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Grassland: the story on HearLore | HearLore
Grassland
The most carbon-rich ecosystems on Earth are not the rainforests, but the grasslands, where up to 81 percent of the total carbon is stored deep underground in root systems that can extend several meters below the surface. This vast, unseen network of fibrous roots holds the soil together and acts as a massive carbon sink, storing about twenty percent of global soil carbon stocks. While the world often looks to trees for climate solutions, the grasses that dominate these biomes have been quietly sequestering carbon for millions of years, creating deep, fertile soils that support life above ground. The grasslands cover between 31 and 69 percent of the Earth's land area, making them one of the largest biomes on the planet, yet they remain one of the most misunderstood and threatened environments. From the steppes of Central Asia to the prairies of North America, these open landscapes have shaped the evolution of life on Earth, supporting the greatest aggregations of large animals, from the African elephant to the plains bison. The history of grasslands is a story of adaptation, fire, and the delicate balance between grazing animals and the plants they consume, a relationship that has persisted since the Late Miocene epoch, approximately 5 million years ago.
Fire And The First Farmers
The first true grasslands emerged around 5 million years ago during the Late Miocene in the New World and the Pliocene in the Old World, appearing as existing forest biomes declined and the climate shifted to become hotter and drier. Before the arrival of humans, these landscapes were maintained by natural forces such as fire, grazing by wild herbivores, and freezing temperatures, which prevented trees from taking hold. The appearance of mountains in the western United States during the Miocene and Pliocene epochs created a continental climate favorable to the evolution of these open spaces, allowing grasses to spread across continents except Antarctica. When humans began farming, they inadvertently created semi-natural grasslands by clearing forests, a process that began in Europe after the Neolithic Period. Ancient meadows and pastures were the parts of the cleared land that were suitable for cultivation, and over centuries, the removal of plants by grazing animals and later by mowing farmers led to the co-existence of diverse plant species. This human intervention transformed the landscape, creating habitats that are now among the most species-rich ecosystems in the world, yet they are also among the most threatened due to modern agricultural practices. The semi-natural grasslands first appeared when humans started farming, and the biodiversity of the plants evolved to adapt to these new conditions, creating a unique ecological legacy that persists today.
The Biodiversity Paradox
Common questions
What percentage of global soil carbon is stored in grasslands?
Grasslands store about 20 percent of global soil carbon stocks. This underground biomass creates deep, fertile soils with high organic matter content, making soil carbon account for about 81 percent of the total ecosystem carbon in grasslands.
When did the first true grasslands emerge on Earth?
The first true grasslands emerged around 5 million years ago during the Late Miocene in the New World and the Pliocene in the Old World. These landscapes appeared as existing forest biomes declined and the climate shifted to become hotter and drier.
How much of European semi-natural grassland disappeared during the 20th century?
Almost 90 percent of the European semi-natural grasslands do not exist anymore, having disappeared during the 20th century due to political and economic reasons. The original wild-plant communities have been replaced by sown monocultures of cultivated varieties of grasses and clovers.
What is the economic cost of global grassland degradation per year?
Global losses from grassland degradation are estimated to be over 7 billion dollars per year. The most significant threat to grasslands is human land use, especially agriculture and mining.
Which countries participated in the UN Decade on Restoration for 2021 to 2030?
The United Nations General Assembly proclaimed the UN Decade on Restoration for the period 2021 to 2030, involving a joint resolution by over 70 countries. This initiative is led by the United Nations Environment Programme and the Food and Agriculture Organization.
A single square meter of chalk downland in England can support over 40 species of plants, and a European record found on a meadow in Estonia described 76 species of plants in just one square meter, making these ecosystems some of the most species-rich on the planet. Despite this incredible density of life, almost 90 percent of the European semi-natural grasslands do not exist anymore, having disappeared during the 20th century due to political and economic reasons. The original wild-plant communities have been replaced by sown monocultures of cultivated varieties of grasses and clovers, such as perennial ryegrass and white clover, which are poor in wild plant species. This loss has had devastating consequences for the fauna that depends on these habitats, including specialists like the snipe, the little bustard, and the black rhino. The removal of key species, such as buffalo and prairie dogs within the American West, and the introduction of invasive species, like cane toads in northern Australia, have disrupted the balance in these ecosystems and damaged a number of other species. The grasslands are home to a number of the foremost magnificent animals on the planet, including elephants, bison, lions, and cheetahs, but when hunting is not controlled or is conducted illegally, species can become extinct. The biodiversity of the plants evolves to adapt to the new conditions, but the rapid changes in land use have outpaced the ability of many species to survive.
The Carbon And The Climate
Grasslands hold about twenty percent of global soil carbon stocks, with grasses often accounting for 60 to 80 percent of the biomass carbon in this ecosystem, stored in extensive fibrous root systems that can extend several meters below the surface. This underground biomass creates deep, fertile soils with high organic matter content, making soil carbon account for about 81 percent of the total ecosystem carbon in grasslands. However, grasslands have suffered large losses of organic carbon due to soil disturbances, vegetation degradation, fires, erosion, nutrient deficiencies, and water shortages. The type, frequency, and intensity of the disturbance can play a key role in the soil organic carbon balance of grasslands, and good grassland management can reverse historical soil carbon losses. Climate change poses a significant threat to these ecosystems, as increasing CO2 concentration in the air increases plant growth, but the advantages of elevated CO2 are limited by factors including water availability and available nutrients, particularly nitrogen. Studies indicate that nutrient depletion may happen faster in drier regions, and with factors like plant community composition and grazing, the effects of elevated CO2 on plant growth will vary with local climate patterns. The relationship of improved biodiversity with carbon storage is subject of research, and the lack of agreement on the amount of carbon that can be stored in grassland ecosystem is partly caused by different methodologies applied to measure soil organic carbon and limited respective datasets.
The Battle For The Land
Global losses from grassland degradation are estimated to be over 7 billion dollars per year, with the most significant threat to grasslands being human land use, especially agriculture and mining. In 1960, 49.7 percent of the land was covered with forest, and there was more semi-natural grassland at 18.8 percent than arable land at 15.8 percent, but by 2015, the semi-natural grassland cover had decreased to 10.6 percent. A quarter of semi-natural grassland was lost through intensification, converted into arable or pasture land and forests, and it is more likely that intensification will occur in flat semi-natural grasslands, especially if the soil is fertile. The management of grasslands is changing permanently, with increased use of mineral fertilizers, and borders and field edges are removed to enlarge fields and level the terrain to facilitate the use of agricultural machinery. Vast areas of grassland are affected by woody encroachment, which is the expansion of woody plants at the expense of the herbaceous layer, caused by a combination of human impact and environmental factors. The professional study of dry grasslands falls under the category of rangeland management, which focuses on ecosystem services associated with the grass-dominated arid and semi-arid rangelands of the world, and rangelands account for an estimated 70 percent of the earth's landmass.
Restoration And The Future
The United Nations General Assembly has proclaimed the UN Decade on Restoration for the period 2021 to 2030, involving a joint resolution by over 70 countries, led by the United Nations Environment Programme and the Food and Agriculture Organization. Restoration methods and measures include prescribed fires, appropriate management of livestock and wild herbivores, tree cutting, shrub removal, invasive species control, and the reintroduction of native grasses and forbs via seeding or transplant. A main challenge for grassland restoration is how to overcome seed limitation, and the cost of grassland restoration is highly variable with scarce data. Despite growing recognition of the importance of grasslands, understanding of restoration options remains limited, and successful grassland restoration has several dimensions, including recognition in policy, standardization of indicators of degradation, scientific innovation, knowledge transfer, and data sharing. A study in Brazilian Subtropical Highland Grasslands found that grasslands without traditional land management, which uses fire every two years and extensive cattle grazing, can disappear within 30 years. This study showed that grasslands inside protected areas, in which fire is not allowed and cattle grazing is banned, were quickly replaced by shrubs, demonstrating that many grasslands and other open ecosystems depend on disturbances such as wildfires, controlled burns, or grazing to persist.