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Historically forests have covered some prairies, mountain slopes, and mountains. Lightening and mankind have started fires and have
burned down extensive amounts of vegetation. A forest is any area which has a high density of trees, covers large areas of the globe, functions as animal habitats, acts as a hydrologic flow modulator, and conserves soil. Like jungles, forests are typically carbon neutral, as once the trees die they decompose and produce CO2 from respiration. The biomass per unit area in a forest is high compared to other vegetation communities. Like most environments for life,
forests can be classified in many different ways: evergreen or deciduous; broad-leafed trees, needle-leaved trees, or mixed; Boreal in the subarctic, temperate, tropical and subtropical; or combinations of climatic zones and principal types of trees: 1. temperate needle-leaf, 2. temperate broad-leaf and mixed, 3. tropical moist, 4. tropical dry, 5. sparse trees and parkland, and 6. forest plantations.3.228
Mountain land forms extend above the surrounding terrain in a specific area. Typically mountains are 1.25-1.55 miles (2-2.5 km) high and are formed by collision of plate tectonics. Mountains cover 54% of Asia, 36% of North America, 25% of Europe, 22% of South America, 17% of Australia, and
3% of Africa, or a total of 24% of Earth's land surface area. Anyone who has spent time in the mountains is aware of the wide variety of lifeforms existing on
mountain slopes, even above the tree line, where temperatures get too cold for trees to grow.3.229
Caves occur as lava tubes, in glaciers, under the sea, in jungles, in the mountains surrounding deserts, under the prairies, in forests, and in the mountains. A cave is defined as any natural underground void large enough for a human to enter. Solution caves are the largest and most abundant caves. These are typically formed in limestone, which dissolves under the action of rainwater and groundwater charged with carbonic acid (H2CO3) and naturally occuring organic acids. The dissolution process forms karsts, which grow to become sinkholes and underground drainage. Calcium carbonate formations produced through slow precipitation create stalactites and stalagmites, many of which, like at Carlsbad Cavern in New Mexico, are very dramatic.
Inhabitants of caves are called troglobites (cave-limited species), troglophiles (occur in other environments), and trogloxenes (cannot complete their life cycle in caves). Troglobites include shrimp, fish, insects. Troglophiles include bats, cave crickets, cave spiders.3.230
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paradoxes