By: Percival Knight

Grasslands are an extremely important ecosystem, as they help support a diversity of life and act as a base for many local food webs. A significant portion of all land area is made up of these ecosystems, and they can be found on virtually every continent. But what if I told you that these crucial, life supporting ecosystems were under threat? A large portion of Earth’s native grasslands have been lost due to changes in land use. The loss of these habitats threatens a multitude of different species and ecological systems. But what can be done about it? Well, researchers are working to better understand what actions we can take to mitigate the severity of our impact. One of the ways we can do this is through the protection of historical grasslands and working with nature to preserve these places.

Key words:

• Grazer- a group of animals, typically hooved, that primarily feed on grasses
• Non-native species– species that do not originate in the given ecosystem in which they now are found
• Coevolution– the process by which organisms interact and affect each other over time.
• Species richness– the number of different species that can be found within a given area

What is a Grassland? Why are they Important?

Grasslands are characterized by their mostly absence of woody plants, primarily trees. They may become dominated by grasses due to periodic drought, wil

dland fires, or insufficient rainfall. Grasslands cover around one-third of all land area and support upwards of 800 million people world-wide (Price and Sitters et. al.). In some regions, these habitats have been around for thousands of years. Grasses, one of the primary types of plants found in these habitats, are an incredibly biodiverse group, containing upwards of 10,000 different species (Grasslands)! This abundance supports an incredible range of herbivores, which many other animals also rely on. Grasslands are also extremely important for pollinators. Wildflowers attract and feed everything from bees, to butterflies, to birds! When managed properly, these systems can also help limit soil and nutrient erosion, regulate the water cycle, provide food for humans and wildlife, and even help remove carbon dioxide from the atmosphere. Over the last century however, many of these habitats have been drastically affected by human populations.

 

 

A History of Mismanagement

There are a number of land use changes over the last century that have had significant impacts on the health and abundance of grassland ecosystems. Land use conversion is the practice of taking otherwise ecologically healthy land and changing it in some way to better serve human needs. This may involve placing non-native animals, like cattle, to graze on the grasses, or the clearing of the land altogether. Changing farming practices, like the removal of native plants to instead plant food crops, the increased use of pesticides, the introduction of non-native species, overgrazing, and development, all have had great impacts on grassland habitats.

Today up to half of all temperate grasslands have been converted to other uses, and only

about 1% of original tallgrass prairie still exists today

(National Geographic)

The impact humans have had on these environments has drastically intensified over the last century. The Green Revolution, a period during the mid-20^th century, brought significant increases in agricultural production. Crops were altered to become more resistant to drought and disease, the input of fertilizers increased, and new chemicals were introduced to protect crops from unwanted insects and fungi. Though all these innovations increased the overall crop yield, helping to feed a growing population, they also produced many negative ecological consequences.

Human understanding of ecology is also relatively new. Over the last century we have developed a far greater understanding of the relationships between species in a given ecosystem. One of these new understandings is how the introduction of non-native species may affect ecosystems. We now know that non-native species may “outcompete” native species, or simply out-consume and out-reproduce them. This may lead to the overall degradation of the ecosystem. If an ecosystem becomes overrun with non-natives, the abundance and richness of native species may decline. This may then lead to the decline of other species that rely on them for food.

This phenomenon primarily occurs within the context of “co-evolution”, or the process by which different organisms may interact with and affect each other over time. A great example of this concept, that is often referred to, is the relationship between plants and pollinators. Plants may attract an insect or bird with nectar, and in return, the pollinator transports the plants pollen to other individuals to help the plant reproduce. Researchers have learned that one way to maintain the health of Grasslands, is by working within the context of this idea.

Working with Nature

In a recent publication by Nature Ecology & Evolution, researchers, Jodi Price, Judith Sitters, Timothy Ohlert, and a number of other contributors, discuss how grazing, and herbivory can be beneficial to grassland ecosystems. They found that this is primarily true for grassland ecosystems that were older, or in the case of their study, greater than 500 to 10,000 years old. The team found evidence to support the notion that in older grassland habitats the presence of grazers helped to actually increase species diversity.

How did they figure this out?

Well, to set up their experiment, the researchers selected 57 grassland sites, some greater than 500 years old, and some younger. These sites were located on 6 of the 7 continents and already had grazers present. They then fenced off portions of the land to prevent the grazers from feeding in those areas. They then measured the changes within the plots over time.

What did they find?

They found that on grasslands that were greater than 500 years old, removing grazers led to the increase in a select few “tall-statured grasses”. Because of their height, these taller plants had more access to sunlight than those of a shorter stature. Because of this, they were able to out-compete smaller, grazing-adapted plants. Over the duration of the experiment, the researchers found that many of the sites that were fenced off saw decreases in diversity and species richness, a measure that looks at how many different species can be found within a given area. Diversity is slightly different from species richness; in that it includes abundance in its measurement. The researchers found that many of the plants that were benefitting from the presence of grazers were native on these older sites. This may be due to the co-evolution of these two groups over time.

So, what does this all mean?

This research provides us with a greater insight in to how to better manage historical grasslands. Again, these habitats, like many others, are among some of the most threatened by changes in land use. It is vital that they are managed properly because of their supporting role for a wide variety of different organisms. Humans also benefit from healthy grassland ecosystems as they help preserve and regulate soils and nutrients, support pollinator populations, and help regulate atmospheric gases.

To properly manage these habitats, it is incredibly important to work with nature, and within this idea of co-evolution. We do this by maintaining and allowing grazer populations to continue to do what they do best. Feed on grasses.

 

References

5.23: Coevolution. (2021). Biology. Retrieved October 17, 2022, from https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book%3A_Introductory_Biology_(CK-12)/05%3A_Evolution/5.23%3A_Coevolution

Grasslands. Fauna & Flora International. (2017, December 3). Retrieved October 17, 2022, from https://www.fauna-flora.org/environments/grasslands/

MooMooMath and Science. (2018, December 19). Temperate grasslands-biomes of the world. YouTube. Retrieved October 17, 2022, from https://www.youtube.com/watch?v=I0zeAMkCFpY

Price, J.N., Sitters, J., Ohlert, T. et al. Evolutionary history of grazing and resources determine herbivore exclusion effects on plant diversity. Nat Ecol Evol 6, 1290-1298 (2022).

Wolters, C. (2021, May 3). Grasslands threats and solutions, facts and information. Environment. Retrieved October 17, 2022, from https://www.nationalgeographic.com/environment/article/grassland-threats