Sustaining Aquatic Biodiversity

Core Case Study: A Biological Roller Coaster

Ride in Lake Victoria

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

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.

11-1 What Are the Major Threats to Aquatic

Biodiversity? Concept 11-1 Aquatic species are

threatened by habitat loss, invasive species, pollution, climate change, and overexploitation, all made worse by the growth of the human population.

Three General Patterns of Marine Biodiversity

The greatest marine biodiversity occurs in coral reefs, estuaries, and the deep-ocean floor

Biodiversity is higher near coasts than in the open sea because of the greater variety of producers and habitats in coastal areas

Biodiversity is higher in the bottom region of the ocean than in the surface region because of the greater variety of habitats and food sources on the ocean bottom

Human Activities Are Destroying and Degrading

Aquatic Habitats 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.

Shrimp farms in areas that were once mangrove

forests

Additional ways humans degrade our ocean environment

HUMAN IMPACTS ON AQUATIC BIODIVERSITY

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

Invasive Species Are Degrading

Aquatic Biodiversity Invasive species Threaten native species Disrupt and degrade whole ecosystems

Three examples Water hyacinth: Lake Victoria (East

Africa) Asian swamp eel: waterways of south

Florida Purple loosestrife: indigenous to Europe

Treating with natural predators—a weevil species and a leaf-eating beetle—Will it work?

Asian Rice Eel

Population Growth and Pollution

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

It’s just a plastic bag! It can’t hurt anyone.

Sea turtle off the coast of Florida

What can you do to make sure this does

not continue?

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.

Human impacts on marine biodiversity

Coral reef destruction

Sea level rising Destruction of

mangrove forests Trawler nets

destroying ocean floor

Invasive species Coastal

development Trash Overfishing

Industrial fish harvesting methods

Trawler fishing: dragging net along ocean floor

Purse-seine fishing: surround fish with net

Long-line fishing: 80 miles of fishing line with thousands of baited hooks

Drift-net fishing: 80 miles of drifting nets below the surface

Problems with industrial fish harvesting methods

Trawler fishing: like clear-cutting forest; destroys ocean floor; captures endangered seals and turtles

Purse-seine fishing: kills hundreds of dolphins

Long-line fishing: hooks endangered sea turtles, albatross, pilot whales, sharks, dolphins

Drift-net fishing: kills non-target fish species and marine mammals

Fig. 11-7, p. 256

Fish farming in cage

Trawler fishing

Spotter airplane

Sonar

Trawl flapTrawl 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

Trawler fishing

By-catch

Purse-seine fishing

Long-line fishing

Several countries have banned the use of drift nets or they

are carefully monitoring the use of

drift nets

Drift-nets catch and

kill anything caught in the net

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.

Case Study: Protecting Whales: A Success

Story… So Far Cetaceans: Toothed whales and baleen whales

1946: International Whaling Commission (IWC)

1970: U.S. Stopped all commercial whaling Banned all imports of whale products

1986: moratorium on commercial whaling Pros Cons

Case Study: Holding Out Hope for

Marine Turtles Carl Safina, Voyage of the Turtle Studies of the leatherback turtle

Threats to the leatherbacks Trawlers Pollution Climate change

Communities protecting the turtles

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 (TEDs). 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 of human activities.

Figure 12-4

Laws and international treaties protecting marine

biodiversity CITES (Convention on International Trade in

Endangered Species ) Global Treaty on Migratory Species Marine Mammal Protection Act ESA (Endangered Species Act of 1973 ) Whale Conservation and Protection Act International Convention on Biological Diversity Offshore fishing

Exclusive economic zones High seas

Law of the Sea Treaty Marine Protected Areas (MPAs)

Exclusive Economic Zone

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.

Fisheries scientists

Conservationists

Citizens Business

interests Developers Politicians

Integrated Coastal Management

Competing for the same resource – identify shared problems and goals and attempt to develop workable, cost-effective, and adaptable solutions that preserve biodiversity and environmental quality while meeting economic and social needs.

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.

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 11.13 Natural capital restoration: wetland restoration at

Fort Erie, Ontario, Canada before (right) and after (left).

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

similar to 11-14

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.

PROTECTING, SUSTAINING, AND RESTORING LAKES AND

RIVERS We 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 helps protect a tiny fraction of U.S. wild and scenic rivers from dams and other forms of development. National Wild and Scenic Rivers Act

(1968).

Fig. 11-16, p. 270