Chapter 12Chapter 12Sustaining Aquatic Biodiversity
Lake VictoriaLake Victoria
Lake Victoria has lost their endemic fish species-the cichlid- to large introduced predatory fish.
Figure 12-1Figure 12-1
Reasons for Lake Victoria’s loss of Reasons for Lake Victoria’s loss of biodiversity:biodiversity:
◦Introduction of Nile perch.◦Lake experienced algal blooms from
nutrient runoff.◦Invasion of water hyacinth has blocked
sunlight and deprived oxygen.◦Nile perch is in decline because it has eaten
its own food supply.
AQUATIC BIODIVERSITYAQUATIC BIODIVERSITYLittle is known about the
biodiversity of the world’s marine and freshwater systems.◦The greatest marine biodiversity
occurs in coral reefs, estuaries and the deep ocean floor.
◦Biodiversity is higher near the coast and surface because of habitat and food source variety.
Don’t forget HIPPODon’t forget HIPPO
HUMAN IMPACTS ON AQUATIC HUMAN IMPACTS ON AQUATIC BIODIVERSITYBIODIVERSITYApproximately 20% of the world's coral
reefs have been destroyed.During the past 100 years, sea levels
have risen 10-25 centimeters.We have destroyed more than 1/3 of
the world’s mangrove forests for shipping lanes.
HUMAN IMPACTS ON AQUATIC HUMAN IMPACTS ON AQUATIC BIODIVERSITYBIODIVERSITY
Area of ocean before and after a trawler net, acting like a giant plow, scraped it.
Importance of zooxanthallaeFigure 12-2Figure 12-2
HUMAN IMPACTS ON AQUATIC HUMAN IMPACTS ON AQUATIC BIODIVERSITYBIODIVERSITYHarmful invasive species are an
increasing threat to marine and freshwater biodiversity.◦Bioinvaders are blamed for about 2/3 of fish
extinctions in the U.S. between 1900-2000.Almost half of the world’s people live
on or near a coastal zone and 80% of ocean water pollution comes from land-based human activities.
Population Growth and Population Growth and PollutionPollution
Each year plastic items dumped from ships and left as litter on beaches threaten marine life.
Figure 12-3Figure 12-3
Overfishing and Extinction: Overfishing and Extinction: Gone Fishing, Fish GoneGone Fishing, Fish Gone
About 75% of the world’s commercially valuable marine fish species are over fished or fished near their sustainable limits.◦Big fish are becoming scarce.◦Smaller fish are next.◦We throw away 30% of the fish we catch.◦We needlessly kill sea mammals and birds.
Fig. 12-A, p. 255
Fish farming in cage
Trawler fishing
Spotter airplane
Sonar
Trawl flap
Trawl lines
Purse-seine fishing
Trawl bagFish school
Drift-net fishingLong line fishing
Lines with hooks
Fish caught by gills
Deep sea aquaculture cage
Float Buoy
Why is it Difficult to Protect Why is it Difficult to Protect Aquatic Biodiversity?Aquatic Biodiversity?Rapid increasing human impacts, the
invisibility of problems, citizen unawareness, and lack of legal jurisdiction hinder protection of aquatic biodiversity.◦Human ecological footprint is expanding.◦Much of the damage to oceans is not visible
to most people.◦Many people incorrectly view the oceans as
an inexhaustible resource.
PROTECTING AND SUSTAINING PROTECTING AND SUSTAINING MARINE BIODIVERSITYMARINE BIODIVERSITYLaws, international treaties, and
education can help reduce the premature extinction of marine species.
Since 1989 the U.S. government has required offshore shrimp trawlers to use turtle exclusion devices.◦Sea turtle tourism brings in almost three
times as much money as the sale of turtle products.
PROTECTING AND SUSTAINING PROTECTING AND SUSTAINING MARINE BIODIVERSITYMARINE BIODIVERSITY
Six of the world’s seven major turtle species are threatened or endangered because o human activities.
Figure 12-4Figure 12-4
Case Study: The Florida Case Study: The Florida Manatee and Water HyacinthsManatee and Water Hyacinths
Manatee can eat unwanted Water Hyacinths.
Endangered due to:◦Habitat loss.◦Entanglement from
fishing lines and nets.◦Hit by speed boats.◦Stress from cold.◦Low reproductive rate
Figure 12-BFigure 12-B
Commercial Whaling
After many of the world’s whale species were overharvested, commercial whaling was banned in 1960, but the ban may be overturned.Figure 12-6Figure 12-6
Case Study: Case Study: Commercial WhalingCommercial Whaling
Despite ban, Japan, Norway, and Iceland kill about 1,300 whales of certain species for scientific purposes.◦Although meat is still sold
commercially.
Figure 12-5Figure 12-5
Revamping Ocean PolicyRevamping Ocean PolicyTwo recent studies called for an
overhaul of U.S. ocean policy and management.◦Develop unified national policy.◦Double federal budget for ocean research.◦Centralize the National Oceans Agency.◦Set up network of marine reserves.◦Reorient fisheries management towards
ecosystem function.◦Increase public awareness.
Fig. 12-7, p. 261
SolutionsManaging Fisheries
Fishery Regulations
Set catch limits well below the maximum sustainable yield
Improve monitoring and enforcement of regulationsEconomic Approaches
Sharply reduce or eliminate fishing subsidies
Charge fees for harvesting fish and shellfish from publicly owned offshore waters
Certify sustainable fisheriesProtected Areas
Establish no-fishing areas
Establish more marine protected areas
Rely more on integrated coastal management
Consumer Information
Label sustainably harvested fish
Publicize overfished and threatened species
Bycatch
Use wide-meshed nets to allow escape of smaller fish
Use net escape devices for sea birds and sea turtles
Ban throwing edible and marketable fish back into the sea
Aquaculture
Restrict coastal locations for fish farms
Control pollution more strictly
Depend more on herbivorous fish species
Nonnative Invasions
Kill organisms in ship ballast water
Filter organisms from ship ballast water
Dump ballast water far at sea and replace with deep-sea water
PROTECTING, SUSTAINING, PROTECTING, SUSTAINING, AND RESTORING WETLANDSAND RESTORING WETLANDS
Requiring government permits for filling or destroying U.S. wetlands has slowed their loss.
Why are wetlands so important?Figure 12-8Figure 12-8
Fig. 12-9, p. 264
Solutions
Protecting Wetlands
Legally protect existing wetlands
Steer development away from existing wetlands
Use mitigation banking only as a last resort
Require creation and evaluation of a new wetland before destroying an existing wetland
Restore degraded wetlands
Try to prevent and control invasions by nonnative species
Case Study: Case Study: Restoring the Florida Restoring the Florida EvergladesEvergladesThe world’s largest ecological
restoration project involves trying to undo some of the damage inflicted on the Everglades by human activities.◦90% of park’s wading birds have vanished.◦Other vertebrate populations down 75-95%.◦Large volumes of water that once flowed
through the park have been diverted for crops and cities.
◦Runoff has caused noxious algal blooms.
Restoring the Restoring the Florida Florida EvergladesEverglades
video
Figure 12-10Figure 12-10
PROTECTING, SUSTAINING, PROTECTING, SUSTAINING, AND RESTORING LAKES AND AND RESTORING LAKES AND RIVERSRIVERSDams can provide many human benefits
but can also disrupt some of the ecological services that rivers provide.◦119 dams on Columbia River have sharply
reduced (94% drop) populations of wild salmon.
◦U.S. government has spent $3 billion in unsuccessful efforts to save the salmon.
◦Removing hydroelectric dams will restore native spawning grounds.
PROTECTING, SUSTAINING, PROTECTING, SUSTAINING, AND RESTORING LAKES AND AND RESTORING LAKES AND RIVERSRIVERSWe can help sustain freshwater
fisheries by building and protecting populations of desirable species, preventing over-fishing, and decreasing populations of less desirable species.
A federal law protecting rivers from development or dams.◦National Wild and Scenic Rivers Act (1968).
Fig. 12-11, p. 267
• Deliver nutrients to sea to help sustain coastal fisheries
• Deposit silt that maintains deltas
• Purify water
• Renew and renourish wetlands
• Provide habitats for wildlife
Natural Capital
Ecological Services of Rivers