The history between humans and grasslands is long and interesting from the large savannas of Africa, where we as homosapiens began our evolution, to the Stone Age, where we first discovered unique uses for grains, and into modern times where our intricate farming systems still rely heavily on the incredible ecosystems within the planet’s grasslands.
These vast, flat areas of land are deceptively diverse, full of life, and teeming with fascinating fauna and flora. Even in the harsh, freezing climate of the Arctic, there are thriving grasslands supporting a beautiful variety of plants and animals.
Everything within this important biome is part of a working web of life, down to the very soil that supports it all.
- Grasslands account for up to 40% of the Earth’s land surface
- There are two types of grasslands; tropical and temperate
- Grasslands usually lie between deserts and mountain climates
- Fire is necessary for grassland health
- Less than 10% of the world’s grassland is protected
- Grasslands are found on every continent except Antarctica
- Millions of acres have been lost to human development
- Grasslands act as carbon sinks
What are Grasslands?
Grasslands are sprawling, flat areas of land found on every continent on Earth, except Antarctica, and generally fall into either the ‘tropical’ or ‘temperate’ category. Most of these lie between mountain and desert regions and were formed with the global increase in temperature following the most recent ice age, over 11,500 years ago.
The common thread between these various biomes is their primary vegetation and the diversity of the animals they support. Symbiotic relationships between native animals and plant life are very important for grasslands to flourish, and even seemingly destructive events like wildfires are necessary for the survival of these ecosystems.
The grasses themselves have evolved to grow even after being nibbled down to the roots. One quarter of the Earth’s total surface is covered by grasslands, and temperatures average between -20℃ (4℉) to 30℃ (86℉), though there are more extreme variations such as the Arctic tundras. Rainfall is considered moderate in these biomes, averaging between 25 centimeters (10 inches) to 101 centimeters (40 inches) per year. These ecosystems contain some of the most diverse and lush food webs on the planet. Grassland soil is nutrient-rich, making these areas ideal for agriculture and human development, often to the detriment of the local ecosystems. The health of grasslands is threatened by things like poaching, agriculture, overgrazing, and climate change.
The Unique World of Grasslands
Grasslands make up a massive amount of the Earth’s land area, both combined and individually. The Great Plains, for instance, stretch 2,251 miles from Canada to Mexico and consist of 400 million acres of North America. The entire country of Germany could fit inside the Great Plains more than four and a half times. Savannas cover approximately five million square miles of Africa’s surface, about half of the total surface area of the continent. In total, grasslands account for up to 40 percent of the terrestrial surface area and 25 percent of the total surface area on Earth. It’s no wonder that they are some of the most important biomes on Earth.
Temperate and Tropical
Throughout the world, there are many different types of grasslands, which can be classified as ‘temperate’ or ‘tropical.’ Temperate grasslands are situated farther from the equator, have greater temperature fluctuations, and receive less rainfall throughout the year than their tropical counterparts.
They consist of the previously mentioned North American prairies, the Eurasian Steppes, and the Pampas of South America, among many others. Tropical grasslands, on the other hand, border the equator on either side, prominently on the edge of tropical rainforests, and have a few species of trees and shrubs that have evolved to survive in their drier climates alongside the grasses.
Some of the more renowned areas in this category are the Serengeti Plains in Tanzania, the Australian Downs, and the Everglades of North America. The soil differs between these two factions as well. Temperate soil is richer than its tropical counterpart. Deep root systems in prairies and steppes turn decaying plant mass into the fertile Earth that makes for such wonderful farmland.
Savannas, on the other hand, contain more porous, easily draining soil. The fertile layer of humus (decayed plant matter) is thin and closer to the surface. Components like when rainfall happens are very important. For example, if rainfall were spread evenly throughout the year, many grasslands would simply turn to forests. Intense rainfall for several months followed by heat, and even drought, is part of what helps these unique ecosystems to thrive.
Plants and Animals
Vegetation and wildlife tend to develop symbiotic relationships throughout any ecosystem. This is especially true in grasslands. African Savannas and North American Prairies alike can support up to twenty-five species of large herbivores in any given area without strain on the local ecosystems.
These species often live in massive herds (for instance, on the savannas, zebras can congregate in groups of a thousand), with some animals eating up to 300 pounds of food per day. That’s over 60 times as much as an adult human eats in a day.
A grassland’s ability to support this massive population depends on everything in the biome working together. The soil must be lush and nutrient-dense to support the extensive root systems, which support the growth of vegetation, that in turn feeds the herbivores, who feed the carnivores, and everything (animal excrement, plant matter, and the animals themselves) ultimately goes back into the soil.
Grasses and other native ground cover come in countless varieties, each of which brings its own attributes to the soil. Legumes such as clover and alfalfa fix nitrogen from the atmosphere and turn it into a form of nitrogen other plants can use.
The larger animals disturb the soil with their hooves or by rooting and spread seeds throughout the freshly turned Earth. Birds and other small animals help disperse seeds as well. Many of these small animals prefer habitats prepared by others within the ecosystem.
Bison, for instance, will often be followed by prairie dogs, who are prey to numerous predators, such as ferrets, foxes, and hawks, and provide habitats for other small animals who are partial to nesting within the prairie dog colonies. Different species of plants and animals work symbiotically like this to create a complex and delicate food web that sustains the entire ecosystem.
The Human Impact
The qualities that make grasslands so appealing to this diverse array of wildlife also make them prime locations for human use. Rich soils and flatlands are ideal for agriculture and animal husbandry, while an abundance of wildlife offers easy hunting.
It makes sense that humans would be drawn to these lush areas with their relatively mild climates. However, human interaction is often responsible for drastic declines in the health of these ecosystems. Before European settlers expanded across North America, the Great Plains were home to millions of large grazers and predators.
There was an abundance of land and food for the wildlife to share with indigenous tribes. With the settlers came a different style of agriculture, meant to produce food for much larger populations. Now millions of acres of prairie have been turned into farmland, and the majority of the wildlife has been hunted to near extinction.
Humans have killed off wild predators to protect their domesticated flocks. These predators play a very important part in the population control of their prey. Poaching of predators ultimately leads to severe overgrazing and eventual famine, as the pieces of the food web start to collapse.
With the increase in human development, wildfire suppression has, of course, become commonplace. Many seeds in grassland biomes like it hot and will only sprout after the soil has been scorched by fire.
The roots and seeds are protected by the soil, while grass fires burn off natural detritus and other matter. This allows new growth to spring forward. Aggressive fire suppression limits the growth of these seeds and stunts the diversity of the flora.
Excess fertilizers from farmlands and animal waste from domestic herds create runoff. Agricultural runoff, both from livestock and crops, can contaminate waterways, making them unusable for wildlife and humans alike and further destroying soil health.
Studies have shown that grasslands are currently more effective carbon sinks (natural areas with the ability to absorb carbon from the atmosphere) than forests because they are resistant to the effects of drought and wildfire.
These beautiful places are necessary for the greater health of the planet. Even so, less than ten percent of the world’s grasslands are currently protected.