climate and biodiversity chapter 5. importance of mountains – islands of biodiversity rapid change...
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Importance of Mountains – Islands of Biodiversity
• Rapid change as elevation changes – Many different biomes, high
diversity• Contain majority of the world’s
forests– High diversity, endemics, refuge
• Regulate climate– Snow tops reflect radiation
• Key in the hydrological cycle– STOREHOUSES OF WATER
Watersheds
• Rivers begin in mountains or at higher elevation
• Surface water becomes runoff into streams
• Watersheds or drainage basins deliver runoff, sediment, and dissolved substances to streams
• Streams join to form rivers
Three Zones in the Downhill Flow of Water
• Source zone– Mtn headwater streams flow
swiftly down steep slopes and cut a deep V-shaped valley. Rapids and waterfalls are common
• Transition zone– Low-elevation streams
merge and flow down gentler slopes. The valley broadens and the river begins to meander
• Floodplain zone– At an even lower elevation a
river wanders and meanders slowly across a broad nearly flat valley. At its mouth, it may divide into may separate channels as it flows across a delta built up of river borne sediments and into the sea.
Rain and snowLake
RapidsGlacier
Waterfall
Source Zone
Flood plain
Tributary
Transition Zone
Depositedsediment
Oxbow lake
Floodplain Zone
Salt marsh
WaterSediment
Delta
Ocean
Fig. 5-31, p. 102
Stepped Art
Three Zones of a Watershed
Watersheds
• Nutrients in the water– Come from
surrounding ecosystems• Leaves• Feces• Insects• Surface
water runoff brings biomass
Freshwater Wetlands
• Inland wetlands– Marshes– Swamps– Prairie potholes– Floodplains– Arctic tundra
Freshwater Wetlands• Ecological services
– Extremely productive (shelter and food for many, including fish)
– High species diversity– Increased nutrient cycling– Absorb runoff to decrease flooding and
then release water slowly (groundwater recharge)
– Large filters of pollutants and sediments (like a sponge) – water purification, erosion control
– Protection from storm surge
Freshwater Wetlands
• Economic services– Recreation (boating, birding, wildlife
viewing, walking, fishing)– Fisheries– Trapping and hunting– Commercial harvest (nuts, berries,
cranberries, grains, fish, peat, forestry)– Medicine
Human Impacts on Freshwater Systems
• Dams and canals fragment 40% of world’s largest rivers– Decrease flow of sediments
• Flood control levees alter rivers– Increase speed, cut away sediments
• Cities and farmlands add pollutants– Overload filter
• Many wetlands drained or filled– Increased flooding and erosion, decreased
storm protection
Coastal Wetlands – Ecological Services
• Provide the same services as freshwater wetlands
• COASTAL DUNES – – Protection from erosion, high tides and
storm surge– Dune grass and plant roots hold sand in
place
• Nesting for endangered & threatened species– Piping plover, Loggerhead sea turtles
• Development should occur beyond second dunes– Economic value often outweighs ecologic