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