Steppe regions are areas of grasses, shrubs and herbaceous plants. Steppes' difficult climatic conditions of low moisture, high winds and temperature extremes discourage the growth of trees.
The Great Plains of the United States are one of the four major steppe regions of the world. This prairie extends from Alberta and Saskatchewan down to Texas. Human activities such as converting vast stretches of grassland into farmland have caused an enormous loss of topsoil and biodiversity. Another change created by humans was the introduction of foreign weeds such as tumbleweed. When Volga Germans fled from Russia to escape conscription under Alexander the Third, they inadvertently brought these invasive plants along with their durum wheat seeds. The intermountain North American steppe includes the Columbia Plateau, the Great Basin and the Colorado Plateau. The mountain ranges along the western United States block most of the maritime rain from reaching the interior. Shrubs such as sagebrush predominate in the western portion because winter precipitation is the main source of moisture but on the eastern edge, grasslands increase because of occasional rainfall provided by the thunderstorms of the North American monsoons. Fire is also an important element because grass quickly grows back after a fire while sagebrush recovers slowly. Steppes By Michael Bone, Dan Johnson, Panayoti Kelaidis, Mike Kintgen and Larry G, Vickerman was published by Timber Press in 2015.
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Humans are changing ocean environments and the species of seaweed that grow there. Oceans are warming and acidifying. One alarming result is that Pacific kelp forests are dying back.
Seaweed habitats are being damaged or created by human intervention. Dredge fishing can strip away seaweed along with other ocean life. The construction of concrete wharves and breakwaters remove sand and rock suitable for seaweed growth. Conversely, fertilizer runoff can enable the growth of nuisance seaweeds along the coast. The oceans' gyres once kept different kinds of seaweed separate but now human activity is causing changes to ocean currents which then intermix different species. The Panama Canal and the Suez Canal have both provided channels for new varieties. Ships' ballast water has been the conduit for seaweed spores to move around the world on its shipping lanes. John H. Bothwell's Seaweeds of the World was published by Princeton University Press in 2023. |
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