Great American Prairies – the most endangered ecosystem on earth?

When people think about endangered or threatened ecosystems, often the Amazon rainforest or the Great Barrier Reef come to mind. And, they are important. There’s another, less well-known yet very important ecosystem that’s endangered – the Great American Prairie.

Prairies and grasslands are some of the most endangered (and least talked about) ecosystems on earth. Grassland biomes have just as much, if not more, biological diversity as any of these other ecosystems. But, most of that diversity is under ground, in the soil beneath the prairies.

Great Plains prairies used to be home to tens of millions of native Bison. When people moved west into the plains states, they used this fertile soil into food production. Farmers, agronomists and land managers are trying restore more native prairie for its biodiversity and soil health qualities. Credit: Jaclyn Fiola

Grasslands are naturally found around the globe. They are common in areas that have extreme or fickle weather patterns, especially as it relates to rainfall. Grasslands are often found in the centers of continental land masses. In these “middle spaces”, moisture from the oceans has less effect on the rainfall patterns. This can lead to either minimal amounts of annual rainfall or seasonal rainfall patterns that result in long periods of drought. Grasslands and prairies are considered more resilient to extreme weather and even climate change than other ecosystems.

In North America, the Great Plains used to cover more area. They stretched from the Rocky Mountains to the upper regions of the Mississippi River delta, from the Canadian provinces of Alberta and Saskatchewan to south Texas. When European settlers arrived on the Great Plains, it’s estimated that the grasslands covered 1 billion acres of land! That land supported a herd of bison with between 30 and 60 million animals.

In some regions, 80% of the prairie land is now gone. In the very eastern regions of the Plains, estimates are that less than 0.01% of those prairies remain! Although bison numbers have rebounded some in recent years, the number of wild bison in the late 1800s was less than 500 animals. Sadly, most of the bison found today (less than 500,000) are in private herds managed by landowners, not in wild herds migrating across the grasslands of history.

Why have the prairies disappeared and what is lost when an ecosystem like that is gone? The primary culprit in the lost prairie is agriculture. Without question, those agricultural advances have led to incredibly productive lands that are critical to the health, economy, and food security. However, some of those advances have led to ecological disasters that continue to threaten our future. The balancing act between restoring prairie, while growing food is an area that scientists can research. But there are many variables, including population growth, economics, and even politics, that affect the success of land management.

Grasses have deep roots systems that protect the soil from erosion. Some roots dig several feet deep. They also build soil organic matter and improve biodiversity. Prairies support life in their soils – from microbial to small mammals like prairie dogs. Credit: Chathu Wijewardena

Grass ecosystems are incredible soil builders. Grasses produce massive fibrous root systems each growing season. Year after year, those root systems decay, adding large amounts of organic matter to the soil. This leads to deep, fertile soils that can also grow large amounts of corn, wheat, and other major food crops. You only have to look at the regions of the USA that are considered the “breadbasket” of the nation to see that those regions were once native grasslands.

A major impact of these deep root systems is their ability to store carbon. In a world where we discuss climate change, “carbon sequestration” is an important topic. Native prairies are a tool that help store carbon.

One historic ecological disaster, the Dust Bowl, resulted from settlers turning prairie into agricultural land (they had to eat, of course). They began farming like they did in Europe, planting wheat and corn, and using lots of tillage. They initially experienced abundant rainfall and profitable yields. But the land eventually experienced a characteristic, prolonged drought. One that lasted for almost 15 years.

At that point, the grasses that held the soil in place for generations, were gone. They blew away. The tilled – and uncovered – soil was blown in every direction by the violent winds of the open prairie. The Dust Bowl of the 1930s became a reality.

The lessons of the dust bowl have taught us that the grasses of the prairie ecosystem provide numerous functions. First, they hold the soil in place during prolonged drought periods. Many native prairies have now been returned to grass ecosystems. However, those grasslands are often non-native, managed grasslands, not the native prairies.

Even homeowners can improve their soil using prairie grasses and flowers. Residential prairie gardens offer an aesthetic, and perhaps also functional, addition to the urban landscape through a diversity of flowering perennials and tall grasses. Photo credit: M. Johnston

The original native prairie ecosystems supported a broad diversity of plants. These included the more obvious grasses to a whole range of flowering forbs such as coneflower or prairie blazing star or black-eyed Susans. This plant life fed an even more impressive diversity of insects and animals, from unique pollinating insects to waterfowl. It also supported an impressive group of mammals such as prairie dogs and antelope. Birds have been a strong indicator of the decline of prairie habitat. “Prairie birds” have shown greater population losses than any bird group in North America.

Many farmers are using prairie strips, or riparian buffers along the edges of their cultivated fields. They are also putting some of their “unproductive” land (based on yields) into native habitats. Some municipalities have begun to add prairie management along with their stormwater systems. These grasses and native plants absorb water into the soil better than domestic grass – and certainly more than cement ditches and channels.

It’s difficult to put a value on things like “threatened species” of plants, animals or insects. But it’s impossible to know their value once they are lost completely. While it would be foolish to think that we can reverse all the changes that have occurred across the prairies over the last 200 years, it is not impossible for local groups, states, and nations to recognize that the Great American Prairie ecosystems are almost gone and do something to change that trend.

Answered by Mike Richardson, University of Arkansas

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