Grassland
The appearance of mountains in the western United States during the Miocene and Pliocene epochs, a period of some 25 million years, created a continental climate favourable to the evolution of grasslands.
[9] Following the Pleistocene ice ages (with their glacials and interglacials), grasslands expanded in the hotter, drier climates, and began to become the dominant land feature worldwide.
For example steppe-tundra dominated in Northern and Central Europe whereas a higher amount of xerothermic grasslands occurred in the Mediterranean area.
The semi-natural grasslands contain many species of wild plants, including grasses, sedges, rushes, and herbs; 25 plant-species per 100 square centimeters can be found.
For example, original North American prairie grasslands or lowland wildflower meadows in the UK are now rare and their associated wild flora equally threatened.
[14] Owing to semi-natural grasslands being referred to as one of the most-species rich ecosystems in the world and essential habitat for many specialists, also including pollinators,[8] there are many approaches to conservation activities lately.
[7] Unfortunately, a large amount of red-listed species are specialists of semi-natural grasslands and are affected by the landscape change due to agriculture of the last century.
In many parts of the world, "unimproved" grasslands are one of the most threatened types of habitat, and a target for acquisition by wildlife conservation groups or for special grants to landowners who are encouraged to manage them appropriately.
Dominant trees for the semi-natural grassland are Quercus robur, Betula pendula, Corylus avellana, Crataegus and many kinds of herbs.
These invertebrates, along with symbiotic fungi, extend the root systems, break apart hard soil, enrich it with urea and other natural fertilizers, trap minerals and water and promote growth.
[19] Grasslands provide a range of marketed and non-marketed ecosystem services that are fundamental to the livelihoods of an estimated one billion people globally.
[23] 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 (SOC) balance of grasslands.
Bedrock, irrigation practices, soil acidification, liming, and pasture management can all have potential impacts on grassland organic carbon stocks.
[32] To feed a growing human population, most of the world's grasslands are converted from natural landscapes to fields of corn, wheat or other crops.
Grassland vegetation is often a plagioclimax; it remains dominant in a particular area usually due to grazing, cutting, or natural or man-made fires, all discouraging colonization by and survival of tree and shrub seedlings.
[33] Some of the world's largest expanses of grassland are found in the African savanna, and these are maintained by wild herbivores as well as by nomadic pastoralists and their cattle, sheep or goats.
Hunting cultures around the world often set regular fires to maintain and extend grasslands and prevent fire-intolerant trees and shrubs from taking hold.
Much grassland in northwest Europe developed after the Neolithic Period when people gradually cleared the forest to create areas for raising their livestock.
Another common predicament often experienced by the ill-fated grassland creatures is the constant burning of plants, fueled by oxygen and many expired photosynthesizing organisms, with the lack of rain pushing this problem to further heights.
Thus effects of elevated CO2 on plant growth will vary with local climate patterns, species adaptations to water limitations, and nitrogen availability.
A study of a California grassland found that global change may speed reductions in diversity and forb species are most prone to this process.
[22] A map created by the World Resources Institute in collaboration with the IUCN identifies 2 billion hectares for potential forest restoration.
[40][41] It is expected that non-native grasses will continue to outperform native species under warmer and drier conditions that occur in many grasslands due to climate change.
Rangelands account for an estimated 70% of the earth's landmass; thus, many cultures including those of the United States are indebted to the economics that the world's grasslands have to offer, from producing grazing animals, tourism, ecosystems services such as clean water and air, and energy extraction.
Woody encroachment is caused by a combination of human impact (e.g. fire exclusion, overstocking and resulting overgrazing) and environmental factors (i.e. increased CO2 levels in the atmosphere).
[49] Successful grassland restoration has several dimensions, including recognition in policy, standardisation of indicators of degradation, scientific innovation, knowledge transfer and data sharing.
Other animals of this region include deer, prairie dogs, mice, jack rabbits, skunks, coyotes, snakes, foxes, owls, badgers, blackbirds, grasshoppers, meadowlarks, sparrows, quails, hawks and hyenas.
However, during the Pleistocene glacial periods (commonly referred to as ice ages), a grassland known as steppe-tundra or mammoth steppe occupied large areas of the Northern Hemisphere.
These areas were very cold and arid and featured sub-surface permafrost (hence tundra) but were nevertheless productive grassland ecosystems supporting a wide variety of fauna.
