evidence for understanding both the glacial and postglacial development of flora and fauna today. 

Plant Fossils

In order to map flora communities of 18,000-16,000 years ago, Baker and his lab studied pollen and plant macrofossils. The pollen samples found were mostly degraded, although pine, spruce, and sedge species could be clearly identified. The samples found in Iowa from the Wisconsinan period contained low pollen concentrations, which match low pollen concentrations found in tundra and tree-line areas in eastern Canada today. Spruce and dwarf birch macrofossils were found in abundance, which are native boreal forest species and extend to the northern tree limit today. Many of the less common macrofossils represent arctic-alpine plants found today only in the tundra. Several species found normally grow along water, suggesting a pond was present at one time. Both the pollen and plant macrofossils match species found in eastern Canada presently, suggesting open conditions between the forest limit and the limit of tree species in a tundra environment. 

Insect and Vertebrate Fossils

The remains of the insects found were remarkably well preserved, showing species that could occur today within or near forest/tundra transition zone. Close analogues to the insect communities at the Conklin Quarry only exist today in tree-line environments where temperatures average 10-12°C in July (compared to 23°C Iowa today). The taxa of vertebrate macrofossils are found presently, like the insects, only in tundra environments. Some fossils, such as the singing vole, are found today only near running water, which suggests an ephemeral steam or a wet environment. 

 

Fig.1: Map of North America (1986). All flora and fauna populations represent 1986 conifer and insect populations found in Conklin Quarry site.

Communities Today

While both the plant and animal fossils represent species presently found in tundra, Baker et al. found that these communities shifted over time. The insect and animal species found in the quarry are present today in northern coastal regions in Canada and Alaska, while the plant species (conifers) grow primarily in a large swath across Canada (Fig.1). Between 18,000-16,000 years ago and now, the analogue communities, or flora and fauna that evolve and develop together, have changed. Baker et al.’s research shows that the evolution of communities is dynamic, and that flora and fauna populations dissociated from one another as glaciers retreated. These results suggest that biological communities can evolve, disassociate, and even disappear over time. Instead of focusing just on certain ecosystems, conservation efforts might find understanding the community evolution beneficial. If the relationships between various species change and even disappear over time, perhaps the aim to restore prairies to match their relic counterparts should be reexamined.

Baker, R.B., R. Sanders Rhodes II, T.J. Fresst, G.R. Hallberg, J.A. Janssens. 1986. “A full-glacial biota from southeastern Iowa USA.” Journal of Quaternary Science 1 (2) 91-107.