Chapter 11
Sustaining Aquatic Biodiversity
Core Case Study: A Biological Roller Coaster Ride in Lake Victoria
• Loss of biodiversity and cichlids
• Nile perch: deliberately introduced
• Frequent algal blooms– Nutrient runoff– Spills of untreated sewage– Less algae-eating cichlids
Lake Victoria Is a Large Lake in East Africa
Natural Capital Degradation: The Nile Perch
Marine Biodiversity
• #1 is coral reefs• Higher in coastal zone than open sea• Higher on bottom region than surface region
b/c of greater habitat variety and food sources
HIPPCO
• Also applies to marine habitat• Habitat alteration
– Trawlers drag nets weighted with heavy chains– Dams and excess water withdrawal
Invasives
• Water hyacinths in Lake Victoria• Asian Swamp eel can travel over land
• Purple loosestrife: introduced from EuropeEuropean predators have been introduced
Fig. 11-4, p. 252
Lake Wingara
Introduced carp eat algae that stabilize sediment on lake bottom
Fig. 11-A, p. 253
Population, Pollution, Climate Change
• In ten years, 80% of world population will live near coast
• Nitrate runoff continues to increase (fertilizer)• Average sea level rise is 4 – 8 inches in past
100 years– Coral reefs too far from surface – Low lying islands submerged (Maldives: now 5ft
above sea level)– Coastal wetlands (and mangroves) may be lost
Overfishing
• Industrial fishing is unsustainable• Fishprint• Commercial extinction
– Newfoundland’s cod fishery is closed (20,000 fishers and processors out of work)
– When desirable fish go, small, young fish are target, so little chance for recovery
– 1/3 of fish catch is bycatch
Commercial Fishing Methods
• Sonar, GPS, and huge nets increase yield of commercial operations– 75% of commercial fisheries are fished at or
beyond their sustainable yield
3 Fishing Methods
• Trawler fishing– Scrape ocean bottom– Huge, some trawler nets can cover 12 jumbo jets
• Purse-seine fishing– Used for fish near surface (tuna, dolphin safe?)
• Longlining– Up to 80 miles long, thousands of hooks– Can catch sea turtles, dolphins
Fig. 11-7, p. 256
Fish farming in cage
Trawler fishing Spotter airplane
Sonar Purse-seine fishing
Drift-net fishing
Long line fishing Float Buoy
lines with hooks
Deep sea aquaculture cage Fish caught
by gills
Drift Nets
• Tennis net with larger weave that may be 40 miles long and 50 feet deep– May break loose and kill fish for years
• Fish get caught between threads– Bycatch: unwanted fish, sea birds, sea turtles
• UN has banned nets longer that 1.6 miles– Voluntary, hard to monitor
TEDs
• http://www.youtube.com/watch?v=y71cgxmyMO4
Laws and Treaties
• CITES• ESA
Whales
• Cetaceans• Marine mammals• Toothed whales
– Feed on squid, etc (porpoise)• Baleen whales
– Filter feeders; krill (blue whale)• 8/11 major species commercially extinct
Whales
• Blue whale near extinction– 25 years to reproductive age, one offspring every
2-3 years• IWC
– Since 1970, US banned whaling and imports– Since 1986, international ban has been successful– Japan: scientific purposes - restaurants– Norway defies banDebate about current population
Sea Turtles
• 6/7 are endangered• Leatherback has survived 100 million years• Eggs deposited at night on beaches• Babies hatch together and move across beach
to the sea • Nets, long line, hunters affect population• Plastic bags• TEDs
Fig. 11-10, p. 260
Marine Sanctuaries
• Offshore fishing limit is 200 statute miles– exclusive economic zone– Marine protected areas (MPAs)
• High seas• Marine reserves would include areas in high
seas– Population doubles, biodiversity increases– Benefits nearby fisheries– $12-14 billion/year, 1 million jobs
CO2 Problems
• IUCN indicates coral reefs can survive global warming if overfishing, pollution are curbed
• CO2 + water = carbonic acid – Dissolves calcium carbonate shells– Possibly most damaging consequence of increase
of CO2 concentration
Integrated coastal management
– Fishers, business owners, politicians, scientists, citizens develop long term solutions
– Great Barrier Reef Marine Park is managed by ICM
Fishery Populations
• Maximum sustainable yield (MSY) vs optimum sustainable yield (OSY)– OSY takes into account consequences to other
species and error
Subsidies
• Government subsidies encourage overfishing– $30-34 billion given to fishers per year– $10-14 billion encourages overfishing and
expansion of industry
Individual Transfer Rights
• Government gives each fisher a percentage of the total allowable catch (TAC) for a fishery in a year
• Worked in Alaska’s halibut fishery• Problems
– Private fishers own public water, public pays for system
– Monopoly possibility– TACs are usually too high
Sustainable Seafood
• Certification• Marine Stewardship Council (MSC)
– “Fish Forever” ecolabel– Walmart agreed to sell only MSC certified seafood
by 2011
Fig. 11-12, p. 265
SOLUTIONS
Managing FisheriesFishery Regulations BycatchSet catch limits well below the maximum sustainable yield
Use wide-meshed nets to allow escape of smaller fish
Improve monitoring and enforcement of regulations
Use net escape devices for seabirds and sea turtlesBan throwing edible and marketable fish back into the sea
Economic ApproachesSharply reduce or eliminate fishing subsidiesCharge fees for harvesting fish and shellfish from publicly owned offshore waters
AquacultureRestrict coastal locations for fish farmsControl pollution more strictly
Certify sustainable fisheriesProtect Areas
Establish no-fishing areas
Depend more on herbivorous fish species
Establish more marine protected areas
Nonnative Invasions
Rely more on integrated coastal management
Kill organisms in ship ballast water
Consumer InformationFilter organisms from ship ballast water
Label sustainably harvested fish Dump ballast water far at sea and replace with deep- sea waterPublicize overfished and
threatened species
Wetlands
• In US, more than 50% of 1900 wetlands have been lost– What happened?
• Soon, coastal wetlands could be under water– Feeding stops for migratory bird flyways affected– Commercial fish and shellfish populations affected
Government can help
• Zoning laws could be used to prevent further development
• A federal law requires a permit to dump dredged material into wetlands bigger than 3 acres
Mitigation Banking
• Policy that allows development of a wetland as long as another wetland area is created or restored
• Most attempts to create wetlands fail– Why?
The Everglades
• Originally, 60 mile wide sheet of water flowing from Lake Okeechobee to Florida Bay
• Now less than half its original size– In 1948, a water control project was completed– Drained for farmland (sugarcane)– Paved over– Nutrient runoff from agBiodiversity loss: invasives, habitat loss, fragmentation from urbanization
Kissimmee River
• Feeds into Lake Ocheechobee• b/w 1962 and 1971, US Army Corps of Engineers
straightened the river– Flood control, but – rapid flow of water drained land north of Lake
Ocheechobee– Water was diverted for crops and cities, so– Less flow into Florida Bay causes salinity and
temperature to increase– More nutrients cause algae bloom
Fig. 11-14, p. 268
Restoration
• In 1990, US and state government agreed to fund restoration project
• Among other projects, the Corps of Engineers will restore meandering flow of river
• Cost = $10 billion• Sugarcane growers convinced Florida
legislature to increase allowable P discharge limit and delay date of implementation of limit
Dams
• Columbia River in northwest– 119 dams; 19 hydroelectric dams– Interfere with spawning salmon who must return
upstream to lay eggs• Population down by 94%
• Snake River in Washington State– Similar scenario, environmentalists want small
hydroelectric dams taken down