Chapter 12

Sustaining Aquatic Biodiversity

Chapter Overview Questions

• What do we know about aquatic biodiversity, and what is its economic and ecological importance?

• How are human activities affecting aquatic biodiversity?

• How can we protect and sustain marine biodiversity?

• How can we manage and sustain the world’s marine fisheries?

Chapter Overview Questions (cont’d)

• How can we protect, sustain, and restore wetlands?

• How can we protect, sustain, and restore lakes, rivers, and freshwater fisheries?

Updates Online

The latest references for topics covered in this section can be found at the book companion website. Log in to the book’s e-resources page at www.thomsonedu.com to access InfoTrac articles.

• InfoTrac: Green to the gills. Paul Greenberg. The New York Times Magazine, June 18, 2006 p54(L).

• InfoTrac: Net losses. H. Bruce Franklin. Mother Jones, March-April 2006 v31 i2 p54(4).

• InfoTrac: Fish and your health. Lynn Keiley. Mother Earth News, April-May 2006 i215 p128(4).

• Sustainable Ecosystems Institute• Marine Protected Areas• USGS: Coastal Ecosystems

Video: Whaling, Overfishing, Fishery Management

• This video clip is available in CNN Today Videos for Environmental Science, 2004, Volume VII. Instructors, contact your local sales representative to order this volume, while supplies last.

Core Case Study: A Biological Roller Coaster Ride in Lake

Victoria

• Lake Victoria has lost their endemic fish species to large introduced predatory fish.

Figure 12-1Figure 12-1

Core Case Study: A Biological Roller Coaster Ride in Lake

Victoria

• Reasons for Lake Victoria’s loss of 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 BIODIVERSITY• We know fairly little 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.

• The world’s marine and freshwater systems provide important ecological and economic services.

HUMAN IMPACTS ON AQUATIC BIODIVERSITY

• Human activities have destroyed, disrupted or degraded a large proportion of the world’s coastal, marine and freshwater ecosystems.– Approximately 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 BIODIVERSITY

• Area of ocean before and after a trawler net, acting like a giant plow, scraped it.

Figure 12-2Figure 12-2

HUMAN IMPACTS ON AQUATIC BIODIVERSITY

• Harmful 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 Pollution

• Each year plastic items dumped from ships and left as litter on beaches threaten marine life.

Figure 12-3Figure 12-3

Overfishing and Extinction: Gone 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 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 MARINE BIODIVERSITY

• Laws, 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 MARINE 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 Manatee 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

Case Study: 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: Commercial 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

Fig. 12-5, p. 258

Toothed whales Sperm whale with squid

Killer whale

NarwhalBottlenose dolphin

Baleen whales

Blue whale

Fin whaleBowhead whale

Right whale

Sei whaleHumpback whale

Gray whale

Minke whale

How Would You Vote?Should carefully controlled commercial whaling be resumed for species with populations of 1 million or more?– No. The hunting of whales is no longer

necessary and simply encourages disrespect for these intelligent giants.

– Yes. Some whale species have recovered and products from them are valuable resources for humans.

PROTECTING AND SUSTAINING MARINE BIODIVERSITY

• Fully protected marine reserves make up less than 0.3% of the world’s ocean area.– Studies show that fish populations double, size

grows by almost a third, reproduction triples and species diversity increases by almost one fourth.

• Some communities work together to develop integrated plans for managing their coastal areas.

Revamping Ocean Policy

• Two 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.

MANAGING AND SUSTAINING MARINE FISHERIES

• There are a number of ways to manage marine fisheries more sustainably and protect marine biodiversity.

• Some fishing communities regulate fish harvests on their own and others work with the government to regulate them.– Modern fisheries have weakened the ability of

many coastal communities to regulate their own fisheries.

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, AND RESTORING WETLANDS

• Requiring government permits for filling or destroying U.S. wetlands has slowed their loss, but attempts to weaken this protection continue.

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

Environmental Response

• Ecological Restoration: the process of repairing the damage caused by humans.

Environmental Response

• Remediation (clean up): Removal of environmental pollutants or contaminants for the general protection of the environment

Environmental Response• Reclamation: the conversion of wasteland into land suitable for

use of habitation or cultivation.• Restoration: returning a habitat to a condition similar to it’s natural

state. Restoration attempts to bring lands modified by human use back to their natural state; however, determining the “pre-disturbance” state of most ecosystems is difficult and because ecosystems continually change, complete restoration is rarely a realistic goal.

• Rehabilitation: turning a degraded ecosystem back into a functional ecosystem, not necessarily the original state. Rehabilitation, which aims to revive important ecological services on degraded lands, is becoming particularly important in mountainous regions, arid lands, and irrigated crop lands.

• Replacement: replacing a degraded ecosystem with another type (ex. Forest land replaced by grassland). This is a type of rehabilitation, but NOT a type of restoration as the natural state is not achieved.– Mitigation: creating an artificial ecosystem to perform a specific

function; make less harsh

Case Study: Restoring the Florida Everglades

• The 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 Florida

Everglades

• The project has been attempting to restore the Everglades and Florida water supplies.

Figure 12-10Figure 12-10

PROTECTING, SUSTAINING, AND RESTORING LAKES AND

RIVERS• Lakes are difficult to manage and are

vulnerable to planned or unplanned introductions of nonnative species.

• For decades, invasions by nonnative species have caused major ecological and economic damage to North America’s Great lakes.– Sea lamprey, zebra mussel, quagga mussel,

Asian carp.

PROTECTING, SUSTAINING, AND RESTORING LAKES AND

RIVERS• Dams 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.

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