© 2011 pearson education, inc. ap environmental science mr. grant lesson 79 emptying the oceans...
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© 2011 Pearson Education, Inc.
AP Environmental Science
Mr. Grant
Lesson 79
Emptying the Oceans
&
Marine Conservation
© 2014 Pearson Education, Inc.
Mastery Check
Describe three ways plastics affect marine life.
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Objectives:
• Define the term marine reserve.
• Review the current state of ocean fisheries and reasons for their decline.
• Evaluate marine protected areas and reserves as innovative solutions.
• TED - Legendary ocean researcher Sylvia Earle shares astonishing images of the ocean -- and shocking stats about its rapid decline -- as she makes her TED Prize wish: that we will join her in protecting the vital blue heart of the planet.
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Marine Reserve: A marine protected area that is highly protected, and is effective as a complete sanctuary; no extractive uses are permitted, and very few (or no) other human uses (including scientific research) are permitted.
Define the term marine reserve.
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Review the current state of ocean fisheries and reasons for their decline.• Over half the world’s marine fish populations are fully exploited,
28% are overexploited, and only 20% can yield more without declining.
• Global fish catches have stopped growing since the late 1980’s, despite increased fishing effort and improved technologies.
• People began depleting marine resources long ago, but impacts have intensified in recent decades.
• Commercial fishing practices include drift netting, long-line fishing, and trawling, all of which capture non-target organisms, called bycatch.
• Non-target species are killed when they are captured as bycatch while fishing for commercially-valuable species.
• Today’s oceans hold only one-tenth as many large animals that they did before industrialized commercial fishing.
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Review the current state of ocean fisheries and reasons for their decline.
• As fishing intensity increases, fish become smaller and fishermen switch to less-desirable species.
• Consumers can encourage good fishery practices by shopping for sustainable seafood.
• Marine biodiversity loss affects ecosystem services.
• Traditional fisheries management has not stopped declines, so many scientists feel that ecosystem-based management is needed.
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Emptying the Oceans
Overharvesting is the worst marine problem We are putting unprecedented pressure on marine
resources Half the world’s marine fish populations are fully
exploited and can’t be fished more intensively
28% of fish population are overexploited and heading to extinction
Total fisheries catch leveled off after 1988 despite increased fishing effort
The maximum wild fisheries potential has been reached
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Emptying the oceans
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The global fisheries catch has increased
It is predicted that populations of all ocean species we fish for today will collapse by 2048
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Emptying the Oceans
If current trends continue, it is predicted that populations of all ocean species we fish for today will collapse by 2048
If fisheries collapse as predicted, we will lose their ecosystem services Productivity will decline, and they will become more
sensitive to disturbance
Filtering of water will decline, causing more harmful algal blooms and beach closures
Aquaculture is relieving some of the pressure on wild stocks, but it has its own set of environmental problems
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We have long overfished
People began depleting sea life centuries ago
Species have been hunted to extinction: Caribbean monk seal, Steller’s sea cow, Atlantic gray whale
Decreased sea turtle populations cause overgrowth of sea grass and can cause sea grass wasting disease
Overharvesting nearly exterminated many whale species
People never thought groundfish could be depleted Local populations dwindled as far back as the 19th century
New approaches or technologies were needed to increase catch rates
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Fishing has industrialized
Factory fishing = huge vessels use powerful technologies to capture fish in huge volumes
Driftnets = transparent nylon mesh nets that drift with the current
Used for herring, sardines, mackerel, sharks, shrimp
Longline fishing = extremely long (up to 80 km or 50 mi) lines with several thousand baited hooks
Used for tuna and swordfish
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Fishing has industrialized
Trawling = using cone shaped nets with weights at the bottom and floats at the top to catch pellagic fish
Bottom trawling = using weighted nets that drag across the seafloor to catch groundfish or scallops
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Fishing practices kill nontarget animals and damage ecosystems Bycatch = the accidental capture of animals
A 2011 report found that 17% of all commercially harvested fish were captured unintentionally
Driftnetting drowns dolphins, turtles, and seals Fish die on deck
Banned in international waters
But is still used in national waters Longline fishing kills turtles, sharks, and over
300,000 seabirds/year Methods (e.g., flags) are being developed to limit
bycatch
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Fishing practices kill nontarget animals
Fisheries bycatch is one of the biggest problems facing the world's oceans
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Fishing practices kill nontarget animals and damage ecosystems Dolphins are trapped in nets used to catch tuna
Hundreds of thousands of dolphins were killed
The 1972 Marine Mammal Protection Act forced fleets to try to free dolphins Bycatch dropped dramatically
Other nations fished for tuna, and bycatch increased The U.S. government required that nations exporting
tuna to the United States minimize dolphin bycatch “Dolphin-safe” tuna uses methods to avoid bycatch
Other species (sharks) are still being caught Dolphin populations have not yet recovered
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Dolphin deaths have declined, but …
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Fishing practices kill nontarget animals and damage ecosystems Bottom trawling causes bycatch and harms entire
ecosystems
Heavy nets crush organisms and damage sea bottoms Especially destructive to complex areas (e.g., reefs)
It equals clear-cutting and strip mining
The average spot of the sea floor in the Georges Bank has been trawled three times, destroying young cod as bycatch
Bycatch of cod while fishing for other species in the Grand Banks nearly doubled from 2006 to 2009
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Bottom-trawling destroys ecosystems
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Modern fishing fleets deplete marine life rapidly
Grand Banks cod have been fished for centuries Catches more than doubled with industrial trawlers
Record-high catches lasted only 10 years
Georges Bank cod fishery also collapsed
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Modern fishing fleets deplete marine life rapidly
Worldwide, industrialized fishing is depleting marine populations with astonishing speed 90% of large-bodied fish and sharks are eliminated
within 10 years after fishing begins
Populations stabilize at 10% of their former levels
Communities were very different before modern fishing Removing animals at higher trophic levels allows prey
to proliferate and change communities
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Industrialized fishing is destroying fisheries
Oceans today contain only one-tenth of the large-bodied animals they once did
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Modern fleets deplete marine life rapidly
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Several factors mask declines
Industrialized fishing has depleted stocks But global catch has remained stable for the past 20 years
How can stability mask population declines? Fishing fleets travel farther to reach less-fished areas
Fleets fish in deeper waters (now at 250 m)
Fleets spend more time fishing and set more nets
Improved technologies: faster ships, sonar mapping, satellite navigation, thermal sensing, aerial spotting
Fleets expend more effort to catch the same number of fish
At some point, there will not be enough fish left
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We are “fishing down the food chain”
Figures on total global catch do not tell the whole story
As fishing increases, the size and age of fish caught decline 10-year-old cod, once common, are now rare
As species become too rare to fish, fleets target more abundant species Shift from large, desirable species to smaller, less
desirable ones
This entails catching species at lower trophic levels
“Image makeovers” renamed formerly undesirable fish “Orange roughy” was once called “slimehead”
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We are “fishing down the food chain”
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Purchasing choices influence fishing practices
Best choices: farmed catfish, mussels, oysters, tilapia
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Marine biodiversity loss erodes ecosystem services
Factors that deplete biodiversity threaten ecosystem services we get from the oceans
Systems with reduced species or genetic diversity show less primary and secondary production They are less able to withstand disturbance
Biodiversity loss reduces habitat for nurseries for fish and shellfish
Less diversity leads to reduced filtering and detoxification, resulting in algal blooms, dead zones, fish kills, beach closures
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Diversity loss erodes ecosystem services
Accelerating Loss of Ocean
Species Threatens
Human Well-Being.
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Fisheries management has been based on maximum sustainable yield Maximizes harvest while maintaining fish for the future
Managers may limit the harvest or restrict gear used
Despite management, stocks have plummeted Requires accurate measurement of fish numbers
Overestimates have resulted in overharvesting
Ecosystem-based management shifts away from species and toward the larger ecosystem Considers the impacts of fishing on habitat quality, species
interactions, and long-term effects
Sets aside areas of oceans free from human interference
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Fisheries management
Successful management of summer flounder has resulted in an increase in adult fish stock.
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Evaluate marine protected areas and reserves as innovative solutions.
• We have established fewer protected areas in the oceans than we have on land, and most marine protected areas allow many extractive activities.
• No-take marine reserves can protect ecosystems while also boosting fish populations and making fisheries sustainable.
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We can protect areas in the ocean
Marine protected areas (MPAs) = most are along the coastlines of developed countries They still allow fishing or other extractive activities
Marine reserves = areas where fishing is prohibited Leave ecosystems intact, without human interference
Improve fisheries, because young fish will disperse into surrounding areas
Many commercial and recreational fishers and businesses do not support reserves To be successful, establishment needs to be sensitive
to concerns of local residents
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We can protect areas in the ocean
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Reserves can work for both fish and fishers
A 2001 review showed that after just one to two years of establishment, marine reserves: Increased densities of organisms by 91% Increased biomass by 192% Increased organism size by 31% Increased species diversity by 23%
Benefits inside reserve boundaries include: Rapid and long-term increases in abundance,
diversity, and productivity of marine organisms Decreased mortality and habitat destruction Decreased likelihood of extirpation of species
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Reserves work for both fish and fisheries
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Reserves can work for both fish and fishers
Areas outside reserves also benefit A “spillover effect” occurs when individuals of
protected species spread outside reserves Larvae of species protected within reserves “seed the
seas” outside reserves
Improved fishing and ecotourism
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Areas outside reserves also benefit
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Reserves can work for both fish and fishers
Local residents who were opposed changed to supporting reserves once they saw their benefits
Once commercial trawling was stopped on Georges Bank: Populations of organisms began to recover
Fishing in adjacent waters increased
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How should reserves be designed?
Reserves should be able to Protect ecosystems
Sustain fisheries
Include people
Most studies suggest that 20–50% of the ocean should be protected in no-take reserves How large should the reserves be?
How many should we have?
Where should they be located?
Involving fishers is crucial in coming up with answers
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How should reserves be designed?
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TED Video
Sylvia Earle has been at the frontier of deep ocean exploration for four decades. She's led more than 50 undersea expeditions, and she's been an equally tireless advocate for our oceans and the creatures who live in them.
" We've got to somehow stabilize our connection to nature so that in 50 years from now, 500 years, 5,000 years from now there will still be a wild system and respect for what it takes to sustain us."
Sylvia Earle
Sylvia Earle's TED Prize wish to protect our oceans (18:16)